Jan. 12, 2012 at 8:10 PM ET
Even the astronomers on the science team for NASA's Kepler planet-hunting mission are marveling at the new worlds they're finding.
There's certainly a lot to marvel at: Just this week, Kepler astronomers announced the discovery of not just one, but two binary-star systems that have at least one planet each, reviving visions of the double sunset on Luke Skywalker's home world in the "Star Wars" saga. Another group of scientists drew on data from Kepler to detect the three smallest exoplanets yet discovered, including one just about the size of Mars.
The revelations at the American Astronomical Society's winter meeting in Austin, Texas, demonstrated that the number and diversity of the planets being found beyond our own solar system is growing by leaps and bounds. An august group of space commentators, including yours truly, celebrated the diversity during today's Weekly Space Hangout. And astronomers were celebrating in Austin as well."Any kind of system you can think of, if it doesn't violate the laws of nature, it probably exists somewhere out there," Virginia Trimble, an astronomer at the University of California at Irvine, told reporters. "So as long as people think up new techniques, they will also find new types of planets. There will surely be lots of new, neat stuff in the coming years."
In an email, Berkeley astronomer Geoffrey Marcy, who has been in on the planet quest for 20 years and is a member of the Kepler science team, went positively gushy over the latest findings ... but also pointed out that the quest has really just begun:
"The NASA Kepler space telescope has discovered well over 2,000 strong candidate planets around other stars. No exoplanet survey is even close to this coverage and statistical integrity.
"For each of those exoplanets Kepler finds, we have detailed knowledge of the planet's orbital period and the planet's orbital distance from its host star. More impressively, we know the planet's size (diameter) quite accurately. For some of the planets, we have also measured their mass and density, with some planets found to be definitively solid.
"With this wealth of information about over 2,000 planets, we continue to study the occurrence of planets around other stars. This work gives us a census of planets in the Milky Way galaxy. The 2,000 exoplanets is still too few to give an accurate answer. A useful census of humans on Earth requires that well over 2,000 people be surveyed. So it is with planets in the Milky Way galaxy. A useful census requires that thousands be sampled, and with accuracy. We desire integrity in our surveys of planets and people.
"Three weeks ago, the Kepler team announced the first two Earth-size planets. Only Kepler has sensitivity to Earth-size planets. [Now we have announced] the first Mars-size planet around another star. ... These discoveries by Kepler will mark an historic moment in the history of science, approaching the trans-oceanic voyages of the 15th century and the first steps on the moon. Kepler is indeed finding new worlds."
The Kepler mission identifies potential new worlds by looking for the telltale dips of starlight that occur when a planet passes over the disk of its parent sun. Other methods are used to confirm the mass of alien planets, including a method that checks for a characteristic gravitational wobble in stars that have planets. And yet another method, called microlensing, was used in another study released this week that estimated there could be 160 billion planets in the Milky Way. There's a chance that estimate will turn out to be too high. There's a better chance it'll turn out to be too low. But in either case, astronomers now recognize there could be tens of billions of new worlds out there.
Some of those worlds no doubt will have the conditions conducive to life as we know it. Studying such planets could help us one of the deepest questions we have about the universe: Are we alone?
But in order to do that, the quest has to continue. Right now, funding for the $600 million Kepler mission is due to run out in November, and discussions about an extension are under way. Theoretically, Kepler could gather enough data by November to detect Earth-size planets in Earth-scale orbits around sunlike stars, but an extension would provide scientists with more confidence about their existing candidates — and also give them the chance to cast a wider net.
Chances are the mission will be extended. "It would seem to me just nuts to have it out there and turn it off," one astronomer, Greg Laughlin of the University of California at Santa Cruz, told Space.com. But the success of Kepler (and its European counterpart, COROT) should get people talking about what to do for an encore. So brace yourself for an alphabet soup of exoplanet-mission acronyms ranging from EChO to MPF to PLATO to WFIRST.
Odds and ends from the week in space: