Tidally detached exomoons, also known as orphaned exomoons [1] or ploonets, [2] are hypothetical exoplanets that were formerly exomoons of another planet, before being ejected from their orbits around their parent planets by tidal forces during planetary migration, and becoming planets in their own right. [3] [4] As of 2024, no tidally detached moons have yet been definitively detected, but they are believed to be likely to exist around other stars, and potentially detectable by photometric methods. Researchers at Columbia University have suggested that a disrupting detached exomoon may be causing the unusual fluctuations in brightness exhibited by Tabby's Star. [5]
The term ploonet, a blend of the words planet and moon, [6] [7] was first used in a 2019 paper in the Monthly Notices of the Royal Astronomical Society . [2] [8] It received attention from mainstream media sources, [2] [9] [10] with CNET calling it "charmingly goofy". [11]
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 confirmation of the detection occurred in 1992. A different planet, first detected in 1988, was confirmed in 2003. As of 1 July 2024, there are 6,660 confirmed exoplanets in 4,868 planetary systems, with 995 systems having more than one planet. The James Webb Space Telescope (JWST) is expected to discover more exoplanets, and to give more insight into their traits, such as their composition, environmental conditions, and potential for life.
HD 6434 is a star in the southern constellation of Phoenix. Yellow dwarfs such as this are not very luminous, so at a distance of 138 light years it is not visible to the unaided eye. However, with binoculars it is readily visible under ideal observing conditions, having an apparent visual magnitude of 7.71. The star is drifting further from the Sun with a radial velocity of +23 km/s.
An exomoon or extrasolar moon is a natural satellite that orbits an exoplanet or other non-stellar extrasolar body.
A shepherd moon is a small natural satellite that clears a gap in planetary ring material or keeps particles within a ring contained. The name is a result of their limiting the "herd" of the ring particles as a shepherd.
HAT-P-1b is an extrasolar planet orbiting the Sun-like star HAT-P-1, also known as ADS 16402 B. HAT-P-1 is the dimmer component of the ADS 16402 binary star system. It is located roughly 521 light years away from Earth in the constellation Lacerta. HAT-P-1b is among the least dense of any of the known extrasolar planets.
HD 189733 b is an exoplanet in the constellation of Vulpecula approximately 64.5 light-years away from the Solar System. Astronomers in France discovered the planet orbiting the star HD 189733 on October 5, 2005, by observing its transit across the star's face. With a mass 11.2% higher than that of Jupiter and a radius 11.4% greater, HD 189733 b orbits its host star once every 2.2 days at an orbital speed of 152.0 kilometers per second, making it a hot Jupiter with poor prospects for extraterrestrial life.
The habitability of natural satellites is the potential of moons to provide habitats for life, though it is not an indicator that they harbor it. Natural satellites are expected to outnumber planets by a large margin and the study of their habitability is therefore important to astrobiology and the search for extraterrestrial life. There are, nevertheless, significant environmental variables specific to moons.
WASP-12b is a hot Jupiter orbiting the star WASP-12, discovered in April of 2008, by the SuperWASP planetary transit survey. The planet takes only a little over one Earth day to orbit its star, in contrast to about 365.25 days for the Earth to orbit the Sun. Its distance from the star is only the Earth's distance from the Sun, with an eccentricity the same as Jupiter's. Consequently, it has one of the lowest densities for exoplanets. On December 3, 2013, scientists working with the Hubble Space Telescope (HST) reported detecting water in the atmosphere of the exoplanet. In July 2014, NASA announced finding very dry atmospheres on three exoplanets orbiting sun-like stars.
HD 65216 b is an extrasolar planet located approximately 115 light-years away in the constellation of Carina, orbiting the star HD 65216. This planet was discovered by the Geneva Extrasolar Planet Search Team in 2003. Like most planet candidates so far, it was detected with the radial velocity method.
Kepler-16b is a Saturn-mass exoplanet consisting of half gas and half rock and ice. It orbits a binary star, Kepler-16, with a period of 229 days. "[It] is the first confirmed, unambiguous example of a circumbinary planet – a planet orbiting not one, but two stars," said Josh Carter of the Center for Astrophysics | Harvard & Smithsonian, one of the discovery team.
An exocomet, or extrasolar comet, is a comet outside the Solar System, which includes rogue comets and comets that orbit stars other than the Sun. The first exocomets were detected in 1987 around Beta Pictoris, a very young A-type main-sequence star. There are now a total of 27 stars around which exocomets have been observed or suspected.
Gravitational capture occurs when one object enters a stable orbit around another.
The Next-Generation Transit Survey (NGTS) is a ground-based robotic search for exoplanets. The facility is located at Paranal Observatory in the Atacama desert in northern Chile, about 2 km from ESO's Very Large Telescope and 0.5 km from the VISTA Survey Telescope. Science operations began in early 2015. The astronomical survey is managed by a consortium of seven European universities and other academic institutions from Chile, Germany, Switzerland, and the United Kingdom. Prototypes of the array were tested in 2009 and 2010 on La Palma, and from 2012 to 2014 at Geneva Observatory.
Tabby's Star is an F-type main-sequence star in the constellation Cygnus approximately 1,470 light-years from Earth. A distant red dwarf companion has been reported, making Tabby's Star a binary stellar system.
Tabetha "Tabby" Suzanne Boyajian is an American astronomer and associate professor at Louisiana State University. She works in of stellar interferometry, stellar spectroscopy, exoplanet research, and high angular resolution astronomy, all particularly at optical and infrared wavelengths. Boyajian was the lead author of the September 2015 paper "Where's the Flux?", which investigated the highly unusual light curve of KIC 8462852; the star is colloquially known as Tabby's Star in her honor.
In astronomy, a disrupted planet is a planet or exoplanet or, perhaps on a somewhat smaller scale, a planetary-mass object, planetesimal, moon, exomoon or asteroid that has been disrupted or destroyed by a nearby or passing astronomical body or object such as a star. Necroplanetology is the related study of such a process.
EPIC 204376071 is an M-type star in the constellation of Scorpius. Parallax measurements by the Gaia space observatory put the star at a distance of about 440 light-years from Earth. It is likely a member of the Upper Sco association, and is young enough that it has not yet become a main-sequence star.
Kepler-1708b is a Jupiter-sized exoplanet orbiting the Sun-like star Kepler-1708, located in the constellation of Cygnus approximately 5,600 light years away from Earth. It was first detected in 2011 by NASA's Kepler mission using the transit method, but was not identified as a candidate planet until 2019. In 2021, a candidate Neptune-sized exomoon in orbit around Kepler-1708b was found by astronomer David Kipping and colleagues in an analysis using Kepler transit data. However, subsequent research has raised discrepancies about the possible existence of an exomoon, similar to that of Kepler-1625b.