In a recent presentation, Kepler co-investigator Dimitar Sasselov preempted the official announcement that the exoplanet-hunting Kepler Space Telescope has discovered about 140 candidate worlds orbiting other stars that are “like Earth.”

Usually, announcements like these happen after an official press release, but during the TEDGLobal conference in Oxford, U.K., Sasselov unexpectedly dropped the groundbreaking news in one of his presentation slides.

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“You can see here the small planets dominate the picture,” he casually said while referring to a graph depicting the different exoplanet sizes and their number as of July 2010.

Although he refers to these exoplanets as “candidate” Earth-like worlds, Sasselov goes on to talk about the statistical prevalence of small planets throughout the Milky Way.

Before Kepler, only the larger exoplanets could be seen. This is fairly obvious; large gas giants are easier to detect over the great interstellar distances. The highly sensitive Kepler has now leveled the playing field, indicating that there are many more exoplanets twice the size of Earth and smaller.

Undoubtedly, this is huge news. If officially confirmed by NASA — and only then would it be advisable to pop the champagne corks — the discovery of dozens of worlds of comparable size to Earth is historic.

Although it has largely been assumed to be the case, Kepler will have proven that our planet is not unique in our galaxy. If there are so many Earth-like worlds out there, will any be home to extraterrestrial life?

Speculation about the existence of alien life will have another strong case to suggest that if planets like Earth are not rare, than perhaps “life as we know it” is ubiquitous throughout the Milky Way.

A screen grab from Dimitar Sasselov’s TED presentation. Note the bar labeled “like Earth.”

The unofficial “data leak” by Sasselov comes hot on the heels of some controversy that erupted last month over how Kepler data should be shared with the astronomical community. Data on 400 exoplanet candidates (presumably the same exoplanets presented in Sasselov’s talk) were being withheld by the Kepler science team so they could publish news on any important discoveries first.

As our own Nicole Gugliucci pointed out in her fascinating June 15 article: “The 400 candidates are being withheld by the Kepler team so that they can do follow-up work and publish their results. This is generally considered a fair system where the principal investigators have the data for a set amount of time before having to make it public.”

Usually, NASA data is considered proprietary for a year after the data are gathered. This allows the mission scientists to have first dibs on the data they’ve invested a lot of time, energy and money collecting. After this time, other research groups can have access.

This may be common practice, but for a mission that’s looking for worlds like our own, there’s a high degree of impatience for the data to become public.

Although these Kepler results were supposed to remain secret until February 2011, Sasselov has given the world an unofficial glimpse into the possible discovery of Earth-like extra-solar planets. But by the looks of things, we’re not talking about one or two “second Earths.” We could be looking at a galaxy with a dominance of small rocky worlds.

“The statistical result is loud and clear. 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.” –Dimitar Sasselov

There’s a bittersweet feeling to this announcement. Although the news is groundbreaking, it’s a shame that it was leaked during a TED talk rather than being released via official channels from the whole Kepler team.

Keith Cowing, of, goes one step further, pointing out that it’s wrong for this news to be announced in the U.K., only for the news to finally break weeks later.

“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,” Cowing adds. “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.”

Although this announcement could have been handled much better (personally, I think it might be best until we hear what NASA has to say), all indications are that we are about to have our eyes opened to the possibility that Earth is no longer a unique world. It belongs to a common type of planet found throughout our galaxy.

Watch Dimitar Sasselov’s TED talk:

Sources: ScienceInsider, SpaceRef, TED

Image credit: ESO