Earth-Size Planets

Article excerpt

Astronomers have discovered two Earth-size planets that survived getting caught in the red-giant expansion of their host star.

Steve Kawaler, an Iowa State University professor of physics and astronomy and a leader of the Kepler Asteroseismic Investigation, helped the research team study data from the Kepler space telescope to confirm that tiny variations of light from a star were actually caused by two planets of that star.

The findings are published in the journal Nature. Stephane Charpinet of the Institut de Recherche en Astrophysique et Planetologie in Toulouse, France, is the lead author and leader of the research team.

"This is a snapshot of what our solar system might look like after several billion more years of evolution," Kawaler says. "This can help us learn about the future of planetary systems and of our own Sun."

Kawaler says the researchers have studied pulsations of the planets' host star (KIC 05807616, an old star just past its red-giant state and with an exposed core) for about two years. While analyzing the data, Charpinet noticed two tiny variations repeated in 5.76- and 8.23-hour intervals.

He asked other astronomers--including Kawaler--to analyze the original Kepler data and a subsequent set of data to see if they could also see the variations.

"We saw them in the same place and the same periodicity," Kawaler says. "So we knew they were real."

That led to the next question: So what are they?

Kawaler, working 26 years ago with the late Carl Hansen of the University of Colorado, studied the fastest and slowest rates that stars could pulsate. Using that result, the team could conclude the variations seen by Kepler were too slow to be caused by the star itself. And so the astronomers started testing the idea that the variations were from two planets orbiting the star. …