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MIT team discovers an exoplanet that orbits its star in 8.5 hours

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In the time it takes you to complete a single workday, or get a full night’s sleep, a small fireball of a planet 700 light-years away has already completed an entire year. 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. ...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.

The researchers will report their discovery of Kepler 78b in The Astrophysical Journal [preprint:]. In a separate paper, published in Astrophysical Journal Letters [], members of that same group, along with others at MIT and elsewhere, observed KOI 1843.03, a previously discovered exoplanet with an even shorter orbital period: just 4.25 hours. order for the planet to maintain its extremely tight orbit around its star, it would have to be incredibly dense, made almost entirely of iron -- otherwise, the immense tidal forces from the nearby star would rip the planet to pieces.

In their discovery of Kepler 78b, the team that wrote the Astrophysical Journal paper looked through more than 150,000 stars that were monitored by the Kepler Telescope, ....

“I was just looking by eye, and all of a sudden I see this extra drop of light right when it was expected, and it was really beautiful,” Sanchis-Ojeda recalls. “I thought, we’re actually seeing the light from the planet. It was a really exciting moment.” ...Roberto Sanchis-Ojeda:

[ Written by Jennifer Chu, MIT News Office ]

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