New exoplanet with a subsaturnian mass discovered in the disk of the Milky Way

Using microlensing techniques, an international team of astronomers discovered a new, distant world. The exoplanet, designated OGLE-2018-BLG-0799Lb, is about five times less massive than Jupiter and orbits a low-mass dwarf star. This is reported in an article posted on the arXiv preprint server.

Microlensing is a useful method for detecting alien worlds in the inner galactic disk and bulge, where it is difficult to find planets by other methods.

Bulge is the central bright ellipsoidal component of spiral and lenticular galaxies. The galaxy’s bulge is composed primarily of old stars moving in elongated orbits; typical bulge populations are red giants, red dwarfs, type II supernovae, RR Lyrae variables, globular clusters.

Microlensing makes it easier to spot distant objects by using the stars in the background as “lights”. If a star moves in front of another star, light from a distant star is deflected by the gravitational pull of a nearer star and a farther star increases. Microlensing does not depend on the light of the host stars; thus, researchers can detect planets even if the parent stars cannot be found.

The planet OGLE-2018-BLG-0799 was discovered in May 2018 using the OGLE optical gravitational lensing experiments. OGLE is a Polish astronomical project based at the University of Warsaw that searches for dark matter and extrasolar planets. It uses a 1.3-meter telescope at the Las Campanas Observatory in Chile.

Astronomers from the OGLE Collaboration and others conducted follow-up observations of OGLE-2018-BLG-0799 using NASA’s Spitzer Space Telescope. In the course of their observations, they discovered a massive new planet orbiting a dwarf star.

The newly discovered exoworld has a mass of about 0.22 times that of Jupiter, which has allowed researchers to classify it as a planet of sub-Saturn mass. It revolves around a dwarf star with a mass of about 0.08 solar masses, it is 1.27 AU distant from its host. The discovered system is located about 14,400 light-years from Earth, in the disk of the Milky Way. OGLE-2018-BLG-0799Lb is just the second planet orbiting a very low-mass dwarf, identified by Spitzer.

However, astronomers emphasize that, due to the systematics of the Spitzer telescope’s photometry, it is too early to draw definitive conclusions about the properties of the system. According to the study, there is ambiguity in the measurement of parallax and, therefore, it is possible that the host of this system is a more massive star and is located farther in the galactic bulge than was assumed.

Therefore, the researchers propose further studies of the system, especially measurements of adaptive optics, to eliminate all uncertainties.

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