In the search for answers, one must look in the most unexpected places. With life only ever being recorded on one world, much speculation has gone into possible life in other areas of the galaxy. Questions like “Are we alone?” or “Does life exist elsewhere?” have pushed humanity to explore the other regions of the ever-expanding universe in hopes of finding some shred of proof for the possibility of other life forms. The first place astronomers began to look was in the current solar system, but then they set their eyes on another set of targets: exoplanets.

An exoplanet planet, otherwise known as an extrasolar planet, is any planet that maintains an orbits around a star that is not the Sun. Current recorded exoplanets come in all shapes and sizes, that range from a size that is bigger than Jupiter to smaller than the Earth[1]. In order to find these planets and systems that exist thousands of light-years away, scientists must use a variety of methods in order to detect them. These processes can be split into two different categories: direct and indirect detection. Direct detection is simply taking a direct image of the planet itself; however, this is usually not easy because planets are very faint light sources. Most of the detection comes from indirect methods: astrometry, gravitational microlensing, pulsar timing, transit method and Doppler wobble are all methods for detecting exoplanets in a variety of different ways [2]. There are a variety of reasons of why scientists are searching for exoplanets, but perhaps one of the most compelling reasons is the idea of finding life and answering once and for all the age old question: is life a rare event, or common occurrence?

One of the most interesting discoveries of recent times in the search for exoplanets can be found within the system of Kepler-62. Existing 1,200 light-years away from Earth in the Lyra constellation, this solar system of five planets all orbit a 7 billion year old K2 dwarf star. On April 18^th, 2013, Kepler-62 was found in the field of vision of the Kepler Spacecraft, a satellite from NASA’s Kepler Mission which is used to detect planets that are transiting stars [3]. The research team of William J. Borucki et al. used the transit discovery method, which is a photometric method that detects planets as they pass in front of a star, which creates a drop in the brightness of the star. The specific K2 star of the Kepler-62 system has a luminosity of about 0.21 solar luminosities, a radius around 0.64 solar radii, a mass near 0.69 solar masses, a temperature approximately 4925K (the Sun’s temperature is 5778K, making it 853K cooler), and based on typical K star lifetimes, it should end its current lifecycle and change to a red giant in 13 billion years [3]. Also, the K2 Star is only 2/3rds the size of the sun and is only 1/5th as bright [4].

Within this system exists one of the most potentially habitable exoplanets to date: Kepler-62e. This little world contains certain characteristics that make it a prime candidate for life, and could possibly answer many questions in the future search for exoplanets. Based on the habitable zones, planetary equilibrium temperature, parameters of the planet, possibility of an atmosphere, and the evolution of the star, the possibility of life does not seem far-fetched.

The Areas of Habitability

            Within every planetary system exists a habitable zone, the area where water can exist as a liquid, found to be between 273K and 373K [5]. The habitable zone of a system can be calculated through a series of equations, which will be used to find the inner and outer habitable zones of Kepler-62 [6]. In order to find the inner habitable zone, you use the following equation:  = 0.95AU , where  stand for the inner habitable zone boundary, the 0.95AU represents the distance in astronomical units from the star and is based on Earth’s solar system’s inner habitable zone, and the  stands for the luminosity of the star in terms of solar luminosities. Because it is known that Kepler-62 is only 1/5^th the luminosity of the Sun, 0.2 would be used for the term . Once 0.2 is plugged into the equation, the end result is equal to 0.42AU, meaning that the inner habitable zone exists at a distance of 0.42 astronomical units.

In order to find the outer habitable zone, the same equation must be used, but the initial 0.95AU must be changed to 1.4AU to represent the outer boundary in relation to the Earth’s solar system’s habitable zone. The equation to find the outer limit of the habitable zone is as follows:  = 1.4AU , where  is the outer habitable zone boundary, the 1.4AU represents the distance in astronomical units from the star and is based on Earth’s solar system’s outer habitable zone, and the  stands for the luminosity of the star in terms of solar luminosities. Like in the first equation, 0.2 would be used for the term . Once 0.2 is plugged into the equation, the end result is equal to 0.63AU, meaning that the outer habitable zone ends at a distance of 0.63 astronomical units.

This data shows that habitable zone of Kepler-62 would have to lie between 0.42AU and 0.63AU. Both of these are less than half of the distances of the habitable zones in Earth’s solar system. However, even though the habitable zone is smaller, Kepler-62e lies within the habitable zone at 0.427AU [3].

A Planet and its Temperature

            Another important piece of information is the planetary equilibrium temperature, a theoretical temperature of the planet if it were simply a black body being heated only by the star [7]. The following equation shows the way to determine the equilibrium temperature if Kepler-62e had a similar albedo to Earth but no atmosphere [8]:  = 254K , where  stands for the planetary equilibrium temperature, the 254K is the given temperature based on Earth’s temperature in degrees Kelvin,  is the luminosity of the star in solar luminosities, and  is the distance from the star in astronomical units. In this equation,  would be 0.2 solar luminosities because Kepler-62 is only 1/5^th the luminosity of the Sun, and  would be 0.43 astronomical units because that is how far Kepler-62e is from Kepler-62. If these points were plugged into the equation, the equilibrium temperature would be equal to 259K.

A similar equation would be used if Kepler-62e had a greenhouse effect:  = 287K . The difference between this equation and the previous equation is the addition of 33 degrees Kelvin to the initial temperature to take into consideration the extra heat added under the greenhouse effect. For this equation,  is the luminosity of the star in solar luminosities, and  is the distance from the star in astronomical units.  would again be 0.2 solar luminosities, and  would again be 0.43 astronomical units. The final result of this equation would an equilibrium temperature of 292K.

If Kepler-62e did, indeed, have a similar albedo to that of Earth’s, it would also share a striking resemblance in terms of planetary equilibrium temperature, being about only 5K hotter in both instances. To clarify, Earth’s albedo was used in this equation because direct imaging is required to find a planet’s albedo, which has not yet been done for Kepler-62e.

Characteristic of a Planet

            The parameters of the planet are also important to keep under consideration when exploring the habitability of a planet. One major parameter is the mass of Kepler-62e, which can be found through the following equation [9]: .  represents the mass of the star in kilograms,  represents the velocity of the star in meters per second,  is the mass of the planet in kilograms, and  is the velocity of the planet in meters per second.

In order to find the mass, one must first find all the other variables in the equation. The only variable that remains unknown is the velocity of the planet, which can be found in the following equation [9]: .  is the radius of the orbit and is in units of meters, while  is the period, which is how long it takes to go around the star, and is measured in seconds.  would be used for  because that is the radius of the orbit for Kepler-62e, and  would be used for  because that is the length it takes for Kepler-62e to go around its star. Once these are put into the equation, the equals 253.5 .

Now that  is known, it’s possible to solve for the mass of the planet [9]: . For , or the mass of the star,  kilograms would be plugged in, because that is the recorded mass of Kepler-62. For , or velocity of the star, meters per second would be put in, because that is the current velocity of Kepler-62. For , or velocity of the planet, 254 meters per second would be put because that is the velocity of Kepler-62e. This equation found the mass ofKepler-62e to be. Online sources estimate the mass to be around  [3]. This minor difference is just due to rounding in the equations.

Potentiality of a Possible Atmosphere

            The atmospheric conditions of Kepler-62e are not currently known [3]. However, it is big enough to possibly stay warm enough on the inside for a magnetic field to exist, and this field could protect a possible atmosphere from solar stripping. And because it is within the galactic habitable zone, it must have a high enough ratio of elements to have similar composition to that of terrestrial planets within our own solar system [10]. Also, if there are water oceans on the surface of the planet like scientists hypothesize, then some sort of atmosphere must be present for the water to remain in its liquid state. For liquid water to exist there must be enough pressure in the atmosphere; if there is not enough pressure, it would either become gaseous or solidify into ice [8]. Simply put, if there is liquid water there must also be an atmosphere.

A Change in a Star

            Over the course of time, stars change and evolve, dramatically affecting the habitable zone of its surrounding planets as time continues to go by. It’s important to keep the star type and age into consideration when exploring and searching for possible places where life could be found. In this particular instance, Kepler-62 is a K2 dwarf star that is approximately 7 billion years old. K stars make up 15% of all stars and have lifetimes of about 20 billion years. K stars transform from orange dwarfs into red giants, then planetary nebula, and end up as a white dwarf. This means that Kepler-62 will eventually get brighter as it ages, pushing the habitability zone further outward over time. Because Kepler-62e is at the inner edge of the habitable zone, it will leave the habitable zone sooner than its fellow planet Kepler-62f. However, it will take much longer for this process to occur than it would for our Sun because of Kepler-62’s smaller size.

