Newly Discovered Planet Has Longest Yearly Revolution

Kepler 421b

The exoplanet orbits an orange Type-K star which lies roughly 1,000 light years from Earth.

Recently discovered Kepler-421b takes 704 Earth days to complete one orbit which, researchers say, give it the longest year known for any transiting alien world. Around the size of Uranus, the exoplanet is located about 1,000 light-years from Earth in the constellation Lyra. It was spotted by NASA’s Kepler space telescope- adding 421b to a long list over 1,000 alien planets the spacecraft has discovered to date.

So far, the majority of Kepler’s finds have been worlds that orbit relatively close to their parent stars since they transit relatively frequently. The instrument has generally required three transits to conclusively identify an exoplanet. According to researchers, Kepler-421b was detected after it crossed its host star’s face just twice.

421b circles its parent star (a cooler and dimmer sun than Earth’s) at an average distance of 100 million miles (160 million kilometers). This distance places the exoplanet outside its solar system’s boundary between gaseous and rocky planets- referred to as the “snow line”. The fact that 421b, a gaseous planet, has remained behind that line is remarkable because most giant world migrate inward significantly over time and eventually complete their orbit in days or even hours

In a statement, lead study author David Kipping from the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts said, “Finding Kepler-421b was a stroke of luck. 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 does not have the longest year of any known alien planet. Many non-transiting worlds have much more radical orbits, such as the gas giant GU Piscium b that takes about 160,000 years to complete one rotation around its host star.

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Photo Credit: David A. Aguilar

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