| 词条 | V391 Pegasi |
| 释义 |
| name = V391 Pegasi }}{{Starbox observe | epoch = J2000.0 | constell = Pegasus | ra = {{RA|22|04|12.2}} | dec = {{DEC|+26|25|08}} | appmag_v = +14.57 }}{{Starbox character | class = sdB | variable = V361 Hydrae (or sdBVr) }}{{Starbox astrometry | dist_ly = 4570 | dist_pc = 1400 | absmag_v = +3.84 }}{{Starbox detail | age = >10 × 109 | mass = 0.5±0.05 | radius = 0.23±0.03 | gravity=5.15 | luminosity = 15.4 | temperature = 29300 ± 500 }}{{Starbox catalog | names = HS 2201+2610 }}{{Starbox reference | Simbad = V391+Peg | ARICNS = }}{{Starbox end}} V391 Pegasi, also catalogued as HS 2201+2610, is a blue-white subdwarf star approximately 4,570 light-years away in the constellation of Pegasus. The star is classified as an "extreme horizontal branch star". It is small, with only half the mass and a bit less than one-quarter the diameter of the Sun. It has luminosity 15.4 times the Sun.{{Citation needed|date=September 2007}} It could be quite old, perhaps in excess of 10 Gyr. It is a pulsating variable star of the V361 Hydrae type (or also called sdBVr type).{{citation needed|date=February 2014}} FormationSubdwarf B stars such as V391 Pegasi are thought to be the result of the ejection of the hydrogen envelope of a red giant star at or just before the onset of helium fusion. The ejection left only a tiny amount of hydrogen on the surface - less than 1/1000 of the total stellar mass. The future for the star is to eventually cool down to make a low mass white dwarf. Most stars retain more of their hydrogen after the first red giant phase, and eventually become asymptotic giant branch stars. The reason that some stars, like V391 Pegasi, lose so much mass is not well known.{{citation needed|date=February 2014}} Planetary systemIn 2007, a gas giant planet designated V391 Pegasi b was found in orbit by variable star timing method. This planet around an "extreme horizontal branch" star provided clues about what could happen to the planets in the Solar System when the Sun turns into a red giant within the next 5 billion years.{{citation needed|date=February 2014}} {{OrbitboxPlanet begin}}{{OrbitboxPlanet| exoplanet = b | mass = >3.2±0.7 | period = 1170±44 | semimajor = 1.7±0.1 | eccentricity = 0.00 }}{{Orbitbox end}} ReferencesSources
External links
4 : B-type subdwarfs|Pegasus (constellation)|Very rapidly pulsating hot stars|Objects with variable star designations |
| 随便看 |
|
开放百科全书收录14589846条英语、德语、日语等多语种百科知识，基本涵盖了大多数领域的百科知识，是一部内容自由、开放的电子版国际百科全书。