A Whole New World

            Much speculation has gone into what the world of Kepler-62e would really look like. Current computer models are suggesting that it is covered by “uninterrupted oceans”, which could mean that much of the life of the planet would exist deep within the recesses of the only-aquatic environment [11]. Scientists also believe in the possibility of bird-like creatures that might exist, but doubt that there would be a technologically advanced species like humanity because they would not have easy access to electricity or metallurgy. However, if there is any land, it would change the possibilities completely [11]. With the idea of a world covered in water, it is theorized that Kepler-62e could either be liquid down to the core or have a solidified surface beneath a shallow ocean. If the latter model is true, this would be more conducive to life as we know it [12]. According to computer models, Kepler-62e would also probably have a very cloudy sky, and would be warm and humid all the way to the polar regions of the planet [13].

So, are you tired of living on land? Exhausted of living above the ocean? Wishing you could spend your days deep within large pools of liquid? Well, wish no more! Introducing your new soon-to-be-home planet of Kepler-62e! Believed to be completely submerged under oceans, you’ll never have to worry about seeing dry land again. With nice cloudy skies, and humid and warm weather around the clock, you’ll be glad you left the dry, cold Earth. Come and see all the hundreds of new species of aliens being discovered every day! Spend you days relaxing in your new under-water home, submerged beneath the ocean in a structure housing you and your loved ones. And food will never be a problem; scientists are working around the clock to uncover which aliens can be eaten and used as food sources, and they are finding more and more with each passing day. So what are you waiting for? Pack up your things and come move to Kepler-62e, the most Earth-like exoplanet around!

Final Thoughts

            The discovery of the Kepler-62 star system and its subsequent planets has re-invigorated the search for life on exoplanets. With the finding of such an Earth-like planet, science has become hopeful that this discovery will lead to further information on the potentiality of life in the universe. Because it was only discovered this year, much research has to be done before any definitive answers can be found, but based on the current data, there is a reason to believe Earth might not be the only home to organisms in the universe.

Works Cited

[1] “The MEarth Project – What Are Exoplanets?” The MEarth Project – What Are Exoplanets? N.p., n.d. Web. 21 Oct. 2013.

[2] “Detecting Extrasolar Planets.” – Space Art and Astronomical Illustrations. N.p., n.d. Web. 21 Oct. 2013.

[3] “Kepler-62: A Five-Planet System with Planets of 1.4 and 1.6 Earth Radii in the Habitable Zone.” Kepler-62: A Five-Planet System with Planets of 1.4 and 1.6 Earth Radii in the Habitable Zone. N.p., n.d. Web. 21 Oct. 2013.

[4] NASA’s Eyes. Computer software. Eyes on the Solar System. N.p., n.d. Web. 21 Oct. 2013.

[5] “Habitable Zone.” Habitable Zone. N.p., n.d. Web. 21 Oct. 2013.

[6] Lasarova, Mariana. Homework #5. Colorado Springs, CO. 2013. Print.

[7] “Equilibrium Temperatures of Planets.” Home Page – Home Page. N.p., n.d. Web. 21 Oct. 2013.

[8] Lasarova, Mariana. Homework #4. Colorado Springs, CO. 2013. Print.

[9] Bennett, Jeffrey O., G. Seth. Shostak, and Bruce M. Jakosky. Life in the Universe. San Francisco, CA: Addison Wesley, 2003. Print.

[10] “Galactic Habitable Zones.” Galactic Habitable Zones. N.p., n.d. Web. 21 Oct. 2013.

[11] “What Might Alien Life Look Like on New ‘Water World’ Planets?” Space.com. N.p., n.d. Web. 21 Oct. 2013.

[12] Nature.com. Nature Publishing Group, n.d. Web. 21 Oct. 2013.

[13] “Water Planets in the Habitable Zone: A Closer Look at Kepler 62e and 62f.” SciTech Daily. N.p., n.d. Web. 21 Oct. 2013.

Since the dawn of man, the origin of life has always been debated time and time again. Whether its religion, pseudoscience or Darwin’s Theory, the origin and evolution of life still remains largely in question. Although there are many hypotheses, few  have been tested well enough to bear the name of an accepted theory. As humanity develop a better scope of the world we live in and the technology to explore it, we began to search for life outside of mother Earth. We do so in hope that by finding and learning about life outside our world, we will be able to discover more about ourselves. As we reach beyond our Solar System, we looked for other Earth-sized planets, since the only assumption we can make is that a planet as big as Earth within the habitable zone of its host star could maintain life. We ourselves is the very proof of that statement. Planets outside of our solar system are thus called exoplanets, short for extrasolar planets. Searching for other life forms on exoplanets may sound like a walk in the park, but even the study of the study of life is an art to itself. There many ways searching for a planet: direct imaging, transits and eclipses, microlensing, Doppler effect, Pulsar timing and perhaps half a dozen more.

The planet introduced in this paper is WASP-12b. It is roughly 870 light-years away from us in the winter constellation of Auriga. It was discovered in 2008, by the UK’s WASP, Wide Area Search for Planets. The WASP surveyor uses transit methods to search the skies, detecting drops in light signatures as a planet passes in front or behind a star. Each star exerts a consistent and stable amount of energy, demonstrated in its luminosity. When a planet passes in front of the star, between our line of sight, it diminishes the light signatures of the sun.  (http://www.superwasp.org/wasp_planets.htm)  (all data regarding WASP-12 and WASP-12b from superwasp.org)

Basically, if the star is a light bulb and the planet is a pebble, we are trying to detect the “shadow” that the pebble casts when it is placed in front of it. The graph above is the light curve of WASP-12 as WASP-12b transits it. Note the slight drop in the middle of the graph. This is how WASP-12b was discovered. Since WASP-12 is a G-star, a relatively low-mass star, it will slowly grow bigger and more luminous, becoming a giant. When it completely fuses all its hydrogen into helium, it will change into a white dwarf.

WASP- 12b orbits around its star WASP-12. WASP-12 is a G0 star with a luminosity of 1.26 that of our Sun’s. It is 60% large than our Sun is (1.58 Solar Radii) and 30% heavier (1.29 solar masses).[1] Since the Sun is a G2 star, WASP-12 is slightly hotter than our Sun is, with our Sun being 5800 K and WASP-12 being 6350K. The most special phenomenon about the relationship of WASP-12 and WASP-12b is that WASP-12 is slowly absorbing WASP12-b. Since stars grow over time, WASP-12 is slowly growing into WASP12-b’s orbit. Given their minimal distance between the sun and the planet, it gives WASP 12-b incredible temperatures, perhaps even one of the hottest hot Jupiters we have discovered. WASP 12-b is much bigger than Jupiter, with a 1.83 Jupiter radii and 1.39 Jupiter masses. Since it orbits its star at an extremely close distance of 0.0226 AU, it has an incredibly short orbital period of 1.091 Earth days. this means that it takes a little more than one Earth rotation for WASP 12-b to complete a full orbit of its star.

Given the extreme conditions of WASP-12b, it is highly unlikely that WASP-12b would habit any life at all. The following equation is used to find the surface temperature of WASP-12b:

 Solving for SurfaceTemp in the above equation, the surface temperature appears to be 1800 K. Note that this equation does not include the tidal heating caused by WASP-12b’s immediate distance to the WASP-12. Taking the tidal heating into account, WASP-12b would be superheated to 2560 K. This is extremely hot, also the first piece of evidence that suggest that life could not on this planet. One of the most important requirements for life, water, could not exist in its solvent form at this temperature.

To further show that WASP-12b is not habitable, we will now show the habitable zone of WASP-12 and that WASP-12b does not lie within that boundary. The habitable zone equation will be used to find the inner and outer edge of the habitable zone of the star WASP-12.

Since the luminosity of WASP-12 is 1.26 times that of our Sun’s, we get D_inner as 1.07 AU and D_outer as 1.57 AU. The width of the habitable zone is thus 0.50 AU. WASP-12b is only 0.0226 AU away from its star WASP-12, so it clearly does not lie within the habitable zone of its star.

With regards to life on WASP-12b, it is true that it is far too hot for life as we know it to exist. WASP-12b, a hot Jupiter also has no solid surface, especially since the tidal heating from its star causes it to warp into an “egg” shaped planet. The heating also causes WASP-12b’s atmosphere to expand. But one thing about its composition does interest us. Among most hot Jupiter exoplanets that we’ve found have had a 1:2 carbon-oxygen ratio. But on WASP-12b, carbon-oxygen ratio was 2:1, twice the concentration of what it is normally. Moreover, its methane concentration is 100 times that of what astronomists speculated. Carbon and methane concentrations are important to us because life is carbon-based and methane is a by-product of life. Even though life may not exist on WASP-12b, another planet without its system would have similar composition. If such a planet does exist within the habitable zone of WASP-12, it may as well inhabit life.

