An international team of astronomers reporting in the Astrophysical Journal (arXiv.org) has discovered an Earth-sized exoplanet called Kepler 78b that orbits its parent star in a mere 8.5 hours.
Kepler 78b orbits its parent star in only 8.5 hours (NASA / JPL-Caltech).
The astronomers, led by Dr Buchhave from the University of Copenhagen, looked through more than 150,000 stars that were monitored by NASA’s Kepler Telescope. Their goal was to look for Earth-sized planets with very short orbital periods.
“We’ve gotten used to planets having orbits of a few days. But we wondered, what about a few hours? Is that even possible? And sure enough, there are some out there,” explained co-author Dr Joshua Winn of the Massachusetts Institute of Technology.
Kepler 78b is extremely close to its star – about 40 times closer than Mercury is to our Sun. Its orbital radius is only about 3 times the radius of the parent G-type star Kepler 78, also known as KIC 8435766.
The planet is most certainly not habitable, due to its extreme proximity to its host star.
The team estimated that Kepler 78b’s surface temperatures may be as high as 3,000 degrees Kelvin, or more than 5,000 degrees Fahrenheit. In such a scorching environment, the top layer of the planet is likely completely melted, creating a massive, roiling ocean of lava.
What’s most exciting to astronomers is that they were able to detect light emitted by the planet — the first time that researchers have been able to do so for an exoplanet as small as Kepler 78b. This light, once analyzed with larger telescopes, may give scientists detailed information about the planet’s surface composition and reflective properties.
Kepler 78b is so close to its star that scientists hope to measure its gravitational influence on the star. Such information may be used to measure the planet’s mass, which could make Kepler 78b the first Earth-sized planet outside our own Solar System whose mass is known.
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Bibliographic information: Roberto Sanchis-Ojeda et al. 2013. Transits and Occultations of an Earth-sized Planet in an 8.5 hr Orbit. ApJ 774, 54; doi: 10.1088/0004-637X/774/1/54
