Alpha Pictoris (α Pic, α Pictoris) is the brightest star in the southern constellation of Pictor. It has an apparent visual magnitude of 3.27,[2] which is bright enough to be viewed from urban areas in the southern hemisphere. This is actually a binary star system, whose components complete an orbit every three years and seven months.[7] It is close enough for its distance to be measured using parallax shifts, which yields a value of roughly 97 light-years (30 parsecs) from the Sun, with a 5% margin of error.[1] Alpha Pictoris has the distinction of being the south pole star of the planet Mercury.[14]
Properties
The primary component is classified as a Lambda Boötis star.[15] The stellar classification of A8 Vn kA6[4] shows this peculiarity, with the kA6 notation indicating weaker than normal calcium K-lines in the spectrum. The 'n' following the main sequence luminosity class of V indicates the absorption lines in the spectrum are broad and nebulous. This is caused by the rapid spin of the star, which has a high projected rotational velocity of 206 km/s.[10] Spectroscopy shows narrow, time-varying absorption features being caused by circumstellar gas moving toward the star. This is not the result of interstellar matter, but a shell of gas along the orbital plane. Alpha Pictoris is categorized as a rapidly rotating shell star that may have recently ejected mass from its outer atmosphere.[16][17]
Alpha Pictoris A is larger than the Sun, with a 60% greater mass[7] and a 355% greater radius.[8] Its estimated age is roughly 660 million years,[11][12] even though it is already nearing its main sequence lifetime, having gone through 94% of the expected timespan on this stage of evolution.[3] It is radiating 40 times as much luminosity as the Sun from its outer atmosphere at an effective temperature of 7,451 K.[9] At this heat, the star glows with the white hue of an A-type star.[18] It is also one of the brightest known Delta Scuti variables.[19] The space velocity components of this star in the galactic coordinate system are U = -22, V = -20 and W = -9 km/s.[20]
Data from the Hipparcos mission uncovered the presence of a binary companion[15] with a companion orbiting at a semimajor axis of around 3.25 AU, or three times the distance from Earth to the Sun.[7][a] Alpha Pictoris is an X-ray source, which is unusual for an A-type star since stellar models don't predict them to have magnetic dynamos. This emission may instead be originating from the companion.[16][21]
Notes
- ^ a b Calculated using a3 = (M1 + M2) • P2,
where a is the semi-major axis in astronomical units, M1 and M2 are the primary and secondary's mass respectively, in M☉, and P is the period in years.
References
- ^ a b c d e f van Leeuwen, F. (November 2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
- ^ a b c d Johnson, H. L.; Iriarte, B.; Mitchell, R. I.; Wisniewskj, W. Z. (1966). "UBVRIJKL photometry of the bright stars". Communications of the Lunar and Planetary Laboratory. 4: 99–110. Bibcode:1966CoLPL...4...99J.
- ^ a b c Zorec, J.; Royer, F. (January 2012). "Rotational velocities of A-type stars. IV. Evolution of rotational velocities". Astronomy & Astrophysics. 537: A120. arXiv:1201.2052. Bibcode:2012A&A...537A.120Z. doi:10.1051/0004-6361/201117691. S2CID 55586789. Alpha Pictoris' database entry at VizieR.
- ^ a b Gray, R. O.; et al. (July 2006). "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 parsecs: The Northern Sample I". The Astronomical Journal. 132 (1): 161–170. arXiv:astro-ph/0603770. Bibcode:2006AJ....132..161G. doi:10.1086/504637. S2CID 119476992.
- ^ Wilson, R. E. (1953). "General Catalogue of Stellar Radial". Carnegie Institute Washington D.C. Publication. Washington D.C.: Carnegie Institution Publication 601. Bibcode:1953GCRV..C......0W.
- ^ Pizzolato, N.; Maggio, A.; Sciortino, S. (September 2000). "Evolution of X-ray activity of 1-3 Msun late-type stars in early post-main-sequence phases". Astronomy and Astrophysics. 361: 614–628. Bibcode:2000A&A...361..614P.
- ^ a b c d e f g Dholakia, Shishir; Murphy, Simon J; Huang, Chelsea X; Venner, Alexander; Wright, Duncan (2024-11-13). "A catalogue of binary stars from phase modulation in the first four years of TESS mission photometry". Monthly Notices of the Royal Astronomical Society. 536 (3): 2313–2323. arXiv:2410.19729. Bibcode:2025MNRAS.536.2313D. doi:10.1093/mnras/stae2551. ISSN 0035-8711.
