View source for PSR B1257+12 C

{{Short description|Super-Earth orbiting PSR B1257+12 C}}
{{Infobox planet
| name = PSR B1257+12 C / Phobetor
| image = Exoplanet Comparison PSR B1257+12 C.png
| caption = Size comparison of Phobetor with Earth and Neptune
<br />(Based on selected hypothetical [[:File:Exoplanet Comparison PSR B1257+12 C.png#Summary|modeled compositions]])
<!-- DISCOVERY           -->| discoverer = [[Aleksander Wolszczan]]
| discovery_site = Poland
| discovered = 22 January 1992
| discovery_method = Pulsar Timing
<!-- DESIGNATIONS        -->
<!-- ORBITAL             -->| apsis = astron
| semimajor = {{convert|0.46|AU|e6km|abbr=unit}}<ref name="konacki2003">{{cite journal | url=http://www.iop.org/EJ/article/1538-4357/591/2/L147/17269.html | author=Konacki, M. | author2=Wolszczan, A. | title=Masses and Orbital Inclinations of Planets in the PSR B1257+12 System | journal=The Astrophysical Journal | volume=591 | issue=2 | pages=L147–L150 | date=2003 | doi=10.1086/377093 | bibcode=2003ApJ...591L.147K | arxiv=astro-ph/0305536 | s2cid=18649212 | access-date=2009-09-13 | archive-date=2020-01-04 | archive-url=https://web.archive.org/web/20200104010006/http://www.iop.org/EJ/article/1538-4357/591/2/L147/17269.html | url-status=dead }}</ref>
| eccentricity = 0.0252 ± 0.0002<ref name="konacki2003"/>
| period = 98.2114 ± 0.0002<ref name="konacki2003"/> [[day|d]]
| inclination = 47 ± 3<ref name="konacki2003"/><ref group="note">The method used to determine the inclination includes a degeneracy because of the impossibility of determining whether the orbital motion is clockwise or anticlockwise. The alternate value of the inclination is 133 ± 3°.</ref>
| time_periastron = 2,449,766.5 ± 0.1<ref name="konacki2003"/>
| arg_peri = 108.3 ± 0.5<ref name="konacki2003"/>
| star = [[PSR B1257+12|Lich]]
<!-- PHYS CHARS          -->| mean_radius = ~1.5 {{Earth radius|link=y}}
| mass = 3.9 (± 0.2)<ref name="konacki2003"/> {{Earth mass|sym=y|link=y}}
| single_temperature = {{cvt|169|K|C F}}<ref>[http://www.extrasolar.net/planettour.asp?PlanetID=28 Extrasolar Visions - PSR 1257+12 C] {{webarchive|url=https://web.archive.org/web/20101226042333/http://extrasolar.net/planettour.asp?PlanetID=28 |date=December 26, 2010 }}</ref>
<!-- ATMOSPHERE          --> 
<!-- NOTES               -->}}
'''PSR B1257+12 C''', alternatively designated '''PSR B1257+12 d''' and also named '''Phobetor''', is a [[super-Earth]] [[exoplanet]] orbiting the [[pulsar]] [[PSR B1257+12|Lich]] approximately {{convert|2315|ly|pc e15km|abbr=off|lk=on|0}} away from [[Earth]] in the [[constellation]] of [[Virgo (constellation)|Virgo]]. It was one of the first planets ever discovered outside the [[Solar System]]. It was discovered using the [[Methods of detecting exoplanets#Pulsar timing|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]] (IAU) launched [[NameExoWorlds]], a process for giving proper names to certain exoplanets and their host stars.<ref>[http://www.iau.org/news/pressreleases/detail/iau1404/ NameExoWorlds: An IAU Worldwide Contest to Name Exoplanets and their Host Stars]. IAU.org. 9 July 2014</ref> The process involved public nomination and voting for the new names.<ref>{{Cite web |url=http://nameexoworlds.iau.org/process |title=NameExoWorlds The Process |access-date=2015-09-05 |archive-date=2015-08-15 |archive-url=https://web.archive.org/web/20150815025117/http://www.nameexoworlds.iau.org/process |url-status=dead }}</ref> In December 2015, the IAU announced the winning name was Phobetor for this planet.<ref>[http://www.iau.org/news/pressreleases/detail/iau1514/ Final Results of NameExoWorlds Public Vote Released], International Astronomical Union, 15 December 2015.</ref><ref>[http://nameexoworlds.iau.org/systems/106 The Proposals page for Mu Arae] {{Webarchive|url=https://web.archive.org/web/20170405053828/http://nameexoworlds.iau.org/systems/106 |date=2017-04-05 }}, International Astronomical Union, 2016-01-03.</ref> The winning name was submitted by the Planetarium Südtirol Alto Adige in [[Karneid]], [[Italy]]. [[Phobetor]] is, in [[Ovid]]'s ''[[Metamorphoses]]'', one of the thousand sons of [[Somnus]] (Sleep) who appears in dreams in the form of beasts.<ref>[[Ovid]], ''[[Metamorphoses]]'' [https://www.loebclassics.com/view/ovid-metamorphoses/1916/pb_LCL043.165.xml 11.638&ndash;641].</ref>

==Characteristics==

[[File:Artist's concept of PSR B1257+12 system.jpg|thumb|left|An artist's conception of the pulsar planet Phobetor with bright aurorae.]]

