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A rogue planet, also termed a free-floating planet (FFP) or an isolated planetary-mass object (iPMO), is an interstellar object of planetary mass which is not gravitationally bound to any star or brown dwarf.
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-390L is a star thought to be a spectral type M. This galactic bulge star is located in the Scorpius constellation at a far distance of about 21,500 light years, near the border with Sagittarius.
The Optical Gravitational Lensing Experiment (OGLE) is a Polish astronomical project based at the University of Warsaw that runs a long-term variability sky survey (1992–present). The main goals are the detection and classification of variable stars, discovery of microlensing events, dwarf novae, and studies of the structure of the Galaxy and the Magellanic Clouds. Since the project began in 1992, it has discovered a multitude of extrasolar planets, together with the first planet discovered using the transit method (OGLE-TR-56b) and gravitational microlensing. The project has been led by professor Andrzej Udalski since its inception.
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-169L is a dim and distant magnitude 20 galactic bulge star located about 2,700 parsecs away in the constellation Sagittarius. If it is a main sequence star, then it is most likely a red dwarf with about half of the mass of the Sun. Other possibilities are a white dwarf star, or a neutron star or black hole.
OGLE-2005-BLG-169Lb is an extrasolar planet located approximately 2,700 parsecs away in the constellation of Sagittarius, orbiting the star OGLE-2005-BLG-169L. This planet was discovered by the OGLE project using the gravitational microlensing method. Based on a most likely mass for the host star of 0.49 solar mass (M☉), the planet has a mass of 13 times that of Earth (ME). Its mass and estimated temperature are close to those of Uranus. It is speculated that this planet may either be an ice giant like Uranus, or a "naked super-Earth" with a solid icy or rocky surface.
Any planet is an extremely faint light source compared to its parent star. For example, a star like the Sun is about a billion times as bright as the reflected light from any of the planets orbiting it. In addition to the intrinsic difficulty of detecting such a faint light source, the light from the parent star causes a glare that washes it out. For those reasons, very few of the exoplanets reported as of January 2024 have been observed directly, with even fewer being resolved from their host star.
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-2007-BLG-192Lb, occasionally shortened to MOA-192 b, is an extrasolar planet approximately 7,000 light-years away in the constellation of Sagittarius. The planet was discovered orbiting the low-mass star MOA-2007-BLG-192L. It was found when it caused a gravitational microlensing event on May 24, 2007, which was detected as part of the MOA-II microlensing survey at the Mount John University Observatory in New Zealand.
A circumbinary planet is a planet that orbits two stars instead of one. The two stars orbit each other in a binary system, while the planet typically orbits farther from the center of the system than either of the two stars. In contrast, circumstellar planets in a binary system have stable orbits around one of the two stars, closer in than the orbital distance of the other star. Studies in 2013 showed that there is a strong hint that a circumbinary planet and its stars originate from a single disk.
The Microlensing Follow-Up Network is an informal group of observers who monitor high magnification gravitational microlensing events in the Milky Way's Galactic Bulge. Its goal is to detect extrasolar planets via microlensing of the parent star by the planet. μFUN is a follow-up network - they monitor microlensing events identified by survey groups such as OGLE and Microlensing Observations in Astrophysics (MOA).
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.
MOA-2011-BLG-262L is a red dwarf with an orbiting exoplanet, both detected through the gravitational microlensing event MOA-2011-BLG-262. It was once believed to be either an exoplanet with 3.2 times the mass of Jupiter and a exomoon with 0.47 times Earth's mass or a red dwarf with a mass of 0.11 solar masses orbited by a ~17 M🜨 planet, but the latter scenario was confirmed in 2024 based on observations of the host star by the Keck telescope, 10 years after the ending of the microlensing event.
KMT-2020-BLG-0414L is a white dwarf star about 4,000 light-years away in the constellation Sagittarius, which is orbited by an Earth-mass exoplanet and a brown dwarf.
References
- 1 2 Albrow, M. D.; et al. (2000). "Detection of Rotation in a Binary Microlens: PLANET Photometry of MACHO 97-BLG-41". The Astrophysical Journal. 534 (2): 894–906. arXiv: astro-ph/9910307 . Bibcode:2000ApJ...534..894A. doi:10.1086/308798. S2CID 3000437.
- ↑ Bennett, D. P.; et al. (1999). "Discovery of a planet orbiting a binary star system from gravitational microlensing". Nature. 402 (6757): 57–59. arXiv: astro-ph/9908038 . Bibcode:1999Natur.402...57B. doi:10.1038/46990. S2CID 205061885.
- ↑ Jung, Youn Kil; et al. (2013). "Reanalysis of the Gravitational Microlensing Event MACHO-97-BLG-41 Based on Combined Data". The Astrophysical Journal Letters. 768 (1). L7. arXiv: 1303.0952 . Bibcode:2013ApJ...768L...7J. doi:10.1088/2041-8205/768/1/L7. S2CID 118390991.
