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PSR B1257+12, alternatively designated PSR J1300+1240, is a millisecond
pulsar A pulsar (''pulsating star, on the model of quasar'') is a highly magnetized rotating neutron star that emits beams of electromagnetic radiation out of its Poles of astronomical bodies#Magnetic poles, magnetic poles. This radiation can be obse ...
, from the
Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...
, in the
constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...
Virgo Virgo may refer to: Arts and entertainment * Virgo (film), a 1970 Egyptian film * Virgo (character), several Marvel Comics characters * Virgo Asmita, a character in the manga ''Saint Seiya: The Lost Canvas'' * ''Virgo'' (album), by Virgo Four, ...
, rotating at about 161 times per second (faster than the blade of a blender). It is also named Lich, after a powerful, fictional undead creature. The pulsar has a
planetary system A planetary system is a set of gravity, gravitationally bound non-stellar Astronomical object, bodies in or out of orbit around a star or star system. Generally speaking, systems with one or more planets constitute a planetary system, although ...
with three known pulsar planets, named "Draugr" (PSR B1257+12 b or
PSR B1257+12 A PSR B1257+12 b, alternatively designated PSR B1257+12 A, also named Draugr, is an extrasolar planet approximately away in the constellation of Virgo. The planet is the innermost object orbiting the pulsar Lich, making it a pulsar planet in t ...
), "Poltergeist" (PSR B1257+12 c, or PSR B1257+12 B), and "Phobetor" (PSR B1257+12 d, or PSR B1257+12 C). They were both the first
extrasolar planet An exoplanet or extrasolar planet is a planet outside the Solar System. 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 detect ...
s to be discovered and the first pulsar planets to be discovered—B and C in 1992 and A in 1994. A is the lowest-mass planet yet discovered by any observational technique, having somewhat less than twice the mass of Earth's moon.


Nomenclature

The convention that arose for designating pulsars was that of using the letters PSR (Pulsating Source of Radio) followed by the pulsar's
right ascension Right ascension (abbreviated RA; symbol ) is the angular distance of a particular point measured eastward along the celestial equator from the Sun at the equinox (celestial coordinates), March equinox to the (hour circle of the) point in questio ...
and degrees of
declination In astronomy, declination (abbreviated dec; symbol ''δ'') is one of the two angles that locate a point on the celestial sphere in the equatorial coordinate system, the other being hour angle. The declination angle is measured north (positive) or ...
. The modern convention prefixes the older numbers with a B meaning the coordinates are for the 1950.0
epoch In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured. The moment of epoch is usually decided b ...
. All new pulsars have a J indicating 2000.0 coordinates and also have declination including minutes. Pulsars that were discovered before 1993 tend to retain their B names rather than use their J names, but all pulsars have a J name that provides more precise coordinates of its location in the sky. On their discovery, the planets were designated PSR 1257+12 A, B, and C, ordered by increasing distance. They were discovered before the convention that extrasolar planets receive designations consisting of the star's name followed by lower-case Roman letters starting from "b", in order of discovery, was established. However, they are listed under the latter convention on astronomical databases such as
SIMBAD SIMBAD (the Set of Identifications, Measurements and Bibliography for Astronomical Data) is an astronomy, astronomical database of objects beyond the Solar System. It is maintained by the Centre de données astronomiques de Strasbourg (CDS), Fr ...
and the
Extrasolar Planets Encyclopaedia The Extrasolar Planets Encyclopaedia (also known as Encyclopaedia of exoplanetary systems and Catalogue of Exoplanets) is an astronomy website, founded in Paris, France at the Meudon Observatory by Jean Schneider in February 1995, which maintains ...
, with A becoming b, B becoming c, and C becoming d. In July 2014, the
International Astronomical Union The International Astronomical Union (IAU; , UAI) is an international non-governmental organization (INGO) with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach, education, and developmen ...
launched NameExoWorlds, a process for giving proper names to certain exoplanets and their host stars. The process involved public nomination and voting for the new names. In December 2015, the IAU announced the winning names, submitted by the Planetarium Südtirol Alto Adige in Karneid,
Italy Italy, officially the Italian Republic, is a country in Southern Europe, Southern and Western Europe, Western Europe. It consists of Italian Peninsula, a peninsula that extends into the Mediterranean Sea, with the Alps on its northern land b ...
, were Lich for the pulsar and Draugr, Poltergeist, and Phobetor for planets A, B, and C, respectively: * A ''
lich In fantasy fiction, a lich () is a type of undead creature with magical powers. Various works of fantasy fiction, such as Clark Ashton Smith's " The Empire of the Necromancers" (1932), had used ''lich'' as a general term for any corpse, animat ...
'' is an
undead The undead are beings in mythology, legend, or fiction that are deceased but behave as if they were alive. A common example of an undead being is a cadaver, corpse reanimated by supernatural forces, by the application of either the deceased's o ...
creature known for controlling other undead creatures with magic. * ''
Draugr The draugr or draug (; ; ; , ''drauv''; , ''dröger'') is a corporeal undead creature from the sagas and folktales of the Nordic countries, with varying ambiguous traits. In modern times, they are often portrayed as Norse mythology, Norse super ...
'' refers to undead creatures in
Norse mythology Norse, Nordic, or Scandinavian mythology, is the body of myths belonging to the North Germanic peoples, stemming from Old Norse religion and continuing after the Christianization of Scandinavia as the Nordic folklore of the modern period. The ...
. * ''
Poltergeist In German folklore and ghostlore, a poltergeist ( or ; ; or ) is a type of ghost or spirit that is responsible for physical disturbances, such as loud noises and objects being moved or destroyed. Most claims or fictional descriptions of polter ...
'' is a name for
supernatural Supernatural phenomena or entities are those beyond the Scientific law, laws of nature. The term is derived from Medieval Latin , from Latin 'above, beyond, outside of' + 'nature'. Although the corollary term "nature" has had multiple meanin ...
beings that create physical disturbances, from the German for "noisy ghost". * '' Phobetor'' is, in
Ovid Publius Ovidius Naso (; 20 March 43 BC – AD 17/18), known in English as Ovid ( ), was a Augustan literature (ancient Rome), Roman poet who lived during the reign of Augustus. He was a younger contemporary of Virgil and Horace, with whom he i ...
's ''
Metamorphoses The ''Metamorphoses'' (, , ) is a Latin Narrative poetry, narrative poem from 8 Common Era, CE by the Ancient Rome, Roman poet Ovid. It is considered his ''Masterpiece, magnum opus''. The poem chronicles the history of the world from its Cre ...
'', one of the thousand sons of Somnus (Sleep) who appears in dreams in the form of beasts. In 2016, the IAU organized a
Working Group on Star Names The International Astronomical Union (IAU) established a Working Group on Star Names (WGSN) in May 2016 to catalog and standardize proper names for stars for the international astronomical community. It operates under Division C – Education ...
(WGSN) to catalog and standardize proper names for stars (including
stellar remnant In astronomy, the term compact object (or compact star) refers collectively to white dwarfs, neutron stars, and black holes. It could also include exotic stars if such hypothetical, dense bodies are confirmed to exist. All compact objects have a ...
s). In its first bulletin of July 2016, the WGSN explicitly recognized the names of exoplanets and their host stars approved by the Executive Committee Working Group Public Naming of Planets and Planetary Satellites, including the names of stars adopted during the 2015 NameExoWorlds campaign. This stellar remnant is now so entered in the IAU Catalog of Star Names.


