Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Carina |
Right ascension | 10h 56m 11.57814s [1] |
Declination | −60° 27′ 12.8107″ [1] |
Apparent magnitude (V) | 6.96 [2] (5.7–9.0) [3] |
Characteristics | |
Spectral type | LBV [4] |
U−B color index | −0.58 [2] |
B−V color index | +0.61 [2] |
Variable type | LBV [5] |
Astrometry | |
Proper motion (μ) | RA: −4.808 [1] mas/yr Dec.: +1.955 [1] mas/yr |
Parallax (π) | 0.1925 ± 0.0165 mas [1] |
Distance | 17,000 ± 1,000 ly (5,200 ± 400 pc) |
Absolute magnitude (MV) | ~−8 (at minimum) [4] |
Details | |
Mass | 55 [6] M☉ |
Radius | 50 [7] –552 [8] R☉ |
Luminosity | 600,000–900,000 [9] [lower-alpha 1] L☉ |
Temperature | 8,000–26,000 [7] K |
Rotation | 13±2 [10] days |
Rotational velocity (v sin i) | 220±50 [10] km/s |
Other designations | |
Database references | |
SIMBAD | data |
AG Carinae (AG Car) is a star in the constellation Carina. It is classified as a luminous blue variable (LBV) and is one of the most luminous stars in the Milky Way. The great distance (20,000 light-years) and intervening dust mean that the star is not usually visible to the naked eye; its apparent brightness varies erratically between magnitude 5.7 and 9.0.
The star is surrounded by a nebula of ejected material at 0.4–1.2 pc from the star. The nebula contains around 15 M☉, all lost from the star around 10,000 years ago. There is an 8.8-parsec-wide empty cavity in the interstellar medium around the star, presumably cleared by fast winds earlier in the star's life. [4] [6]
AG Carinae is apparently in a transitional phase between a massive class O blue supergiant and a Wolf–Rayet star, where it is highly unstable and suffers from erratic pulsations, occasional larger outbursts, and rare massive eruptions. The spectral type varies between WN11 at visual minimum and an early A hypergiant at maximum. [4] At visual minimum the star is about 65 R☉ and 20,000–24,000 K, while at maximum it is over 400 R☉ and 8,000 K. The temperature varies at different minima. [7] [12]
One study calculated that the bolometric luminosity of AG Carinae decreases during its S Doradus-type outbursts, unlike most LBVs which remain at approximately constant luminosity. The luminosity drops from around 1.5 million L☉ at visual minimum to around 1 million L☉ at visual maximum, possibly due to the energy required to expand a considerable fraction of the star. [4]
Evolutionary models of the star suggest that it had a low rotation rate for much of its life, but current observations show fairly rapid rotation. [6]
Models of LBV progenitors of type IIb supernovae list AG Carinae as matching the final stellar spectrum prior to core collapse, although the models are for stars with 20 to 25 times the mass of the Sun while AG Carinae is thought to be considerably more massive. [13] The initial mass of the star would have been around 100 M☉ and is now thought to be 55–70 M☉. [4] [6]
Parallaxes from data release 1 (DR1) of the Gaia mission suggest a much closer distance to AG Carinae and its neighbour Hen 3-519 than previously accepted, around 2,000 parsecs. Then both stars would be less luminous than LBVs and it is argued that they would be former red supergiants whose unusual characteristics are the result of binary evolution. [14]
The earlier Hipparcos parallax for AG Carinae had a margin of error larger than the parallax itself and so gave little information about its distance. [15] The distance of 6,000 parsecs is based on assumptions about the properties of LBVs, models of interstellar extinction, and kinematical measurements. [4] The Gaia DR1 parallax, derived from the combination of the first year of Gaia measurements with Tycho astrometry, is 0.40±0.22 mas . The Gaia team recommend that a further 0.3 mas systematic error is allowed for (i.e. added to the formal margin of error). [16] A 2017 study argues that the 0.3 mas systematic margin of error can be ignored and that the implied distance to AG Carinae is 2.50±1.41 kpc . [14]
In Gaia Data Release 2, the parallax is 0.1532±0.0291 mas, suggesting a distance around 6,500 pc. [17] A 2019 observation yields a most likely distance of 4,650 pc. [9] Gaia Early Data Release 3 gives a parallax of 0.1925±0.0165 mas, although with a non-trivial level of excess astrometric noise where there was none in Gaia DR2. [1]
S Doradus is one of the brightest stars in the Large Magellanic Cloud (LMC), a satellite galaxy of the Milky Way, located roughly 160,000 light-years away. The star is a luminous blue variable, and one of the most luminous stars known, having a luminosity varying widely above and below 1,000,000 times the luminosity of the Sun, although it is too far away to be seen with the naked eye.
Luminous blue variables (LBVs) are rare, massive and evolved stars that show unpredictable and sometimes dramatic variations in their spectra and brightness. They are also known as S Doradus variables after S Doradus, one of the brightest stars of the Large Magellanic Cloud.
P Cygni is a variable star in the constellation Cygnus. The designation "P" was originally assigned by Johann Bayer in Uranometria as a nova. Located about 5,300 light-years from Earth, it is a hypergiant luminous blue variable (LBV) star of spectral type B1-2 Ia-0ep that is one of the most luminous stars in the Milky Way.
