NASA's Kepler Is Planning To Seek Orphan Planets

NASA's Kepler space telescope has completed its search for earth-like planets in our solar system. The latest mission is to seek "free-playing planets" in order to find out how common these orphan planets are. Hence, it is on a K2 mission.

Orphan worlds are planets without host stars, which have been ejected from solar system families due to gravitational dynamics. They tend to get attracted by tidal forces. However, as they are tough to locate, their existence or number is still not clear to scientists.

Hence, scientists are going to use microlensing, a phenomenon that occurs when the gravity of an orphan planet magnifies light from a remote star in the background.

"For a lensing event that's due to just a single object, the most salient feature of the light curve is the time scale," said Calen Henderson, an astronomer with NASA's Jet Propulsion Laboratory in Pasadena, Calif. "In general, a shorter time scale is potentially indicative of a lower-mass lensing object."

Such a free-floating planet leading to a lensing event might happen over days, or even hours.

"If you're just monitoring one star, it's very, very rare to capture a microlensing event," Henderson said. "That would only happen once per individual star every maybe 300,000 years. It's a fishing expedition. Microlensing events are rare. They're unpredictable and so what microlensing surveys have done for decades is just try to play the numbers game," he said.

There might be variations in the brightness of the stars due to stellar flares, while others are due to bodies in the foreground that change the light of the star in the background.

"What we're going to try to do with K2 is look for those events that are due to a lensing system that is just a free-floating planet," Henderson said.

The K2 team thus plans to use ground-based surveys along with the Kepler space telescope so that they can get a couple of perspectives of the lensing events and work out the mass of the objects that lead to the lensings.

"It's the first chance that we will have to actually measure the masses of these objects and the first chance to find out if the ones we find that are low-mass are (gravitationally) bound to a host star or not," Henderson concluded.

NASA's Kepler team hopes that it can give an insight into these unique orphan planets after the end of the K2 mission.