TW Piscis Austrini
 DSS image of Fomalhaut, field of view 2.7×2.9 degrees. Credit NASA, ESA, and the Digitized Sky Survey 2. Acknowledgment: Davide De Martin (ESA/Hubble) |
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| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Piscis Austrinus (Fomalhaut A+B), Aquarius (Fomalhaut C) |
| Fomalhaut | |
| Right ascension | 22h 57m 39.0465s |
| Declination | −29° 37′ 20.050″ |
| Apparent magnitude (V) | 1.16 |
| TW Piscis Austrini | |
| Right ascension | 22h 56m 24.05327s |
| Declination | −31° 33′ 56.0351″ |
| Apparent magnitude (V) | 6.48 |
| LP 876-10 | |
| Right ascension | 22h 48m 04.47s |
| Declination | −24° 22′ 07.5″ |
| Apparent magnitude (V) | 12.618 |
| Characteristics | |
| Spectral type | A3 V / K5Vp / M4V |
| U−B color index | 0.08 / 1.02 / ? |
| B−V color index | 0.09 / 1.10 / 1.683 |
| Variable type | None / BY Draconis / ? |
| Astrometry | |
| Fomalhaut | |
| Radial velocity (Rv) | +6.5 km/s |
| Proper motion (μ) |
RA: +328.95 mas/yr Dec.: −164.67 mas/yr |
| Parallax (π) | 129.81 ± 0.47mas |
| Distance | 25.13 ± 0.09 ly (7.70 ± 0.03 pc) |
| Absolute magnitude (MV) | 1.72 |
| TW Piscis Austrini | |
| Radial velocity (Rv) | +6 km/s |
| Proper motion (μ) |
RA: −331.11 mas/yr Dec.: −158.98 mas/yr |
| Parallax (π) | 131.42 ± 0.62mas |
| Distance | 24.8 ± 0.1 ly (7.61 ± 0.04 pc) |
| Absolute magnitude (MV) | 7.08 |
| Details | |
| Fomalhaut | |
| Mass | 1.92±0.02 M☉ |
| Radius | 1.842±0.019 R☉ |
| Luminosity | 16.63±0.48 L☉ |
| Surface gravity (log g) | 4.21 cgs |
| Temperature | 8,590 K |
| Metallicity [Fe/H] | −0.03 to −0.34 dex |
| Rotational velocity (v sin i) | 93 km/s |
| Age | (4.4±0.4)×108 years |
| TW Piscis Austrini | |
| Mass | 0.725 ± 0.036 M☉ |
| Radius | 0.629 ± 0.051 R☉ |
| Luminosity | 0.19 L☉ |
| Temperature | 4,711 ± 134 K |
| Rotational velocity (v sin i) | 2.93 km/s |
| Age | 4.4 × 108 years |
| Other designations | |
| Fomalhaut: α Piscis Austrini, α PsA, Alpha PsA, 24 Piscis Austrini, CPD −30° 6685, FK5 867, Gl 881, HD 216956, HIP 113368, HR 8728, SAO 191524 | |
| TW Piscis Austrini: Fomalhaut B, TW PsA, Gl 879, HR 8721, CD -32°17321, HD 216803, LTT 9283, GCTP 5562.00, SAO 214197, CP(D)-32 6550, HIP 113283 | |
| LP 876-10: Fomalhaut C, 2MASS J22480446-2422075, NLTT 54872, GSC 06964-01226 | |
| Database references | |
| SIMBAD | AC |
| AB | |
| A (Fomalhaut) | |
| B (TW PsA) | |
| C (LP 876-10) | |
| planet b | |
| Exoplanet Archive | data |
| ARICNS | A (Fomalhaut) |
| B (TW PsA) | |
| Extrasolar Planets Encyclopaedia |
data |
Fomalhaut, also designated Alpha Piscis Austrini (α Piscis Austrini, abbreviated Alpha PsA, α PsA) is the brightest star in the constellation of Piscis Austrinus and one of the brightest stars in the sky. It is a class A star on the main sequence approximately 25 light-years (7.7 pc) from the Sun as measured by the Hipparcos astrometry satellite. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. It is classified as a Vega-like star that emits excess infrared radiation, indicating it is surrounded by a circumstellar disk. Fomalhaut, K-type main-sequence star TW Piscis Austrini, and M-type, red dwarf star LP 876-10 constitute a triple system, even though the companions are separated by several degrees.
Fomalhaut holds a special significance in extrasolar planet research, as it is the center of the first stellar system with an extrasolar planet candidate (designated Fomalhaut b, later named Dagon) imaged at visible wavelengths. The image was published in Science in November 2008. Fomalhaut is the third brightest star (as viewed from Earth) known to have a planetary system, after the Sun and Pollux.
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