Alpha Pictoris

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Brightest star in the southern constellation of Pictor

title: "Alpha Pictoris" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["pictor", "a-type-main-sequence-stars", "gliese-and-gj-objects", "bright-star-catalogue-objects", "hipparcos-objects", "henry-draper-catalogue-objects", "durchmusterung-objects", "southern-pole-stars", "lucidae"] description: "Brightest star in the southern constellation of Pictor" topic_path: "science/astronomy" source: "https://en.wikipedia.org/wiki/Alpha_Pictoris" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Brightest star in the southern constellation of Pictor ::

| name = α Pictoris | image= |image=Pictor constellation map.svg|alt=|float=center|width=240 |label=|position=right |mark=Red circle.svg|mark_width=12|mark_link=α Pic |x=164|y=878 |caption=Location of α Pictoris (circled) | epoch = J2000 | ra = | dec = | appmag_v = 3.27 | constell = Pictor | type = Main sequence | class = A8 Vn kA6 | b-v = +0.21 | u-b = +0.13 | variable = | radial_v = +20.6 | prop_mo_ra = −66.07 | prop_mo_dec = +242.97 | parallax = 33.78 | p_error = 1.78 | parallax_footnote = | absmag_v = 0.86 | reference = | period_unitless = days | axis_unitless = 3.25 AU | eccentricity = | inclination = | node = | periastron = BJD | periarg = | component1 = A | mass = | radius = 3.55 | luminosity = | temperature = | metal_fe = | gravity = | age_myr = 660 | rotational_velocity = 213.5 | component2 = B | mass2 = | temperature2 = | names = CD−61°1478, Gl 248, HD 50241, HIP 32607, HR 2550, LTT 2656, SAO 249647. | Simbad = alf+Pic

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, 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. It is close enough for its distance to be measured using parallax shifts, which yields a value of roughly 97 ly from the Sun, with a 5% margin of error. Alpha Pictoris has the distinction of being the south pole star of the planet Mercury.

Properties

The primary component is classified as a Lambda Boötis star. The stellar classification of A8 Vn kA6 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. 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.

Alpha Pictoris A is larger than the Sun, with a 60% greater mass and a 355% greater radius. Its estimated age is roughly 660 million years, even though it is already nearing its main sequence lifetime, having gone through 94% of the expected timespan on this stage of evolution. It is radiating 40 times as much luminosity as the Sun from its outer atmosphere at an effective temperature of . At this heat, the star glows with the white hue of an A-type star. It is also one of the brightest known Delta Scuti variables. The space velocity components of this star in the galactic coordinate system are U = -22, V = -20 and W = -9 km/s.

Data from the Hipparcos mission uncovered the presence of a binary companion with a companion orbiting at a semimajor axis of around 3.25 AU, or three times the distance from Earth to the Sun. 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.

Notes

References

References

  1. (11 December 2019). "The first view of δ Scuti and γ Doradus stars with the TESS mission". Monthly Notices of the Royal Astronomical Society.
  2. (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.
  3. (November 2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics.
  4. (2017-10-01). "Fundamental parameters and infrared excesses of Tycho-Gaia stars". Monthly Notices of the Royal Astronomical Society.
  5. (September 2000). "Evolution of X-ray activity of 1-3 Msun late-type stars in early post-main-sequence phases". Astronomy and Astrophysics.
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  7. (February 2007). "Rotational velocities of A-type stars. III. Velocity distributions". Astronomy and Astrophysics.
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  9. (January 2001). "Ages of A-Type Vega-like Stars from uvbyβ Photometry". The Astrophysical Journal.
  10. (1966). "UBVRIJKL photometry of the bright stars". Communications of the Lunar and Planetary Laboratory.
  11. (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.
  12. Wilson, R. E.. (1953). "General Catalogue of Stellar Radial". Carnegie Institution Publication 601.
  13. "LTT 2656".
  14. (November 2007). "Astrometric Orbits for Hipparcos Stochastic Binaries". The Astrophysical Journal Supplement Series.
  15. (March 2008). "Debris Disks around Nearby Stars with Circumstellar Gas". The Astrophysical Journal.
  16. (November 2007). "X-ray emission from A-type stars". Astronomy and Astrophysics.
  17. Gliese, W.. (1969). "Catalogue of Nearby Stars". Veröffentlichungen des Astronomischen Rechen-Instituts Heidelberg.
  18. (2007). "Moore on Mercury: the planet and the missions". Springer.
  19. (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.
  20. (December 21, 2004). "The Colour of Stars". [[Commonwealth Scientific and Industrial Research Organisation]].

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pictora-type-main-sequence-starsgliese-and-gj-objectsbright-star-catalogue-objectshipparcos-objectshenry-draper-catalogue-objectsdurchmusterung-objectssouthern-pole-starslucidae