CfA: Transiting Exoplanet with Longest Known Year

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CfA: Transiting Exoplanet with Longest Known Year

Post by bystander » Tue Jul 22, 2014 10:45 pm

Transiting Exoplanet with Longest Known Year
Harvard-Smithsonian Center for Astrophysics | 2014 Jul 21
Image
This artist's conception shows the Uranus-sized exoplanet Kepler-421b, which orbits an
orange, type K star about 1,000 light-years from Earth. Kepler-421b is the transiting
exoplanet with the longest known year, circling its star once every 704 days. It is
located beyond the "snow line" – the dividing line between rocky and gaseous planets
– and might have formed in place rather than migrating from a different orbit.
(Credit: David A. Aguilar (CfA))
Astronomers have discovered a transiting exoplanet with the longest known year. Kepler-421b circles its star once every 704 days. In comparison, Mars orbits our Sun once every 780 days. Most of the 1,800-plus exoplanets discovered to date are much closer to their stars and have much shorter orbital periods.

"Finding Kepler-421b was a stroke of luck," says lead author David Kipping of the Harvard-Smithsonian Center for Astrophysics (CfA). "The farther a planet is from its star, the less likely it is to transit the star from Earth's point of view. It has to line up just right."

Kepler-421b orbits an orange, type K star that is cooler and dimmer than our Sun. It circles the star at a distance of about 110 million miles. As a result, this Uranus-sized planet is chilled to a temperature of -135° Fahrenheit.

As the name implies, Kepler-421b was discovered using data from NASA's Kepler spacecraft. Kepler was uniquely suited to make this discovery. The spacecraft stared at the same patch of sky for 4 years, watching for stars that dim as planets cross in front of them. No other existing or planned mission shows such long-term, dedicated focus. Despite its patience, Kepler only detected two transits of Kepler-421b due to that world's extremely long orbital period.

The planet's orbit places it beyond the "snow line" - the dividing line between rocky and gas planets. Outside of the snow line, water condenses into ice grains that stick together to build gas giant planets. ...

Discovery of a Transiting Planet Near the Snow-Line - David M. Kipping et al
  • arXiv.org > astro-ph > arXiv:1407.4807 > 17 Jul 2014

Kepler-421: First Transiting Exoplanet Found at the “Frost-Line”
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