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Last week, Rob told you how scientists announced that they'd found two Earth-like planets orbiting the star Kepler-62. One of those, Kepler-62e, now ranks as the most Earth-like exoplanet we've ever found. Of course, all of this is relative.
What I like about this chart is that it kind of shows you how "Earth-like" doesn't really mean, "Man, that is totally exactly like Earth." Instead, you should translate it more as, "Welp, this is about the closest to Earth that we've found so far." Even Kepler-62e, as you can see, is much larger than the Earth and Mars. And size matters when it comes to actual habitability. As does density — and we don't know what Kepler-62e is made of yet. It's also worth noting that #2 on this list, the infamous Gleise 581g, is really a planet candidate, rather than a planet. We aren't actually certain it exists, just yet.
Popular Science has a neat little breakdown explaining what life might be like on Kepler-62e, if we could go there. But it's worth keeping the context in mind on these Earth-like planets. Don't pack your bags just yet.
At his Psychology Today blog, Michael Chorost delves into a question about exoplanets that I've not really thought much about before — how easy they would be to leave.
Many of the potentially habitable exoplanets that we've found — the ones we call "Earth-like" — are actually a lot bigger than Earth. That fact has an effect — both on how actually habitable those planets would be for us humans and how easily any native civilizations that developed could slip the surly bonds of gravity and make it to outer space.
The good news, says Chorost is that the change in surface gravity wouldn't be as large as you might guess, even for planets much bigger than Earth. The bad news: Even a relatively small increase in surface gravity can mean a big increase in how fast a rocket would have to be going in order to leave the planet. It starts with one equation — SG=M/R^2.
Let’s try it with [exoplanet] HD 40307g, using data from the Habitable Exoplanet Catalog. Mass, 8.2 Earths. Radius, 2.4 times that of Earth. That gets you a surface gravity of 1.42 times Earth.
... it’s amazingly easy to imagine a super-Earth with a comfortable gravity. If a planet had eight Earth masses and 2.83 times the radius, its surface gravity would be exactly 1g. This is the “Fictional Planet” at the bottom of the table. Fictional Planet would be huge by Earth standards, with a circumference of 70,400 miles and an area eight times larger.
Does that mean we could land and take off with exactly the same technology we use here, assuming the atmosphere is similar? Actually, no. Another blogger, who who goes by the moniker SpaceColonizer, pointed out that Fictional Planet has a higher escape velocity than Earth. Put simply, escape velocity is how fast you have to go away from a planet to ensure that gravity can never bring you back. For Earth, escape velocity is about 25,000 miles per hour. Fictional Planet has an escape velocity 68% higher. That’s 42,000 miles per hour.
Thanks to Apollo 18, who also helped with the math for Chorost's post.
Earlier this week, we learned that there is (most likely) at least one planet orbiting the star Alpha Centauri B. If you want to get really in-depth on this discovery, how it was made, and what it means, you should be reading Paul Gilster's Centauri Dreams blog.
I wanted to highlight this image, specifically, in order to quote some particularly evocative writing that Gilster posted yesterday. Cue the stirring music:
When planet-hunter Greg Laughlin (UC-Santa Cruz) took his turn at the recent press conference announcing the Alpha Centauri B findings, he used the occasion to make a unique visual comparison. One image showed the planet Saturn over the limb of the Moon. Think of this as the Galilean baseline, for when Galileo went to work on the heavens with his first telescope, the Moon was visually close at hand and Saturn a mysterious, blurry object with apparent side-lobes.
Laughlin contrasted that with [this image], showing the Alpha Centauri stars as viewed from Saturn, a spectacular vista including the planet and the tantalizing stellar neighbors beyond. Four hundred years after Galileo, we thus define what we can do — a probe of Saturn — and we have the image of a much more distant destination we’d like to know a lot more about. The findings of the Geneva team take us a giant step in that direction, revealing a small world of roughly Earth mass in a tight three-day orbit around a star a little smaller and a little more orange than the Sun. What comes next is truly interesting, both for what is implied and for what we are capable of doing.
