PSR B1257 12 C
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PSR B1257+12 C, alternatively designated PSR B1257+12 d and also named Phobetor, is a
super-Earth A super-Earth is a type of exoplanet with a mass higher than Earth, but substantially below those of the Solar System's ice giants, Uranus and Neptune, which are 14.5 and 17.1 times Earth's, respectively. The term "super-Earth" refers only to t ...
exoplanet 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 det ...
orbiting the
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 ...
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 ...
approximately away from
Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...
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 ...
of
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, ...
. It was one of the first planets ever discovered outside the
Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...
. It was discovered using the pulsar timing method, where the regular pulses of a pulsar are measured to determine if there is a planet causing variations in the data. 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 ...
(IAU) launched
NameExoWorlds NameExoWorlds (also known as IAU NameExoWorlds) were various projects managed by the International Astronomical Union (I.A.U.) to encourage names to be submitted for astronomical objects, notably exoplanets. The accepted names would later be cons ...
, 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 name was Phobetor for this planet. The winning name was submitted by the Planetarium Südtirol Alto Adige in
Karneid Karneid (; ) is a ''comune'' (municipality) in South Tyrol in northern Italy, located about east of the city of Bolzano and a village. It is also the location of Karneid castle. Geography As of 30 November 2010, it had a population of 3,311 an ...
,
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 ...
. 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 In Roman mythology, Somnus ("sleep") is the personification of sleep. His Greek counterpart is Hypnos. Somnus resided in the underworld. According to Virgil, Somnus was the brother of Death ( Mors), and according to Ovid, Somnus had a 'thousand' ...
(Sleep) who appears in dreams in the form of beasts.


Characteristics


Mass, radius and temperature

Phobetor is a
super-Earth A super-Earth is a type of exoplanet with a mass higher than Earth, but substantially below those of the Solar System's ice giants, Uranus and Neptune, which are 14.5 and 17.1 times Earth's, respectively. The term "super-Earth" refers only to t ...
, an exoplanet that has a
radius In classical geometry, a radius (: radii or radiuses) of a circle or sphere is any of the line segments from its Centre (geometry), center to its perimeter, and in more modern usage, it is also their length. The radius of a regular polygon is th ...
and
mass Mass is an Intrinsic and extrinsic properties, intrinsic property of a physical body, body. It was traditionally believed to be related to the physical quantity, quantity of matter in a body, until the discovery of the atom and particle physi ...
larger than that of Earth. It has an
equilibrium temperature The planetary equilibrium temperature is a theoretical temperature that a planet would be if it were in radiative equilibrium, typically under the assumption that it radiates as a black body being heated only by its parent star. In this model, th ...
of . It has a mass of 3.9 and a likely radius of 1.5 , based on its mass.


Host star

The planet orbits a
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 ...
named
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 ...
. The stellar remnant has a mass of 1.4 and a radius of around 0.000015 (10
kilometre The kilometre (SI symbol: km; or ), spelt kilometer in American English, American and Philippine English, is a unit of length in the International System of Units (SI), equal to one thousand metres (kilo- being the SI prefix for ). It is the ...
s). It has a surface temperature of ≤ and is one billion years old, with a small margin of error. In comparison, the Sun is about 4.6 billion years old and has a surface temperature of 5,778 K. The star's
apparent magnitude Apparent magnitude () is a measure of the Irradiance, brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction (astronomy), ...
, or how bright it appears from Earth's perspective, is 12.2. Therefore, it is too dim to be seen with the naked eye.


Orbit

Phobetor orbits its host star about every 98 days at a distance of (close to the orbital distance of Mercury from the Sun, which is 0.38 AU).


