Astronomy:TW Piscis Austrini
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Short description: Star in the constellation Piscis Austrinus
Coordinates: 
22h 56m 24.0533s, −31° 33′ 56.0351″
  | |
| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| 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[1] mas/yr Dec.: −158.602[1] mas/yr |
| Parallax (π) | 131.5525 ± 0.0275[1] mas |
| Distance | 24.793 ± 0.005 ly (7.602 ± 0.002 pc) |
| Absolute magnitude (MV) | 7.08[5] |
| Details | |
| Mass | 0.725 ± 0.036[3] M☉ |
| Radius | 0.629 ± 0.051[3] R☉ |
| Luminosity | 0.19[5] L☉ |
| Temperature | 4,711 ± 134[3] K |
| Rotation | 10.3[6] days |
| Rotational velocity (v sin i) | 2.93[3] km/s |
| Age | 440[5] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
| ARICNS | data |
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.[8]
A visual band light curve for TW Piscis Austrini, adapted from Busko and Torres (1978).[9] 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.[10] 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.[8]
Planetary system
In 2019, an exoplanet candidate around Fomalhaut B was detected by astrometry, but this remains unconfirmed.[11][12]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (years) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b (unconfirmed) | 1.2+0.7 −0.6 MJ |
— | 25+52 −21 |
— | — | — |
References
- ↑ 1.0 1.1 1.2 1.3 1.4 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940 Gaia DR3 record for this source at VizieR.
- ↑ 2.0 2.1 2.2 Samus, N. N. et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S 1: B/gcvs. Bibcode: 2009yCat....102025S.
- ↑ 3.0 3.1 3.2 3.3 3.4 Demory, Brice-Olivier; Ségransan, Damien; Forveille, Thierry; Queloz, Didier; Beuzit, Jean-Luc; Delfosse, Xavier; Di Folco, Emmanuel; Kervella, Pierre et al. (October 2009). "Mass-radius relation of low and very low-mass stars revisited with the VLTI". Astronomy and Astrophysics 505 (1): 205–215. doi:10.1051/0004-6361/200911976. Bibcode: 2009A&A...505..205D.
- ↑ 4.0 4.1 Johnson, H. L.; Mitchell, R. I.; Iriarte, B.; Wisniewski, W. Z. (1966). "UBVRIJKL photometry of the bright stars". Communications of the Lunar and Planetary Laboratory 4 (99): 99. Bibcode: 1966CoLPL...4...99J.
- ↑ 5.0 5.1 5.2 5.3 Mamajek, E.E. (August 2012). "On the Age and Binarity of Fomalhaut". Astrophysical Journal Letters 754 (2): L20. doi:10.1088/2041-8205/754/2/L20. Bibcode: 2012ApJ...754L..20M.
- ↑ Mamajek, Eric E. (2013). "The Solar Neighborhood. XXX. Fomalhaut C". The Astronomical Journal 146 (6): 154–163. doi:10.1088/0004-6256/146/6/154. Bibcode: 2013AJ....146..154M.
- ↑ "V* TW PsA -- Variable of BY Dra type". SIMBAD. Centre de Données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=GJ+879&submit=SIMBAD+search. Retrieved 2010-01-20.
- ↑ 8.0 8.1 Bob King (2014-10-01). "Fomalhaut: A crazy-wide triple stat". Sky & Telescope. https://skyandtelescope.org/astronomy-news/fomalhaut-falls-amazing-triple-star10012014/. Retrieved 2020-06-13. "Though it may appear isolated in the barren October sky, Fomalhaut has company. It feels the gravitational tug of the magnitude +6.5 star TW Piscis Austrini, 2° to the south. Both are 25 light-years distant and move in tandem across space, partaking of the same proper motion. They form a true double star with an actual separation of 5.5 trillion miles, or 0.91 light-year."
- ↑ Busko, I. C.; Torres, C. A. O. (March 1978). "Flare activity by BY Draconis stars". Astronomy and Astrophysics 64: 153–160. Bibcode: 1978A&A....64..153B. https://ui.adsabs.harvard.edu/abs/1978A&A....64..153B. Retrieved 23 February 2022.
- ↑ Fred Schaaf (31 March 2008). The Brightest Stars: Discovering the Universe through the Sky's Most Brilliant Stars. Wiley. ISBN 978-0-470-24917-8. https://books.google.com/books?id=9LT1q0Il3-YC.
- ↑ Joe Rao (2019-09-23). "Fomalhaut, 'Royal' Star of Autumn, Swims with the Southern Fish". Space.com. https://www.space.com/fomalhaut-autumn-star-skywatching.html. Retrieved 2020-06-13. "Believe it or not, an extrasolar planet might also be circling TW Piscis Austrini. NASA's Transiting Exoplanet Survey Satellite (TESS), a space telescope that's searching for planets around the brightest stars in Earth's night sky, recently found a possible candidate circling this star. It's almost the same size as our Earth, and orbits the star about every 10 days at a distance of 7.5 million miles from it."
- ↑ 12.0 12.1 De Rosa, Robert J.; Esposito, Thomas M.; Hirsch, Lea A.; Nielsen, Eric L.; Marley, Mark S.; Kalas, Paul; Wang, Jason J.; Macintosh, Bruce (7 October 2019). "The Possible Astrometric Signature of a Planetary-mass Companion to the Nearby Young Star TW Piscis Austrini (Fomalhaut B): Constraints from Astrometry, Radial Velocities, and Direct Imaging". Astronomical Journal 158 (6): 225. doi:10.3847/1538-3881/ab4c9b. Bibcode: 2019AJ....158..225D. https://arxiver.moonhats.com/2019/10/09/the-possible-astrometric-signature-of-a-planetary-mass-companion-to-the-nearby-young-star-tw-piscis-austrini-fomalhaut-b-constraints-from-astrometry-radial-velocities-and-direct-imaging-epa/.
External links
- TW Piscis Austrini at SolStation.
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