Twin Earth? Hardly
An artist's impression of the new planet Kepler-22b. Illustration courtesy Caltech/NASA
NASA’s Kepler mission was launched in March 2009. Its mission, to survey our region of the Milky Way galaxy looking for Earth-size and smaller planets. It does this very simply by pointing a 0.95-meter aperture Schmidt telescope with a 12 degree diameter field-of-view (FOV). It is pointed at a single group of stars for the three and one-half or more year duration of the mission and recording data. In the first 16 months of operation Kepler has detected 2,326 candidate planets, 48 of which lie in or near the habitable zone around other stars, that is the region where a planet of Earth-like size, composition and atmospheric pressure can maintain liquid water on its surface.
On December 5 NASA announced that Kepler had confirmed its first planet in the habitable zone. Kepler-22b, is the smallest planet, found so far, to orbit in the middle of the habitable zone of a star similar to our sun. But a word of caution, despite the media hype of a ‘Twin Earth’ that followed the announcement, there is a lot we don’t know about Kepler-22b. We do know that it is about 600 light years away and 2.4 times the radius of Earth. It orbits its parent star Kepler-22 every 290 days. This puts it well within the habitable zone as, though its orbit is closer than ours, Kepler-22 is of lower mass and cooler than our Sun. What we don’t know about Kepler-22b is its mass, so we have no idea if it is a rocky or a gaseous planet or even if it has an atmosphere. If Kepler-22b is rocky then its gravity would be 2.4 times that of Earth.
Image credit: NASA/Ames/JPL-Caltech
Kepler-22b was detected using the transit method which measured the dimming of light from Kepler-22 as the planet passed in front of the star. This gives us the planet’s size. To find the mass we need to measure the radial velocity of the star: as the planet orbits it exerts a small but detectable gravity tug on its parent star, that causes the star to wobble and this can be measured to give the mass of the planet.
Our methods of detecting exoplanets are becoming more and more sophisticated and we are finding them almost everywhere we look. Over 700 have been discovered since 1995 when the first exoplanet, 51 Pegasi was found. Whereas before we were only able to detect ‘Hot Jupiters’, large gas giants orbiting close to a star, we are now able to detect smaller and smaller planets and new technology like ExoplanetSat, that comprises very small and inexpensive satellites, will extend the search. It is perhaps not helpful if every new discovery is met with such overblown hype. When the time comes that we do discover Earth’s twin, and I have no doubt that we will, the public will feel that they have heard it all before.
Discovering such a planet would be hugely significant, a major step to finding life elsewhere. As, friend of Urban Times, Lewis Dartnell explained in a recent interview
“the next step, once Kepler has looked at a lot of planets, will be to see what their atmospheres are made of, using infrared spectroscopy.
“If one or two of them have oxygen in the atmosphere, it may be a transient thing – like Venus, undergoing a runaway greenhouse effect – but if we find, say, 20 Earth-like planets, all with the signature of oxygen in their atmosphere, then that would be very unlikely. Life would be the more reasonable explanation.”
I hope we can quiz Lewis further on this subject in the second part of our podcast. Watch this space.
Now if FTL neutrinos could exist and we could have them go even faster than the Italian ones, then we might be able to send Kepler-22b residents your article! ;o))
Sarah, Mike, Ant...thank you so much : )
Well done Jenny - nice balnced reporting! Your articles are much more interesting than the genral media hype rubbish! Keep up the great work! :o))
Great article Jen, a perfect antidote to the ridiculous mainstream media reporting of the story.
Another great article Jenny. I am always excited about the possibility of life on other planets. I so want it to be true! It would open up so many possibilities and there would be so many new things to learn (hopefully). Thanks
Guest. (Don't be a stranger, introduce yourself on Twitter : ) Kepler may not have the capability to detect radio signals but our radio scopes are taking note & checking Kepler's discoveries for signs of intelligence. 2,326 candidate planets have been found by Kepler alone & there are other exoplanet hunters out there so this will take time. But let's not get ahead of ourselves. Life may be only microbial but still be of huge significance. IF Kepler-22b is similar in composition to Earth and 2.4 times our size then yes a 100lb person would weigh 240lbs there. We just don't know enough yet, but we will. Watch this space.
Thanks again Jen! Too shy to tweet. Got that way from asking another physic major questions at another message board where one of them points out my ignorance and then also igores a question they'd been asked about DARK FLOW and the possibilty of our getting sucked into another BIGGER UNIVERSE that may GOBBLE us up??? Ugh. If it's not our SUN turning into a RED GIANT, its ANDROMEDA that wants to EAT US? Or some other Universe that may be an even bigger bully who wants to have us for a meal? ;) Anyhow, yes will also keep watching this space for the newest and latest updates from you!
