Astronomers Discover Ancient Star With 5 Earth-Sized Planets

Posted on January 27, 2015

Kepler-444 and its five planets

Astronomers analyzing data from NASA's Kepler spacecraft have discovered an ancient star with five Earth-sized planets. The star, Kepler-444, is at least 11.2 billion years old.

The star is about 25% smaller than our Sun. It is located 117 light-years away from Earth. The astronomers say the size of the five planets range in size from Mercury to Venus. They are all very close to their star and have orbits less than 10 days. These makes them all hotter than Mercury and uninhabitable for life as we understand it.

Although these planets are too close to their star to be inhabitable, the discover suggests planets around Earth's size have been forming for billions and billions of years. A research paper on the discover is published here in the Astrophysical Journal. The astronomers say, "We thus show that Earth-size planets have formed throughout most of the Universe's 13.8-billion-year history, leaving open the possibility for the existence of ancient life in the Galaxy."

Steve Kawaler, an Iowa State University professor of physics and astronomy, and co-author of the paper, adds, "This is one of the oldest systems in the galaxy. Kepler-444 came from the first generation of stars. This system tells us that planets were forming around stars nearly 7 billion years before our own solar system."

Kawaler helped the astronomers determine the size of Kepler-444 by studying sound waves within the star. The sound waves affect the star's temperature and create pulsating changes in brightness. The changes provide clues to the star's diameter, mass and age.

Image: Tiago Campante/Peter Devine