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Gravitational microlensing is an astronomical phenomenon caused by the gravitational lens effect. It can be used to detect objects that range from the mass of a planet to the mass of a star, regardless of the light they emit. Typically, astronomers can only detect bright objects that emit much light (stars) or large objects that block background light. These objects make up only a minor portion of the mass of a galaxy. Microlensing allows the study of objects that emit little or no light.
OGLE-2005-BLG-390Lb is a super-Earth exoplanet orbiting OGLE-2005-BLG-390L, a star 21,500 ± 3,300 light-years from Earth near the center of the Milky Way, making it one of the most distant planets known. On January 25, 2006, Probing Lensing Anomalies NETwork/Robotic Telescope Network (PLANET/Robonet), Optical Gravitational Lensing Experiment (OGLE), and Microlensing Observations in Astrophysics (MOA) made a joint announcement of the discovery. The planet does not appear to meet conditions presumed necessary to support life.
OGLE-2003-BLG-235L (MOA-2003-BLG-53L) is a star in the constellation of Sagittarius. The first gravitational microlensing event for which a planet orbiting the lens was detected around this star. The event occurred in during July 2003. Two groups observed and independently detected the event: the Optical Gravitational Lensing Experiment (OGLE) and the Microlensing Observations in Astrophysics (MOA), hence, the double designation. It is an orange dwarf star of spectral type K, which is accompanied by a giant planet.
OGLE-2005-BLG-071L is a distant, magnitude 19.5 galactic bulge star located in the constellation Scorpius, approximately 11,000 light years away from the Solar System. The star is probably a red dwarf with a mass 43% of that of the Sun.
MOA-2009-BLG-387Lb is an exoplanet in the orbit of the red dwarf MOA-2009-BLG-387L. Its discovery was announced on February 21, 2011, making it the eleventh planet discovered using gravitational microlensing. The planet is thought to be over twice the mass of Jupiter and to have an orbit 80 percent larger than that of Earth's, lasting approximately 1,970 days. However, its exact characteristics are difficult to constrain because the characteristics of the host star are not well known.
MOA-2009-BLG-387L is a red dwarf in the Sagittarius constellation that is host to the planet MOA-2009-BLG-387Lb. The star is estimated to be nearly 20,000 light years away and approximately one fifth the mass of the Sun, although large confidence intervals exist, reflecting the uncertainties in both the mass and distance. The star drew the attention of astronomers when it became the lens of gravitational microlensing event MOA-2009-BLG-387L, in which it eclipsed a background star and created distorted caustics, an envelope of reflected or refracted light rays. Analysis of the caustic events and of follow-up observational data led to the planet's discovery, which was reported in February 2011.
MOA-2010-BLG-477L is a star whose existence was detected when it caused a microlensing event in August, 2010. The microlensing event also revealed the existence of a planet orbiting the star. At first the star was thought to be about 0.67 times the mass of the Sun, in the main-sequence phase of its stellar evolution. But by the time the star should have been separated enough in the sky from the source star of the microlensing event it was not detected, implying that it is actually a dim white dwarf star.
OGLE-2016-BLG-1195Lb is an extrasolar planet located about 22,000 light-years from Earth, in the galactic bulge, orbiting the 0.57±0.06 M☉ star OGLE-2016-BLG-1195L, discovered in 2017. The planet was detected using gravitational microlensing techniques managed by the Korea Astronomy and Space Science Institute and the Spitzer Space Telescope. Initially, it was believed the planet has a mass similar to Earth and is located about the same distance from its host star as the Earth is from the Sun, although it was expected to be much colder.
OGLE-2016-BLG-1190Lb is an extremely massive exoplanet, with a mass about 13.4 times that of Jupiter (MJ), or is, possibly, a low mass brown dwarf, orbiting the G-dwarf star OGLE-2016-BLG-1190L, located about 22,000 light years from Earth, in the constellation of Sagittarius, in the galactic bulge of the Milky Way.
OGLE-2018-BLG-0799Lb is a sub-Saturn-mass exoplanet discovered by the Optical Gravitational Lensing Experiment (OGLE) collaboration, through a gravitational microlensing event that occurred in May 2018. The discovery was announced in October 2020, and published in August 2022.
OGLE-2019-BLG-0960Lb is an exoplanet that was discovered in January 2021 by gravitational microlensing. It is approximately twice the mass of Earth, making it a super-Earth. At the time of discovery, it was the lowest mass-ratio planet to be detected via microlensing; that is, the least massive planet relative to the mass of its host star. Its host star, OGLE-2019-BLG-0960L, has an mass between 0.3 and 0.6 M☉.
KMT-2022-BLG-0440L b is a Neptune-like exoplanet, located 11,415 light years away in the constellation of Sagittarius. It was discovered in 2023.
References
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- 1 2 3 4 Zang, Weicheng; Han, Cheongho; Kondo, Iona; Yee, Jennifer C.; et al. (November 2021). "An Earth-mass planet in a time of COVID-19: KMT-2020-BLG-0414Lb". Research in Astronomy and Astrophysics . 21 (9): 239. arXiv: 2103.01896 . Bibcode:2021RAA....21..239Z. doi:10.1088/1674-4527/21/9/239.
- 1 2 3 4 5 6 7 8 Zhang, Keming; Zang, Weicheng; El-Badry, Kareem; Lu, Jessica R.; et al. (September 2024). "An Earth-mass planet and a brown dwarf in orbit around a white dwarf". Nature Astronomy : 1–8. arXiv: 2409.02157 . Bibcode:2024NatAs.tmp..237Z. doi:10.1038/s41550-024-02375-9.
{{cite journal}}: CS1 maint: bibcode (link) - ↑ Kipping, David (January 2024). "The giant nature of WD 1856 b implies that transiting rocky planets are rare around white dwarfs". Monthly Notices of the Royal Astronomical Society . 527 (2): 3532–3541. arXiv: 2310.15219 . Bibcode:2024MNRAS.527.3532K. doi: 10.1093/mnras/stad3431 .
