FILTERED: With telescopes on Earth, astronomers can detect starlight trickling through the atmosphere of distant planets such as GJ 1214 b, depicted here in an artist's conception.
Image: Paul A. Kempton
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The Best Science Writing Online 2012
Showcasing more than fifty of the most provocative, original, and significant online essays from 2011, The Best Science Writing Online 2012 will change the way...
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Someday in the coming years, if astronomers finally succeed in locating a virtual Earth twin outside the solar system—a tiny dot of a world at a temperate, life-enabling distance from a sunlike star—the achievement will hardly be cause for resting on observational laurels. Instead another race will begin: to characterize the planet and its atmosphere and to determine if the world is truly habitable or, tantalizingly, if it is already inhabited by some extraterrestrial life-form.
In the meantime, astronomers are honing their techniques on the closest thing available—so-called super-Earths, just a few times the mass of our own planet, which are too hot to be habitable but are interesting in their own right. To that end, a team of researchers has managed to capture the light spectrum of a super-Earth backlit by its host star. The measurements provide an unprecedented glimpse of the atmosphere of a relatively small planet; most worlds that have been located in other planetary systems are behemoths more massive than Jupiter. The research appears in the December 2 issue of Nature. (Scientific American is part of Nature Publishing Group.)
The few known super-Earths whose orbits are fortuitously aligned so that they transit—pass in front of their host star—from Earth's vantage point provide a unique laboratory for planetary investigations. As a transiting planet moves through its orbit, starlight filtering through its atmosphere or reflected off its dayside can be spectroscopically measured to identify individual molecular species. In the case of a potentially habitable transiting planet, the same technique could be used to look for the signatures of biological activity. (The potentially habitable super-Earth announced by a team of astronomers in September and later questioned by a rival team does not appear to transit, limiting the possibility of such detailed study.)
"This is the most accessible way to study these planets' atmospheres," says lead study author Jacob Bean of the Harvard-Smithsonian Center for Astrophysics. "The light from the host star passes through part of the atmosphere, and the chemical species imprint their signature on the light."
Bean and his colleagues took advantage of a favorable planetary alignment to measure the spectrum of GJ 1214 b, a transiting super-Earth orbiting a small star about 40 light-years away. (The world is named by convention for its host star, GJ 1214.) The exoplanet, which is about 2.6 times as wide as Earth and about six times as massive, was discovered in 2009.
Even though it is a small planet, GJ 1214 b blots out a relatively large fraction of its star's light when it transits, thanks to the host star's diminutive size, just one-fifth the diameter of the sun. And, as an added bonus, the planet appears relatively broad for its mass, indicating the presence of a substantial atmosphere. "1214 b is like the perfect super-Earth for study," Bean says.
GJ 1214 b transits every 38 hours or so, passing in front of its host star and revealing itself by shading the star's light for about an hour. Bean tracked GJ 1214 b through two of those planetary transits using one of the 8.2-meter telescopes at the Very Large Telescope atop Cerro Paranal in Chile, parsing the observed light into its individual wavelengths. The resulting spectrum was essentially smooth, without any sharp peaks indicative of absorption by specific molecules. "It just looks like a flat line, but that's a very powerful constraint on the planet's atmosphere," Bean says.
The new research indicates two plausible explanations for the atmosphere of GJ 1214 b, each of which has implications for the planet's interior makeup. The lack of absorption features means that GJ 1214 b cannot have a diffuse hydrogen atmosphere unless it also has a high cloud layer that blocks the starlight from streaming through. That could indicate that the planet is a sort of mini-Neptune—a rocky core sheathed in ice and gas—or a terrestrial world that spewed out a hydrogen atmosphere from molten rock. "That would be kind of fantastic," Bean says of the latter option. The alternative explanation is a dense steam atmosphere that hugs tightly to GJ 1214 b, probably stemming from a planet that began as a ball of ice before drifting closer to its star, where the heat vaporized that ice to steam.
"We cannot distinguish between these two scenarios—puffy with clouds or dense water vapor," Bean says, although he notes that looking at the planet in longer infrared wavelengths could allow a glimpse inside the cloud layer, if indeed it is there. "I think within the next year we'll begin to solve the puzzle of this planet," he says.