Read the rest of this post, which explains what happens next with the research and why astronomers will be focusing their planet-hunting efforts on Alpha Centauri B.
Last night, astronomers with the European Southern Observatory announced that they'd found a planet orbiting Alpha Centauri B — an orange star a little smaller and a little less bright than our own Sun. That's important, because, while more than 700 planets have been found outside our solar system, this one — Alpha Centauri Bb (yeah, I know) — is by far the closest. To give you an idea of what we're talking about in distance here, imagine that we are Kansas City and Mars is Toledo. Alpha Centauri Bb is like Tokyo — but you have to get there the long way around and nobody has invented the boat or the plane yet. Basically, it's closer than any other planet we know of outside our solar system, but not really close close. Just 4.37 light years is still more than 25 trillion miles, which is still a long ways away.
Likewise, Alpha Centauri Bb is classified as an "Earth-like" planet, but that shouldn't give you any ideas of colonizing it Zefram Cochrane-style. Bb is way too close to its star for that — closer, even, than Mercury is to our own Sun.
But you should still be excited about this. Terrible, filing-cabinet name aside, Alpha Centauri Bb is jeffing epic. Until now, we didn't think our closest neighboring solar system had any planets at all. And because of the way planets work, writes Lee Billings at the Centauri Dreams blog, this single find means we're much, much more likely to discover other Centaurian worlds. Billings is a former guest blogger here at BoingBoing and his work on exoplanets is second to none. I highly recommend reading his full piece:
Anyone in the Southern Hemisphere can look up on a clear night and easily see Alpha Centauri — to the naked eye, the three suns merge into one of the brightest stars in Earth’s sky, a single golden point piercing the foot of the constellation Centaurus, a few degrees away from the Southern Cross. In galactic terms, the new planet we’ve found there is so very near our own that its night sky shares most of Earth’s constellations. From the planet’s broiling surface, one could see familiar sights such as the Big Dipper and Orion the Hunter, looking just as they do to our eyes here.
• Read Lee Billings' full post about Alpha Centauri Bb, and keep an eye on the Centauri Dreams blog for further updates/analysis.
• In the late 1980s, NASA considered sending an unmanned probe to Alpha Centauri B. It would have taken 100 years to get there, using nuclear explosions to create thrust.
Image: Marco Lorenzi via NASA's Astronomy Picture of the Day
We've talked before about scientists using Rockethub to fund basic laboratory research—stuff that's important, but not likely to lead immediately to new technologies or other marketable products.
It's often hard to find the funding necessary to support this kind of research, and crowd funding is a great way to leverage public interest in science. Better yet, there's now a whole crowd-funding website dedicated specifically to the sciences.
The video above explains one of the projects that's trying to raise money through Petridish right now. David Kipping is a Harvard postdoc and a NASA Carl Sagan fellow. He wants to conduct the first ever survey of exomoons—moons outside our solar system.
Partially, his research is about understanding the universe. Knowing more about exomoons will teach us a lot about how solar systems, in general, work. But it's also about that tickly, exciting possibility of life on other planets. As we all learned from watching Return of the Jedi, it is possible to have a habitable moon. So far, the search for habitable exoplanets hasn't taken moons into consideration. Kipping's study would change that. But to make it work, he needs to buy a supercomputer. And for that, he needs your help. Kipping is within $3500 of his goal and has 14 days left to go.
Find lots more scientific research that needs your support.
Kepler-22b is a newly confirmed exoplanet, orbiting a Sun-like star 600 light years away from Earth. The exoplanet sits in the "habitable zone"—a range of orbits around a star that are, based on what we know about life on Earth, most likely to provide the right conditions for life to happen.
That is pretty damn cool. But it does not mean there must be life on Kepler-22b. As Phil Plait explains on the Bad Astronomy blog, there's a lot we don't know about this exoplanet yet, and "within the habitable zone" is not a guarantee of habitability. Case in point: Our solar system. Earth is within the Sun's habitable zone. But so are Mars and Venus, and you may have noticed that they are not especially teeming with life.
