Earth is no Longer ‘One of a Kind’

For this special little planet, today has been a very big day.

Although we’ve speculated that planets the size of Earth must exist elsewhere in the cosmos, it wasn’t until one of the co-investigators working with the Kepler Space Telescope said he had statistical evidence that worlds of the approximate size of Earth appear to dominate our Milky Way.

We now know Earth isn’t unique.

Alas, this historic news didn’t come without controversy. It was unofficially broken at a TED conference in Oxford earlier this month and only after a recording of a presentation given by Dimitar Sasselov was posted online did the news get out. What’s more, the announcement only became clear when Sasselov referred to a presentation slide depicting a bar chart with the different sizes of exoplanets discovered by Kepler:

A slide from Dimitar Sasselov's TED presentation.

This slide shows the number of exoplanets discovered up until this month, binned by size. We have Jupiter-like exoplanets, Saturn-like exoplanets and Neptune-like exoplanets, all compared with Earth’s radius.

The heart-stopping moment comes when looking at the bar that represents Earth-like exoplanets (i.e. worlds with a radius of below 2 Earth radii, or “<2 Re"). According to Sasselov, Kepler has detected a lot of Earth-like worlds, so many in fact that they dominate the picture. From what we have here, it would appear that around 140 exoplanets are considered to be like Earth.

“The statistical result is loud and clear,” said Sasselov. “And the statistical result is that planets like our own Earth are out there. Our Milky Way galaxy is rich in these kinds of planets.”

But why the controversy? Isn’t this good news?

It would appear that the Kepler co-investigator chose not to wait until the official press release from NASA. He publicized these groundbreaking results in the U.K. at an event where you had to buy tickets to attend. This isn’t usually the stage you’d expect this kind of discovery to be announced — a move that will undoubtedly upset many.

“What is really annoying is that the Kepler folks were complaining about releasing information since they wanted more time to analyze it before making any announcements,” Keith Cowing, of, wrote in a SpaceRef article today. “And then the project’s Co-I goes off and spills the beans before an exclusive audience – offshore. We only find out about it when the video gets quietly posted weeks later.”

This sentiment is understandable. Only last month there was some frustration vented at the Kepler team for holding back data on 400 exoplanet candidates. While this might be standard practice — the discovering team should be allowed some time to publish work on any discoveries they have uncovered — telling the world’s scientists they will have to wait until February 2011 before they can get their hands on this invaluable data was a bridge too far.

In light of this, for a Kepler scientist to then jump the gun and disclose a groundbreaking discovery at an international conference without the backing of an official NASA release seems a little hypocritical.

But there is another argument to put out there: Why should anyone sit on such a profound discovery? Perhaps NASA and the Kepler team should have issued an earlier press release announcing to the world that 140 candidate Earth-like worlds have been detected and that further work will need to be done to confirm.

Ultimately, this controversy is just background noise when compared to what we have learned today. Official confirmation or not, Dimitar Sasselov’s message is clear. Although these detections need to be confirmed (hence why these worlds are referred to as “candidates”), it would appear there is an overwhelming preponderance of exoplanets measuring 2 Earth radii or less.

For me, that fact alone is astonishing — the first scientific evidence that worlds of Earth dimensions are not rare.

Earth is no longer unique.

For more, read my Discovery News article, “Kepler Scientist: ‘Galaxy is Rich in Earth-Like Planets‘”

11 thoughts on “Earth is no Longer ‘One of a Kind’”

  1. I am amazed by this discovery. (Yes, I have the iphone app that alerts me when a new exoplanet is announced.) Yet, I am frustrated by one aspect of this that is posted where ever I see this story.It's this – we have not found ANY “Earth LIKE” planets. We have found many (far more than I expected) “Earth SIZED” planets. I think this is a very important distinction, one that seems to be lost in the buzz of the idea. An “Earth Like” planet might be defined as having breathable atmosphere, a gravity of .8-1.2G, water, and if all my fantasies were to come true, then it would have plants and animals! Then it would be “Earth Like”. I'd evern be willing to accept 2:5 of these. Until then, in my mind, it remains “Earth Sized”.I wonder what the world would do, if we found an honest “Earth Like” planet. I remain hopeful!Thanks, and take care. mjl

    1. Very good point. Yes, “Earth-like” sounds rather definite, but in this context it does mean “Earth-sized.” As you say, it's all semantics, we won't find a real Earth-like world (with an atmosphere plus evidence to suggest that it could support life) for a long while yet. For now, we're just talking dimensions ;)Cheers, Ian

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  2. Those Scientist were right to stay far away from NASA. NASA keeps too many discoveries under lock and key. The people of the world need the truth. It seems that NASA have no choice but keep secrets since it being funded by a country with lot s of secrets.

  3. It is good to know that our planet is not “One of a Kind”. Maybe one day we should visit some of “earth kind” planets and discover new scientific facts and go further in space research program, like in movies.

  4. Recently,I was vexed with some means of acronym.And I seached the Internet for a long time,the most feeling is troublesome. Finally,I found a very good website which provides a searchable database of over 8 million acronyms, abbreviations and meanings. Covers: business, international, chat, organizations, common acronyms, computers, science, technology, government, telecommunications, and military acronyms.And now I just share it for you: Acronym ListAstronomy: it does a help!!

  5. This process of lookin for the an Earth-like planet reminds me of a dog running after a car…if he actually got one what would he do with it?Politics aside this serously cool! Prof Richard Pogge of Ohio State University who works on the microlensing method of finding planets, said that Kepler Team would probably be the first guys to find Earth-analogs.Go team planet-finders!!

  6. I agree with Michael Laine…and was just going to post the same thing…the article is talking at same sized planets as Earth…I mean, who really cares? Does it even matter in the scheme of things if they’re not similar enough to support life? Are they surrounding a central star like our sun, is it the right distance, does it have a similar orbit structure, etc.?

    Earth-sized doesn’t mean a damned thing…yes, good info to know, but nothing that should blow our hair back.

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