Email Peter Sur at psur@hawaiitribune-herald.com. By PETER SUR ADVERTISING Tribune-Herald staff writer Astronomers announced a small discovery that may have big implications for the number of planets orbiting other stars. It’s a tiny star with three miniature planets, and each
By PETER SUR
Tribune-Herald staff writer
Astronomers announced a small discovery that may have big implications for the number of planets orbiting other stars.
It’s a tiny star with three miniature planets, and each of the planets is less massive than the Earth but more massive than Mars. The exoplanets were observed with the Kepler space telescope and
confirmed with Mauna Kea’s Keck Observatory and California’s Palomar Observatory.
Observations from the Keck telescope were crucial in determining the size of the planets.
The planets have not been imaged directly, but their sizes have been inferred through observations.
The Kepler mission involves a space telescope that is pointed at one region in the sky for several years. The telescope observes 150,000 stars and searches for the miniscule amount of dimming that happens when a planet moves across, or transits, the disk of a star.
After several transits, astronomers can rule out other causes of a particular star dimming. From this data, astronomers can work out the size of the planets and of the star.
The three small exoplanets that are being announced today orbit a star that has been given the name KOI-961; the acronym “KOI” means “Kepler Object of Interest.” Astronomers have pegged the radius of each planet to be 78 percent, 73 percent and 57 percent that of the Earth, making them small, rocky bodies around a star with just 15 percent the mass of our sun.
Each planet whips around the star in less than two days, and has an average surface temperature of around 900 degrees, give or take.
The relatively dim star made it easier for astronomers to find the planets, Geoff Marcy of the Kepler team told the Tribune-Herald. He compared the dimming observed during the transit to a fly landing on a dim light bulb, as opposed to a fly landing on a spotlight.
But don’t think about visiting these small worlds any time soon. The newly found solar system is about 150 light-years away from the Earth.
The significance in this discovery is how common planets are turning out to be. Marcy said there are about 200 billion stars in the Milky Way, and about half of those stars are estimated to host planets. Further, most of the stars are low-mass red dwarfs like KOI-961, hinting that the Milky Way alone is home to many billions of planets. The big question that remains is: How many of these planets are favorable for life to develop?
“This is the tiniest solar system found so far,” said John Johnson of NASA’s Exoplanet Science Institute at the California Institute of Technology. “It’s actually more similar to Jupiter and its moons in scale than any other planetary system. The discovery is further proof of the diversity of planetary systems in our galaxy.”
Email Peter Sur at psur@hawaiitribune-herald.com.
