New Planets, By Leaps and Bounds

Remember when we thought our solar system might be unique in the universe? When we had no evidence--other than maybe a gut feeling, a hunch--that there were other planets beyond our solar family? It wasn't so long ago. It was 1992 when astronomers discovered the first extrasolar planets, around a dead star called a pulsar. The first planet around a "living" star was discovered just three years later.

We've come far, fast. Though we often emphasize that science advances incrementally and not in great "Eureka!" leaps, going from zero exoplanets to more than 500 in less than two decades feels pretty, well, leapy. In the months and years to come, that number is going to keep leaping ahead thanks in large part to the Kepler space telescope, which is busy staring at stars and searching for telltale brightness dips that might indicate the presence of eclipsing planets. In fact, if you watched NOVA's Hunting the Edge of Space when it premiered less than a year ago, you heard this:

Kepler has already discovered several new exoplanets. It hasn't found an Earth-like planet yet, but astronomers believe it is only a matter of time.

A matter of time, sure--but not much time. Earlier this month, scientists announced that Kepler had spotted 1,235 planet candidates ("candidates" because most still must be confirmed using a second detection technique), including 68 candidates that are about the same size as Earth. Of those 68, five orbit in the "habitable zone," where the temperature could be right to support liquid water.

How Kepler's planetary candidates break down by size. Image courtesy NASA/Kepler Mission/Wendy Stenzel.

At one of this morning's AAAS sessions, astronomer Sara Seager of MIT took us on an illustrated tour of some of these newly-discovered planets. There's Kepler-10b, "the first unquestionably rocky planet orbiting a star outside our solar system," which orbits so close to its star (more than 20 times closer than Mercury orbits the Sun) that lava oceans and rivers spill over its surface. This NASA animation captures an artist's conception of what it might be like to fly over Kepler-10b.

Then there's Kepler-7b, with the highest albedo of any known exoplanet. Albedo is a measure of reflectivity (you could say that Kepler-7b is the shiniest exoplanet), and this suggests that the planet is probably enveloped by highly-reflective clouds. Things get stranger still in the Kepler-11 system, where six confirmed planets orbit so tightly that they would all fit within Venus' orbit; five of the six orbit closer than Mercury. And in the yet-to-be confirmed system KOI-730, two planets share the same orbit like sprinters on a single lane of a track.

Kepler is turning up a "bonanza" of planets, as Harvard astronomer Matthew Holman put it, a weird and wild menagerie that is challenging our models of how planets form and bringing us ever closer to discovering a truly Earth-like world. So, if you catch a rebroadcast of Hunting the Edge of Space, in this small way it will already be out of date. We just can't keep up. And though it's part of my job as a researcher to make sure that our shows are up-to-the-minute, in this case, I think being out-of-date is something to celebrate.

User Comments:

This is a good piece. However, something bothered me.

"When we had no evidence--other than maybe a gut feeling, a hunch--that there were other planets beyond our solar family?"

Gut feelings and hunches aren't evidence. Not in science. Not in law.

It could have easily been written:
"When all we had was a gut feeling or a hunch that there were other planets beyond our solar family, when there was not yet any evidence."

Or it could have been written many other ways.

The reason this bothers me is, scientific "evidence"--and science generally--are things many lay people don't understand. And since this article is for lay people, not scientists, I think it's important to be extra careful with words like "evidence," "proof," "facts," "theory," etc.


Hi Shayne,
Thank you for this thoughtful comment! I absolutely agree. If I had it to write over again, would phrase it in one of the ways you suggested so as not to leave the impression that a "hunch" qualifies as evidence.
Thanks again!


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