If the life does exist on WASP-12b, they would mostly live in the higher atmosphere where water vapor could exist. They would have to be large, buoyant bodies that can regulate its altitude at will in case of the solar winds. They may be large creatures resembling jelly fish, but could inflate themselves to the size of a blimp. Since the planet is 870 light-years away, it would take far too long for us to get there with our current technology, we may never have a real image of WASP-12b being eaten away by its star. Overall, WASP-12b is a fascinating discovery and confirms a phenomenon that scientists have long suspected, but had not been able to confirm with legitimate data.

BIBLIOGRAPHY

http://www.superwasp.org/wasp_planets.htm

http://www.nasa.gov/mission_pages/hubble/science/planet-eater.html

http://en.wikipedia.org/wiki/Stellar_classification

http://en.wikipedia.org/wiki/WASP-12http://content.time.com/time/health/article/0,8599,2035754,00.html

http://en.wikipedia.org/wiki/WASP-12b

Introduction

If Earthling’s ever encounter extraterrestrial life, we will share one thing in common. Us and whatever life we contact, complex or not, will have originated on a planet. Life cannot exist on or in a star because of the extreme conditions nor can it exist on gas giants or icy giants. Life probably cannot and does not exist in or on asteroids and even if it did current detection methods are far from strong enough to detect or study asteroids throughout the galaxy. Astronomers do not search for life in black holes or solar nebulas or supernovas, for obvious reasons. The search for life focuses almost entirely on planets comprised primarily of water or rock. Studying these worlds, scientists hope to find life and if not simply planetary science.

Detection

On December 16, 2009,  the MEarth Project confirmed the detection of an exo-planet orbiting nearby red dwarf star, Gliese 1214. The planet, named Gliese  1214b, Gliese tells us the planet orbits a star in the three-star system, Gliese, the number specifies the host star it orbits within the Gliese star system and the letter specifies which planet it is. Its host star Gliese 1214 is located in our immediate neighborhood within the Milky Way galaxy. Gliese 1214b floats forty-two light years away from Earth in the constellation Ophiuchus.

The MEarth Project detected Gliese 1214b using the transit method. To use this method, the observation point must be somewhat edge on in order to observe a planetary eclipse of the host star. As Gliese 1214b passed in front of Gliese 1214, instruments observed 1.50 % a dip in the host stars total luminosity.

With the telescopes fixed on this star the MEarth Project eliminated the possibility that such a dip was caused by an asteroid or comet, when thirty eight hours later they detected the same decrease in overall brightness. Using only transit detection methods, the MEarth Project determined Gliese 1214b’s orbital period and subsequently its orbital velocity, its mass, and its semi-major axis.

Planetary Metrics and Composition

Gliese 1214b orbits Gliese 1214 at a distance of 0.0140 Astronomical Units and completes one full orbit every 38 hours. It is 6.36 times the mass of Earth and its radius is 2.69 times Earth’s. Being larger than Earth and the other terrestrial planets yet smaller than the ice giants of our solar system, Neptune and Uranus, it is characterized as a Super Earth. Such a size raises questions of composition that in 2009 scientists did not have sufficient evidence to answer.

Initially, scientists postulated it was composed mostly of water, though this could not be confirmed. Also, using its mass and radius scientists calculated its density and found it to be denser than water at 5.0 g/cc. Recent research confirms these claims and raises interesting possibilities regarding the habitability of the planet. Gliese 1214b is, in fact, comprised of water and it harbors a thick water vapor atmosphere. The atmosphere was detected using the Rayleigh Effect. When scientists ran models using its observed radius and compared them to actual observations, they differed. They determined that the origin of this difference was caused by a larger radius than scientists previously accounted for. This difference must be the result of a high atmosphere.

Rayleigh Effect diagrams.

http://www.naoj.org/Pressrelease/2013/09/03/

A Thick Watery Atmosphere

The thick atmosphere exerts an incredible amount of pressure on Gliese 1214b’s surface. In addition, the surface temperature is estimated at a range of 393-555 K. The calculations below confirm Gliese 1214b’s extremely high surface temperatures.

At these high temperatures and high pressures, water cannot exist, on the surface, as a liquid. Therefore life, similar to life on Earth, cannot exist on Gliese 1214b’s surface. But, life may exist in its watery core, much like the possibility that life exists in the subsurface ocean, of Jupiter’s moon, Europa.

The conditions superfluid water exists at.

http://web.mit.edu/newsoffice/2012/superfluid-phase-transition-0118.html

            Because Gliese 1214b is relatively close to Earth, it offers an opportunity for further study of its atmosphere and internal composition that will increase the accuracy of our estimates and knowledge of its surface and internal conditions. Currently, scientists speculate the presence of “hot ice”, “superfluid water” and “plasma water” on its surface. Life, like life on Earth, cannot exist or evolve in these extreme phases of water. Such a possibility cannot be ruled out because some sort of thermophile may be able to withstand the grueling temperatures and high pressures on its surface, or in the subsurface ocean.

Though this does not seem possible becuase at these high temperatures complex chemistry, essential to life, breaks down. Without the formation of chemical bonds life, of any kind, simply cannot form.

This does not completely eliminate the possibility of life. Below the surface, temperatures may be lower therefore liquid water could exist. The discovery and confirmation, of a subsurface ocean comprised of, at least primarily liquid water would greatly increase the probability of life existing on Gliese 1214b.

A Migratory Planet’s Icy Origins

The presence of liquid water is anomaly because of its close proximity to its host star. Gliese 1214b is such a large planet comprised of approximately 75.0% water. Therefore it is unlikely that asteroid and comet impacts provided all of Gliese 1214b’s water. The nebular theory of solar system formation does not account for Gliese 1214b’s semi-major axis of 0.0140 AU’s. Astronomers hypothesize that Gliese 1214b must have accreted outside the frostline, as an icy planet, explaining the presence of water. Then, they speculate that it gradually migrated inwards, melting the ice and, thus, accounting for the presence of liquid water.

Its original position and subsequent migration inwards inhibited the formation of possibly habitable conditions. When it was icy, habitability was impossible. These uninhabitable conditions must have persisted until it reached its final stable orbit. In its current orbit, Gliese 1214b is outside the habitable zone. The inner boundary of Gliese 1214’s habitable zone is 0.05 Au’s from the star and its outer boundary is 0.08 AU’s from the star. Using the fraction of Gliese 1214b’s luminosity to the Sun’s luminosity, I calculated these boundaries.

Although Gliese 1214b orbits outside the habitable zone, it may still harbor life. This fact simply eliminates the possibility of liquid water existing on the surface, but it may exist elsewhere on the planet.

Life may exist and may have existed since Gliese 1214b’s conception in a subsurface ocean, protected from impacts by a thick icy crust. The migration further confounds the unlikeliness of intelligent complex beings existing on Gliese 1214b. Simple microbial life may exist underneath its surface. It is a possibility, but an incredible small one because of the intense heat and pressure inflicted on the planet by its thick water vapor atmosphere.

Just because life does not persist on Gliese 1214b does not nullify its scientific importance. Astronomers and scientists, alike, are enthused by the opportunity to study its atmosphere and try to determine the causes for its inward migration. This “steamy water world” provides an excellent chance to challenge and strengthen our theory of solar system formation and planetary science. Its proximity to Earth ensures that such studies and resulting discoveries will be a part of the near scientific future.

Bibliography

“Astronomers Find World with Thick, Inhospitable Atmosphere and an Icy Heart | ESO.” Www.eso.org. European Southern Observatory, 16 Dec. 2009. Web. 22 Oct. 2013. <http://eso.org/public/news/eso0950/&gt;.

Bennett, Jeffrey O., G. Seth. Shostak, and Bruce M. Jakosky. Life in the Universe. 3rd ed. San Francisco, CA: Addison Wesley, 2003. Print.

“Gliese 1214.” Open Exoplanet Catalogue. MIT, n.d. Web. 17 Oct. 2013. <http://openexoplanetcatalogue.com/system.html?id=Gliese%201214%20b&gt;.

“GJ 1214 B.” Wikipedia. Wikimedia Foundation, 13 Sept. 2013. Web. 22 Oct. 2013. <http://en.wikipedia.org/wiki/GJ_1214_b&gt;.

Hadhazy, Adam. “Super-Earth or Mini-Neptune? New Technique to Probe Exoplanet Habitability.” Space.com. N.p., 4 Oct. 2013. Web. 22 Oct. 2013. <http://www.space.com/23079-alien-planets-super-earth-mini-neptune.html&gt;.

“New Type of Alien Planet Is a Steamy ‘Waterworld’” Space.com. N.p., 21 Feb. 2012. Web. 22 Oct. 2013. <http://www.space.com/14634-alien-planet-steamy-waterworld-gj1214b.html&gt;.

