Observation data Epoch J2000 Equinox J2000 | |
---|---|
Constellation | Crater |
Right ascension | 11h 00m 33.85257s [2] |
Declination | −18° 19′ 29.5827″ [2] |
Apparent magnitude (V) | 8.1 - 9.5 [3] |
Characteristics | |
Evolutionary stage | AGB [4] |
Spectral type | M7/8III [5] |
Variable type | SRb [6] |
Astrometry | |
Radial velocity (Rv) | 20.94±1.50 [2] km/s |
Proper motion (μ) | RA: −29.373±0.180 [2] mas/yr Dec.: −2.499±0.172 [2] mas/yr |
Parallax (π) | 4.7027 ± 0.1528 mas [2] |
Distance | 690 ± 20 ly (213 ± 7 pc) |
Details | |
Mass | 1.91 [7] M☉ |
Radius | 633 [8] R☉ |
Luminosity | 8,151 [8] L☉ |
Surface gravity (log g) | −0.86 [8] cgs |
Temperature | 3,295 [9] K |
Other designations | |
Database references | |
SIMBAD | data |
R Crateris is a star about 700 light years from the Earth in the constellation Crater. It is a semiregular variable star, ranging in brightness from magnitude 8.1 to 9.5 over a period of about 160 days. [3] It is not visible to the naked-eye, but can be seen with a small telescope, or binoculars. [11] R Crateris is a double star; the variable star and its magnitude 9.9 F8V companion are separated by 65.4 arcseconds. [12]
Friedrich August Theodor Winnecke discovered that the star is variable in 1861. In 1907 it appeared with its variable star designation, R Crateris, in Annie Jump Cannon's Second Catalog of Variable Stars. [13] Although the period for large brightness changes in R Crateris is listed as ~160 days, in 1982 Silvia Livi and Thaisa Bergmann reported small (~0.1 magnitude) variations on timescales of less than one hour. The rapid variations seem to be more regular when the star is near maximum brightness. [14]
R Crateris is an oxygen-rich asymptotic giant branch star, losing mass at a rate of 8×10−7 solar masses per year via a stellar wind. [4] At large distances from the star, the wind is expanding into space at 11.7±0.3 km/sec. [15]
Near-infrared radiation from R Crateris was detected in the first Two-Micron Sky Survey, published in 1969. [16] It was detected in the far-infrared by the IRAS satellite, and that emission was resolved by IRAS, showing that the star is surrounded by a large circumstellar shell containing dust. [17] High resolution far-infrared images of R Crateris taken by the Herschel Space Observatory show that the emitting region of the shell, roughly 280 arcseconds (0.94 light year) across, consists primarily of two non-concentric arcs well separated from the star itself. The arcs are probably bowshocks formed as the dusty stellar wind collides with the interstellar medium. [18] The total mass of the shell, including both dust and gas, is estimated to be about (6.4±2)×10−2 solar masses. [19] Infrared imaging of the innermost (sub-arcsecond) portion of the dust shell shows a bipolar structure. [4] [20]
In the early 1970s, maser emission from OH and H2O was detected in R Cratoris' circumstellar shell. [21] SiO maser emission was detected in 1985. [22] Thermal (non-maser) emission from CO was detected in 1986. [23]
With the high angular resolution provided by Very Long Baseline Interferometry, the H2O maser emission is seen to arise from small (milli-arcsecond) blobs, whose proper motions through the inner region of the circumstellar shell can be measured. These observations give additional evidence that R Cratoris has developed a bipolar stellar wind. [24]
The asymptotic giant branch (AGB) is a region of the Hertzsprung–Russell diagram populated by evolved cool luminous stars. This is a period of stellar evolution undertaken by all low- to intermediate-mass stars (about 0.5 to 8 solar masses) late in their lives.
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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.
VY Canis Majoris is an extreme oxygen-rich red hypergiant or red supergiant and pulsating variable star 1.2 kiloparsecs from the Solar System in the slightly southern constellation of Canis Major. It is one of the largest known stars, one of the most luminous and massive red supergiants, and one of the most luminous stars in the Milky Way.
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W Hydrae is a Mira-type variable star in the constellation Hydra. The star is nearly located within the Solar neighborhood, between 75 and 120 parsecs, likely at 320 light years from the Sun. It has a visual apparent magnitude range of 5.6 to 10. In the near-infrared J band it has a magnitude of -1.7, is the 7th brightest star in the night sky, and is even brighter than Sirius.
An OH/IR star is an asymptotic giant branch (AGB) or a red supergiant or hypergiant star that shows strong OH maser emission and is unusually bright at near-infrared wavelengths.
IRC +10420, also known as V1302 Aquilae, is a yellow hypergiant star located in the constellation of Aquila at a distance of 4-6 kiloparsecs of the Sun.
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Y Centauri or Y Cen is a semiregular variable star in the constellation of Centaurus.
IK Tauri or NML Tauri is a Mira variable star located about 280 parsecs (910 ly) from the Sun in the zodiac constellation of Taurus.
ST Camelopardalis, abbreviated ST Cam, is a carbon star in the constellation of Camelopardalis. It has a radius of 244 R☉.
EX Lupi is a young, single T-Tauri star in the southern constellation of Lupus. An irregular variable, it is the prototype of young, low-mass eruptive stars named EXors, with EX Lupi being this object's variable star designation. At its minimal activity level, EX Lupi resembles a classical T-Tauri star of the M0 dwarf type. The low latitude of this star, at a declination of −40°, makes it difficult for northern observers to view. Based on parallax measurements, it is located at a distance of about 505 light years from the Sun. The star lies next to a gap in the Lupus cloud complex, a star forming region.
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