As a sci-fi fan, I am elated at some recent astronomy news.
Aliens are an important part of science fiction. Obviously not all science fiction has to do with outer space (Blade Runner, The Matrix, etc.), and not all science fiction that takes place in outer space is focused on alien life (Firefly, Battlestar Galactica). Still, aliens are an important part of many sci-fi universes (Star Wars, Star Trek, to name a couple biggies). For centuries, humans have asked the question Are we alone? and then imagined What would happen if we aren't? Aliens are our gateway to new and amazing technology; their discovery will bind humanity together and bring peace; they will give diversity and tolerance a new meaning... Or they'll try to kill or conquer us all. That's always a possibility (a likely possibility according to Stephen Hawking, of course).
But in order for any of these sci-fi dreams (and nightmares) to come true, there has to be life outside of our tiny blue planet. For a long time, people have said that the conditions on Earth which make it habitable are so incredibly unlikely that the chance of there being another planet similarly suitable for life is infinitesimally small. Others, myself included, have believed that with so many planets in the galaxy (in the universe!) even something with a small chance could happen many times. Not that we'd necessarily ever find another one of these habitable planets--it's just likely that one's out there somewhere. Right?
Well, my sci-fi dreams just got one huge step closer to maybe being true. Astronomers have found a planet that may be suitable for life! (See the abstract submitted to the for the Astrophysical Journal here, and various reports from CNN and Associated Press.) Enter the beautiful Gliese 581g. Not exactly the sexiest name; its sun is called Gliese 581, and as the sixth planet discovered in the solar system, it gets the "g" designation (because the sun itself is "a"). We can't get too excited yet, since we don't know if the planet actually has water (necessary for life...as we know it, at least), but it does have temperatures that would allow liquid water, it's the right size and distance from Gliese 581 to have an atmosphere without being an ice giant, and it's rocky. A lot of astronomers are very excited about this; they say there have been false alarms before regarding the discovery of habitable planets, but this one looks like it may be the real deal.
So what do we know about Gliese 581g? It's a little larger than the Earth in diameter and about three or four times the Earth's mass. It is closer to its sun than we are to ours; it takes only 36.6 Earth days to complete its orbit. Gliese 581 is a red dwarf star about one third the strength of our sun, which I guess is why Little G (Can I call it that? Uh, maybe not.) can be closer to it than Earth is to our sun while still being habitable. The planet rotates slowly and is actually tidally locked to Gliese 581, meaning that one side always faces the sun and one side faces away (like how the same side of the moon always faces the Earth). Temperatures on the planet range from -25 to 160 degrees (the article I got this from didn't mention which scale, but I'm going to go with Fahrenheit), presumably on the "night" hemisphere and the "day" hemisphere, respectively, but the terminator--the "twilight zone" of eternal sunrise/sunset--is quite comfy, described as "shirt-sleeve weather" by article co-author Steven Vogt of UC Santa Cruz.
Reading the descriptions of Gliese 581g definitely reminded me of Mass Effect. Both Mass Effect 1 and 2 had dozens upon dozens of planets, and even if you couldn't land on most of them, you could always get a short description of them, often including surprising, funny, or informative details. Heck, it's how I knew to use the term "tidally locked" to describe Gliese 581g. Take the planet Chasca from ME1:
Chasca is tidally-locked to Matano. The same side always faces the sun, resulting in a scorching day side and a frozen night side. In the temperate areas around the terminator, temperatures average around 30 Celsius. Combined with a nitrogen-oxygen atmosphere, this slender band of habitable terrain allows limited colonization by humans.
In fact, I counted 10 planets from ME1 alone that were described as tidally locked. See, video games can be fun and educational. Gliese 581g could totally be one of the planets described in Mass Effect. And that makes my geeky little self very happy.
Gliese 581 is dim enough that you can't see it from Earth without a telescope, but if you have one, it can apparently be found in the area of the constellation Libra. The star is about 120 trillion miles away, which sounds like a lot for us Earth-bound folks, but on the scale of our galaxy, it's right in our neighborhood. 20 light years away! We can observe from the Earth what the planet looked like just 20 years ago. My mind is totally blown. A possibly habitable planet. Just 20 light years away. The astronomers connected with the article seem to think it is highly likely that the planet could have life (though, granted, they are understandably even more psyched about it all than I am), and they've done some calculations to estimate that as many as 10-20% of stars may have Earth-sized planets in the habitable zone. I'll take that with a grain of salt, though, since I don't want to get my hopes up too high.
So it's rocky and likely has an atmosphere and a band of nice temperatures for habitation. But what are the chances it actually has life? Vogt has high hopes for the presence of water due to there being right temperatures for liquid water, and since we've found life wherever we've found water on Earth, he thinks there's a good chance something is living there. The fact that Gliese 581 is a dwarf star, which will last longer than our own sun, gives the planet more time to develop life, as well. And, as Vogt says, "It's pretty hard to stop life once you give it the right conditions." And we're not expecting little green men or sexy blue ladies. Extraterrestrial mold, algae, or bacteria would even be beyond remarkable. Though sexy, intelligent, and benevolent aliens would certainly be appreciated. Either way, it's all pretty frakking amazing.
Let the new sci-fi stories begin.
Update 7/20/12: See follow-up post here. Also, this planet is apparently nicknamed "Zarmina".