“Observations Indicate Super-Earth GJ 1214 B Has a Water-Rich Atmosphere.” SciTech Daily. N.p., 4 Sept. 2013. Web. 22 Oct. 2013. <http://scitechdaily.com/observations-indicate-super-earth-gj-1214-b-water-rich-atmosphere/&gt;.

Rayleigh Scattering (physics).” Encyclopedia Britannica Online. Encyclopedia Britannica, 17 Oct. 2013. Web. 22 Oct. 2013. <http://www.britannica.com/EBchecked/topic/492483/Rayleigh-scattering?sections=49248&gt;.

Zolfagharifard, Ellie. “Super-Earth 40 Light Years Away ‘is Rich in Water with a Thick, Steamy Atmosphere’, Confirm Japanese Astronomers.” Mail Online. N.p., 5 Sept. 2013. Web. 22 Oct. 2013. <http://www.dailymail.co.uk/sciencetech/article-2412151/Super-Earth-GJ-1214b-40-light-years-away-rich-water-steamy-atmosphere.html&gt;.

Christian Bladon

Mariana Lazarova

PC 120 Life in the Universe

October 20, 2013

Life in a Multiple Star System?

                                    Fig.1 Artist rendition of the planet surface[1]

Introduction

Exoplanets, the great celestial bodies away from our solar system that may one day serve as colonies in the stars to mankind.  An exoplanet is a planet outside of our solar system, orbiting a star many light years away from us.  Hard to detect, humankind has only learned of their existence in the past 30 years, and cataloging them in the past 20 years.  Extremely difficult to identify due to the extreme distances between Earth and them, physicists use a variety of methods, both direct and indirect, to discover them.  Researchers use data collected from enormous telescopes, along with extremely advanced mathematics, to measure the gravitational distortion a star might receive from an exoplanet, the change in luminosity a star may present as an exoplanet drifts past it, and the Doppler shift of a star as it moves around its own orbit to identify potential new homes for the human race. 

As mankind has become increasingly versed in the layout of the galaxy, it has become apparent that although there are likely many habitable planets out there, there are also many more planets that aren’t.  Because Earth is only able to sustain a certain amount of people and their pollution, it has become viable for scientists to search for new planets in the Galaxy to inhabit, so mankind may survive and thrive in future generations.  Against the odds of finding much, it is for this reason that research is being funded to discover these potential new homes as quickly as possible.  With nearly 300 billion stars in the galaxy, and possibly more planets orbiting them, it is surprising that as recently as 2012, a possibly habitable planet named Gliese 667Cc has been discovered in the Scorpius constellation.  Orbiting the star Gliese 667C, part of a three star binary system nearly 22.1 light years away, Gliese 667Cc was discovered using the radial velocity method of exoplanet identification.  By measuring the Doppler shift that the star demonstrated in its own orbit, it was deduced that the star had a number of orbiting planetary bodies around it.  By measuring the shift in the spectral lines of the star, the change in radial velocity of a star signals that the gravity of an orbiting planet is pulling it (See Equation 1: Radial Velocity due to Planet).  Originally discovered this way, the planet was first found by the European Southern Observatory’s HARPS telescopic spectrograph by researchers at the University of Gottingen and Carnegie Institution for Science.  The planet as of right now holds the most promise of any yet discovered for a potential home for undiscovered life.

The star itself, Gliese 667C, is extremely different from that of Earth’s sun.  With a luminosity only 1.4% of the sun’s, Gliese 667C is a red dwarf star, of the classification M1.5V.  Burning at around 3700 degrees Kelvin, the star’s heat hardly compares to the intense 5,778 degrees Kelvin that the sun puts out.  Bound in a binary system of three stars, Gliese 667A and 667B orbit each other extremely closer, while Gliese 667C circles the pair from 230 astronomical units away.  Speculated to be 2 billion years old, the M type star is much smaller than the Earth’s sun, and so should live for many more billions of years until it finally transitions into its next stage of evolution.  Red Dwarfs of the M star type are the most common of all in the galaxy, and take trillions of years to mature.  As such, there are currently none in the next stage of evolution.

Thesis

Aside from all of these factors influencing how habitable the planet is, it also resides within the Habitable Zone of Gliese 667C, the distance from the star at which water can be found in liquid form.  The combination of all of these make Gliese 667Cc the most likely habitable exoplanet yet discovered, although the vast distance between it and Earth make it only possible to speculate and hypothesize on what the planet is actually like.  Despite being extremely similar to Earth, it seems unlikely that the planet is actually habitable, or carries any form of life.  Judging by researchers lack of knowledge on the exoplanet, chances are that Gliese 667Cc is for some reason or other inhabitable, due to such reasons as higher infrared radiation, a different atmosphere or the occasional spike in solar activity from the nearby star that could sterilize the planet.

                        Fig.2 The habitable ring around Gliese 667C[2]

Supporting Data

The planet’s habitability is defined by a multitude of calculations and observations, which point towards its potential for housing life as being more likely than any other planet yet discovered.  Gliese 667Cc orbits its star within the habitability zone, the ring around a star between two distances wherein liquid water may form.  By multiplying the square root of the star’s luminosity with either .95au, for the inner boundary, or 1.4au, for the outer boundary, the habitable zone edges can be found, and placed against the average distance a planet is from its star (see Equation 2: Habitable Zone Calculation).  Next, by taking the planets Albedo, or reflectivity, it is possible to estimate the average surface temperature of a planet, which for Gliese 667Cc is a temperate 277.4 degrees Kelvin.  This almost matches Earth’s average temperature, which is 287 degrees Kelvin, with the help of the planet’s atmosphere.  Classified as a super-Earth type planet, the mass of Gliese 667Cc is roughly 4.4 times greater than Earth, while still being considered habitable.  However, the result of this increased size is that gravity also goes up.  On the surface of the planet, is believed that gravity would be twice as strong as that on Earth, meaning a person would weigh twice what they normally do.  Due to the planet’s strong similarities to Earth, estimated to be around 90%, it can be assumed that a similar atmosphere would cover the planet, helping the planet retain heat in much the same way as Earth does.  It can be assumed that the equation for the planet’s temperature equilibrium, or the average temperature of the planet’s surface in simpler terms.  Using the planet’s estimated albedo, which is about 11% that of the Earth, the average temperature on Gliese 667Cc comes out to be 277.4 degrees Kelvin, within 10 degrees Kelvin of Earth’s termperature (see Equation 3: Albedo Calculation / Temperature Equilibrium).  However, unlike the sun, Gliese 667C is a much more slowly developing star.  Although the Habitable Zone in the solar system will likely shift in the next few billion years, it is unlikely that this will occur at Gliese 667C.  This means that if Gliese 667Cc is in fact a habitable exoplanet, it could be used as a home for mankind for an indefinitely great period of time.

                        Fig. 3 A comparison of Earth against the other possibly habitable planets[3]

Species Speculation

In truth, the surface of the planet is more similar than not to terrestrial locations, such as the Grand Canyon.  With deep, trench like canyons acting as the path for relatively shallow rivers, a pleasant biota of flora grow near the edge of the water.  Bleached a deep, blood red, the short grass and ferns pick up the increased levels of infrared light from Gliese 667C as a higher source of energy than the visible light on the planet.  Most surprising of all, however, is the presence of two main species of conflicting amphibians and reptiles.  The amphibians resemble a mix of an eel and a frog, having an extremely elongated body typically two feet in length, with powerful hind-legs, and surprisingly dexterous forearms.  Surviving off of algae in the canyon rivers of the planet as a main source of food, this species is in constant evolutionary conflict with the reptile like predators they share the planet with.  The reptiles, in contrast to the long shape of the amphibious species, are extremely compact, resembling a rounder version of a Crocodile and a Komodo Dragon.  However, what sets them apart as a predator is their right forearm; a retractable arm with razor-like claws capable of rocketing out to full length (about a foot) in less than .03 seconds.  Although they may be the only two organisms of complex structure and movement, the two species offer a wide variety of colors and regional mutations that are fairly noticeable.  The higher levels of infrared light, combined with the excess radiation of solar flares at a much closer distance to the orbiting star cause mutations to occur within the organisms DNA at a rate nearly 100x that of Earth.  Unfortunately, the tidal locking of the planet to its sun means that the planet’s organisms can only survive along a ring a few kilometers in width around the planet, where there is a perpetual state of semi-day and semi-night.  If visiting the area, most scientists recommend taking a small raft down one of the many rivers, to reduce impact upon the relatively fragile ecosystem, while also decreasing stress from the planets higher gravity force.  These trips are not for the casual adventurer, as the extra force of gravity upon the body calls for a high level of fitness to counteract the natural extra strain put upon the body.

