A distant star and its planet have been discovered that bear a close resemblance to our own Sun and Earth. The Kepler-160 system system was found in data from the exoplanet-hunting Kepler Space Telescope, which looked for dips in brightness caused by planets transiting across their stars’ discs.
This photometric transit method favours the detection of Earth-sized planets around dim, red dwarf stars rather than around those like our Sun.
Red dwarfs are relatively cool, however, and emit high-energy solar flares: characteristics that could render such planets more hostile to life.
Read more about the Kepler Space Telescope:
- Interview: planet-hunting with Kepler
- A history of the Kepler Space Telescope
- How the Kepler Space Telescope came to be
But Kepler-160, the host star of this newly discovered exoplanet, is only slightly larger than our Sun and has a temperature of 5,200˚C: only 300˚C cooler.
Astronomers already knew the star had two Neptune-sized exoplanets orbiting it from an initial analysis of the Kepler data, but there were fluctuations in their timing that suggested another might be present.
A team from the Max Planck Institute for Solar System Research (MPS) went back over the data using a new technique to tease out the subtle signs of two smaller exoplanets moving around the star.
“Our analysis suggests that Kepler-160 is orbited by a total of 4 exoplanets and not by 2,” says René Heller from MPS, who led the team.
One of the 2 new stars could only be detected indirectly, but the other, KOI-456.04, is 1.9 times the radius of Earth and orbits its star once every 378 days – just 13 days longer than an Earth year.
“Our improvement is important in the search for small, Earth-sized exoplanets,” says Heller. “The planetary signal is so faint that it’s almost hidden in the noise of the data.”
Its Sun-like host star means the light falling on the planet will be very similar to our own sunshine, rather than the infrared-laden light of a red dwarf.
“KOI-456.04 is relatively large compared to many other planets that are considered potentially habitable. However, it’s the combination of its size, at less than double that of Earth, and its solar-type host star that makes it so special and familiar,” says Heller.
Ezzy Pearson is BBC Sky at Night Magazine’s News Editor.