Hi again Jen! Thanks for your reply! So nice to finally meet you. After reading and following links in your tweets, it also already feels "as if" I know you. Still confused though: Here's what the article says: We do know that it is about 600 light years away and 2.4 times the radius of Earth If Kepler-22b is rocky then its gravity would be 2.4 times that of Earth. So IF it's a rocky planet, then how much would someone who weighs 100 lbs weigh on KEPLER 22B? Ever see the RODDENBERRY Spin off series called ANDROMEDA? The main character in that show was suppose to be a HEAVY WORLDER (meaning he came from a planet where the effect of gravity was suppose to have been more than what we have here on Earth). So are you also saying our HUMAN TWINS from KEPLER 22B (if they exist) would be LIGHT WORLDERS? And is 600 LIGHT YRS too far away to pick up any kind of radio signals, or whatever else it is that we'd use, as a way to try and determine whether or not we have some HUMAN TWINS living there?
Rob. I hope they have the Cantina band to listen to! http://www.youtube.com/watch?v=z-qd198SFwo
Good point Rob. So once we find life, the hunt will be on to find 'Human's twin'. I hope by then that as a species we have realised that our differences are just as important, as our similarities. I for one would be very disappointed if intelligent life was EXACTLY like us
Yes, lets hope for similar rather than identical. Hopefully in a millennia or two our decendants will be sat with lots of other interesting lifeforms in the Mos Eisley Cantina, getting very mellow and thinking "ain't life wonderful?"...
Hi Jen, Love your article and following what else you tweet that shows up at the Prof Brian Cox twitter site. So if we weigh 100 lbs, does that mean we'd weigh 240 lbs on this other planet? Ugh. Can't imagine what that would feel like to live there. One's arm would probably get tired just attempting to brush one's hair and teeth?
Hi guest! No, you can't compare surface gravity that way, gravity "wears off" fast with the distance and to take a nearby (?) example, you would only weight 89 lbs on the surface (such as it is) of Uranus even though Uranus has 14.5 times the mass of Earth. You must know both the mass and the radius of the body to calculate the surface gravity. A body with four times the Earth mass and four times Earth's radius would give a surface gravity 0.25 times that of Earth.
Thanks Lehndal. I thought I was going to scream if I read one more headline declaring we had found Earth's twin. Media hype does more to misrepresent science & confuse the public than a whole parliament of politicians!
Yes, the media world had another bright bauble to play with for a while and it does falsely raise hope - I definitely fell for it untill I'd read up a bit more. But I can't help thinking that our lifeform is truly on the verge of making some incredible discoveries. Our desperate need to know if life is out there, if we're the standard model, and if there really are more totally Earth-like planets out there is understandable - as (relatively), social creatures we want company and we're inquisitive. So, even if we find wonderful new microbial lifeforms doing the backstroke in Titan's lovely cold Ethane/Methane lakes - as wonderful as that will be; we'll keep on looking for different versions of "us". And when we do, watch as the worlds media really gets going!
What a clear and sober presentation of what Kepler actually found! There is no end to the misleading presentations I've seen in the newspapers. Thank you Jenny.
Thanks Waddell. We are VERY new to this. We only found our first exoplanet in 1995! back then we thought our Solar System was 'special' Now we find them everywhere we look. I think the same will happen with life. Soon enough we will detect signs of life elsewhere and as we perfect & refine our methods I bet we will find it cropping up all over the place! At least that is my hope
Completely agree Waddell. We only have one example (Earth) to go on. Even here we find extremophile organisms thriving where we never thought life could survive before. We find the building blocks of life throughout space so entirely possible that life can take a hold in a very wide range of environments and perhaps life is opportunistic & even 'the norm' throughout the cosmos. We have only just begun to look
Yes, and that is an encouraging view. Actually it is a stimulating one in that we do not exclude looking behind EVERY door for answers. Every once in awhile I look up, and I see a slice of the Cosmos quivering. Not to worry, it is just laughing at our scientific immaturity . Not to say we are backward, just awkward in some respects. I like your article. It activates both Cosmic awareness and curiosity.
We are, daily, learning more and more about ourselves, our planet and our solar systems, but the most persistent question in my mind is are we the rule or the exception? This is not a denial of life elsewhere in the Cosmos, this is a curiosity as to whether our formula for life is the standard or, as I have asked, the exception. We need a healthy oxygen environment, but do other, yet discovered, life forms need it as well? Most likely we are the standard, but I think from a hypothesized inquiry we should also consider the possibility of a different standard. If we do this, we open wider the exploratory door into exoplanet environments and possible life forms.
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