Alpha Pictoris
Encyclopedia
Alpha Pictoris is the brightest star
in the constellation
Pictor
with an apparent magnitude
of 3.30. It is located about 99 light years from the Sun
. This is a relatively young Lambda Boötis star
at 660 million years of age, and is rotating rapidly with a projected stellar rotation
rate of 206 km/s or greater.
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 instead may be 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 the outer atmosphere.
Data from the Hipparcos mission indicate this may be an unresolved binary with a companion orbiting at a semimajor axis of 1 AU
, or the same distance that the Earth orbits 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.
The space velocity components of this star are U = -22, V = -20 and W = -9 km/s.
Alpha Pictoris has the distinction of being the south pole star
of Mercury
.
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
in the constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
Pictor
Pictor
Pictor is a small and faint constellation in the southern sky , located between the brilliant star Canopus and the Large Magellanic Cloud. Its name is Latin for painter, but it is in fact an abbreviation of its original name Equuleus Pictoris, the 'painter's easel', and it is normally represented...
with an apparent magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
of 3.30. It is located about 99 light years from the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
. This is a relatively young Lambda Boötis star
Lambda Boötis star
A Lambda Boötis star is a type of peculiar star which has an unusually low abundance of iron peak elements in its surface layers. One possible explanation for this is that it is the result of accretion of metal-poor gas from a circumstellar disc. The prototype is Lambda Boötis....
at 660 million years of age, and is rotating rapidly with a projected stellar rotation
Stellar rotation
Stellar rotation is the angular motion of a star about its axis. The rate of rotation can be measured from the spectrum of the star, or by timing the movements of active features on the surface....
rate of 206 km/s or greater.
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 instead may be a shell of gas along the orbital plane. Alpha Pictoris is categorized as a rapidly rotating shell star
Shell star
A shell star, also termed Gamma Cassiopeiae variable , is a star having a spectrum that exhibits features indicating a circumstellar disc of gas surrounding the star at the equator. They exhibit irregular variations in their luminosity due to the outflow of matter...
that may have recently ejected mass from the outer atmosphere.
Data from the Hipparcos mission indicate this may be an unresolved binary with a companion orbiting at a semimajor axis of 1 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
, or the same distance that the Earth orbits 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.
The space velocity components of this star are U = -22, V = -20 and W = -9 km/s.
Alpha Pictoris has the distinction of being the south pole star
Pole star
The term "Pole Star" usually refers to Polaris, which is the current northern pole star, also known as the North Star.In general, however, a pole star is a visible star, especially a prominent one, that is approximately aligned with the Earth's axis of rotation; that is, a star whose apparent...
of Mercury
Mercury (planet)
Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 Earth days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about its axis for every two orbits...
.