Astronomers Discover Exoplanet with the Longest Orbital Period

Astronomers have discovered an exoplanet with the longest orbital period among all known exoplanets. This information is reported on the website of the Harvard-Smithsonian Center for Astrophysics (CfA).

The exoplanet, named 'Kepler-421b', was discovered using the transit method. It orbits a star of spectral class K, located about 1000 light-years from Earth in the constellation Lyra.

'The discovery of 'Kepler-421b' was a stroke of luck. The farther a planet is from its star, the lower the chances of seeing a transit from the perspective of an Earth observer. They must align just right', - says David Kipping, the lead author of the study from the Harvard-Smithsonian Center for Astrophysics (CfA).

The orbit of the exoplanet lies beyond the 'snow line' at a distance of about 110 million kilometers from its parent star. The exoplanet's orbital period is 704 Earth days, its sizes are roughly comparable to those of Uranus, and its temperature is about -135 °F (-92.78 °C).

'The 'snow line' is the area where simple compounds (such as methane, carbon dioxide, etc.) crystallize. It can also be defined as the boundary between gas and rocky exoplanets.

'The snow line is one of the most important markers in the theory of planet formation. We believe that all gas giants must form beyond this distance', - Kipping adds.

Since gas giant planets can be found very close to their stars, with orbital periods lasting just a few days or even hours, astronomers think that many exoplanets migrate inward in the early stages of their history. However, the case of 'Kepler-421b' shows that such migration is not necessary. This planet may have formed precisely where it was discovered.

'This is the first example of a potentially non-migrating gas giant in a transit system that we have found', - concludes David Kipping.