===Mass, radius and temperature===
Phobetor is a [[super-Earth]], an exoplanet that has a [[radius]] and [[mass]] larger than that of Earth. It has an [[equilibrium temperature]] of {{cvt|567|K|C F}}.<ref name="PHL">{{Cite web| title=PSR 1257 12 d (Hot Superterran) | url=http://www.hpcf.upr.edu/~abel/phl/hec_plots/hec_orbit/hec_orbit_PSR_1257_12_d.png | archive-url=https://web.archive.org/web/20160826011328/http://www.hpcf.upr.edu/~abel/phl/hec_plots/hec_orbit/hec_orbit_PSR_1257_12_d.png | archive-date=2016-08-26}}</ref> It has a mass of 3.9 {{Earth mass|sym=y}} and a likely radius of 1.5 {{Earth radius}}, based on its mass.

===Host star===
The planet orbits a [[pulsar]] named [[PSR B1257+12|Lich]]. The stellar remnant has a mass of 1.4 {{Solar mass}} and a radius of around 0.000015 {{Solar radius}} (10 [[kilometre]]s). It has a surface temperature of ≤{{val|28856|ul=K|fmt=commas}} and is one billion years old, with a small margin of error. In comparison, the Sun is about 4.6 billion years old<ref>{{cite web |url=http://www.universetoday.com/18237/how-old-is-the-sun/ |title=How Old is the Sun? |author=Fraser Cain |date=16 September 2008 |publisher=[[Universe Today]] |access-date=19 February 2011}}</ref> and has a surface temperature of 5,778 K.<ref>{{cite web |url=http://www.universetoday.com/18092/temperature-of-the-sun/ |title=Temperature of the Sun |author=Fraser Cain |date=September 15, 2008 |publisher=Universe Today |access-date=19 February 2011}}</ref>

The star's [[apparent magnitude]], 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 {{val|0.46|ul=AU|fmt=commas}} (close to the orbital distance of Mercury from the Sun, which is 0.38 AU).

==Formation==
{{multiple image
| align = left
| direction = horizontal
| width = 
| header = Pulsar planet formation scenarios
| caption_align = center
| header_align = center
| image1 = Aссretion Spins Pulsar to Millisecond Range.jpg
| width1 = 225
| caption1 = Artist's impression of a pulsar accreting material from a stellar companion
| image2 = 4U 0142+61 paint.jpg
| width2 = 200
| caption2 = Artist's impression of a fallback disk forming around a pulsar
}}
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]] 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]] 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.<ref name="Formation">{{cite journal | author=Podsiadlowski, P. | title=Planet Formation Scenarios | journal=Planets Around Pulsars; Proceedings of the Conference, California Inst. Of Technology, Pasadena, Apr. 30-May 1, 1992 | pages=149–165 | date=1993 | volume=36 | bibcode=1993ASPC...36..149P }}</ref>

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]] exceeded its [[Roche lobe]] and began spilling material onto the neutron star, with the transfer being so dramatic that it forms a [[Thorne–Żytkow object]]. However, this does not explain how the pulsar would reach a spin rate of 6 milliseconds, so the model is still being questioned.<ref name="Formation"/>

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.<ref name="Formation"/>

The most widely accepted model for the formation of the planets around Lich is that they were a result of two [[white dwarf]]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]], at which point it would experience core collapse and transform into a rapidly rotating [[neutron star]], or, to be precise, a pulsar. After the explosion, the disk around the pulsar would still be massive enough (about 0.1 {{Solar mass}}) to form planets, which would likely be [[terrestrial planet|terrestrial]], due to them being composed of white dwarf material such as [[carbon]] and [[oxygen]].<ref name="Formation"/>

==Nomenclature==
{{further|Extrasolar planet#Nomenclature}}

Phobetor, the common name for the planet, is the name of a character in [[Metamorphoses|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 [[Latin alphabet|Roman letters]] starting from "b" was established.<ref name="planetnaming">{{cite arXiv |title=On the naming convention used for multiple star systems and extrasolar planets |date=2010 |eprint=1012.0707 |class=astro-ph.SR |last1= Hessman |first1=F. V. |last2= Dhillon |first2=V. S. |last3= Winget |first3=D. E. |last4= Schreiber |first4=M. R. |last5= Horne |first5=K. |last6= Marsh |first6=T. R. |last7= Guenther |first7=E. |last8= Schwope |first8=A. |last9= Heber |first9=U.}}</ref> However, it is listed under the latter convention on astronomical databases such as [[SIMBAD]] and the [[Extrasolar Planets Encyclopedia]]. Hence the alternative designation PSR B1257+12 d.<references group="note"/>

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]] and degrees of [[declination]]. The modern convention prefixes the older numbers with a B meaning the coordinates are for the 1950.0 [[Epoch (astronomy)|epoch]]. 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.<ref>Lyne, Andrew G.; Graham-Smith, Francis. ''Pulsar Astronomy.'' Cambridge University Press, 1998.</ref>

{{notelist}}

== See also ==

* [[List of exoplanets discovered before 2000]] - SPR B1257+12 d

==References==
{{Reflist}}

* {{cite journal | bibcode=1992Natur.355..145W | author=Wolszczan, A. | author2=Frail, D. | title=A planetary system around the millisecond pulsar PSR1257 + 12 | journal=[[Nature (journal)|Nature]] | volume=355 | issue=6356 | pages=145–147 | date=1992 | doi=10.1038/355145a0| s2cid=4260368 }}

==External links==
{{commons category}}
* [https://web.archive.org/web/20051230112904/http://www.astro.psu.edu/users/alex/pulsar_planets.htm Pulsar Planets]

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{{PSR B1257+12}}
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[[Category:Super-Earths]]
[[Category:Pulsar planets]]
[[Category:Virgo (constellation)]]
[[Category:Terrestrial planets]]
[[Category:Exoplanets discovered in 1992]]
[[Category:Exoplanets detected by timing]]
[[Category:Exoplanets with proper names]]