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An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not then recognized as such. The first confirmed detection of an exoplanet was in 1992 around a pulsar, and the first detection around a main-sequence star was in 1995. A different planet, first detected in 1988, was confirmed in 2003. As of 19 December 2024, there are 5,811 confirmed exoplanets in 4,340 planetary systems, with 973 systems having more than one planet. In collaboration with ground-based and other space-based observatories the James Webb Space Telescope (JWST) is expected to give more insight into exoplanet traits, such as their composition, environmental conditions, and potential for life.
Gamma Cephei is a binary star system approximately 45 light-years away in the northern constellation of Cepheus. The primary is a stellar class K1 orange giant or subgiant star; it has a red dwarf companion. An exoplanet has been confirmed to be orbiting the primary.
HD 168443 is an ordinary yellow-hued star in the Serpens Cauda segment of the equatorial constellation of Serpens. It is known to have two substellar companions. With an apparent visual magnitude of 6.92, the star lies just below the nominal lower brightness limit of visibility to the normal human eye. This system is located at a distance of 127 light years from the Sun based on parallax, but is drifting closer with a radial velocity of −48.7 km/s.
HD 169830 is a star in the southern constellation of Sagittarius. It has a yellow-white hue and is dimly visible to the naked eye with an apparent visual magnitude of +5.90. The star is located at a distance of 120 light years from the Sun based on parallax. It is drifting closer with a radial velocity of −17.3 km/s, and is predicted to come as close as 20.7 ly (6.4 pc) in 2.08 million years. HD 169830 is known to be orbited by two large Jupiter-like exoplanets.
HD 150706 is a star with an orbiting exoplanet in the northern constellation of Ursa Minor. It is located 92 light years away from the Sun, based on parallax measurements. At that distance, it is not visible to the unaided eye. However, with an apparent visual magnitude of 7.02, it is an easy target for binoculars. It is located only about 10° from the northern celestial pole so it is always visible in the northern hemisphere except for near the equator. Likewise, it is never visible in most of the southern hemisphere. The star is drifting closer to the Sun with a radial velocity of −17.2 km/s.
HD 38529 is a binary star approximately 138 light-years away in the constellation of Orion.
HD 1237 is a binary star system approximately 57 light-years away in the constellation of Hydrus.
Gamma Cephei Ab, formally named Tadmor, is an exoplanet approximately 45 light-years away in the constellation of Cepheus. The planet was confirmed to be in orbit around Gamma Cephei A in 2003, but was first suspected to exist around 1988.
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.
109 Piscium b is a long-period extrasolar planet discovered in orbit around 109 Piscium. It is about 5.74 times the mass of Jupiter and is likely to be a gas giant. As is common for long-period planets discovered around other stars, it has an orbital eccentricity greater than that of Jupiter.
HD 114762 b is a small red dwarf star, in the HD 114762 system, formerly thought to be a massive gaseous extrasolar planet, approximately 126 light-years (38.6 pc) away in the constellation of Coma Berenices. This optically undetected companion to the late F-type main-sequence star HD 114762 was discovered in 1989 by Latham, et al., and confirmed in an October 1991 paper by Cochran, et al. It was thought to be the first discovered exoplanet
Gliese 86 is a K-type main-sequence star approximately 35 light-years away in the constellation of Eridanus. It has been confirmed that a white dwarf orbits the primary star. In 1998 the European Southern Observatory announced that an extrasolar planet was orbiting the star.
HD 176051 is a spectroscopic binary star system approximately 49 light years away from Earth in the constellation Lyra. The pair orbit with a period of 22,423 days and an eccentricity of 0.25. Compared to the Sun, they have a somewhat lower proportion of elements more massive than helium. Their individual masses are estimated at 1.07 and 0.71 solar masses (M☉). The system is moving closer to the Sun with a radial velocity of −47 km/s and will reach perihelion in about 269,000 years when it comes within roughly 17 ly (5.1 pc) of the Sun.
An exoplanet is a planet located outside the Solar System. The first evidence of an exoplanet was noted as early as 1917, but was not recognized as such until 2016; no planet discovery has yet come from that evidence. What turned out to be the first detection of an exoplanet was published among a list of possible candidates in 1988, though not confirmed until 2003. The first confirmed detection came in 1992, with the discovery of terrestrial-mass planets orbiting the pulsar PSR B1257+12. The first confirmation of an exoplanet orbiting a main-sequence star was made in 1995, when a giant planet was found in a four-day orbit around the nearby star 51 Pegasi. Some exoplanets have been imaged directly by telescopes, but the vast majority have been detected through indirect methods, such as the transit method and the radial-velocity method. As of 24 July 2024, there are 7,026 confirmed exoplanets in 4,949 planetary systems, with 1007 systems having more than one planet. This is a list of the most notable discoveries.
References
- ↑ "NASA Exoplanet Archive" . Retrieved 20 December 2019.
- ↑ Campbell, Bruce; Walker, G. A. H.; Yang, S. (1988). "A Search for Substellar Companions to Solar-type Stars". The Astrophysical Journal. 331: 902. Bibcode:1988ApJ...331..902C. doi: 10.1086/166608 .
- ↑ Hatzes, Artie P.; et al. (2003). "A Planetary Companion to Gamma Cephei A". The Astrophysical Journal. 599 (2): 1383–1394. arXiv: astro-ph/0305110 . Bibcode:2003ApJ...599.1383H. doi:10.1086/379281. S2CID 11506537.
- ↑ "The planet-host star Iota Horologii".
- ↑ Kiefer, Flavien (17 October 2019). "Determining the mass of the planetary candidate HD 114762 b using Gaia". Astronomy & Astrophysics. 632: L9. arXiv: 1910.07835 . Bibcode:2019A&A...632L...9K. doi:10.1051/0004-6361/201936942. S2CID 204743831.
