Astronomers Discover Icy Earth-Sized Exoplanet

Artist's impression of OGLE-2016-BLG-1195Lb. NASA/JPL-Caltech

An international team of astronomers has discovered an Earth-sized planet orbiting a star at the same distance we are from the Sun. But its star is much smaller and cooler than our own, and the planet is likely an icy world more similar to Pluto.

The discovery, reported in the Astrophysical Journal Letters, was possible thanks to a technique called microlensing. This is when astronomers use distortions in the light of background stars to detect stars and planets. This new object, OGLE-2016-BLG-1195Lb, is 13,000 light-years away – among the furthest exoplanets from Earth.

"This 'iceball' planet is the lowest-mass planet ever found through microlensing," lead author Yossi Shvartzvald, from NASA's Jet Propulsion Laboratory (JPL), said in a statement.

The galactic location of this icy ball is very important. Astronomers are trying to understand what conditions allow for the formation of planets and if they can form anywhere in the galaxy. So far, there's been a lack of planetary detection in the central region – the bulge. This could be due to its higher density than the disk, where the spiral arms (and the Solar System) are found.

In its last three detections, Spitzer has shown that it can discover planets as far as the bulge (but not in the bulge). The fact that we have the ability to see that far but haven't found a bulge planet yet suggests the region might not be planet friendly.

“Although we only have a handful of planetary systems with well-determined distances that are this far outside our solar system, the lack of Spitzer detections in the bulge suggests that planets may be less common toward the center of our galaxy than in the disk," added Geoff Bryden, also at JPL and co-author of the study.

In the next decade, NASA’s next infrared space observatory, WFIRST, will launch and analyze this on a much larger scale. Astronomers will be capable of coming up with a better estimate of the distribution of planets.

"One of the problems with estimating how many planets like this are out there is that we have reached the lower limit of planet masses that we can currently detect with microlensing," Shvartzvald said. "WFIRST will be able to change that."

And it’s not just the planet size that’s a limiting case. The planet’s star itself is an unclear object. It is just 7.8 percent of the mass of our Sun, right on the fence of being a star or a brown dwarf.

At the moment, this seems like a curious case, but there are so many dwarf stars that this object could actually be common in the universe.

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