Alpha Coronae Australis

Alpha Coronae Australis or α Coronae Australis, officially named Meridiana (/məˌrɪdiˈænə/),^[10] is the brightest star in the constellation of Corona Australis and is located about 125 light-years from Earth.

α Coronae Australis

Location of α CrA (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Corona Australis
Right ascension	19h 09m 28.34097s[1]
Declination	−37° 54′ 16.1022″[1]
Apparent magnitude (V)	4.102[2]
Characteristics
Spectral type	A2V[3]
U−B color index	+0.06[4]
B−V color index	+0.04[4]
Astrometry
Radial velocity (Rv)	−18.40±1.78[5] km/s
Proper motion (μ)	RA: +84.87[1] mas/yr Dec.: −95.99[1] mas/yr
Parallax (π)	26.02±0.25 mas[1]
Distance	125 ± 1 ly (38.4 ± 0.4 pc)
Absolute magnitude (MV)	1.11[6]
Details
Mass	2.57[7] M☉
Radius	2.21[3] R☉
Luminosity	31[8] L☉
Surface gravity (log g)	4.08[7] cgs
Temperature	9,916±337[7] K
Rotational velocity (v sin i)	195[9] km/s
Age	254[2] Myr
Other designations
Meridiana, α CrA, Alf CrA, CD−38°13350, FK5 718, GC 26360, HD 178253, HIP 94114, HR 7254, SAO 210990, IRAS 19060-3759, 2MASS J19092834-3754157[4]
Database references
SIMBAD	data

Nomenclature

α Coronae Australis (Latinised to Alpha Coronae Australis) is the star's Bayer designation.

It is the only star in the constellation with a traditional proper name, Alphekka Meridiana (Latin for 'Alphekka South'), after Alphecca, the brightest star in the constellation Corona Borealis.^{[citation needed]} The name Alphecca or Alphekka is Arabic, short for نير الفكّة nayyir al-fakka "the bright (star) of the broken (ring of stars)".^[11] In 2016, the IAU organized a Working Group on Star Names (WGSN)^[12] to catalog and standardize proper names for stars. The WGSN approved the name Meridiana for this star on 5 September 2017 and it is now so included in the List of IAU-approved Star Names.^[10]

In Chinese, 鱉 (Biē), meaning River Turtle, refers to an asterism consisting of Alpha Coronae Australis, Alpha Telescopii, Eta¹ Coronae Australis, Zeta Coronae Australis, Delta Coronae Australis, Beta Coronae Australis, Gamma Coronae Australis, Epsilon Coronae Australis, HD 175362, Kappa² Coronae Australis and Theta Coronae Australis.^[13] Consequently, the Chinese name for Alpha Coronae Australis itself is 鱉六 (Biēliù, English: the Sixth Star of River Turtle.).^[14]

Properties

Alpha Coronae Australis belongs to the spectral class A2Va, making it an A-type star like Vega. Like the latter, it has excess infrared radiation, which indicates it may be ringed by a disk of dust.^[8] It has an apparent magnitude of +4.10.^[4] The star's mass and radius are estimated at 2.3 times the Sun's mass and radius. With an effective temperature of roughly 9,100 K, the star radiates a total luminosity of about 31 times the Sun's.^[8] This star is roughly 254 million years old.^[2] A rapidly rotating star, it spins at almost 200 km per second at the equator, making a complete revolution in approximately 14 hours,^[9] close to its breakup velocity.

See also

• Lists of stars in the constellation Corona Australis
• Class A Stars
• Vega
• Circumstellar disk