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 | 620 –710 (pulsation) [7] R☉ |
Luminosity | 62,000 - 89,000 [7] L☉ |
Temperature | 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, making it very faintly visible to the naked eye of an observer with excellent observing conditions, when the star is near its peak brightness.
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. [10] The MK spectral class is M0 - M1.5 Iab. [11]
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☉. [12]
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. [13]
KY Cygni is a red supergiant of spectral class M3.5Ia located in the constellation Cygnus. It is approximately 4,700 light-years away.
119 Tauri is a red supergiant star in the constellation Taurus. It is a magnitude 4 star, visible to the naked eye under good observing conditions. A semiregular variable, its angular diameter has been measured at about 10 mas. It is a similar star to Betelgeuse although redder and more distant.
KW Sagittarii is a red supergiant star, located approximately 2,420 parsecs away from the Sun in the direction of the constellation Sagittarius. It is one of the largest known stars, with a diameter about 1,000 times larger than the Sun. If placed at the center of the Solar System, the star's surface would engulf Mars, coming close to Jupiter's orbit.
R Andromedae is a Mira-type variable star in the constellation Andromeda. Its spectral class is type S because it shows absorption bands of zirconium monoxide (ZrO) in its spectrum. It was among the stars found by Paul Merrill to show absorption lines of the unstable element technetium, establishing that nucleosynthesis must be occurring in stars. The SH molecule was found for the first time outside earth in the atmosphere of this star. The star is losing mass due to stellar winds at a rate of 1.09×10−6M☉/yr.
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.
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. It is a 6th magnitude star faintly visible to the naked eye under very good observing conditions.
WOH G64 is an unusual yellow hypergiant star in the Large Magellanic Cloud (LMC) satellite galaxy in the southern constellation of Dorado.
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.
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.
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.
Westerlund 1 W26 or Westerlund 1 BKS AS is a red supergiant located at the outskirts of the Westerlund 1 super star cluster. It is one of the largest known stars and the most luminous supergiant stars discovered so far with radius calculated to be in excess of a thousand times the solar radius, and a luminosity of over 200,000 times the solar luminosity. If placed at the center of the Solar System, its photosphere would engulf the orbit of Jupiter.
HR 5171, also known as V766 Centauri, is a yellow hypergiant in the constellation Centaurus. 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 is 3.6 kpc from Earth.
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.
V915 Scorpii is a hypergiant and semiregular variable star, located 1,718 parsecs (5,600 ly) away in the constellation Scorpius. Its apparent magnitude varies between 6.22 and 6.64, being heavily diminshed by 2.93 magnitudes due to interstellar extinction.
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.
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.