[ Alpha Pictoris has the distinction of being the south pole star of the planet Mercury.[25]]Properties
With an estimated age of 660 million years,[19][20] this is a relatively young Lambda Boötis star.[28] The stellar classification of {{nowrap|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.[21] 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][32]
Alpha Pictoris is larger than the Sun, with twice[11] the mass and a 60% greater radius.[14] It is radiating 13[15] times as much luminosity as the Sun from its outer atmosphere at an effective temperature of {{val|7530|u=K}}.[16] At this heat, the star glows with the white hue of an A-type star.[37] The space velocity components of this star in the galactic coordinate system are U = -22, V = -20 and W = -9 km/s.[38]
Data from the Hipparcos mission indicate this may be an unresolved binary system with a companion orbiting at a semimajor axis of around 1 AU, or the same distance that the Earth orbits from the Sun.[28] 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][41]
References
1. ^1 2 3 {{citation | last1=Pizzolato | first1=N. | last2=Maggio | first2=A. | last3=Sciortino | first3=S. | title=Evolution of X-ray activity of 1-3 Msun late-type stars in early post-main-sequence phases | journal=Astronomy and Astrophysics | volume=361 | pages=614–628 |date=September 2000 | bibcode=2000A&A...361..614P }}
2. ^1 2 {{cite journal | last1=Pasinetti Fracassini | first1=L. E. | last2=Pastori | first2=L. | last3=Covino | first3=S. | last4=Pozzi | first4=A. | title=Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics | journal=Astronomy and Astrophysics | volume=367 | pages=521–524 |date=February 2001 | doi=10.1051/0004-6361:20000451 | bibcode=2001A&A...367..521P | arxiv=astro-ph/0012289 | issue=2 }}
3. ^1 2 3 4 5 {{cite journal | last1=Hempel | first1=M. | last2=Schmitt | first2=J. H. M. M. | title=High resolution spectroscopy of circumstellar material around A stars | date=2003 | journal=Astronomy and Astrophysics | volume=408 | pages=971–979 | doi=10.1051/0004-6361:20030946 | bibcode=2003A&A...408..971H | issue=3}}
4. ^1 2 {{cite journal | last1=Royer | first1=F. | last2=Zorec | first2=J. | last3=Gómez | first3=A. E. | title=Rotational velocities of A-type stars. III. Velocity distributions | journal=Astronomy and Astrophysics | volume=463 | issue=2 |date=February 2007 | pages=671–682 | doi=10.1051/0004-6361:20065224 | bibcode=2007A&A...463..671R|arxiv = astro-ph/0610785 }}
5. ^1 2 {{cite journal | author=Su, K. Y. L. | title=Debris Disk Evolution around A Stars | journal=The Astrophysical Journal | volume=653 | issue=1 | pages=675–689 |date=December 2006 | doi=10.1086/508649 | bibcode=2006ApJ...653..675S | arxiv=astro-ph/0608563 |display-authors=etal}}
6. ^1 2 {{cite journal | last1=Song | first1=Inseok | last2=Caillault | first2=J.-P. | last3=Barrado y Navascués | first3=David | last4=Stauffer | first4=John R. | title=Ages of A-Type Vega-like Stars from uvbyβ Photometry | journal=The Astrophysical Journal | volume=546 | issue=1 | pages=352–357 |date=January 2001 | doi=10.1086/318269 | bibcode=2001ApJ...546..352S | arxiv=astro-ph/0010102 }}
7. ^1 2 {{citation | last1=Malagnini | first1=M. L. | last2=Morossi | first2=C. | title=Accurate absolute luminosities, effective temperatures, radii, masses and surface gravities for a selected sample of field stars | journal=Astronomy and Astrophysics Supplement Series | volume=85 | issue=3 | pages=1015–1019 |date=November 1990 | bibcode=1990A&AS...85.1015M }}