Conclusion

Gliese 667Cc resides as the planet most likely capable of life that we have yet discovered, although there are still discrepancies as a home for potential new life.  The lack of information on the planet’s surface will slowly reduce in the coming years as more and more information is gained on the system, although labeling it the “holy grail”[4] of life on an exoplanet may be immature.  This does not detract from the excitement over the discovery of the exoplanet, as any new planet with the possibility of life pushes humankind one step closer to branching off from earth, and becoming a space-faring civilization.

Sources

– Wedemeyer-Böhm, Sven. “Life on Gliese 667Cc?” – Institute of Theoretical Astrophysics. Institute of Theoretical Astrophysics, 17 Feb. 2012. Web. 21 Oct. 2013. <http://www.mn.uio.no/astro/english/research/news-and-events/news/astronews-2012-02-17.html&gt;.

– “More Talk About Gliese 667Cc, The “Holy Grail” of Exoplanets.” Space Oddities – What I Didn’t Learn in Science Class. WordPress.org, 28 Apr. 2012. Web. 21 Oct. 2013. <http://lilspaceoddities.wordpress.com/2012/04/28/more-talk-about-gliese-667-cc-the-holy-grail-of-exoplanets/&gt;.

– Creager, Charles, Jr. ” Gliese 667Cc, The Latest “Habitable” Planet.” Gliese 667Cc. N.p., n.d. Web. 21 Oct. 2013. <http://gscim.com/Science_News/4-12/Gliese_667Cc.html&gt;.

– Delfosse, Xavier. “The HARPS Search for Southern Extra-solar Planets. XXXIII. Super-Earths around T.” The HARPS Search for Southern Extra-solar Planets. XXXIII. Super-Earths around T. Astronomy and Astrophysics, May 2012. Web. 21 Oct. 2013. <http://adsabs.harvard.edu/abs/2013A&A…553A…8D&gt;.

– Gregory, Philip C. “Additional Keplerian Signals in the HARPS Data for Gliese 667C from a Bayesian Re-analysis.” Adsabs.harvard.edu. Eprint ArXiv:1212.4058, Dec. 2012. Web. 21 Oct. 2013. <http://adsabs.harvard.edu/abs/2012arXiv1212.4058G&gt;.

Pictures:

http://lilspaceoddities.files.wordpress.com/2012/04/gliese667cc.jpg

http://lilspaceoddities.wordpress.com/2012/04/28/more-talk-about-gliese-667-cc-the-holy-grail-of-exoplanets/

Gliese 667Cc (planet) measurements:

Orbital Period: 28.123 days / 2.43 x 10⁶ seconds

Semi-Major Axis: 0.1251 au / 1.87 x 10¹⁰ meters

Radial Velocity: 2.1 m/s

85% similarity to Earth

Receives 90% as much light as earth

Mass: 4.45 Earth masses / 2.657 x 10²⁵ kg

Velocity: 48355 m/s

Estimated Temperature: 277.4K

Albedo: 0.11

Gliese 667C (star) measurements:

Classification: Red Dwarf, M1.5

Luminosity: 0.014

Distance to Earth: 6.8 parsecs / 22.1 lightyears

Habitable Zone (me): D_inner = 0.112 au    D_outer = 0.165 au

Habitable Zone (source): D_inner = 0.095 – 0.126 au    D_outer = 0.241 – 0.251 au

Mass: 0.31 Orbital Masses / 6.163 x 10²⁹ kg

Radius: 0.42 Solar Radii / 2.92 x 10⁸m

Equation 1: Radial Velocity due to Planet

V_planet = 2pa_p            =  2 p (1.87 x 10¹⁰m)               =   48355 m/s

               P_p                        (2429827s)

A_p = Semi-Major Axis (planet)

P_p = Period (planet)

M_star x V_star = m_planet x v_planet 

(6.163 x 10²⁹ m/s) x V_star = (2.657 x 10²⁹ kg) x (48355 m/s)

V_star = 2.1 m/s = radial velocity

M_star = Mass (star)

V_star = Velocity (star)

m_planet = Mass (planet)

v_planet = Velocity (planet)

Equation 2: Habitable Zone Calculation:

D_inner = 0.95au(ÖL)

D_inner = .095au (Ö0.014)

D_inner = 0.112au

D_outer = 1.4au(ÖL)

D_outer = 1.4au(Ö0.014)

D_outer = 0.165au

Equation 3: Albedo Calculation / Temperature Equilibrium:

T_eq = 278K x (L)^1/4 x (1-A)^1/4

                        (ÖD)

L = Luminosity

T_eq = Equilibrium Temperature / Average Planet Temperature

A = Albedo / Reflectivity

D = Distance from star

Introduction

Since the beginning of human space exploration, mankind has been expanding its reach further and further across the universe. Other star systems and planets that were not even known to exist just a few decades ago are now actively being observed and studied. While our current technologies do not generally allow us to send spacecraft (especially if there are humans onboard) too much further than around our own solar system, innovations in other fields have allowed scientists to study extremely distant star systems and compare them to ours. More and more powerful telescopes are always being created, and at this point we have found planets orbiting stars over 20,000 light years away. A planet found orbiting a star other than the Sun is called an exoplanet, and even though no exoplanet is near enough to Earth to been seen with the naked eye, these mysterious cousins of ours can mimic conditions in our solar system very closely. We would search for life in our solar system, but unfortunately no planets orbiting the Sun, other than Earth, seem too likely to be home to any life. As a result, exoplanets are sometimes thought of as the key to finding extraterrestrial life in our universe. Because the nebula theory describes how all solar systems are born, the existence of a planet as habitable as our Earth is perfectly plausible, even in an extraordinarily far-off star system. So, when scientists are scanning the sky for exoplanets, they generally try to limit their search of the cosmos to stars similar to our a sun, a G-star on the main sequence.

One of the most habitable exoplanets ever discovered, Kepler-22b, falls directly into this category. The star it orbits, Kepler-22, is a G5 star that lies approximately 620 light years away from us, in the Cygnus constellation. Kepler-22b was confirmed to exist on October 1st, 2011, after its 4th transit was observed by the Kepler space telescope. The transit method used to discover this exoplanet is also one of the more commonly used techniques in exoplanet detection. This method works when the Kepler space telescope detects a drop in the luminosity of a star for a short period of time. The drop in luminosity can be explained by the fact that a planet orbiting the star may have come around and temporarily come in between the star and the Earth, blocking some of the star’s emitted light. If viewed at the proper inclination (which is not always possible when observing distant stars, and therefore makes this technique only occasionally optional), transits of this type can prove the existence of orbiting planets. However, it generally takes three observed transits to convince astronomers that an exoplanet does, in fact, exist. Kepler-22 is actually very similar to the Sun, which only adds to scientific interest in this star system. Its luminosity is about 0.8 that of our Sun, its radius is 0.979 Solar radii, and its average temperature lies at around 5500K, making it only about 200K cooler than the Sun. Kepler-22b appears to be in the closer in fifth or so of its star’s habitable zone, so it is expected that the planet will slowly but surely become uninhabitable as the habitable zone moves outward. Regardless, the planet probably has many hundreds of millions or even billions of years until it is no longer habitable. Because of this and all of its host star’s similarities to our Sun, Kepler-22b gives us a better chance of discovering extraterrestrial biology than any other exoplanet discovered to date.

Mathematical Evidence for physical conditions of Kepler-22b

When researching an exoplanet to decide whether or not it may have conditions fit for life, there are a few things to consider. In order for life to exist, there must be a liquid medium in which different molecules can interact with each other (water is usually considered the most likely liquid medium to give rise to life as it is liquid for a large range of warm temperatures), and for a liquid medium to exist on a planet, a planet must be in its star’s habitable zone. To determine whether or not a planet is in its star’s habitable zone, we use two equations to determine the inner and outer boundaries of the habitable zone:

, where L/L_sun is the luminosity of the star in solar luminosities. For Kepler-22, L would be set equal to 0.75 as it is about 75% as luminous as the Sun. After plugging a few numbers in, we learn that the inner limit of the habitable zone for Kepler-22 lies 0.82 AU from the star, and the outer limit lies 1.21 AU from the star. This means that the range of the habitable zone around Kepler-22 is 0.39 AU. Since Kepler-22b lies at 0.85 AU from its star, it is in well within its habitable zone, although closer to the inner limit. Since stars brighten with age, the habitable zone will continue to expand and move outward as time goes on, and eventually Kepler-22b will no longer be encompassed in its star’s habitable zone.

Kepler-22b is close to the inner edge of its habitable zone.

