54 Habitable Planets? Let’s Call One Claire

Unbelievable. A few days ago we were up to 525 known extrasolar planets according to the Extrasolar Planets Encyclopedia. Nine of them were discovered using the planet-finding Kepler spacecraft. Then on Tuesday NASA scientists announced an additional 1,226 Kepler discoveries for a grand total of 1,751.

The Kepler craft uses a telescope with a 37-inch mirror combined with an ultra-sensitive light measuring device called a photometer to watch for dips in starlight caused by transiting planets. Credit: NASA

How big a number is that? Go out to a rural setting the next clear night and look up at the stars. Now picture nearly every single star you see as a planet – that’s how many planets there are!

The results are based on observations made by the telescope between May and September 2009. Kepler’s unwavering eye stared at 156,000 stars within 2000 light years of Earth, looking for tiny, telltale dips in their brightness caused when a planet or planets transits their host star.

As a planet transits or passes in front of a star, it dims its light in a particular way over time. Analysis of the information reveals the orbit and even the size of extrasolar planets. Credit: NASA

The telescope stared simultaneously at every one of those stars, measuring the brightness of each every 30 minutes. Sifting through the mound of data revealed the signatures of a host of new planet candidates, many of which will have to be confirmed through further observation. Analysis of the amplitude and timing of the dips in the stars’ light will help astronomers determine the planets’ orbits, sizes and masses. So much from such a thin trickle of data.

Here’s the amazing part. Among the new worlds, Kepler found at least 54 that lie within their stars’ habitable zones, where temperatures are moderate enough for liquid water and potentially life to exist. And that after exploring only 1/400 of the sky!

Kepler's 156,000 stars are in the Northern Cross within the circle shown on the map. The Summer Triangle is up in the east at dawn in early February. Created with Stellarium

“The fact that we’ve found so many planet candidates in such a tiny fraction of the sky suggests there are countless planets orbiting sun-like stars in our galaxy,” said William Borucki of NASA’s Ames Research Center, the mission’s science principal investigator.

If you extrapolate Kepler’s bounty across the entire sky, the tally would come to some 20,000 planets within 3,000 light years of Earth where life might be possible.

Now for the breakdown: 288 are “super Earths”(planets a couple times larger than Earth and considerably denser but nowhere near the size of the Jupiter-sized worlds common among exoplanet discoveries); 662 Neptune-sized; 165 the size of Jupiter and 19 larger than Jupiter. Of the 54 worlds in the “habitable zone”, 49 are super Earths and five are similar in size to our own planet.

Artist's view of Kepler-11 and its tightly bound solar system of six planets. All of them have atmospheres of hydrogen and helium instead of the more familiar earthly gases of nitrogen and oxygen. Credit: NASA

One of the coolest is a system of six planets, ranging in size from super Earths to Neptune, revolving around the star Kepler-11 2,000 light years away. It’s the tightest-packed solar system known. The planet Kepler-G revolves at Venus’ distance from its parent star, while the other five have orbits smaller than Mercury’s.  Just like our solar system, they all orbit within the same flat plane, but because they’re so close to their star, the intense heat they receive makes the possibility of life unlikely.

Ever hear of the song Planet Claire by the B-52’s? You know, the place where the air is pink, trees are red and nobody has a head. Given all the new discoveries, I’d like to nominate Claire as a potential future name when the International Astronomical Union (IAU) naming committee decides on official names for so many of these new worlds. We’ve run through all the various Greek and Roman deities, so let’s start using more of the name people give other people, including Claire.

Find a place with a horizon view and look west starting about 15-20 minutes after sunset tonight to find a very fragile moon. Binoculars may be required.

Before signing off today, I wanted to make you aware of an opportunity to see a very young lunar crescent this evening in the southwestern sky some 20 to 30 minutes after sunset tonight. You’ll need excellent skies without haze or cloud and a good horizon view.

The moon will only be a few degrees high for Midwest viewers and a little better placed for those living farther west in the mountain states and the West Coast where the moon at sunset will be 22 and 23 hours old respectively. We don’t get many chances to spot a moon less than a day old. Go for it if you can.

2 Responses

  1. Eli Irvine

    I would love to know the distances from Earth that these Earth-like planets are located at. Maybe the closest ones could be within probe range? I realize most are over 1000 light years, but maybe more research could be done on our closer neighbors. If the end goal is to find us a new home, or even just a mining location, I see no real benefit of finding a habitable planet 2000 light years away. I know there are stars within 10 light years of Earth, and many of them. Why are we not looking closer at them? Just a thought.

    1. astrobob

      Eli, these are excellent questions. Each type of telescope is designed for a specific mission. The Hubble is good at intensely examining one target at a time. Kepler was designed to stare at over 100,000 stars simultaneously in order to get a reasonably good idea of how common planets might be in stars’ habitable zones. To see that many stars at once in Kepler’s field of view, it makes sense to point it at a rich area of the sky like a Milky Way region, where you’ve got a ton of stars to stare at. Since there are far more distant stars than closer ones, Kepler naturally is finding planets around many more distant stars. To study a similar number of nearby stars, Kepler’s field of view would have to impossibly large because the nearby ones are so spread out across the sky.
      Once Kepler does identify interesting candidates, then the Hubble and other large ground telescopes will be pressed into service for detailed study. One feeds the other. Does this help clarify?
      I wish I knew the distances of more of Kepler’s finds. I’ve only heard that most are 2000 light years away.

Comments are closed.