Pulsar


Discovery

PSR B1257+12 was discovered by the Polish astronomer Aleksander Wolszczan on 9 February 1990 using the
Arecibo Arecibo (; ) is a Arecibo barrio-pueblo, city and Municipalities of Puerto Rico, municipality on the northern coast of Puerto Rico, on the shores of the Atlantic Ocean, located north of Utuado, Puerto Rico, Utuado and Ciales, Puerto Rico, Ciale ...
radio telescope. It is a
millisecond pulsar A millisecond pulsar (MSP) is a pulsar with a rotational period less than about 10 milliseconds. Millisecond pulsars have been detected in radio pulsar, radio, X-ray pulsar, X-ray, and gamma ray portions of the electromagnetic spectrum. The leadi ...
, a kind of
neutron star A neutron star is the gravitationally collapsed Stellar core, core of a massive supergiant star. It results from the supernova explosion of a stellar evolution#Massive star, massive star—combined with gravitational collapse—that compresses ...
, with a rotation period of 6.22 
millisecond A millisecond (from '' milli-'' and second; symbol: ms) is a unit of time in the International System of Units equal to one thousandth (0.001 or 10−3 or 1/1000) of a second or 1000 microseconds. A millisecond is to one second, as one second i ...
s (9,650 rpm), and was found to have anomalies in the pulsation period, which led to investigations as to the cause of the irregular pulses. In 1992, Wolszczan and Dale Frail published a famous paper on the first confirmed discovery of planets outside the Solar System. Using refined methods one more planet was found orbiting this pulsar in 1994.


Characteristics

The pulsar is estimated to have a mass of 1.4 , which is typical for most neutron stars and pulsars. The radius is estimated to be around (), also common for pulsars and neutron stars. The pulsar is extremely hot, with a surface temperature of up to around . The pulsar formed one to three billion years ago from a
white dwarf A white dwarf is a Compact star, stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very density, dense: in an Earth sized volume, it packs a mass that is comparable to the Sun. No nuclear fusion takes place i ...
merger, a pair of white dwarfs colliding and collapsing to form a rapidly spinning pulsar. The discovery stimulated a search for planets orbiting other pulsars, but it turned out such planets are rare; only a handful of other pulsar planets have been confirmed.


