NASA’s Kepler planet-hunting spacecraft was deactivated in November 2018, about ten years after it launched. The mission detected over 5,000 candidate exoplanets and 2,662 confirmed exoplanets using the transit method. But scientists are still working with all of Kepler’s data, hoping to uncover more planets in the observations.

A team of researchers have announced the discovery of one more planet in the Kepler data, and this one is nearly a twin of Jupiter.

The planet is called K2-2016-BLG-0005Lb (sorry), and it’s a whopping 17,000 light-years away. That’s almost twice as far away as the next furthest planet discovered by Kepler. Its mass is nearly identical to Jupiter’s, and it orbits its star at the same distance that Jupiter orbits the Sun. Astronomers found the world in Kepler data from 2016.

Kepler found planets using the transit timing method. But it discovered this one differently. It relied on one of Einstein’s predictions; that extremely massive objects have such powerful gravity that they can bend light. It’s called gravitational microlensing.

“The chance that a background star is affected this way by a planet is tens to hundreds of millions to one against.”

Dr. Eamonn Kerins, Principal Investigator for the Science and Technology Facilities Council.

A new paper titled “Kepler K2 Campaign 9: II. First space-based discovery of an exoplanet using microlensing” presents the discovery. It’s available online at the pre-print site and hasn’t been peer-reviewed yet. The lead author is Ph.D. student David Specht from The University of Manchester.

Opportunities to detect exoplanets with gravitational microlensing were heightened between April and July 2016 when Kepler was looking at millions of stars toward the center of the Milky Way. In the microlensing technique, astronomers watch for the light from a background star bent by an exoplanet’s mass in the foreground. That’s not easy to do; it requires precise alignment of the background and foreground from Kepler’s point of view.

“To see the effect at all requires almost perfect alignment between the foreground planetary system and a background star,” said Dr. Eamonn Kerins, Principal Investigator for the Science and Technology Facilities Council (STFC) grant that funded this research. “The chance that a background star is affected this way by a planet is tens to hundreds of millions to one against. But there are hundreds of millions of stars towards the centre of our galaxy. So Kepler just sat and watched them for three months.”

Last year a team of researchers developed a new algorithm to search for microlensing candidates in Kepler data. Some of those same researchers are behind this new study. The researchers developed the algorithm to look for free-floating planet candidates. They found five new candidates, including one that’s “… a caustic-crossing binary event, consistent with a bound planet,” that study said.

That effort expanded the possibilities of the Kepler data, even though NASA didn’t explicitly design the mission for microlensing. “Even through a space telescope not designed for microlensing studies, this result highlights the advantages for exoplanet microlensing discovery that come from continuous, high-cadence temporal sampling that is possible from space,” the authors of the new study write.

The 2021 study “only” found one exoplanet candidate, and this new study confirms its candidacy. But in science, each planet is a data point that tells scientists something, now or in the future.

The image on the left is a Kepler image with K2-2016-BLG-0005Lb shown in a red circle. The image on the right is a Canada-France Hawaii Telescope image of the same region, also with the exoplanet in a red circle. The exoplanet, K2-2016-BLG-0005Lb, is almost identical to Jupiter in terms of its mass and its distance from its star. Astronomers discovered it using data obtained in 2016 by NASA's Kepler space telescope. The exoplanetary system is twice as distant as any seen previously by Kepler, which found over 2,700 confirmed planets before ceasing operations in 2018. Image Credit: Specht et al. 2022.
The image on the left is a Kepler
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