8. ^1 2 3 4 {{cite journal | title=UBVRIJKL photometry of the bright stars | last1=Johnson | first1=H. L. | last2=Iriarte | first2=B. | last3=Mitchell | first3=R. I. | last4=Wisniewskj | first4=W. Z. | date=1966 | journal=Communications of the Lunar and Planetary Laboratory | volume=4 | pages=99–110 | bibcode=1966CoLPL...4...99J }}
9. ^1 {{cite book | last=Wilson | first=R. E. | date=1953 | title=General Catalogue of Stellar Radial | publisher=Carnegie Institution Publication 601 | location=Washington D.C. | bibcode=1953GCRV..C......0W }}
10. ^1 {{cite simbad | title=LTT 2656 | accessdate=2009-09-10 }}
11. ^1 2 {{cite journal | last1=Goldin | first1=A. | last2=Makarov | first2=V. V. | title=Astrometric Orbits for Hipparcos Stochastic Binaries |date=November 2007 | journal=The Astrophysical Journal Supplement Series | volume=173 | issue=1 | pages=137–142 | doi=10.1086/520513 | bibcode=2007ApJS..173..137G |arxiv = 0706.0361 }}
12. ^1 {{cite journal | url=http://iopscience.iop.org/0004-637X/676/1/509/fulltext | last1=Roberge | first1=Aki | last2=Weinberger | first2=Alycia J. | title=Debris Disks around Nearby Stars with Circumstellar Gas |date=March 2008 | journal=The Astrophysical Journal | volume=676 | issue=1 | pages=509–517 | doi=10.1086/527314 | bibcode=2008ApJ...676..509R |arxiv = 0711.4561 }}
13. ^1 {{cite journal | last1=Schröder | first1=C. | last2=Schmitt | first2=J. H. M. M. | title=X-ray emission from A-type stars | journal=Astronomy and Astrophysics | volume=475 | issue=2 |date=November 2007 | pages=677–684 | doi=10.1051/0004-6361:20077429 | bibcode=2007A&A...475..677S }}
14. ^1 {{cite journal | last=Gliese | first=W. | title=Catalogue of Nearby Stars | date=1969 | journal=Veröffentlichungen des Astronomischen Rechen-Instituts Heidelberg | bibcode=1969VeARI..22....1G | volume=22 | page=1 }}
15. ^1 {{citation | first1=Patrick | last1=Moore | title=Moore on Mercury: the planet and the missions | publisher=Springer | date=2007 | isbn=1846282578 | page=121 | url=https://books.google.com/books?id=2_n4T_k7lIIC&pg=PT121 }}
16. ^1 2 3 {{citation | display-authors=1 | last1=Gray | first1=R. O. | first2=C. J. | last2=Corbally | first3=R. F. | last3=Garrison | first4=M. T. | last4=McFadden | first5=P. E. | last5=Robinson | title=Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 parsecs: The Northern Sample I | journal=The Astronomical Journal | volume=132 | issue=1 | pages=161–170 |date=July 2006 | doi=10.1086/504637 | bibcode=2006AJ....132..161G |arxiv = astro-ph/0603770 }}
17. ^1 {{citation|title=The Colour of Stars |date=December 21, 2004 |work=Australia Telescope, Outreach and Education |publisher=Commonwealth Scientific and Industrial Research Organisation |url=http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html |accessdate=2012-01-16 |deadurl=yes |archiveurl=https://www.webcitation.org/6630AbtJZ?url=http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html |archivedate=March 10, 2012 }}
18. ^1 {{citation | last1=Goldin | first1=A. | last2=Makarov | first2=V. V. | title=Unconstrained Astrometric Orbits for Hipparcos Stars with Stochastic Solutions | journal=The Astrophysical Journal Supplement Series | volume=166 | issue=1 | pages=341–350 |date=September 2006 | doi=10.1086/505939 | bibcode=2006ApJS..166..341G |arxiv = astro-ph/0606293 }}