Kepler detects planets when they transit their star, passing directly in front of the star, blocking its light a little bit. The bigger the planet, the more light it blocks. The astronomers going over the data determined that Kepler-22b is about 2.4 times bigger than the Earth. The problem is, that and its distance from its star are all we know. We don’t know if it’s a rocky world, a gaseous one, or what. It may not even have an atmosphere!
Another good post to read on this subject is Matthew Francis' explanation of "habitability" on the Galileo's Pendulum blog. Even the statement, "Kepler 22-b is within the habitable zone," comes along with a lot of assumptions that may or may not turn out to be true.
The following factors are needed to calculate whether a planet is in the habitable zone: The temperature of the host star: the hotter the star, the more it emits light of all wavelengths ... The size of the host star: a large star emits more light from its surface simply because there is more surface area ... The albedo of the planet: how much light gets reflected back into space ... Hand in hand with albedo comes the composition of the planet’s atmosphere—if it has one.
When we say Kepler-22b is in the habitable zone, we're assuming that it has the same atmospheric composition and albedo as Earth. We don't know that. And it's a big leap, bearing in mind (again) that there's not even another planet in our own solar system that shares those characteristics.
I swear, I'm not a fun-hater. Kepler-22b is awesome. Just keep it in context and know that there's still a lot we don't know about this thing.
Size comparison of Kepler-22b via Galileo's Pendulum.
It's hard to illustrate articles about exoplanet research. The pictures from deep-space telescopes just doesn't really look the way your readers want it to look. Instead of an image of a mysterious far-off planet that people can imagine themselves visiting, you get a little blip in the light of a distant star and reams of computer modeling data.
That's why space scientists love artistic renderings—man-made illustrations meant to give you an impression of what an exoplanet might look like. But where do those pictures come from? And how accurate are they? To answer those questions, Txchnologist has a really interesting profile of Dr. Robert Hurt and Tim Pyle, the artists behind most of the artistic renderings you see decorating astronomy news.
Hurt will try to boil the data down to its visual essence and work with Pyle to make sure the image accords with what science knows about it. It’s often possible to glean the planet’s colors based on the content of its atmosphere but much is left to the artists’ imagination and what they want to convey.
“If you want to sell the idea that the planet is the size of Jupiter, you might give it a Jupiter-like storm,” Hurt said, referring to the Great Red Spot.
NASA wanted to link the real binary star system to the fictional Tatooine of Star Wars and even invited a visual effects supervisor who had worked on the movie to the press conference. So at the last minute, the artists decided to switch the position of the suns so the yellow star was higher in the sky, as it is in the movie. The switch meant the lighting pattern on the planet was slightly off, which Hurt heard about from at least one stickler. (There was no scientific reason for the stars to be aligned one way or the other, just artistic preference, Hurt said.)
For the record: Txchnologist is a science news site that's funded by GE, but they aren't strictly an ad for GE. I've chosen to link to them because they have some neat stories that don't seem to be driven by marketing or heavily biased. But I wanted to let you know what's up with the site, in case you stumble across something there that is more promotion-ish.
The Kepler space telescope has found a new, fun discovery that promises years of great Star Wars jokes. Kepler-16b is a planet that represents a type of system we've never seen before—at least, in the real world. Two hundred light years away, this Saturn-size ball of rock and gas is orbiting two stars at once. Yes, just like Tatooine.
Only, not really. Because Kepler 16b's stars are a bit on the dim side. Here's how Phil Plait explains it:
And while there are two stars involved in heating the planet, their light is pretty feeble. Even at its distance of a little over 100 million kilometers (65 million miles) from the pair — roughly the same distance at which Venus orbits the Sun — Kepler-16b is cold: the temperature at its cloud tops (assuming it’s a gas giant like Saturn) would be at best -70°C (-100°F).
So any visions you have of Luke Skywalker standing in the desert with his leg resting on a rock while he wistfully watches the two suns set in the west may have to wait. Even if the planet has a big moon (which these observations cannot yet detect) conditions there would be a bit chillier than on Tatooine. More like Hoth.
The video above is a stream of the Kepler 16b press conference. You can also find that video online at this link.