TW Piscis Austrini

"Fomalhaut B" redirects here. For the former exoplanet candidate, see Fomalhaut b.
TW Piscis Austrini
Location of TW Piscis Austrini (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Piscis Austrinus
Right ascension 22h 56m 24.05256s[1]
Declination −31° 33′ 56.0306″[1]
Apparent magnitude (V) 5.44–6.51[2]
Characteristics
Spectral type K5Vp[3]
U−B color index 1.02[4]
B−V color index 1.10[4]
Variable type BY Draconis[2]
Astrometry
Radial velocity (Rv)+6.79±0.12[1] km/s
Proper motion (μ) RA: 330.203 mas/yr[1]
Dec.: −158.602 mas/yr[1]
Parallax (π)131.5525 ± 0.0275 mas[1]
Distance24.793 ± 0.005 ly
(7.602 ± 0.002 pc)
Absolute magnitude (MV)7.08[5]
Details[6]
Mass0.704±0.016 M☉
Radius0.658±0.009 R☉
Luminosity0.19[5] L☉
Temperature4,610±67 K
Metallicity [Fe/H]−0.07±0.03 dex
Rotation10.3[7] days
Rotational velocity (v sin i)2.93[3] km/s
Age440[5] Myr
Other designations
TW PsA, Gl 879, HR 8721, CD−32°17321, HD 216803, LTT 9283, GCTP 5562.00, SAO 214197, CP(D)−32°6550, HIP 113283[8]
Database references
SIMBADdata
ARICNSdata

TW Piscis Austrini (also known as Fomalhaut B) is a main sequence star in the constellation Piscis Austrinus. It lies relatively close to the Sun, at an estimated distance of 24.8 light-years (7.6 parsecs). To an observer on Earth the star is visually separated from its larger companion Fomalhaut (A) by 2 degrees—the width of four full moons.[9]

A visual band light curve for TW Piscis Austrini, adapted from Busko and Torres (1978).[10] The error bar shown on the left-most point applies to all points.

The name TW Piscis Austrini is a variable star designation. This is a variable star of the type known as a BY Draconis variable, with surface brightness variations causing the changes as the star rotates. It varies slightly in apparent magnitude, ranging from 6.44 to 6.51 over a 10.3-day period.[2]

TW Piscis Austrini lies within a light-year of Fomalhaut.[11] Due to sharing the same proper motion, and the same estimated age of approximately 440 ± 40 million years, astronomers now consider them to be elements of a multiple star system.[5] A third star, dimmer and more widely separated, Fomalhaut C, gives the system the widest visual separation, to observers from Earth, at approximately 6 degrees.[9]

  1. ^ a b c d e Cite error: The named reference GaiaDR3 was invoked but never defined (see the help page).
  2. ^ a b c Cite error: The named reference gcvs was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference aaa505_1_205 was invoked but never defined (see the help page).
  4. ^ a b Cite error: The named reference clpl4 was invoked but never defined (see the help page).
  5. ^ a b c d Cite error: The named reference age_mam was invoked but never defined (see the help page).
  6. ^ Cite error: The named reference Gomes2021 was invoked but never defined (see the help page).
  7. ^ Cite error: The named reference Mamajek was invoked but never defined (see the help page).
  8. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  9. ^ a b Cite error: The named reference skyandtelescope2014-10-01 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Busko was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference schaaf2008 was invoked but never defined (see the help page).