The Kepler space telescope has spotted an exoplanet that has the longest know year yet: 704 days. In contrast, Mars takes 780 days to complete one circle around the Sun. It revolves around a star named Kepler-421, and scientists have named this exoplanet Kepler-421b. It orbits its star at a distance of 110 miles. Kepler-421 is located in the direction of constellation Lyra.

Gaseous Planet Discovered Kepler Exoplanet

Finding Kepler-421b was a stroke of luck

Data collected from the Kepler observatory shows that the Uranus-size exoplanet has an average temperature of -135F (-93C). It is about 1,040 light years away from the Earth. So far, scientists have identified 1,800 exoplanets. Most of them are closer to their stars and have much shorter revolving periods.

Exoplanets (planets that orbit other suns) are almost impossible to detect directly. So, scientists determine their presence based on the effects they have on their local stars. To find new exoplanets, they measure the gravitation push and pull between the planet and its star. Another method to find alien planets is when they pass between their local star and our world, temporarily blocking some of that star’s light.

Kepler was launched in 2009 to discover planets around other stars, which could help us find the possibility of life on exoplanets. The ones that are closer to their stars are easy to detect. David Kipping of the Harvard-Smithsonian Center for Astrophysics and lead author of the study, said the discovery of Kepler-421b was a stroke of luck. The Kepler telescope observed the same patch of sky for four years, looking for the dimming and brightening of stars as planets cross in front of them.

Kepler-421b is outside the ‘snow line’

Despite such a long exposure, Kepler could detect only two exposures of this exoplanet due to that planet’s long orbital period of 704 days. The Kepler-421 is an orange star, and is cooler than our Sun. Astronomers said that the exoplanet is beyond the “snow line,” the dividing line in the space between rocky planets like Earth and gas planets like Jupiter. Beyond the snow line, water condenses to form ice grains that combine together to build gas planets.