Exoplanetary Thoughts for 2010

Several stories stick in my mind as we approach the New Year, presented here in no particular order, but merely as material for musing. The detection (by the MEarth Project) of a transiting ‘super-Earth’ this past month opens up interesting areas for speculation. Gliese 1214b is roughly 6.5 times as massive as Earth, orbiting an M-dwarf some forty light years from our Solar System. You’ll recall we discussed this one in terms of possible study of its atmosphere.

Abundant Small Worlds

On the always interesting systemic site, Greg Laughlin notes that the orbital period of this planet is a mere 1.58 days. In fact, the planet is separated from the system barycenter by 0.014 AU, which turns out to be the smallest separation yet measured for any planet. What stands out here is the density of the red dwarf. Says Laughlin: “Gliese 1214 is more than twice as dense as lead. The density of the Sun, on the other hand, is bubblegum by comparison.”

The result: a planet/star separation that isn’t quite as tight as it seems, a reminder of just how tiny M-dwarfs really are. Here’s Greg’s diagram of the system:

But what I want to focus on is what Gliese 1214b implies. In the recent post, Greg goes on to say:

Gliese 1214b lies at enough stellar radii from Gliese 1214 that its a-priori transit probability was only about 7%. The Mearth survey currently covers only ~2000 stars, and so the fact that the discovery was made so quickly was probably not luck, but rather points to the existence of a very large number of low-mass planets orbiting small stars.

Indeed, and recent trends tell us we’ll be learning a good deal more about such worlds. The MEarth Project reminds us of the viability of continuing transit surveys that will look for true Earth analogs around low-mass M-dwarfs. Is 2010 the year we’ll find such a world? The potential is there, but it’s also true that in addition to transits, our radial-velocity capabilities are being sharpened all the time. And then, of course, we have space-based missions like Kepler and CoRoT, the results of which should enliven the coming year.

Charting Nearby Brown Dwarfs

More musings: The recently launched WISE (Wide-Field Infrared Survey Explorer) satellite has jettisoned its protective cover. Up next for the 40-centimeter telescope and four infrared detector arrays is the adjustment of the spacecraft to match the rate of the onboard scanning mirror, which allows WISE to counteract the spacecraft’s motion to take ‘freeze-frame’ snapshots of the sky every eleven seconds, totaling some 7500 images per day.

Image: This is the central region of the Milky Way Galaxy as viewed in infrared light. The image is a composite of mid-infrared imagery from the MSX satellite and near-infrared imagery from the 2MASS survey. WISE images will be similar in quality. Credit: WISE/MSX/2MASS.

WISE begins its infrared survey in mid-January, and we’ll see ‘first-light’ images released to the public in about a month, after the telescope has been fully calibrated. Again we think in terms of significant discoveries within the next year, for in addition to WISE’s detection of asteroids and distant, dusty galaxies, the spacecraft has the ability to detect nearby brown dwarfs in numbers beyond anything we’ve been able to achieve before. WISE has a primary mission lasting nine months, ending when its coolant evaporates, but it’s possible that may be long enough to spot a brown dwarf closer than Alpha Centauri. At any rate, our brown dwarf catalog should be beefed up considerably.

Planetary Formation from Another Epoch

Further afield, New Scientist offers a brief comment on the work of Erin Mentuch (University of Toronto), whose analysis of the light from 88 remote galaxies, emitted when the universe was between a quarter and a half of its current age, shows what appears to be the signature of circumstellar disks. From the article:

The galaxies’ light output peaks at two distinct wavelengths. One represents the combined light of a galaxy’s stars; the other, at longer wavelengths, comes from the glow of its interstellar dust. In each case, Mentuch noticed a faint third component between the two peaks. Whatever produces this light is too cold to be stars and too warm to be dust. The most likely source is circumstellar discs – embryonic solar systems around young stars. “It’s the most surprising result I’ve ever worked on,” says Roberto Abraham, who collaborated with Mentuch.

Perhaps not as surprising as all that, given that it fits our current model of abundant planetary formation, but useful in that it may help us get a handle on planet formation in an earlier stage of the universe’s existence. Whatever that result, we enter 2010 with great anticipation of data that may change our map of nearby space and add substantially to our catalog of exoplanets, some of which may well be similar to the Earth. From Kepler, CoRoT and WISE to sharpened detection methods here on Earth, the golden age of planetary detection continues and, if we’re lucky, 2010 may just be the year we find a planet around Centauri A or B. Plenty to muse upon in all this, and plenty of excitement building for the New Year.