One of the other large determinants over whether or not we consider a planet habitable is the planet’s temperature. While some heat is necessary for metabolism to occur and therefore for life to exist, too much of it can easily denature proteins and actually cause it to be even more difficult for life to exist. On top of all of this, temperature (and pressure, but the two are relative) decides what phase a substance will be in – solid, liquid or gas – and since it has already been stated that a liquid medium is one of the necessities for life, temperature clearly helps determine whether or not a planet could give rise to life. One of the deciding factors for the temperature of a planet (along with the content of its atmosphere/knowledge about its interior, which current technology is not powerful enough to determine for distance exoplanets like Kepler-22b) is its albedo, or level of reflectivity. A totally white planet has an albedo of 1, meaning all light that hits the planet is reflected back into space, and a totally black planet has an albedo of 0, where all light is absorbed by the planet.

The idea of albedo is simple – the whiter the object, the more reflective it is.

All planets lie somewhere on this range, and generally, as the albedo of a planet approaches 1, the planet will be getting colder, as less and less light is absorbed by the surface. The issue in this category is that it is very difficult for us to accurately determine the temperature or albedo of an exoplanet so far away, although we do have estimates. If you do a quick Google search, you will see that estimates for Kepler-22b’s temperature are generally around 262K. Using this value and setting it equal to the equation:

, where L is the luminosity of the host star in solar luminosities, A is albedo of the planet, and D is the distance at which the planet orbits its star in meters, we can estimate the albedo of the planet. For Kepler-22b to have this temperature of 262K, a fairly moderate temperature probably capable of allowing for life, the albedo has to be 0.07. So, based on this temperature estimate, Kepler-22b is a very dark planet that absorbs most of the light that comes across it. Keep in mind that this albedo is the result of an estimated temperature, so we cannot be sure that it accurately depicts conditions on Kepler-22b. It is worth noting that planets with lower albedos do not reflect a lot of light, so they are difficult to find via direct imaging. However, most exoplanets are discovered using indirect techniques, and Kepler-22b was no exception.

The transit detection method is one of the more popular methods for detecting exoplanets, as it is conducted by measuring luminosities of stars and looking for temporary dips. This is how Kepler-22b was discovered – after the Kepler spacecraft detected the third uniform, temporary, dip in the luminosity of the star Kepler-22, the planet Kepler-22b was confirmed to exist. I briefly explained how the transit detection method works earlier, but once again the idea is this – if a planet lies in between the Earth and an observed star and the planet passes by the star on the side facing us, it will block some (although a very small amount) of the star’s emitted light to us. On the graph of the star’s luminosity, there will be a small dip for a certain amount of time that matches the amount of time it took the planet to cross the plane of the star.

The luminosity of the star is only lowered when its planet is passing in front of it.

The only equation necessary to figure this out is the equation for the area of a circle, πr², in the form πr_sun² – πr_planet². In a normal solar system where the host star is very large compared to its orbiting planets, this value should come out to be very small. This is because the change in emitted light from the star is extremely small, and as a result it is difficult to detect and could occur from any object passing the star. This was exactly the case with Kepler-22b, as its transit only caused a 0.002 decrease in the luminosity of Kepler-22. Because of this, scientists require three confirmed observations of exoplanet transits before they can confidently say that they have discovered a planet.

An atmosphere is of integral importance to the habitability of a planet as it helps decide how intense the pressure is on the surface of the planet and what the objects (and potentially life) on the surface of the planet experience. Think about what the earth’s atmosphere does for us; it provides us with breathable oxygen, protects us from the harsh radiation of the sun, keeps us warm via the greenhouse effect, etc. The many benefits of an atmosphere are obvious, and it might even be safe to say that if Kepler-22b had a sufficient atmosphere of proper composition, there may actually be life on the planet. However, we have no real way of estimating what the atmosphere is like on the planet and also have no way of determining the composition of the planet. As a result, all of our estimates of the temperature and other factors of Kepler-22b are really just that – estimates. All of the factors for habitability sort of work together like a puzzle, so when we figure out one detail, it sometimes helps us figure out another. As for now, however, we simply cannot speak of Kepler-22b in terms of certainty as we just do not have the required technology to study the planet in detail.

The last key factor in determining the habitability of a planet is its host star’s evolution. Since stars go through different phases in their lives, the planets orbiting those stars experience related conditions. As stars grow older, they also get brighter, and as a result their habitable zones both expand and move outward. This has implications for the planets orbiting the star. Since planets will always orbit their star from the same distance for their entire lives, the habitable zone could at one point encompass a planet and at some point in the future have moved beyond the orbit of that planet. Because Kepler-22b lies 0.85 AU from its star, it would actually be too close to be in the habitable zone for a star like our Sun. However, Kepler-22 is a G5 star, not a G2 star like the Sun, so its relatively lower temperature allows its habitable zone to be closer in. The result is that Kepler-22b lies near the inner edge of its star’s habitable zone, but it still has plenty of time before the habitable zone will migrates beyond its orbit.

What if life really does exist on Kepler-22b?

At this point, we simply have to wait to find out more. We have learned as much about Kepler-22b as our current technologies allow us, so until our science improves further, we are at a bit of a standstill. But, based on what we do know, we can make certain assumptions. If Kepler-22b’s temperature really does lie at 262K, that means that the average surface temperature is 11 degrees Fahrenheit. While this is pretty chilly, it is clearly approaching the range that is necessary for water to be liquid. As a result, it seems plausible to imagine Kepler-22b as a cold, icy, wet world similar to Earth’s Arctic regions. While life definitely could exist, it does not seem likely that too many species could exist in abundance at such frigid constant temperatures, although it is hard to say. Certain dominant species would arise that would be immune to the harsh cold and would probably be adapted to spend much of their life in the water. Penguins come to mind when thinking of a well-adapted, versatile species, as they are extremely adept swimmers but still generally congregate on land. Kepler-22b’s temperature would probably cause the planet to be mostly liquid with certain sections frozen over in ice, and this is how evolution would progress. Life would likely start in the ocean, perhaps by underwater volcanoes that provide the disequilibrium that life needs to begin. As time passes and species continue to evolve, certain animals would make their way onto solid ice and start to live and reproduce there. If I was a travel agent hoping to send a family of four to Kepler-22b, it might be hard to convince them to go. For one, there is not enough information about the atmosphere or composition of the planet to even say for sure whether or not they could survive there. This little detail aside, the trip would probably be like a cruise through Alaska, and the family could admire the icy conditions on their ship cruising through the waters. Kepler-22b’s relative proximity to its star (compared to the Earth’s distance to the Sun) might make more for an incredible view, where Kepler-22 could occupy a large chunk of the horizon during sunrise and sunset. All in all, Kepler-22 star system travel agents will not be necessary for a long while, at least until we find some way of safely and reliably conducting interstellar space travel.

What have we learned?

Kepler-22b offers us one of the best known examples of an exoplanet potentially capable of harboring life. Although we do not yet have proof of biological activity in this distant star system, many of the similarities between the Kepler-22 system and our solar system make us believe that Kepler-22b may be the perfect planet for harboring life. Not only is its star very similar to our Sun, Kepler-22b also lies in the habitable zone of its host star, making it seem plausible that liquid water exists on the surface of the planet. At this point, we just hope that new scientific discoveries will allow us to study the planet in further detail, hopefully someday revealing the existence of extraterrestrial life in the Kepler-22 star system.

Finding Other Worlds

In today’s movies we see advanced alien civilizations all the time. The existence of some other intelligent beings on some faraway planet of a distant galaxy is not as far-fetched as it once seemed. Granted, we still have a long way to go before we’re casually visiting any galactic neighbors, but the simple prospect of life existing on a planet besides ours is completely within the scientific scope of our time. That is why we are searching. We are searching the skies, using a variety of detection methods. And for the most part, what we are attempting to detect is exoplanets. Based on our current understanding of life in the universe, exoplanets, specifically Earth-like planets orbiting Sun-like stars, present the most likely environment in which life would arise separately from our planet. So far, a few thousand exoplanets have been discovered (but many not yet confirmed) using several different methods of detection, some more common than others. The majority of exoplanets right now are discovered using radial velocity and planetary transits, but other methods include gravitational microlensing, which uses the magnification of light due to gravity as a planetary litmus test, and pulsar timing, which picks up changes in the orbit of neutron star pulsars due to the effects of orbiting planets. While all methods of detection are effective, some, like transits, are more reliable, easier, and more valuable as far as the information we can gain. This is why in March 2009, NASA launched the Kepler telescope to find Earth-like planets using planetary transits. The telescope uses a

Figure 1-
This shows how perceived brightness changes as a planet transits a star. Credit: CNES

photometer to monitor the apparent brightness of tens of thousands of stars within a 10² degree section of sky. Periodic dips in a star’s brightness can indicate the presence of an exoplanet. In the diagram above ^[1], the light curve shows the dip in brightness as the planet passes in front of the star. Variations in this type of light curve can provide information about the mass, speed, size, and orbit of the planet. But there are also other explanations for dips in brightness, such as “sunspots” on the surface of the star or, although less likely, passing asteroids. In order to confirm the existence of an exoplanet, the photometer’s data must show three regular transits in front of the star, indicating that the object is indeed orbiting. For any planet within the habitable zone of a Sun-like star, these three orbits should take no more than 7.5 years, this being the time that it takes Mars (at the outer boundary of our habitable zone) to complete four orbits. This was also the planned duration of Kepler’s mission, although damages to components on the craft now endanger its completion. Up to this point though, Kepler has discovered 134 confirmed exoplanets and over 3000 unconfirmed planets, giving us at least more information than we had before on the nature and number of planetary systems in the Milky Way Galaxy.

