Observation data Epoch J2000.0 Equinox J2000.0 | |
---|---|
Constellation | Sagitta |
Right ascension | 19h 27m 26.5636s [2] |
Declination | +18° 17′ 45.193″ [2] |
Apparent magnitude (V) | 6.71 - 6.95 [3] |
Characteristics | |
Spectral type | B6-8 Ia-0 [4] |
Apparent magnitude (B) | 8.08 |
Apparent magnitude (J) | 4.13 |
Apparent magnitude (K) | 3.46 |
U−B color index | +0.2 [5] |
B−V color index | +1.2 [5] |
Variable type | α Cyg? [3] |
Astrometry | |
Proper motion (μ) | RA: −1.004 [2] mas/yr Dec.: −5.703 [2] mas/yr |
Parallax (π) | 0.4296 ± 0.0243 mas [2] |
Distance | 7,600 ± 400 ly (2,300 ± 100 pc) |
Absolute magnitude (MV) | −8.7 [4] |
Details | |
Mass | 24.2 [5] M☉ |
Radius | 109 [5] R☉ |
Luminosity | 288,000 [5] L☉ |
Surface gravity (log g) | 1.40 [6] cgs |
Temperature | 11,500 [6] K |
Rotational velocity (v sin i) | 37 [6] km/s |
Age | 7.6 [5] Myr |
Other designations | |
Database references | |
SIMBAD | data |
HD 183143 (HT Sagittae) is a blue hypergiant star located in the constellation of Sagitta.
This star has an apparent magnitude of 6.9, meaning that can be seen with the naked eye under very dark skies and that is an easy target for binoculars or a small telescope.
HD 183143 was included in the first catalogue of Be stars, with distinct Hα emission lines. [7] When emission lines in hot supergiant stars were investigated as indicators of expanding atmospheres and mass loss, HD 183143 was found to have Hα lines with P Cygni profiles, but indications of only modest mass loss. [8] Modern high-resolution spectra show emission in lines from Hα, Hβ, Hγ, and Hδ, formed by the strong stellar wind. [6]
The introduction of spectral standards for supergiants gave HD 183143 as the standard star for the class B7Ia. [9] The spectral type is sometimes given as B7Iae to indicate the presence of the emission lines. [10]
HD 183143 was listed as being variable in 1976, with a very small amplitude. [11] During the Hipparcos mission, its brightness was observed to vary between magnitude 6.71 and 6.95. ASAS-3 photometry shows a period of 40.44 days. [3] HD 183143 was formally announced as a variable star, probably of the α Cygni type, in 1979 and given the variable star designation HT Sagittae. [12]
HD 183143 has been extensively studied because of the diffuse interstellar bands visible in its spectrum. The strongest lines are caused by interstellar atomic iron, potassium, lithium, sodium, and calcium, as well as ionised calcium, and CH and CN molecules. [13] Infrared bands of ionised buckminsterfullerene have also been found in its spectrum. [14] HD 183143 has been proposed as a reference standard for interstellar polarisation. It shows 6% polarisation. [15]
A 2004 study reclassified the spectral type of HD 183143 as B6.8 Ia-0, a hypergiant. The parallax from the original Hipparcos catalogue was 2.70 mas, indicating a distance around 370 pc, but the revised Hipparcos parallax and the Gaia Data Release 3 parallax both indicate distances around 2,000 pc. [2] Comparison of the space velocity and interstellar spectral lines produce a similar distance, with the star lying between the Orion-Cygnus Arm and the Carina–Sagittarius Arm. [4] At that distance, HD 183143 is an extremely luminous star, around 288,000 L☉, with correspondingly high mass and radius. [5]
Mu Cephei, also known as Herschel's Garnet Star, Erakis, or HD 206936, is a red supergiant or hypergiant star in the constellation Cepheus. It appears garnet red and is located at the edge of the IC 1396 nebula. Since 1943, the spectrum of this star has served as a spectral standard by which other stars are classified.
VV Cephei, also known as HD 208816, is an eclipsing binary star system located in the constellation Cepheus, approximately 5,000 light years from Earth. It is both a B[e] star and shell star.
V382 Carinae, also known as x Carinae, is a yellow hypergiant in the constellation Carina. It is a G-type star with a mean apparent magnitude of +3.93, and a variable star of low amplitude.
V509 Cassiopeiae is one of two yellow hypergiant stars found in the constellation Cassiopeia, which also contains Rho Cassiopeiae.
Omicron1 Centauri is a star in the constellation Centaurus. It is approximately 10,000 light years from Earth.
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MY Cephei is a red supergiant located in open cluster NGC 7419 in the constellation of Cepheus. It is a semiregular variable star with a maximum brightness of magnitude 14.4 and a minimum of magnitude 15.5.
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S Persei is a red supergiant or hypergiant located near the Double Cluster in Perseus, north of the cluster NGC 869. It is a member of the Perseus OB1 association and one of the largest known stars. If placed in the Solar System, its photosphere would engulf the orbit of Jupiter. It is also a semiregular variable, a star whose variations are less regular than those of Mira variables.
HD 34626, also known as MZ Aurigae, is an unusual variable star in the northern constellation of Auriga. It has an apparent magnitude of 8.2 and is about 3,300 light years away.
RW Cephei is a K-type hypergiant variable star in the constellation Cepheus, at the edge of the Sharpless 132 H II region and close to the small open cluster Berkeley 94. It is among the largest stars known with a radius of almost 1,000 times that of the Sun (R☉), nearly as large as the orbit of Jupiter.
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.
V4381 Sagittarii is a variable star in the constellation Sagittarius. A white supergiant of spectral type A2/A3Iab, it is an Alpha Cygni variable that varies between apparent photographic magnitudes 6.57 and 6.62. Its visual apparent magnitude is about 6.54.
HD 33579 is a white/yellow hypergiant and one of the brightest stars in the Large Magellanic Cloud (LMC). It is a suspected variable star.
IRC+10420, also known as V1302 Aql, is a yellow hypergiant star located in the constellation of Aquila at a distance of 4-6 kiloparsecs of 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.
WR 24 is a Wolf-Rayet star in the constellation Carina. It is one of the most luminous stars known. At the edge of naked eye visibility it is also one of the brightest Wolf Rayet stars in the sky.
V766 Centauri, also known as HR 5171, is a yellow hypergiant in the constellation Centaurus, either 5,000 or 12,000 light years from Earth. It is said to be either an extreme red supergiant (RSG) or recent post-red supergiant (Post-RSG) yellow hypergiant (YHG), both of which suggest it is one of the largest known stars. The star's diameter is uncertain but likely to be between 1,100 and 1,600 times that of the Sun. It was previously thought to be a contact binary, sharing a common envelope of material with a smaller yellow supergiant and secondary star, the two orbiting each other every 1,304 ± 6 days. However this has since been deemed unlikely. An optical companion, HR 5171B, may or may not be at the same distance as the yellow supergiant.
V915 Scorpii is an orange hypergiant variable star in the constellation Scorpius.
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