Kepler 70b: The Coolest Exoplanet

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

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

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)

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 Router and Rinner, 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, Lstar is the luminosity of the star, and Lnow 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

JR diagram

Untitled

This diagram shows the expected, but nonetheless interesting, correlation between the wealth of countries and the number of successful ascents of Mount Everest from that country. Clearly this is because countries where there is more wealth are more likely to have more people willing to pay the tens of thousands of dollars that it costs to be guided up Everest. These more “representatives” on the mountain means that more people from those countries are likely to summit. But it also reveals some trends that could have deeper implications about certain countries and societies. Now, this does bring up the whole issue of the commercialization of Everest and how it has become a non-climbers mountain in many ways, and I could rant on this topic for hours, but I’ll refrain from that for now because it isn’t essential to explaining the diagram.

“The Main Sequence”

For the most part, countries fall into a moderately strong direct relationship between GDP per capita and the number of ascents on Everest. In this majority relationship, one sees countries like the United States at the very top, with a very high GDP (~50,000) and a very high number of ascents (536). The United States is a perfect example of this relationship, a very high income, and therefore a very high number of people willing to pay to “live their dream” and climb Everest. And on the other end of the main sequence, there are countries like Egypt and Armenia, both with one ascent each, and both with very low GDP’s (in the 6,000 range). Everywhere between there are countries with moderate GDP’s and a moderate number of ascents, filling out the main relationship.

“The Outliers”

While most countries fit into the “main sequence”, there are a few that fall to either side. One that stands out is Nepal, and to a lesser extent China. Both of these countries have very low GDP’s. Yet, they have high numbers of ascents (China with 299, and Nepal with the highest number: 2264). This deviation from the rest of countries can be largely attributed to proximity, Everest being on the border between Nepal and Tibet, and culture. For as long as humans have been climbing Everest, the Sherpa culture of Nepal has been a part of it, acting as guides and porters. Due to this, Nepal has a disproportionately high number of ascents when you look at their wealth. The same goes for China, although to a lesser extent. This shows that, although it has become a big part of the expedition climbing culture, money is not the only thing that matters.

The other outlier group is the countries with very high GDP’s but low numbers of ascents, like Norway and Singapore. Theoretically, there should be lots of ascents from these countries due to their wealth, but there aren’t. This raises the question of how much interest and culture play a role in Everest pursuits. For many, there is a strong desire to conquer and shoot for the highest heights, like for example the United States. That is a deeply engrained part of our culture. But perhaps that isn’t so for every nation.

 

Data From:

http://www.cbc.ca/news2/interactives/everest/

“List of Countries by GDP (PPP) per Capita.” Wikipedia. Wikimedia Foundation, 10 Dec. 2013. Web. 19 Oct. 2013. (

http://en.wikipedia.org/wiki/List_of_countries_by_GDP_(PPP)_per_capita#cite_note-3)

The Ethics of Climate Change?

Although difficult to express  in this medium, that title should be accompanied by quite a bit of sarcasm and cynicism. I recently read an article entitled “The Ethics of Climate Change” which discussed largely the economic and business ethics side of global climate change. And I can’t say I agreed with it. In fact it annoyed me quite a lot. In the article, the author talks about weighing the potential costs against the potential benefits. But when this is the kind of thinking that we are employing  on an issue like this, especially when we are pouring literally billions each year into destroying this planet (people and all), then something needs to change.

Now, of course I realize that businesses are most likely to make a big change in climate change efforts in this country. Where the money is is always where the major players are. And what they’re most likely to listen to, most of the time, is how dumping money into climate change efforts is going to effect them, in which case the previously mentioned article might be on the right track. But this is not how it should be. The fact that our planet is slowly dying should be enough to give them pause. So should the fact that an estimated 5 million people die each year due to the effects of climate change and fossil fuels.

5 million.

7.6 million is the number of people killed by cancer each year.

climmapsmall0906

If that isn’t enough to get through to anybody, then it might be a lost cause… As of now, this is the only planet that we have that is habitable. And as far as we know, we are the only life, let alone intelligent life, in the universe. So it seems irresponsible, if not downright idiotic, to just “let the next generation deal with it”. It shouldn’t matter what is going on in the world, what war we’ve gotten ourselves in to, or what economic throes we are currently in. You can’t put a cost/ benefit analysis on the longevity of the human race. No one can just ignore the death of future generations. And perhaps this is because they don’t have to. They aren’t even made aware of it.

The other major problem with climate change philosophy is public awareness. Compared to other countries, the effort to fight climate change in the United States is just sad. The people who are actually aware of the seriousness of the issue generally don’t have the power or voice to make enough of an impact. The ones who do for some reason like to keep it a secret and ignore its existence. (Remember the whole climate change is a myth thing…) And to me, this just doesn’t make sense.

What I do think is that we need a complete overhaul of how we view climate change and what we are doing about it. If we don’t, we will never make any real progress.

Prehistoric Pollen

A current study out of the Paleontological Institute and Museum at the University of Zurich has documented “plant-like pollen” dating back 100 million years prior to the previously believed origin of flowering flora. This shifted the origin of flowering plants to the early to mid Triassic, rather than the Cretaceous. This fossilized pollen was discovered in two drilling cores from northern Switzerland, about 3000 km south of the site of a previous study in which a different plant like pollen fossil was discovered. This helped to solidify the belief that flowering plant life arose long before previously thought. While we don’t yet know what these plants may have looked like or the exact nature of their life and existence, this discovery acts as a reminder that we still have much to learn about the nature and history of life on Earth, and that before we become too focused in our search for extraterrestrial life, we should allow ourselves to become better acquainted with the life right here on our planet.

