Monday, February 02, 2015
The tightly packed system, named Kepler-444, is home to five small planets in very compact orbits. The planets were detected from the dimming that occurs when they transit the disc of their parent star, as shown in this artist's conception. Image Credit: Tiago Campante/Peter Devine
Astronomers using data from NASA's Kepler mission have discovered a planetary system of five small planets dating back to when the Milky Way galaxy was a youthful two billion years old.
The tightly packed system, named Kepler-444, is home to five planets that range in size, the smallest comparable to the size of Mercury and the largest to Venus. All five planets orbit their sun-like star in less than ten days, which makes their orbits much closer than Mercury's sweltering 88-day orbit around the sun.
"While this star formed a long time ago, in fact before most of the stars in the Milky Way, we have no indication that any of these planets have now or ever had life on them," said Steve Howell, Kepler/K2 project scientist at NASA's Ames Research Center in Moffett Field, California. "At their current orbital distances, life as we know it could not exist on these ancient worlds."
Kepler-444 formed 11.2 billion years ago, when the universe was less than 20 percent its current age. This makes Kepler-444 the oldest known system of terrestrial-size planets, two and a half times older than the Earth.
To determine the age of the star and thus its planets, scientists measured the very small change in brightness of the host star caused by pressure waves within the star. The boiling motion beneath the surface of the star generates these pressure waves, affecting the star's temperature and luminosity. These fluctuations lead to miniscule changes or variations in a star's brightness. This study of the interior of stars is called asteroseismology and allows the researchers to measure the diameter, mass and age of a star.
The Kepler-444 system is approximately 117 light-years away toward the constellation Lyra. A paper reporting this discovery is published in The Astrophysical Journal.
For more information on the discovery, see the University of Birmingham's press release.
Ames is responsible for Kepler's mission operations, ground system development and science data analysis. NASA's Jet Propulsion Laboratory in Pasadena, California, managed Kepler mission development. Ball Aerospace & Technologies Corp. in Boulder, Colorado, developed the Kepler flight system and supports mission operations with the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder. The NASA Exoplanet Archive in Pasadena and the Space Telescope Science Institute in Baltimore archive, host and distribute Kepler science data. Kepler is NASA's 10th Discovery Mission and was funded by the agency's Science Mission Directorate in Washington.