V354 Cephei is a red supergiant star located within the Milky Way. It is an irregular variable located over 13,000 light-years away from the Sun. It has an estimated radius of 1,139 solar radii. If it were placed in the center of the Solar System, it would extend to between the orbits of Mars and Jupiter.
Cygnus OB2 #12 is an extremely luminous blue hypergiant with an absolute bolometric magnitude of −10.9, among the most luminous stars known in the galaxy. This makes the star nearly two million times more luminous than the Sun, although estimates were even higher when the star was first discovered. It is now known to be a binary, with the companion approximately a tenth as bright. A very approximate initial estimate of the orbit gives the total system mass as 120 M☉ and the period as 30 years.
HR Carinae is a luminous blue variable star located in the constellation Carina. It is surrounded by a vast nebula of ejected nuclear-processed material because this star has a multiple shell expanding atmosphere. This star is among the most luminous stars in the Milky Way. It has very broad emission wings on the Balmer lines, reminiscent from the broad lines observed in the spectra of O and Wolf–Rayet stars. A distance of 5 kpc and a bolometric magnitude of −9.4 put HR Car among the most luminous stars of the galaxy.
A hypergiant (luminosity class 0 or Ia+) is a very rare type of star that has an extremely high luminosity, mass, size and mass loss because of its extreme stellar winds. The term hypergiant is defined as luminosity class 0 (zero) in the MKK system. However, this is rarely seen in literature or in published spectral classifications, except for specific well-defined groups such as the yellow hypergiants, RSG (red supergiants), or blue B(e) supergiants with emission spectra. More commonly, hypergiants are classed as Ia-0 or Ia+, but red supergiants are rarely assigned these spectral classifications. Astronomers are interested in these stars because they relate to understanding stellar evolution, especially star formation, stability, and their expected demise as supernovae. Notable examples of hypergiants include the Pistol Star, a blue hypergiant located close to the Galactic Center and one of the most luminous stars known; Rho Cassiopeiae, a yellow hypergiant that is one of the brightest to the naked eye; and Mu Cephei (Herschel's "Garnet Star"), one of the largest and brightest stars known.
V602 Carinae is a red supergiant and variable star of spectral type M3 in the constellation Carina. It is considered to be one of largest known stars, being around 1,000 times larger than the Sun.
HD 168607 is a blue hypergiant and luminous blue variable (LBV) star located in the constellation of Sagittarius, easy to see with amateur telescopes. It forms a pair with HD 168625, also a blue hypergiant and possible luminous blue variable, that can be seen at the south-east of M17, the Omega Nebula.
AFGL 2298, also known as IRAS 18576+0341, is a luminous blue variable star (LBV) located in the constellation Aquila, very close to the galactic plane. Its distance is not well known; it may be anywhere between 23,000 and 42,000 light years away from the Earth. Despite being extremely luminous, it is extremely reddened by interstellar extinction, so its apparent magnitude is brighter for longer-wavelength passbands; in fact, in visual wavelengths it is completely undetectable.
V1429 Aquilae is a candidate luminous blue variable multiple star system located in the constellation of Aquila. It is often referred to by its Mount Wilson Observatory catalog number as MWC 314. It is a hot luminous star with strong emission lines in its spectrum.
AS 314, also known as V452 Scuti, is a protoplanetary nebula once believed to be a white hypergiant star or luminous blue variable located in the constellation of Scutum. It has an apparent magnitude of 9.85 and can be seen with small telescopes.
UY Scuti (BD-12°5055) is a red supergiant star, located 5,900 light-years away in the constellation Scutum. It is also a pulsating variable star, with a maximum brightness of magnitude 8.29 and a minimum of magnitude 10.56, which is too dim for naked-eye visibility. It is considered to be one of the largest known stars, with a radius estimated at 909 solar radii, thus a volume of 750 million times that of the Sun. This estimate implies if it were placed at the center of the Solar System, its photosphere would extend past the orbit of Mars or even the asteroid belt.
HDE 316285 is a blue supergiant star in the constellation Sagittarius. It is a candidate luminous blue variable and lies about 6,000 light years away in the direction of the Galactic Center.
WR 31a, commonly referred to as Hen 3-519, is a Wolf–Rayet (WR) star in the southern constellation of Carina that is surrounded by an expanding Wolf–Rayet nebula. It is not a classical old stripped-envelope WR star, but a young massive star which still has some hydrogen left in its atmosphere.
V528 Carinae is a variable star in the constellation Carina.
BO Carinae, also known as HD 93420, is an irregular variable star in the constellation Carina.
R71 is a star in the Large Magellanic Cloud (LMC) in the constellation Mensa. It is classified as a luminous blue variable and is one of the most luminous stars in the LMC. It lies three arc-minutes southwest of the naked-eye star β Mensae.
V1936 Aquilae is a blue supergiant and candidate Luminous blue variable located in the nebula Westerhout 51, in the constellation Aquila, about 20,000 light years away. The star was originally identified as a massive star in 2000, and was thought to be an O-type supergiant. However, subsequent analyses have shown it to be not O but B-type, as well as being possibly an LBV.
HD 37836 is a candidate luminous blue variable located in the Large Magellanic Cloud and one of the brightest stars in its galaxy.