NASA probe discovers five Earth-sized planets


Published: Tuesday, January 5, 2010 at 9:04 a.m.
Last Modified: Tuesday, January 5, 2010 at 9:04 a.m.

SAN JOSE, Calif. — Its namesake first described the laws of planetary motion. Now a 2,300-pound spacecraft directed by NASA's Ames Research Center is revealing exotic new collections of distant planets that may again transform how we think of our own solar system.

In what astronomers called an exciting step toward detecting Earth-like planets orbiting other stars, the Kepler spacecraft operated by NASA's Silicon Valley base has found five strange new "exoplanets," or planets outside our solar system. The planets announced Monday in Washington, D.C., orbit stars about 1,000 light years from Earth, including one with a density as light as Styrofoam. They orbit so close to their stars that they may glow with the heat of a blast furnace. One searing world, "Kepler 8b," burns at more than 3,000 degrees Fahrenheit, hotter than the melting point of iron.

"It's certainly no place to look for life," said Bill Borucki, the principal investigator with the Kepler mission at Ames. "That will be coming later."

It will probably be 2012 or later before the $591 million mission has enough time to find and confirm the discovery of "Earth analogues" — rocky planets about the size and density of Earth, orbiting sun-like stars at about the same distance, supporting a temperature where liquid water could sustain life.

Launched in March, the Kepler spacecraft, named after the German astronomer Johannes Kepler, is an extraordinarily sensitive light meter parked deep in space. The spacecraft detects the transit of a planet across the star's face by monitoring minute differences in the brightness of the star.

While these are the first new planets found by the probe, its data is already hinting at other intriguing cosmic mysteries, including the stability of our own sun, and the existence of hot, dense objects orbiting close to other stars that could be like burnt-out embers of dying stars.

For an Earth-like planet orbiting at a great enough distance from its star to support life, Kepler scientists will need to process about three years of transit data. Because of their giant size and because they circle their stars as frequently as 3.2 days, the exoplanets announced Monday are much easier for Kepler to see than an Earth-like planet that would transit its star about once a year.

"These planets are just kind of the tip of the iceberg," said Jack Lissauer, a planetary scientist at Ames who is co-investigator on the Kepler mission. "It shows us the iceberg is there, and we have the ability to survey the more interesting parts of the iceberg."

Astronomers detected the first exoplanet in 1995, and several hundred have been found since. But because of Kepler's position in space and its ability to monitor continuously more than 150,000 stars with great precision, the spacecraft is the first instrument able to detect the full range of planets — from gas giants like Jupiter to rocky terrestrial planets like the Earth and Mars, and everything in between.

"We're starting to fill in the picture of the different types of planets in ways that we couldn't before," said Jon Jenkins of the SETI Institute, the mission's co-investigator for data analysis.

Scientists had thought there were two distinct types of planets — terrestrials and gas giants like Jupiter. The new Kepler data, Jenkins said, hints that intermediate-sized planets such as "Neptune and Uranus form in a different fashion than Jupiters and Saturns. There are finer distinctions in how these planets form."

The probe also had reassuring news Monday for those who worry about the future of the source of all life on Earth — the sun. The spacecraft's observations show that a majority of the roughly 43,000 sun-like, "G-class" stars that Kepler observed are as stable or more stable than the sun.

That is good news for scientists who hope to find life elsewhere in the galaxy, because it indicates that there are many stars that might support a benign environment long enough for the evolution of complex life.

But it also seems to indicate, astronomers said, that our sun is more likely to remain stable into the future.

"I'm going to sleep better tonight," said Indiana University astronomer Caty Pilachowski, "knowing we're in a good, safe place."

Reader comments posted to this article may be published in our print edition. All rights reserved. This copyrighted material may not be re-published without permission. Links are encouraged.

Comments are currently unavailable on this article

▲ Return to Top