Formation

When Phobetor and its neighbors were discovered, scientists were puzzled on how the planets formed. Normally, planets orbiting around a massive star would evaporate when its host star exploded in a
supernova A supernova (: supernovae or supernovas) is a powerful and luminous explosion of a star. A supernova occurs during the last stellar evolution, evolutionary stages of a massive star, or when a white dwarf is triggered into runaway nuclear fusion ...
due to the intense heat (up to 1,000,000 K) and radiation. Several theories have been proposed for how the planets around Lich formed. One theory suggested that the planets actually had existed before the host star exploded in a
supernova A supernova (: supernovae or supernovas) is a powerful and luminous explosion of a star. A supernova occurs during the last stellar evolution, evolutionary stages of a massive star, or when a white dwarf is triggered into runaway nuclear fusion ...
about 1 billion years ago; however, this is inconsistent as the ejected material from a supernova would be enough to vaporize any planets close to the star. Also, multiple issues arise with this theory that debates nearly impossible steps on how the planets ended up in their current places. Thus, the scenario has been dropped. One scenario proposed a massive binary system in which the planets formed around, with the more massive companion exploding in a supernova. The neutron star would then orbit the secondary companion (forming an X-ray binary) until the now-
red supergiant Red supergiants (RSGs) are stars with a supergiant luminosity class ( Yerkes class I) and a stellar classification K or M. They are the largest stars in the universe in terms of volume, although they are not the most massive or luminous. Betelg ...
exceeded its
Roche lobe In astronomy, the Roche lobe is the region around a star in a binary system within which orbiting material is gravitationally bound to that star. It is an approximately teardrop-shaped region bounded by a critical gravitational equipotential, ...
and began spilling material onto the neutron star, with the transfer being so dramatic that it forms a
Thorne–Żytkow object A Thorne–Żytkow object (TŻO or TZO), a type of hybrid star, is a conjectured type of star wherein a red giant or Red supergiant star, red supergiant contains a neutron star at its core, formed from the Stellar collision, collision of the gian ...
. However, this does not explain how the pulsar would reach a spin rate of 6 milliseconds, so the model is still being questioned. Another model stated that the planets might have formed from a fallback disk from the supernova remnant. The main problem is that the resulting pulsar would be a radio pulsar, not the type of pulsar that PSR B1257+12 is. Thus, it is unlikely that this was how the planet formed. The most widely accepted model for the formation of the planets around Lich is that they were 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. The white dwarfs would be in a binary orbit, with the orbit slowly decaying until the less-massive white dwarf star filled its Roche lobe. If the mass ratio is large, the less-massive companion would be disrupted, forming a disk around the more massive companion. The star would accrete this material, and would result in its mass increasing until it reaches the
Chandrasekhar limit The Chandrasekhar limit () is the maximum mass of a stable white dwarf star. The currently accepted value of the Chandrasekhar limit is about (). The limit was named after Subrahmanyan Chandrasekhar. White dwarfs resist gravitational collapse pr ...
, at which point it would experience core collapse and transform into a rapidly rotating
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 ...
, or, to be precise, a pulsar. After the explosion, the disk around the pulsar would still be massive enough (about 0.1 ) to form planets, which would likely be
terrestrial Terrestrial refers to things related to land or the planet Earth, as opposed to extraterrestrial. Terrestrial may also refer to: * Terrestrial animal, an animal that lives on land opposed to living in water, or sometimes an animal that lives on o ...
, due to them being composed of white dwarf material such as
carbon Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...
and
oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...
.


Nomenclature

Phobetor, the common name for the planet, is the name of a character in Ovid's ''Metamorphoses''. In Latin, ''phobetor'' literally means "frightener". On its discovery, the planet was designated PSR 1257+12 C and later PSR B1257+12 C. It was discovered before the convention that extrasolar planets receive designations consisting of the star's name followed by lowercase
Roman letters The Latin script, also known as the Roman script, is a writing system based on the letters of the classical Latin alphabet, derived from a form of the Greek alphabet which was in use in the ancient Greek city of Cumae in Magna Graecia. The Gree ...
starting from "b" was established. However, it is 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 Encyclopedia 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 (Extrasolar Planets Encyclopaedia) ...
. Hence the alternative designation PSR B1257+12 d. 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.Lyne, Andrew G.; Graham-Smith, Francis. ''Pulsar Astronomy.'' Cambridge University Press, 1998.


See also

*
List of exoplanets discovered before 2000 This is a list of exoplanets discovered before 2000. For exoplanets detected only by radial velocity, the mass value is actually a lower limit. (See Minimum mass for more information.) While the existence of a substellar companion to Gamma Cephei ...
- SPR B1257+12 d


References

*


External links


Pulsar Planets
{{Sky, 13, 00, 01, +, 12, 40, 57, 980 Super-Earths Pulsar planets Virgo (constellation) Terrestrial planets Exoplanets discovered in 1992 Exoplanets detected by timing Exoplanets with proper names