An international team of astrophysicists has discovered the ruins of a planetary system consisting of the cores of two former giant planets orbiting around the remnants of the core of a red giant.
An artist's impression of planets KOI 55.01 and KOI 55.02 (S. Charpinet)
Analyzing data from NASA’s Kepler spacecraft, a team of astrophysicists led by Stéphane Charpinet of the Institut de Recherche en Astrophysique et Planétologie, France, noticed variations in the brightness of the star KIC 05807616 (or KOI 55) with a 5.76 and 8.23 hour-periodicity. The astrophysicists inferred the presence of two bodies in orbit around the star.
The two worlds, named KOI 55.01 and KOI 55.02, circle their star at record distances of only 897,000 km and 1,137,000 km. They are closer to their host star than any other extrasolar planet ever discovered.
Calculations, conducted by the team, indicate that the size of these bodies must be comparable to that of the Earth, probably 0.76 and 0.87 Earth radii, which makes them the smallest planets ever detected around a still active star.
The star KOI 55 has a surface temperature of about 27,400 °C, the temperature on the illuminated hemispheres of the two planets could reach 7700-8700 °C.
Researchers concluded that planets KOI 55.01 and KOI 55.02 are the remnants of ancient gaseous giants like Jupiter. Towards the end of its life, the host star expanded and became a red giant. The planets orbiting around it were probably engulfed in the star’s outer layers and their envelopes were stripped away.
This finding, published in the journal Nature, sheds new light on the fate of planetary systems.