But the most tantalizing glimpses will have to wait until a more habitable world is found, perhaps by the same search campaign, known as MEarth, that last year located GJ 1214 b. If the project can turn up a more temperate exoplanet nearby, astronomers could use the James Webb Space Telescope, which NASA plans to launch as early as 2015, to scan its atmosphere for molecular constituents and maybe even signs of life. "If we can find these kinds of planets, we're going to have the facilities available in the next decade to study them in detail," Bean says.
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14 Comments
Add CommentUnlike space shows on TV (which I enjoy as much as anyone), reality is that it is so incredibly unlikely that we'd find someplace "just right" that you could land and take off your space helmet and not die very quickly that's barely worth talking about.
Reply | Report Abuse | Link to thisI agree, there are probably a great many rocky planets with water in the so called "goldilocks zone". Many of these may even have atmosphere that are nitrogen and oxygen based. Ok, I'm with you there.
BUT..
Humans need the oxygen level to be very very close to 21% to be healthy. Much over that and you have problems, just a few percent under that and you die quickly.
A tiny bit too much sulfur in the air? Dead.
A bit too much carbon dioxide? Dead.
A few dozen parts per million of carbon monoxide? Dead.
Ozone Layer or van-allen belts a little different? Dead.
Air pressure differences too. Even on earth, if you're used to sea level, you can die by just being on top of a really tall mountain.
This doesn't even begin to consider what happens when you introduce a truly foreign protein to the human immune system.
Ultimately, anywhere we eventually may go (as if we can just skip on over) we'd need habitats. The most likely safe approaches would be actually to stay in orbit and use planets like this (and smaller) as a source of materials and gasses.
Whether another planet can house humans isn't the issue, the thing is finding any other planet with any sort of living organisms is amazing. People who don't get that there are something like 125 billion other Galaxies and don't believe somewhere out there, another large rock, can support life should stop and reevaluate their religion, or their thinking of how we are so superior there is nothing more than us. Its pure arrogance of the human trait to think the Universe revolves around us. It doesn't and if we all were exterminated it would only matter to ourselves.
Reply | Report Abuse | Link to thisIt would be fair if Scientificamerican would have mentioned this telescope belonging to the European Southern Observatory organisation. Besides the mention of the VLT and the link. James Webb is mentioned as a NASA telescope right. Besides the fact that ESA is also a full member of the James Webb telescope, but that`s a different discussion. Also they could mention more about the other astronomers involved like from the University of Göttingen. This article gives the impression of it being a single US based discovery while it involved European Astronomers and using a cutting edge European telescope payed for by European taxpayers. So many websites change articles to the point of complete misinformation. I would say SA does a good job on most of it`s articles. But it couldn`t hurt to be more accurate on some of them. The impression an article leaves should be fair and balanced to the people, instruments and organisations involved. That would be much appreciated here in Europe. Thank you from a Dutch SA reader.
Reply | Report Abuse | Link to thisI recently heard visiting South African cosmologist Dr David Brock state that over 30 specific terrestrial and cosmic conditions had to line up for "human" life to exist on any other planet. As he pointed out the probability of this ever occurring is in probability terms virtually zero. Perhaps, but I wonder if we will ever really know,though we should continue looking and asking this important question. Until then any assertions that life "must" exist elsewhere is based purely on conjecture and "metaphysical" naturalism, having absolutely no empirical basis. Thus, all assertions that there must be life out there somewhere is to be regarded as just another unverified belief, however strongly held. Absence of evidence, always adds up to no evidence, so far.
Reply | Report Abuse | Link to thisSome design eh?
Reply | Report Abuse | Link to thisI still dream with a time that mankind will build a starship to take us to these potentially habitable planets, saving our species from a total extinction.
Reply | Report Abuse | Link to thishttp://www.youtube.com/watch?v=Z8Hwqg9_oA8
HG Wells was on the right lines when the invading, temporarily victorious, Martians all got 'flu and died; AJP (above) also hints at the problem of the microbial / 'alien' protein contact. Even in the unlikely (and probably unrealistic) event of humans in current biological form making it to a 'habitable' planet elsewhere, it's more likely the bugs will get us, along with our crops, than any conflict with larger inhabitants.
Reply | Report Abuse | Link to thisThen again, given our own colonial history, maybe we'll just give them all colds and have the place to ourselves..?!
"Please wash your hands before landing"..
I'm betting against your dream even if you expect to be one of the lucky few chosen to leave - out of the many billions of others who would be left behind, presumedly to suffer a horrible death.