Planetary system


Planets

In 1992, Wolszczan and Frail discovered that the pulsar had two planets. These were the first discovery of
extrasolar planet An exoplanet or extrasolar planet is a planet outside the Solar System. 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 detect ...
s to be confirmed; as pulsar planets, they surprised many astronomers who expected to find planets only around
main-sequence In astronomy, the main sequence is a classification of stars which appear on plots of stellar color versus brightness as a continuous and distinctive band. Stars on this band are known as main-sequence stars or dwarf stars, and positions of star ...
stars. Additional uncertainty surrounded the system, because of a claim of an earlier pulsar planet around PSR 1829-10 that had to be retracted due to errors in calculations. In 1994, an additional planet was discovered. Additionally, this system may have an
asteroid belt The asteroid belt is a torus-shaped region in the Solar System, centered on the Sun and roughly spanning the space between the orbits of the planets Jupiter and Mars. It contains a great many solid, irregularly shaped bodies called asteroids ...
or a
Kuiper belt The Kuiper belt ( ) is a circumstellar disc in the outer Solar System, extending from the orbit of Neptune at 30 astronomical units (AU) to approximately 50 AU from the Sun. It is similar to the asteroid belt, but is far larger—20 times ...
. The planets are believed to be the result of a second round of
planetary system A planetary system is a set of gravity, gravitationally bound non-stellar Astronomical object, bodies in or out of orbit around a star or star system. Generally speaking, systems with one or more planets constitute a planetary system, although ...
formation as a result of two
white dwarf A white dwarf is a Compact star, stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very density, dense: in an Earth sized volume, it packs a mass that is comparable to the Sun. No nuclear fusion takes place i ...
s merging with each other into a pulsar and a resulting disk of material in orbit around the star. Other scenarios include unusual
supernova remnant A supernova remnant (SNR) is the structure resulting from the explosion of a star in a supernova. The supernova remnant is bounded by an expanding shock wave, and consists of ejected material expanding from the explosion, and the interstellar mat ...
s or a quark-nova. However, the white dwarf–white dwarf merge model seems to be the most likely cause of the formation of the planets.


Retracted claim of fourth orbital body

In 1996, a possible
Saturn Saturn is the sixth planet from the Sun and the second largest in the Solar System, after Jupiter. It is a gas giant, with an average radius of about 9 times that of Earth. It has an eighth the average density of Earth, but is over 95 tim ...
-like (100 Earth mass)
gas giant A gas giant is a giant planet composed mainly of hydrogen and helium. Jupiter and Saturn are the gas giants of the Solar System. The term "gas giant" was originally synonymous with "giant planet". However, in the 1990s, it became known that Uranu ...
was announced orbiting the pulsar at a distance of about . The original hypothesis was retracted; a reinterpretation of the data led to a new hypothesis of a
dwarf planet A dwarf planet is a small planetary-mass object that is in direct orbit around the Sun, massive enough to be hydrostatic equilibrium, gravitationally rounded, but insufficient to achieve clearing the neighbourhood, orbital dominance like the ...
one-fifth the size of
Pluto Pluto (minor-planet designation: 134340 Pluto) is a dwarf planet in the Kuiper belt, a ring of Trans-Neptunian object, bodies beyond the orbit of Neptune. It is the ninth-largest and tenth-most-massive known object to directly orbit the Su ...
orbiting PSR B1257+12. It would have an average orbital distance of with an orbital period of approximately 4.6 years. The dwarf planet hypothesis was also retracted because further observations showed that the pulsation anomalies previously thought to reveal a fourth orbital body are "not periodic and can be fully explained in terms of slow changes in the pulsar's dispersion measure".


See also

*
51 Pegasi 51 Pegasi (abbreviated 51 Peg), formally named Helvetios , is a Sun-like star located from Earth in the constellation of Pegasus. It was the first main-sequence star found to have an exoplanet (designated 51 Pegasi b, officially named ...
*
Gamma Cephei Ab Gamma Cephei Ab (abbreviated γ Cephei Ab, γ Cep Ab), formally named Tadmor , is an exoplanet approximately 45 light-years away in the constellation of Cepheus that orbits Gamma Cephei A. The planet was suspected to exist in 1988, and later c ...
* List of exoplanets discovered before 2000 - Draugr, Poltergeist and Phobetor * PSR B1620-26


References


Further reading

* *


External links


Pulsar PlanetsPSR 1257+12
on
The Extrasolar Planets Encyclopaedia
' * *Lytle, Wayne (1992)
"Does This Pulsar Have Orbiting Planets?"
Cornell Theory Center {{DEFAULTSORT:PSR B1257+12 01 Science and technology in Poland Virgo (constellation) Planetary systems with three confirmed planets
Lich In fantasy fiction, a lich () is a type of undead creature with magical powers. Various works of fantasy fiction, such as Clark Ashton Smith's " The Empire of the Necromancers" (1932), had used ''lich'' as a general term for any corpse, animat ...