Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Gemini |
Right ascension | 06h 11m 51.41401s [1] |
Declination | 21° 52′ 05.6452″ [1] |
Apparent magnitude (V) | 6.27 - 7.50 [2] |
Characteristics | |
Spectral type | K5.5 - M1.3 Iab [3] + B4 III: [2] |
U−B color index | +1.77 [4] |
B−V color index | +2.25 [4] |
Variable type | SRc [3] |
Astrometry | |
Radial velocity (Rv) | +20.42 [5] km/s |
Proper motion (μ) | RA: −0.575 [6] mas/yr Dec.: −2.598 [6] mas/yr |
Parallax (π) | 0.3197 ± 0.1301 mas [6] |
Distance | 1,500 [7] pc |
Absolute magnitude (MV) | -6.31 [8] |
Details | |
Mass | 14 [9] M☉ |
Radius | 623, [10] 620 - 710 (pulsation) [7] R☉ |
Luminosity | 68,000 ± 34,900, [10] 62,000 - 89,000 [7] L☉ |
Temperature | 3,750 ± 120, [10] 3,500 - 3,850 [7] K |
Other designations | |
Database references | |
SIMBAD | data |
TV Geminorum (TV Gem / HD 42475 / HR 2190) is a variable red supergiant in the constellation Gemini. Its visual magnitude varies from 6.3 to 7.5.
TV Gem is less than a degree SW of η Geminorum. It is a member of the Gemini OB1 stellar association at around 4,500 light years from Earth. [8]
TV Geminorum is classified as a semi-regular variable star, meaning that its brightness changes are not predictable, but do show some periodicity. The General Catalogue of Variable Stars does not list a period, [3] but the International Variable Star Index gives an uncertain period of 229 days. [2] A detailed study of TV Gem between 1997 and 2014 detects periods of 411 days and 3,137 days. [7]
TV Geminorum changes its size, temperature, and luminosity as its brightness varies. The temperature changes between 3,500 K and 3,850 K, the radius between 620 R☉ and 710 R☉, and the bolometric luminosity between 62,000 L☉ and 89,000 L☉. The majority of the electromagnetic radiation is emitted at wavelengths longer than the visual band, being only around 20,000 times brighter than the sun at visual wavelengths.
The pulsations are not correlated with the brightness changes in the expected way; other pulsating variables are brightest when they are hottest and smallest, but TV Gem does not follow this rule. It has been suggested that the luminosity variations are affected by the formation of supergranules surrounding the star. [7] The spectral type varies in line with the temperature changes, from as early as K5.5 to as late as M1.3. The type M1.3 is assigned by a numerical calculation from photometry. [11] The MK spectral class is M0 - M1.5 Iab. [12]
If TV Gem was at the centre of the solar system, the four inner planets, including the Earth, would be encompassed within the star. It is losing mass at an annual rate of 3.5×10−7M☉. [13]
TV Gem appears to have a very close hot companion. Its existence is inferred from an ultraviolet excess in the spectral energy distribution. The spectral type determined from the ultraviolet portion of the spectrum is B4, appearing to be a giant although it is thought that this is caused by the stellar wind from an underlying main sequence star. It is estimated to have an apparent magnitude of 11.2 and an absolute magnitude of −1.4. [14]
KY Cygni is a red supergiant of spectral class M3.5Ia located in the constellation Cygnus. It is approximately 5,000 light-years away.
119 Tauri is a red supergiant star in the constellation Taurus. It is a semiregular variable and its angular diameter has been measured at about 10 mas.
A yellow hypergiant (YHG) is a massive star with an extended atmosphere, a spectral class from A to K, and, starting with an initial mass of about 20–60 solar masses, has lost as much as half that mass. They are amongst the most visually luminous stars, with absolute magnitude (MV) around −9, but also one of the rarest, with just 20 known in the Milky Way and six of those in just a single cluster. They are sometimes referred to as cool hypergiants in comparison with O- and B-type stars, and sometimes as warm hypergiants in comparison with red supergiants.
KW Sagittarii is a red supergiant, located approximately 1,900 parsecs away from the Sun in the direction of the constellation Sagittarius. It is one of the largest-known stars. If placed at the center of the Solar System, the star's surface would engulf Mars.
Zeta Cephei is a star in the constellation of Cepheus. Zeta Cephei marks the left shoulder of Cepheus, the King of Joppa (Ethiopia). It is one of the fundamental stars of the MK spectral sequence, defined as type K1.5 Ib.
HD 74180 is a binary star in the constellation Vela. It is approximately 3,200 light years from Earth. The primary component is a yellow-white F-type supergiant with a mean apparent magnitude of +3.81, with a 10th magnitude companion 37.5 arcseconds distant.
NO Aurigae is a pulsating variable star in the constellation Auriga. It is an unusually-luminous asymptotic giant branch star about 3,500 light years away.
WOH G64 is an unusual red supergiant (RSG) star in the Large Magellanic Cloud (LMC) satellite galaxy in the southern constellation of Dorado. It is one of the largest known stars, being described as possibly being the largest star known. It is also one of the most luminous and massive red supergiants, with a radius calculated to be around 1,540 times that of the Sun (R☉) and a luminosity around 282,000 times the solar luminosity (L☉).
V602 Carinae is a red supergiant and variable star of spectral type of M3 in the constellation Carina. It is one of largest known stars.
TZ Cassiopeiae(TZ Cas, HIP 117763, SAO 20912) is a variable star in the constellation Cassiopeia with an apparent magnitude of around +9 to +10. It is approximately 8,400 light-years away from Earth. The star is a red supergiant star with a spectral type of M3 and a temperature around 3,600 K.
W Virginis is the prototype W Virginis variable, a subclass of the Cepheid variable stars. It is located in the constellation Virgo, and varies between magnitudes 9.46 and 10.75 over a period of approximately 17 days.
9 Cephei, also known as V337 Cephei, is a variable star in the constellation Cepheus.
PZ Cassiopeiae is a red supergiant star located in the constellation of Cassiopeia, and a semi-regular variable star.
3 Geminorum is a blue supergiant star in the constellation Gemini. It is a small amplitude pulsating variable and a close double star, with a mean combined apparent visual magnitude of about 5.7.
EV Carinae is a red supergiant and pulsating variable star of spectral type M4Ia in the constellation Carina. It is a semiregular variable star with its apparent magnitude varying between 7.4 and 9.0 in the visible band, making it only seen by binoculars or a telescope. Various periods have been identified, but the dominant one is around 347 days. It is an MK spectral standard star for the class M4.5Ia.
BC Cygni is a red supergiant and pulsating variable star of spectral type M3.5Ia in the constellation Cygnus.
RW Cygni is a semiregular variable star in the constellation Cygnus, about a degree east of 2nd magnitude γ Cygni. Its apparent magnitude varies between 8.05 and 9.70 and its spectral type between M3 and M4.
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.
6 Geminorum is a variable star in the zodiac constellation of Gemini, located roughly 5,800 light years away from the Sun. It has the variable star designation BU Geminorum; 6 Geminorum is the Flamsteed designation. At its brightest this reddish hued star is barely visible to the naked eye but is readily visible with binoculars, found southeast of M 35, just to the south of WY Geminorum. It is moving further from the Earth with a heliocentric radial velocity of +27 km/s. The star is a member of the Gemini OB1 association.