U is a possible astronomical body detected by Chile's Atacama Large Millimeter Array (ALMA) during a survey for substellar objects in the Alpha Centauri system.
In images taken on 7 July 2014 (343.5 GHz) and 2 May 2015 (445 GHz), researchers discovered a source in the far infrared located within 5.5 arcseconds of α Cen AB. Based on its proper motion, it was at first thought to be a part of the Alpha Centauri system. Further analysis, however, found that the object must be closer to the Solar System, and that it may be gravitationally bound to the Sun. The researchers suggest that the object may be an extreme trans-Neptunian object (ETNO) beyond 100 AU (15 billion km), a super-Earth at around 300 AU (45 billion km), or a very cool brown dwarf at around 20,000 AU (3 trillion km).
The research was published on the arXiv in December 2015, but was later withdrawn pending further study. Additional observations of the detection at 343.5 GHz could not be made, whereas the detection at 445 GHz was confirmed to greater than 12σ. A single point of data, however, is insufficient for proper analysis, and further observations must be made to better determine this object's nature and its orbit.
Other astronomers have expressed skepticism over this claim. Mike Brown thinks that it is statistically improbable for a new Solar System object to be accidentally observed in ALMA's extremely narrow field of view, whereas Bruce Macintosh suggests that the detections may be artifacts introduced due to ALMA's calibration methods.
Alpha Centauri is the closest star system and closest planetary system to Earth's Solar System at 4.37 light-years from the Sun. The name is Latinized from α Centauri, and abbreviated Alpha Cen or α Cen. It is a triple star system, consisting of three stars: α Centauri A, α Centauri B, and α Centauri C.
Following the discovery of the planet Neptune in 1846, there was considerable speculation that another planet might exist beyond its orbit. The search began in the mid-19th century and continued at the start of the 20th with Percival Lowell's quest for Planet X. Lowell proposed the Planet X hypothesis to explain apparent discrepancies in the orbits of the giant planets, particularly Uranus and Neptune, speculating that the gravity of a large unseen ninth planet could have perturbed Uranus enough to account for the irregularities.
The Solar System is the gravitationally bound system of the Sun and the objects that orbit it, either directly or indirectly. Of the objects that orbit the Sun directly, the largest are the eight planets, with the remainder being smaller objects, the dwarf planets and small Solar System bodies. Of the objects that orbit the Sun indirectly—the natural satellites—two are larger than the smallest planet, Mercury.
Tau Ceti, Latinized from τ Ceti, is a single star in the constellation Cetus that is spectrally similar to the Sun, although it has only about 78% of the Sun's mass. At a distance of just under 12 light-years from the Solar System, it is a relatively nearby star and the closest solitary G-class star. The star appears stable, with little stellar variation, and is metal-deficient.
Proxima Centauri is a small, low-mass star located 4.2465 light-years (1.3020 pc) away from the Sun in the southern constellation of Centaurus. Its Latin name means the "nearest [star] of Centaurus". This object was discovered in 1915 by Robert Innes and is the nearest-known star to the Sun. With a quiescent apparent magnitude 11.13, it is too faint to be seen with the unaided eye. Proxima Centauri is a member of the Alpha Centauri system, being identified as component Alpha Centauri C, and is 2.18° to the southwest of the Alpha Centauri AB pair. It is currently 12,950 AU (0.2 ly) from AB, which it orbits with a period of about 550,000 years.
A star system or stellar system is a small number of stars that orbit each other, bound by gravitational attraction. A large group of stars bound by gravitation is generally called a star cluster or galaxy, although, broadly speaking, they are also star systems. Star systems are not to be confused with planetary systems, which include planets and similar bodies.
90377 Sedna, or simply Sedna, is a large planetoid in the outer reaches of the Solar System that was, as of 2020, at a distance of about 85 astronomical units (1.27×1010 km; 7.9×109 mi) from the Sun, about three times farther than Neptune. Spectroscopy has revealed that Sedna's surface composition is similar to those of some other trans-Neptunian objects, being largely a mixture of water, methane, and nitrogen ices with tholins. Its surface is one of the reddest among Solar System objects. It is a possible dwarf planet. Sedna is approximately tied with 2002 MS4 and 2002 AW197 as the largest planetoid not known to have a moon.
