* Astronomy

Blobrana · L

RE: Kepler 78b

Blobrana · L

Title: A Rocky Composition for an Earth-sized Exoplanet
Author: Andrew W. Howard, Roberto Sanchis-Ojeda, Geoffrey W. Marcy, John Asher Johnson, Joshua N. Winn, Howard Isaacson, Debra A. Fischer, Benjamin J. Fulton, Evan Sinukoff, Jonathan J. Fortney

Planets with sizes between that of Earth (with radius Earth radii) and Neptune (about 4 Earth radii) are now known to be common around Sun-like stars. Most such planets have been discovered through the transit technique, by which the planet's size can be determined from the fraction of starlight blocked by the planet as it passes in front of its star. Measuring the planet's mass-and hence its density, which is a clue to its composition-is more difficult. Planets of size 2-4 Earth radii have proven to have a wide range of densities, implying a diversity of compositions, but these measurements did not extend down to planets as small as Earth. Here we report Doppler spectroscopic measurements of the mass of the Earth-sized planet Kepler-78b, which orbits its host star every 8.5 hours. Given a radius of 1.20 ± 0.09 Earth radii and mass of 1.69 ± 0.41 Earth masses, the planet's mean density of 5.3 ± 1.8 g cm-3 is similar to the Earth's, suggesting a composition of rock and iron.

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Mystery World Baffles Astronomers

Kepler-78b is a planet that shouldn't exist. This scorching lava world circles its star every eight and a half hours at a distance of less than one million miles - one of the tightest known orbits. According to current theories of planet formation, it couldn't have formed so close to its star, nor could it have moved there.
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Earth-sized 'lava world' discovered

A doomed "lava world" with a similar mass and density to that of Earth has been discovered orbiting a star 400 light-years away.
Observations suggest the planet, named Kepler 78b, is composed mostly of rock and iron, much like our own planet.
But its extremely close proximity to its host star - a hundredth of the distance between the Earth and the Sun - remains something of a puzzle.
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Researchers discover that an exoplanet is Earth-like in mass and size

In August, MIT researchers identified an exoplanet with an extremely brief orbital period: The team found that Kepler 78b, a small, intensely hot planet 400 light-years from Earth, circles its star in just 8.5 hours - lightning-quick, compared with our own planets leisurely 365-day orbit. From starlight data gathered by the Kepler Space Telescope, the scientists also determined that the exoplanet is about 1.2 times Earths size - making Kepler 78b one of the smallest exoplanets ever measured.
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MIT team discovers an exoplanet that orbits its star in 8.5 hours

Researchers at MIT have discovered an Earth-sized exoplanet named Kepler 78b that whips around its host star in a mere 8.5 hours - one of the shortest orbital periods ever detected. The planet is extremely close to its star - its orbital radius is only about three times the radius of the star - and the scientists have estimated that its 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.
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