Ross 154
Template:Short description Template:Starbox begin Template:Starbox image Template:Starbox observe Template:Starbox character Template:Starbox astrometry Template:Starbox detail Template:Starbox catalog Template:Starbox reference Template:Starbox end Ross 154 (V1216 Sgr) is a star in the southern zodiac constellation of Sagittarius. It has an apparent visual magnitude of 10.44,<ref name=RECONS/> making it much too faint to be seen with the naked eye. At a minimum, viewing Ross 154 requires a telescope with an aperture of Template:Convert under ideal conditions.<ref name=mills1994/> The distance to this star can be estimated from parallax measurements, which places it at Template:Convert away from Earth.<ref name="Gaia3"/> It is the nearest star in the southern constellation Sagittarius, and one of the nearest stars to the Sun.
DescriptionEdit
This star was first catalogued by American astronomer Frank Elmore Ross in 1925, and formed part of his fourth list of new variable stars.<ref name=aj37_91/> In 1926, he added it to his second list of stars showing a measurable proper motion after comparing its position with photographic plates taken earlier by fellow American astronomer E. E. Barnard.<ref name=aj36_856_124/> A preliminary parallax value of Template:Nowrap was determined in 1937 by Walter O'Connell using photographic plates from the Yale telescope in Johannesburg, South Africa. This placed the star at the sixth position of the then-known nearby stars.<ref name=aj46_1078_204/>
Ross 154 was found to be a UV Ceti-type flare star, with a mean time between major flares of about two days.<ref name=ibvs1221_1/> The first such flare activity was observed from Australia in 1951 when the star increased in magnitude by 0.4.<ref name=jrasc47_23/> Typically, the star will increase by 3–4 magnitudes during a flare.<ref name=ibvs461_1/> The strength of the star's surface magnetic field is an estimated Template:Nowrap.<ref name=apj656_2_1121/> Ross 154 is an X-ray source and it has been detected by several X-ray observatories. The quiescent X-ray luminosity is about Template:Nowrap.<ref name=apj676/> X-ray flare emission from this star has been observed by Chandra observatory, with a particularly large flare emitting Template:Nowrap.<ref name=apj676/>
A stellar classification of M3.5V<ref name=RECONS/> makes this a red dwarf star that is generating energy through the nuclear fusion of hydrogen at its core. It has an estimated 18% of the Sun's mass and 20% of the Sun's radius,<ref name=Pineda2021/> but it is radiating only 0.4% of the luminosity of the Sun.<ref name=Pineda2021/> In contrast to the Sun where convection only occurs in the outer layers, a red dwarf with a mass this low will be entirely convective.<ref name=aaa496_3_787/> Based on the relatively high projected rotation, this is probably a young star with an estimated age of less than a billion years.<ref name=apj676/> The abundance of elements heavier than helium is about half that in the Sun.<ref name=apj676/>
No low-mass companions have been discovered in orbit around Ross 154.<ref name=aj123_4_2027/> Nor does it display the level of excess infrared emission that would suggest the presence of circumstellar dust. Such debris disks are rare among M-type star systems older than about 10 million years, having been primarily cleared away by drag from the stellar wind.<ref name=apj631_2_1161/> The space velocity components of this star in the galactic coordinate system are Template:Nowrap = [–12.2, –1.0, –7.2]Template:Nowrap.<ref name=cdsannot/> It has not been identified as a member of a specific stellar moving group<ref name=mnras328_1_45/> and is orbiting through the Milky Way galaxy at a distance from the core that varies from Template:Convert with an orbital eccentricity of 0.052.<ref name=rmaa34_37/> Based on its low velocity relative to the Sun, this is believed to be a young disk (Population I) star.<ref name=aj79_702/> This star will make its closest approach to the Sun in about 157,000 years, when it comes within Template:Convert.<ref name=al36_3_220/>
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Template:Sky Template:Nearest systems Template:Stars of Sagittarius