- ^ a b McDonald, I.; Zijlstra, A. A.; Watson, R. A. (2017-10-01). "Fundamental parameters and infrared excesses of Tycho-Gaia stars". Monthly Notices of the Royal Astronomical Society. 471 (1): 770–791. arXiv:1706.02208. Bibcode:2017MNRAS.471..770M. doi:10.1093/mnras/stx1433. ISSN 0035-8711. Alpha Pictoris' database entry at VizieR.
- ^ a b c d Borisov, S. B.; Chilingarian, I. V.; Rubtsov, E. V.; et al. (2023). "New Generation Stellar Spectral Libraries in the Optical and Near-infrared. I. The Recalibrated UVES-POP Library for Stellar Population Synthesis". The Astrophysical Journal Supplement Series. 266 (1): 11. arXiv:2211.09130. Bibcode:2023ApJS..266...11B. doi:10.3847/1538-4365/acc321.
- ^ a b Royer, F.; Zorec, J.; Gómez, A. E. (February 2007). "Rotational velocities of A-type stars. III. Velocity distributions". Astronomy and Astrophysics. 463 (2): 671–682. arXiv:astro-ph/0610785. Bibcode:2007A&A...463..671R. doi:10.1051/0004-6361:20065224. S2CID 18475298.
- ^ a b Su, K. Y. L.; et al. (December 2006). "Debris Disk Evolution around A Stars". The Astrophysical Journal. 653 (1): 675–689. arXiv:astro-ph/0608563. Bibcode:2006ApJ...653..675S. doi:10.1086/508649. S2CID 14116473.
- ^ a b Song, Inseok; Caillault, J.-P.; Barrado y Navascués, David; Stauffer, John R. (January 2001). "Ages of A-Type Vega-like Stars from uvbyβ Photometry". The Astrophysical Journal. 546 (1): 352–357. arXiv:astro-ph/0010102. Bibcode:2001ApJ...546..352S. doi:10.1086/318269. S2CID 18154947.
- ^ "LTT 2656". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2009-09-10.
- ^ Moore, Patrick (2007). Moore on Mercury: the planet and the missions. Springer. p. 121. ISBN 978-1846282577.
- ^ a b Goldin, A.; Makarov, V. V. (November 2007). "Astrometric Orbits for Hipparcos Stochastic Binaries". The Astrophysical Journal Supplement Series. 173 (1): 137–142. arXiv:0706.0361. Bibcode:2007ApJS..173..137G. doi:10.1086/520513. S2CID 119586069.
- ^ a b Hempel, M.; Schmitt, J. H. M. M. (2003). "High resolution spectroscopy of circumstellar material around A stars". Astronomy and Astrophysics. 408 (3): 971–979. Bibcode:2003A&A...408..971H. doi:10.1051/0004-6361:20030946.
- ^ Roberge, Aki; Weinberger, Alycia J. (March 2008). "Debris Disks around Nearby Stars with Circumstellar Gas". The Astrophysical Journal. 676 (1): 509–517. arXiv:0711.4561. Bibcode:2008ApJ...676..509R. doi:10.1086/527314. S2CID 18407657.
- ^ "The Colour of Stars". Australia Telescope, Outreach and Education. Commonwealth Scientific and Industrial Research Organisation. December 21, 2004. Archived from the original on February 22, 2012. Retrieved 2012-01-16.
- ^ Antoci, V; et al. (11 December 2019). "The first view of δ Scuti and γ Doradus stars with the TESS mission". Monthly Notices of the Royal Astronomical Society. 490 (3): 4040–4059. arXiv:1909.12018. Bibcode:2019MNRAS.490.4040A. doi:10.1093/mnras/stz2787.
- ^ Gliese, W. (1969). "Catalogue of Nearby Stars". Veröffentlichungen des Astronomischen Rechen-Instituts Heidelberg. 22: 1. Bibcode:1969VeARI..22....1G.
- ^ Schröder, C.; Schmitt, J. H. M. M. (November 2007). "X-ray emission from A-type stars". Astronomy and Astrophysics. 475 (2): 677–684. Bibcode:2007A&A...475..677S. doi:10.1051/0004-6361:20077429.