A Planet With A History

One of these systems, discovered by the Kepler telescope on December 22, 2011, is a small planetary system in the Cygnus constellation orbiting a subdwarf B star called Kepler 70. Although discovered by the Kepler telescope, the actual method of discovery of the exoplanets Kepler 70b and 70c was the reflection of starlight by the planets, rather than the blocking of it. The planet that is of particular interest, mainly due to its more extreme conditions, is Kepler 70b.

Millions of years ago, Kepler 70 was a main sequence star, but a little before 18.4 million years ago, it went through it’s red giant stage, engulfing the two orbiting gas giants (Kepler 70b and 70c). The diagram below^[2] shows how a red giant might pull its satellites into closer orbits before moving to the subdwarf stage.

Figure 2- This shows planetary engulfment during the red giant stage leading to a subdwarf star. This is what is speculated to have occurred in the Kepler 70 system. Credit: Kempton

It is unclear how these planets actually survived being dragged into the red giant envelope of their star and whether their disruption altered the evolution of their host star, but there they remain, as two hot planetary cores, closely orbiting their host star, stripped of any atmosphere they might have once had. The host star, Kepler 70, is currently a subdwarf, meaning that it is a post-red giant fusing helium that will contract to a white dwarf once fusion ceases after about 100 million years. The majority of the time, subdwarf stars are part of a binary star system in which one of the stars somehow strips off the outer layers, leaving only a thin layer of hydrogen and mostly helium. That is the theory anyway. In the case of Kepler 70, the same appears to have happened, but with orbiting planets, rather than another star. This branch off of the typical Hertzprung-Russell diagram can be seen below^[3] as the dark blue band on the left of the diagram. Like white dwarves, the subdwarf Kepler 70 is incredibly hot, with a surface temperature of 27, 730 K (almost five times hotter than our Sun), but it is also still very luminous, with a luminosity of 18.9 solar lumens, likely due to the fact that it is still undergoing fusion. This intensely hot and luminous star, coupled with Kepler 70b’s 0.006 AU 5.7 hour orbit, makes the planet an unlikely candidate for life, to say the least, despite its “coolness factor”.

Figure 3- The extended Hertzprung- Russell diagram of star types, which plots the temperature of stars (K) against the mass and luminosity. Kepler 70 would fall under the dark blue band on the left of the diagram representing subdwarf stars. Credit: Heber (2009, ARAA, 47, 211)

Not Exactly A Hotbed For Life

When looking at the statistics for Kepler 70b, it does not take much to figure out that it is certainly not a habitable planet. The first indicator should be that it is much too close to its host star to be anywhere near the habitable zone. The habitable zone for Kepler 70 can be roughly estimated using eq. {1}, where our Sun’s habitable zone is used for R_outer and R_inner, the inner and outer radial boundaries of our habitable zone (.95 AU and 1.4 AU respectively) and L is the luminosity (L/L_¤) of Kepler 70:

R_hz=R_inner(sq root(L))- R_outer(sq root(L))

In order to do this though, first the luminosity of Kepler 70 must be calculated using eq. {2}, where σ is the Stefan-Boltzman constant (5.67×10^-8Wm^-2K⁴), r is the radius of the star, and T is the temperature of the star.

L=4pi(r)^2(sigma) T^4

When the luminosity is calculated, using the scorching 27,730 K surface temperature of Kepler 70 and the star’s radius of 1.4×10⁸m, it comes out to be 18.9 solar luminosities (L/L_¤), or 18.9 times more luminous than our sun. This number can then be used in eq. {1} to calculate the habitable zone of Kepler 70, which comes out to be 4.13-6.08 AU (using the conservative estimate for our Sun; .95-1.4), or 3.65-7.39 AU (using the optimistic estimate; .84-1.7). No matter which estimate is used though, Kepler 70b orbits at a distance of 0.006 AU from its host star, where it receives extreme radiation. It is not even close to being inside the habitable zone. Although the width of the habitable zone for Kepler 70 is about 5 times wider than that of our Sun, it does no good if the planets are not within it.

What being so far inside of the habitable zone means for Kepler 70b, is that it is hot, and not just “planet hot.” Kepler 70b is hotter than the surface of our Sun. Taking the luminosity found in eq. {2}, the equilibrium temperature can be calculated in eq. {3}, where A is the albedo of the planet, D is the distance to the star, L_star is the luminosity of the star, and L_now is the luminosity of our Sun in its current state (1 L_¤). This equation shows the surface temperature of the planet due solely to stellar radiation, assuming no atmosphere. And since Kepler 70b has no atmosphere, because it was evaporated during Kepler 70’s red giant phase, in which the planet was engulfed, this temperature calculation is relatively true to the actual surface temperature on the planet.

T(eq)=278KxL^1/4x(1-A)^1/4/(sq root(D))

So, using the luminosity of 18.9 L_¤ from eq. {2}, the distance of 0.006 AU to the host star, and an estimated albedo of 0.1, the equilibrium temperature comes out to roughly 7300 K, about 2000 K hotter than the surface of the Sun. There is no doubt that liquid water, or any liquid solvent for life, is impossible on Kepler 70b. Therein lies the irony in that Kepler 70b is the coolest exoplanet.

While there are more factors that contribute to the habitability of a planet, the ones already discussed will, for the most part, ensure that no life can exist. As far as our current understanding leads us to believe, if a planet is not within the habitable zone, it is extremely unlikely to harbor life. It will either be too hot or too cold, and will have too much or too little atmosphere. And given the history of Kepler 70b, it seems unlikely to contain life anyway. At one point, during the star’s main sequence life, it could have been possible that Kepler 70b was in a better proximity for life to arise, being a gas giant with an atmosphere. But now it’s really only a burned up planet core hurtling all too close to a dying star. It has no atmosphere, no water, and no prospects for life. Even if life were somehow possible there, through means that we do not have the science to explain or understand, what kind of life form would want to live there?

What If…

This now marks the departure into sci-fi. Clearly, life is not possible on a planet as hot and barren as Kepler 70b. At over 7000 K one would be hard pressed to find any kind of liquid, especially with such low pressure, since the mass of Kepler 70b is only 0.44 Earth masses. The only kind of life that it seems remotely reasonable to expect would be some kind of thermophile bacteria, but something unlike anything we have ever seen. But that would make for a very boring planet…

COME ONE, COME ALL! CALLING ALL HYPERTHERMOPHILES! THIS COULD BE JUST THE LIFE CHANGING VACATION YOU HAVE NEEDED.

I have no idea know how many times in the last month I have heard from desperate inhabitants of Altair and Canopus looking to escape the summer heat of their home stars. And this could just be the perfect solution.  I am talking about Kepler 70b; and boasting temperatures as low as 7300 K, it is the perfect summer getaway. Due to its close proximity to its sun, you will feel just like you are at home, but with the exotic ambiance of a semi terrestrial world. If you love the extreme, then come try the orbital experience, traveling at over 950,000 km/h! Come experience the natural plasma hot springs! And with only 5 ½ hour days, beautiful sunsets and sunrises are all the more abundant. Here on Kepler 70b, paradise awaits.

Life Might Not Find A Way…

Back in reality, there is really no chance that life could exist on Kepler 70b. The hallmark of habitability is liquid water. Although we have found organisms on Earth that appear to survive without it, it seems unlikely that life could arise in its absence. The habitable zone around our Sun marks the area in which the equilibrium temperature allows for abundant liquid water, given the right atmospheric conditions, as does the habitable zone around the subdwarf Kepler 70. But that zone is from roughly 4 AU away from the star to 6 AU away. If Kepler 70b were within this range, then, given an appropriate atmosphere, it would be possible to have liquid water and theoretically life. But it is not. So the fact that it has no atmosphere is irrelevant. None of the other parameters for habitability matter if the planet is too hot for a liquid solvent for life. That is why, despite their entertainment factor, planets like this one are not prime targets in the search for life. What we are looking for is Earth-like planets orbiting Sun-like stars, because that is what we know. But that is not to say that there is nothing to be learned from systems like Kepler 70, only that the search for extraterrestrial life is going to have to search elsewhere.

