Icy world discovered using microlensing

Gravity has a substantial effect on the appearance of massive objects, often enabling us to see bodies in space that would otherwise be out of view. This technique has been used to discover an icy exoplanet 13,000 lightyears away.

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An artist's impression of icy planet OGLE-2016-BLG-1195Lb, discovered using a technique called microlensing.
Credits: NASA/JPL-Caltech

Astronomers have discovered an icy exoplanet orbiting a star nearly 13,000 lightyears away by observing the effect of gravity on the star’s brightness.

OGLE-2016-BLG-1195Lb orbits a star so small that it may not even be star; it could be a brown dwarf. These objects are like stars, but their cores are not hot enough to generate energy through nuclear fusion. This particular star is just 7.8 per cent the mass of our Sun.

 


Read more about the hunt for exoplanets from BBC Sky at Night Magazine:


 

The exoplanet was found using a technique called microlensing. This technique is much like gravitational lensing in that it takes advantage of how gravity affects the appearance of objects. In this case, the faint light of a faraway star can be temporarily brightened by the gravity of a foreground star orbiting in front of it. An orbiting planet may then cause a dip in the star’s brightness, which can be observed from Earth. This technique has been used to find some of the most distant known exoplanets from Earth.

The star orbited by OGLE-2016-BLG-1195Lb could be an ultra-cool dwarf star like TRAPPIST-1, but while the seven planets recently found around TRAPPIST-1 are close to their host star, this newly-discovered exoplanet is about the same distance as Earth is from the Sun. Given how faint the star is, this would make it an icy world, possibly even colder than Pluto. Any water that did exist on its surface would be frozen.

The exoplanet was discovered using the Korea Microlensing Telescope Network and NASA’s Spitzer space telescope. The discovery will aid astronomers in answering the question as to whether the frequency of planets that exist in the Milky Way is different closer to its bulge.

"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 disc,” says Geoff Bryden, astronomer at NASA's Jet Propulsion Laboratory and co-author of the study.


 

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