Proxima Centauri

Coordinates: Sky mapCoordinates: Sky map14h 29m 42.9487s, −62° 40′ 46.141″

Proxima Centauri
New shot of Proxima Centauri, our nearest neighbour.jpg
Proxima Centauri as seen by Hubble
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
ConstellationCentaurus
PronunciationUK: /,[1] US: i/[2]
Right ascension14h 29m 42.94853s[3]
Declination−62° 40′ 46.1631″[3]
Apparent magnitude (V)11.13[4]
Characteristics
Evolutionary stageMain sequence red dwarf
Spectral typeM5.5Ve[5]
Apparent magnitude (U)14.21[4]
Apparent magnitude (B)12.95[4]
Apparent magnitude (V)11.13[4]
Apparent magnitude (R)9.45[4]
Apparent magnitude (I)7.41[4]
Apparent magnitude (J)5.357±0.023[6]
Apparent magnitude (H)4.835±0.057[6]
Apparent magnitude (K)4.384±0.033[6]
U−B color index1.26
B−V color index1.82
V−R color index1.68
R−I color index2.04
J−H color index0.522
J−K color index0.973
Variable typeUV Ceti ("flare star")[7]
Astrometry
Radial velocity (Rv)−22.204±0.032[8] km/s
Proper motion (μ) RA: −3775.75[3] mas/yr
Dec.: 765.54[3] mas/yr
Parallax (π)768.5 ± 0.2[9] mas
Distance4.244 ± 0.001 ly
(1.3012 ± 0.0003 pc)
Absolute magnitude (MV)15.60[10]
Orbit[8]
PrimaryAlpha Centauri AB
CompanionProxima Centauri
Period (P)547000+6600
−4000
yr
Semi-major axis (a)8700+700
−400
 AU
Eccentricity (e)0.50+0.08
−0.09
Inclination (i)107.6+1.8
−2.0
°
Longitude of the node (Ω)126±5°
Periastron epoch (T)+283+59
−41
Argument of periastron (ω)
(secondary)
72.3+8.7
−6.6
°
Details
Mass0.1221±0.0022[8] M
Radius0.1542±0.0045[8] R
Luminosity (bolometric)0.0017[11] L
Luminosity (visual, LV)0.00005[nb 1] L
Surface gravity (log g)5.20±0.23[12] cgs
Temperature3042±117[12] K
Metallicity [Fe/H]0.21[13] dex
Rotation82.6±0.1[14] days
Rotational velocity (v sin i)< 0.1[14] km/s
Age4.85[15] Gyr
Other designations
Alpha Centauri C, CCDM J14396-6050C, GCTP 3278.00, GJ 551, HIP 70890, LFT 1110, LHS 49, LPM 526, LTT 5721, NLTT 37460, V645 Centauri[16]
Database references
data

Proxima Centauri (from Latin, meaning 'nearest [star] of Centaurus'[1]), or Alpha Centauri C, is a red dwarf, a small low-mass star, about 4.244 light-years (1.301 pc)[9] from the Sun in the constellation of Centaurus.[17][18] It was discovered in 1915 by Robert Innes and is the nearest-known star to the Sun.[15] With an apparent magnitude of 11.05, it is too faint to be seen with the naked eye. With high likelihood, Proxima Centauri forms a third component of the Alpha Centauri system, currently with a separation of about 12,950 AU (1.94 trillion km) and an orbital period of 550,000 years.[8] At present Proxima is 2.18° to the southwest of Alpha Centauri.[19]

Because of Proxima Centauri's proximity to Earth, its angular diameter can be measured directly. The star is about one-seventh the actual diameter of the Sun.[15] It has a mass about an eighth of the Sun's mass (M), and its average density is about 33 times that of the Sun.[nb 2] Although it has a very low average luminosity, Proxima is a flare star that undergoes random dramatic increases in brightness because of magnetic activity.[20] The star's magnetic field is created by convection throughout the stellar body, and the resulting flare activity generates a total X-ray emission similar to that produced by the Sun.[21] The mixing of the fuel at Proxima Centauri's core through convection and its relatively low energy-production rate mean that it will be a main-sequence star for another four trillion years,[22] or nearly 300 times the current age of the universe.[23]