Reply | Report Abuse | Link to thisMoreover I'm betting against the survival of any population that might be sent to another 'New World', as the genetic diversity of any surviving population would not likely be adequate even if millions of fertilized eggs went along.
The environmental conditions of any 'New World' would not likely be conducive to the survival of humans and all the other species necessary to provide for our survival. Without resupply and support from a presumedly distant, abandoned population on Earth the new population would have to be infallibly self-sufficient almost immediately. If we're worried about climate change here, we should be terrified of any other planet.
The best opportunity of finding a truly viable 'New World' was squandered about four hundred years ago by continuing the existing methods of population and resource management. I suggest that the best chance for the continued survival of humanity is the development of effective management methods applied to our population so that we can survive without an infinite supply of required resources.
Alternatively, I'm afraid our dreams will die with us.
About eight years ago while doing research work for my book Fairy Tales from Propagamar (2006), I discovered a galaxy light years away from the Milky Way that had a constellation very similar to the solar system. There was a planet in that constellation that reminded me of earth. I named it Propagamar. That became the subject of my book. I have no doubt that we'll find a planet livable for humans. Life on earth however deserves to be protected. Human life is from a scientific prospective of primordial importance in what has been called "the conquest of space."The science behind this is cross-disciplines focusing on astronomy and biology.
Reply | Report Abuse | Link to thisThe more I learn about the cosmos, the more I understand, but the less I realize I know about it.
Reply | Report Abuse | Link to thisIt sounds like a lot of you are already experts, and don't need to potentially degrade your knowledge by learning from this magazine.
Think about it.
True, David, but I haven't done the calculation, I'll be the first to admit, but would you consider 10% of lightspeed to be a "significant fraction" thereof?
Reply | Report Abuse | Link to thisThe time-dilation equation is based on 1 divided by the square root of 1-v/c, with c being lightspeed, so you would experience *some* time dilation at that velocity (the closer v gets to c, as you already know I'm sure, makes the denominator get closer to zero, which makes the divisor bigger, which means more time dilation.
For it to cause the amount of time dilation you are talking about (millions of years, right?), it seems to me that that means v would have to be a far larger percent of c than 10.
But, I dunno, I just know the equation. I can't actually solve it with real numbers cuz I admittedly fried my brain a long time ago.
Okay, I'm lying- the truth is I'm actually too lazy to solve it. Someone else solve it, you can find it @
http://webcache.googleusercontent.com/search?q=cache:EAojJtFuUPoJ:en.wikipedia.org/wiki/Time_dilation+time+dilation+equation&cd=1&hl=en&ct=clnk&gl=us&client=firefox-a
Someone solve it with real numbers- you have all the values necessary (the only variable is v which is going to be 10% of lightspeed, or 29,979,254.8 m/s )- and tell me if I'm wrong. There, there's my exercise for today. Someone else do the heavy lifting.
Courtney Parsons
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Reply | Report Abuse | Link to this"The more I learn about the cosmos, the more I understand, but the less I realize I know about it.
It sounds like a lot of you are already experts, and don't need to potentially degrade your knowledge by learning from this magazine."
-oldgreywolf
[/unquote]
HAHAHAHA ... YES !!!
Abso-fraggin'-lutely, my friend!!!
Trying to find other planets and assess them I understand, but somehow I just never get over the fascination with trying to find one humans could live on. Certainly the nearest planet is at least tens of light years away. So by the time humans will have conquered living in space for the length of time at speeds of or near the speed of light, we will not need another planet.
Reply | Report Abuse | Link to thisMore than likely, we will totally control our genetic makeup, will live indefinitely, and the very least intelligent among us will have IQs that make Einstein, Hawkin, et. al., look like first graders.
At that point, why would anyone want to be stuck on some boring planet.
It is ridiculous to discuss these exoplanets in terms of whether they are suitable for the kind of life that we have here on Earth. Suppose one or more of them are fit for us. What are you going to do? Try to get there? It takes even a light ray 40 years to get there!
Reply | Report Abuse | Link to thisSo we had better start building a vehicle that can travel at a speed equal to the speed of light or faster!
On the other hand research in this area if leads to finding life in another corner of the universe will teach us snob humans and especially the religous tale tellers that we are not unique in this universe! This is what will raise havoc on Earth.