Bibliography:

Barlow, Brad N. “Brad Newton Barlow.” Research. N.p., n.d. Web. 20 Oct. 2013.

Bennett, Jeffrey O., and G. Seth. Shostak. Life in the Universe. 3rd ed. San Francisco: Pearson Addison-Wesley, 2012. Print.

Charpinet, S., G. Fontaine, P. Brassard, E. M. Green, V. Van Grootel, S. K. Randall, R. Silvotti, A. S. Baran, R. H. Ostensen, S. D. Kawaler, and J. H. Telting. “A Compact System of Small Planets around a Former Red-giant Star.”Nature.com. Nature Publishing Group, 21 Dec. 2011. Web. 20 Oct. 2013.

“Exoplanet.eu.” The Extrasolar Planet Encyclopaedia — KOI-55 B. N.p., n.d. Web. 20 Oct. 2013.

“Kepler (spacecraft).” Wikipedia. Wikimedia Foundation, 20 Oct. 2013. Web. 20 Oct. 2013.

“Kepler-70.” Wikipedia. Wikimedia Foundation, 18 Oct. 2013. Web. 20 Oct. 2013.

“Kepler-70b.” Wikipedia. Wikimedia Foundation, 25 Sept. 2013. Web. 20 Oct. 2013.

Images:

^[1] http://www.cornellcollege.edu/physics/courses/phy312/student-projects/extra-solar-planets/extra-solar-planets.html

^[2] http://www.nature.com/nature/journal/v480/n7378/fig_tab/480460a_F1.html

^[3] http://physics.highpoint.edu/~bbarlow/subdwarfs.html

On Friday my class saw the movie, “Gravity”.  The movie is set in current day space; it opens with astronauts (George Clooney, Sandra Bullock) attempting to install a new instrument on the Hubble space telescope.  All is well until debris from a Russian nuclear test rips through satellites causing a huge cloud of scrap metal to speed towards the telescope and the exposed astronauts.  The third astronaut is killed immediately leaving Clooney and Bullock on their own to fend for themselves as the debris continues to orbit and pummel them.  Using Clooney’s EVA jet pack they make their way to the ISS, in hopes of using one of the re-entry vehicles.  As they arrive the debris hits them again, Clooney is pulled away and drifts to his death, Bullock enters the station and uses the damaged vehicle to travel to the Chinese station.  Once she arrives she enters another, operational re-entry vehicle and tumbles to earth, safely landing in a lake.

The movie, while fun to watch, is riddled with scientific inaccuracies.  To start with, there is only one stable orbital speed per radius, and in the movie the debris is orbiting in the same direction as the stations, making impacts impossible. Another is that George Clooney’s death defies Newton’s laws.  There is no force pulling him, and yet even after coming to rest he is still ripped from the para-cord he is clinging to upon his and Bullock’s arrival to the ISS.

Despite these and many other mistakes, “Gravity” is still a fun movie to watch.  Just remember to take the science with a grain on salt.

In a study conducted in 2011 by the Bureau of Labor Statistics, Current Population Survey, Annual Social and Economic Supplement, of American Adults Age 25 and over (Full-Time Workers), it was found that median annual earnings and degree of education are directly correlated.  http://www.ohe.state.mn.us/dPg.cfm?pageID=948  Its clear by looking at the graph that, as the degree of education goes up, so does the median annual earnings. This linear relationship bares a striking resemblance to the H-R Diagram, which is the diagram used in astronomy to predict the heat of a star versus its luminosity. As stars get older, they get hotter but dimmer, so there is a “main sequence”. However there are distinct outliers, such as Red Super Giants that get very cold and incredibly luminous, or White Dwarfs, which get very dim but extremely hot.

The earnings versus education diagram has a similar path. When people become more educated, they tend to earn more. This is the “main sequence” of the diagram. However there are people who never attain high levels of education, yet earn as much, if not more, than the most educated people in the country. This represents The White Dwarfs, if we relate Temperature to Median Earnings and Luminosity to Education. This would mean that people with high levels of education but low earnings represent the White Dwarfs. So in many ways, the H-R Diagram and the Education versus Earnings Diagram share a similar pattern.

For the past week in class we’ve been discussing the search for exoplanets in neighboring star systems. One of the most important tools that has arisen in astronomy was actually designed for this purpose: the Hertzprung-Russell Diagram, which classifies stars into “Spectral Types” according to their temperature and luminosity. Since its conception in 1913, the H-R diagram has become an integral resource for astronomers because it not only gives us a way to classify stars, but also points out the relationships between different stellar characteristics and even maps out an evolutionary path for most stars.

Our last assignment was to come up with our own H-R diagram, a plot that would define a set of human characteristics that fall in a pattern similar to that of the spectral properties of stars. For my “N-F Diagram”, in order to find a dataset that would exhibit an equivalent of the H-R’s main sequence as well as show an evolutionary trend, I researched the relationship between educational attainment and average annual income in the United States.

Perhaps not surprisingly, all of the sources I referenced indicated a fairly linear trend, with those attaining the highest levels of education making the most money per year, and those without high school diplomas making the least. However, this is an extremely generalized portrait of the country, and certain outliers produce points that don’t fall along the average, main sequence. For example, certain entrepreneurs became very successful after dropping out of high school or college, and thus produce a range on the graph much like that of the giant and supergiant stars on the H-R Diagram. Conversely, some very highly educated professors can make, depending on their school of employment, as low as $50,000-$60,000 a year, and serve as the human equivalent of the H-R’s white dwarves.

While at first glance this might seem like a fairly obvious relationship to choose as a subject of research, the greater implications of this trend invite more complex examination, especially when the additional variable of time is considered. For example, the percentage difference in income between the highest educated and the lowest has increased significantly in the last ten years, meaning that PhDs are making a much higher amount than blue-collar workers in comparison to a decade ago. In addition, the difference in unemployment rates of the highly educated and the less educated has doubled (7.2% for less educated and 2.3% for highly educated in 2001, to 14.3% and 4.3% in 2011). Together, these two trends suggest that there is a weakening demand in our economy for less educated workers, and a growing demand for the highly educated. Whatever is driving this, be it the rapid mechanization of many industries or the lack of blue-collar jobs as a result of economic unrest, it is apparent that people are already taking note of it and making adjustments as necessary. Between 2000 and 2009, the number of high school graduates enrolled in college jumped from 63% to 70%. Kids today are more frequently being told that they need to get into a good college to get a good job, and many schools have standardized their curricula in order to raise SAT and ACT scores and track their students into higher education.

Whatever this general shift may mean for the future of our country, as it stands the relationship between education and income falls almost eerily into the pattern prescribed by the H-R Diagram and its classification of stars in our galaxy. A blatant sign of alien interference, if you ask me.

http://geography.tamu.edu/class/bednarz/ep2Q98_4.pdf

http://www.huffingtonpost.com/steven-strauss/the-connection-between-ed_b_1066401.html

The Hertzsprung-Russel (HR) Diagram is a chart that maps star types based on temperature (x-axis; also can be labeled as color/ spectral type) and luminosity (y-axis). It actually accurately charts stars based on stellar evolution and mass. The main descending linear line is called the “main sequence.” These stars are all in the hydrogen-fusing portion of their evolution, which constitutes most of their lifespan. To the top right, you find red giants and supergiants, the next phase in stellar development. To the lower left you also find white dwarfs: essentially “dead” low mass stars. It is a very important astronomical tool used to identify characteristics of stars and their current phase of life.

Photo Credit: Brinkworth and Thomas, University of Leicester

Our professor has challenged us to make our own version of the HR Diagram (let’s call it an MS Diagram for my initials). The only requirement is that it represents some part of the human experience. I must admit, when trying to come up with an idea for my diagram, I was at a loss. I then thought that there might be a correlation between a person’s income and their carbon footprint. This led me to a study conducted by a high school in the Philippines. Using their data, I was able to construct my own plot on their findings. They are as follows:

As you can tell, individuals with higher incomes use a lot more energy and emit more carbon emissions. This is most likely because of their access to private vehicles and technological luxuries those with lower incomes do without. The income a person is born into is their “main sequence.” Throughout one’s life, they may or may not move up or down a financial bracket, though they most likely will stay in the same place. Movement throughout economic classes would be their “evolution” throughout life.

Though not quite as predictable as the HR Diagram, the MS Diagram provides a good basis for estimating a person’s carbon footprint. Of course, many other factors can affect this as well, like upbringing, environmental awareness, etc. There are always exceptions, but in general it is a generally accurate way to think of the correlation based on the data I have found.