Gallery_Image_10913

 

The Immortal Microbe

Researchers at Harvard University and The Max-Planck Institute have just published a very interesting discovery about one of the most studied microorganisms on Earth. Their studies appear to suggest that S. pombe yeast does not grow old when placed under favorable conditions;  it is immortal. While this might seem unlikely when we think back to the requirements for life, including growth, development, and aging, this discovery is based in the manner in which yeast reproduces. When most asexual microorganisms reproduce, they divide themselves into one mother cell that inherits all of the damage to the cell and continues to age and one daughter cell which is “fully rejuvenated”. So over generations of cells, there is a clear decrease in the generational turnover time as cells become more and more damaged. This is not, however, what occurs with S. pombe.  In yeast, the damage in the cell appears to be divided between the two daughter cells so that each one takes an equal portion of the damage to the mother cell, but both have less overall damage than the mother cell. “If the cell grows and divides fast enough, the damage is diluted with each division. And provided that the total amount of damage does not overcome a certain death threshold, the cells can in theory divide indefinitely (Miguel Coehlo, first author of the paper).”

 

S. pombe

S. pombe

So what does this have to do with the origin of life, or life on other planets? Well, perhaps not a whole lot. But what this does tell us is that we still have a lot to learn about the inner workings of life on our own planet. We are far from understanding exactly how life works. So in the search for life on other planets, we must keep an open mind. It is quite likely that, even if we were to discover life outside of Earth, in the seas of Europa or the ice of Enceladus, we might not recognize it. While life shares many characteristics, there is also inherently an incredible amount of diversity in the development and existence of life. We have a relatively good footing in the definition of life, but we are still at a loss when it comes to the big picture of how and why we are alive. And given that we barely understand our own existence, it seems like we should perhaps broaden our expectations in looking for life in the universe. We never know, after all, what form it will take on and whether it will even remotely resemble the life that we are accustomed to.

deepfield

 

 

Bontemps, Johnny. “A Microbe’s Fountain of Youth.” A Microbe’s Fountain of Youth. Astrobiology Magazine, 4 Oct. 2013. Web. 04 Oct. 2013.

Images:

http://adoubtersramblings.wordpress.com/2010/07/15/07-14-2010-a-fine-tuned-universe/

http://www.astrobio.net/exclusive/5722/a-microbes-fountain-of-youth

 

Alone in the Universe? Or Not?

The field of astrobiology addresses the issues of life and habitability in the universe. While there is still no conclusive evidence that points towards life outside of Earth, there is certainly evidence that suggests habitability on other planets and moons. Given that advanced life already exists on Earth though, there are important considerations (social, religious, individual) regarding the discovery, or lack of discovery, of life.

First of all, if we never discover any signs of current life, or any life for that matter (which seems increasingly unlikely as more discoveries are made), this will impart a significant impact upon human life. This would mean that we are the only living beings in the universe. Although it is quite doubtful that we would ever have the capability to confirm this, the prospect of solitude within the universe, considering its absolute vastness, would be staggering. In addition to a sense of loneliness, knowing that there are no alien brethren out there, this raises questions of purpose. If we truly are the only life in the universe, one has to ask why. Is it possible that there is some reason behind our creation, evolution, and development, that life here, on Earth, has some higher meaning than just a chain of coincidental chemical reactions. Is perhaps our meaning in existence to make it to the point in evolved thought and interpretation that we can understand why and how we came about, chemically and biologically, in our world, such as aspects of the anthropic principle might imply. Or is there some religious truth to our existence, some higher meaning to life and a higher being who oversees it. While it is also unlikely that we will ever discover a “meaning of life”, it is certain that there are many interpretations of our meaning as living beings, and while some are scientifically unlikely, none of them are necessarily wrong. This, in and of itself, gives a bright tint to our dark and lonely existence, the idea that individuals are independent in how they view our purpose on Earth and free to act upon those views however they see fit.

The other possibility is that life is plentiful in the universe, that it is a rather common occurrence, and that our existence on Earth is really nothing special. Given the sheer number of galaxies in the universe containing stars just like our sun, and likely planets just like ours, it seems increasingly doubtful that we are alone in the universe. Now, it is true that we have not found concrete evidence suggesting life that is currently in existence outside of Earth. But this is no reason not to believe that, at some point during the universe’s 4.6 billion year existence, in some corner of its hundreds of billions of galaxies, life has arisen. It seems almost foolish to think that we are truly the only life around. So, if (and I do believe when…) we discover life elsewhere in the universe, there are also some implications for humans. This possibility for life in the universe makes our existence seem far less significant. There is probably no higher meaning or purpose for human life, a potentially large blow to the religious interest on life in the universe. It implies that humans are just another creation of the right combination of planetary conditions. But this doesn’t necessarily mean that life on Earth is pointless and insignificant. While we have no idea if there may be much further evolved societies out among the stars, the things that we humans have accomplished as a race during our time on Earth, in addition to all of the living organisms on Earth, are an incredible feat and a definite “success story” for life in the universe.

So right now, we don’t really know what to think. While there is plentiful evidence suggesting potential life, or at least the necessary conditions for it, we have no definitive evidence for life outside of our home planet. Only time and continued research will tell whether we are the sole inhabitants of the universe, or just another creation of coincidence. No matter what we discover though, the societal impacts here on Earth will be felt.