An Einstein ring, also known as an Einstein–Chwolson ring or Chwolson ring, is created when light from a galaxy or star passes by a massive object en route to the Earth. Due to gravitational lensing, the light is diverted, making it seem to come from different places. If source, lens, and observer are all in perfect alignment, the light appears as a ring.
Sagittarius A* is a bright and very compact astronomical radio source at the Galactic Center of the Milky Way. It is located near the border of the constellations Sagittarius and Scorpius, about 5.6° south of the ecliptic. Sagittarius A* is the location of a supermassive black hole, similar to those at the centers of most, if not all, spiral and elliptical galaxies.
Omega Centauri is a globular cluster in the constellation of Centaurus that was first identified as a non-stellar object by Edmond Halley in 1677. Located at a distance of 17,090 light-years, it is the largest known globular cluster in the Milky Way at a diameter of roughly 150 light-years. It is estimated to contain approximately 10 million stars, and a total mass equivalent to 4 million solar masses, making it the most massive known globular cluster in the Milky Way.
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. However, the first scientific detection of an exoplanet began in 1988. Afterwards, the first confirmed detection came in 1992, with the discovery of several 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 1 March 2021, there are 4,687 confirmed exoplanets in 3,463 systems, with 770 systems having more than one planet. This is a list of the most notable discoveries.
Alpha Centauri Bb was a proposed exoplanet orbiting the K-type main-sequence star Alpha Centauri B, located 4.37 light-years from Earth in the southern constellation of Centaurus, but there has not been enough evidence to support the claim.
Luhman 16 is a binary brown-dwarf system in the southern constellation Vela at a distance of approximately 6.5 light-years from the Sun. These are the closest-known brown dwarfs and the closest system found since the measurement of the proper motion of Barnard's Star in 1916, and the third-closest-known system to the Sun. The primary is of spectral type L7.5 and the secondary of type T0.5 ± 1. The masses of Luhman 16 A and B are 33.5 and 28.6 Jupiter masses, respectively, and their ages are estimated to be 600–800 million years. Luhman 16 A and B orbit each other at a distance of about 3.5 astronomical units with an orbital period of approximately 27 years.
Fast Outgoing Cyclopean Astronomical Lens (FOCAL) is a proposed space telescope that would use the Sun as a gravity lens. The gravitational lens effect was first derived by Einstein, and the concept of a mission to the solar gravitational lens was first suggested by professor Von Eshleman, and analyzed further by Italian astronomer Claudio Maccone and others.
Breakthrough Listen is a project to search for intelligent extraterrestrial communications in the Universe. With $100 million in funding and thousands of hours of dedicated telescope time on state-of-the-art facilities, it is the most comprehensive search for alien communications to date. The project began in January 2016, and is expected to continue for 10 years. It is a component of Yuri Milner's Breakthrough Initiatives program. The science program for Breakthrough Listen is based at Berkeley SETI Research Center, located in the Astronomy Department at the University of California, Berkeley.
An extreme trans-Neptunian object (ETNO) is a trans-Neptunian object orbiting the Sun well beyond Neptune (30 AU) in the outermost region of the Solar System. An ETNO has a large semi-major axis of at least 150–250 AU. Its orbit is much less affected by the known giant planets than all other known trans-Neptunian objects. They may, however, be influenced by gravitational interactions with a hypothetical Planet Nine, shepherding these objects into similar types of orbits.
A circumplanetary disk is a torus, pancake or ring-shaped accumulation of matter composed of gas, dust, planetesimals, asteroids or collision fragments in orbit around a planet. Around the planets, they are the reservoirs of material out of which moons may form. Such a disk can manifest itself in various ways.
2I/Borisov, originally designated C/2019 Q4 (Borisov), is the first observed rogue comet and the second observed interstellar interloper after ʻOumuamua. It was discovered by the Crimean amateur astronomer and telescope maker Gennadiy Borisov on 30 August 2019 UTC
BLC1 is a candidate SETI radio signal detected and observed during April and May of 2019, and first reported on 18 December 2020, spatially coincident with the direction of the Solar system's closest star, Proxima Centauri.
Candidate 1 is an exoplanet candidate directly imaged orbiting Alpha Centauri A in February 2021. It orbits at approximately 1.1 AU away from Alpha Centauri with a period of about a year and has a mass between that of Neptune and one-half that of Saturn. Being this mass, it is likely gaseous and therefore precludes the possibility a rocky planet within Alpha Centauri A's habitable zone, although habitable exomoons could potentially orbit the planet itself.