In 2016, the European Southern Observatory announced the discovery of Proxima b,[24][25][26] a planet orbiting the star at a distance of roughly 0.05 AU (7.5 million km) with an orbital period of approximately 11.2 Earth days. Its estimated mass is at least 1.3 times that of the Earth. The equilibrium temperature of Proxima b is estimated to be within the range of where water could exist as liquid on its surface, thus placing it within the habitable zone of Proxima Centauri,[24][27][28] although because Proxima Centauri is a red dwarf and a flare star, whether it could support life is disputed.[29][30]Previous searches for orbiting companions had ruled out the presence of brown dwarfs and supermassive planets.[31][32]

Observation

In 1915, the Scottish astronomer Robert Innes, Director of the Union Observatory in Johannesburg, South Africa, discovered a star that had the same proper motion as Alpha Centauri.[33][34][35][36] He suggested that it be named Proxima Centauri[37] (actually Proxima Centaurus).[38] In 1917, at the Royal Observatory at the Cape of Good Hope, the Dutch astronomer Joan Voûte measured the star's trigonometric parallax at 0.755±0.028 and determined that Proxima Centauri was approximately the same distance from the Sun as Alpha Centauri. It was also found to be the lowest-luminosity star known at the time.[39] An equally accurate parallax determination of Proxima Centauri was made by American astronomer Harold L. Alden in 1928, who confirmed Innes's view that it is closer, with a parallax of 0.783±0.005.[34][37]

Stars closest to the Sun, including Proxima Centauri[40]

In 1951, American astronomer Harlow Shapley announced that Proxima Centauri is a flare star. Examination of past photographic records showed that the star displayed a measurable increase in magnitude on about 8% of the images, making it the most active flare star then known.[41][42] The proximity of the star allows for detailed observation of its flare activity. In 1980, the Einstein Observatory produced a detailed X-ray energy curve of a stellar flare on Proxima Centauri. Further observations of flare activity were made with the EXOSAT and ROSAT satellites, and the X-ray emissions of smaller, solar-like flares were observed by the Japanese ASCA satellite in 1995.[43] Proxima Centauri has since been the subject of study by most X-ray observatories, including XMM-Newton and Chandra.[44]

In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars.[45] The WGSN approved the name Proxima Centauri for this star on August 21, 2016 and it is now so included in the List of IAU-approved Star Names.[46]

Because of Proxima Centauri's southern declination, it can only be viewed south of latitude 27° N.[nb 3] Red dwarfs such as Proxima Centauri are far too faint to be seen with the naked eye. Even from Alpha Centauri A or B, Proxima would only be seen as a fifth magnitude star.[47][48] It has an apparent visual magnitude of 11, so a telescope with an aperture of at least 8 cm (3.1 in) is needed to observe it, even under ideal viewing conditions—under clear, dark skies with Proxima Centauri well above the horizon.[49]

Other Languages
العربية: قنطور الأقرب
aragonés: Proxima Centauri
asturianu: Proxima Centauri
беларуская: Проксіма Цэнтаўра
brezhoneg: Alpha Centauri C
čeština: Proxima Centauri
français: Proxima Centauri
Bahasa Indonesia: Proxima Centauri
íslenska: Proxima Centauri
Basa Jawa: Proxima Centauri
Kiswahili: Proxima Centauri
македонски: Проксима Кентаур
Bahasa Melayu: Proxima Centauri
Nederlands: Proxima Centauri
norsk nynorsk: Proxima Centauri
oʻzbekcha/ўзбекча: Proksima
پنجابی: کنتوری نال
português: Proxima Centauri
русиньскый: Проксіма Центаурі
sicilianu: Proxima Centauri
Simple English: Proxima Centauri
slovenčina: Proxima Centauri
српски / srpski: Проксима Кентаури
srpskohrvatski / српскохрватски: Proxima Centauri
татарча/tatarça: Проксима Кентавр
українська: Проксима Центавра
Tiếng Việt: Cận Tinh
中文: 比邻星