Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
---|---|
Constellation | Sagittarius |
Right ascension | 17h 45m 40.124s [1] |
Declination | −29° 00′ 29.02″ [1] |
Characteristics | |
Evolutionary stage | Wolf–Rayet star |
Spectral type | Ofpe/WN9 [2] |
Apparent magnitude (J) | 14.75 [3] |
Apparent magnitude (H) | 11.6 [3] |
Apparent magnitude (K) | 9.34 [4] |
Orbit [5] | |
Primary | Sagittarius A* |
Companion | GCIRS 16SW |
Period (P) | 1270±309 yr |
Semi-major axis (a) | 2.32±0.46″ |
Eccentricity (e) | 0.35±0.11 |
Inclination (i) | 113.0±1.3° |
Longitude of the node (Ω) | 113.2±1.4° |
Periastron epoch (T) | 2132±29 |
Argument of periastron (ω) (secondary) | 28±14° |
Orbit [6] | |
Period (P) | 19.4513±0.0011 d |
Semi-major axis (a) | 140.6±4.7 R☉ |
Inclination (i) | 70.85±0.6° |
Periastron epoch (T) | 2451775.102±0.032 |
Details [6] | |
A | |
Mass | ~50 M☉ |
Radius | 54.5±1.8 × 58.2±1.9 × 62.7±2.1 R☉ |
Luminosity | 1,100,000 L☉ |
Surface gravity (log g) | 3.0 cgs |
Temperature | 24,400 K |
B | |
Mass | ~50 M☉ |
Radius | 54.5±1.8 × 58.2±1.9 × 62.7±2.1 R☉ |
Luminosity | 1,100,000 L☉ |
Surface gravity (log g) | 3.0 cgs |
Temperature | 23,500 K |
Other designations | |
GCIRS 16SW, S97, S1-16 [7] | |
Database references | |
SIMBAD | data |
GCIRS 16SW, also known as S97, is a contact binary star located in the Galactic Center. It is composed of two hot massive stars of equal size that orbit each other with a period of 19.5 days. The stars are so close that their atmospheres overlap, and the two stars form an eclipsing binary varying in brightness by 0.35 magnitudes at infrared wavelengths. [6]
GCIRS 16SW orbits Sagittarius A* at approximately 19,000 AU, with a period of approximately 1,270 years. [5] At the stars' estimated mass of about 50 solar masses, they are predicted to have a lifespan of about 4 million years, indicating that the system formed within 0.1 parsecs (0.33 ly ; 21,000 AU ) of Sagittarius A*, instead of having migrated inward from a greater distance. [6]
GCIRS 16SW was classified as a candidate luminous blue variable on the basis of its spectrum and physical properties. [8] This was before it was identified as an eclipsing binary, but it is still treated as a candidate LBV. [9]
Each star is strongly distorted by the gravity of the other star. The polar radius is calculated to be 54.5 R☉, while the radius along the direction of orbital motion is 58.2 R☉. The radius along the line joining the two stars is 62.7 R☉, while the separation of the centres of the two stars is 132.8 R☉. A calculation of properties treating the binary as a single star gave an effective temperature of 24,400 K . [8] The secondary component is found to have a temperature 96% of that of the primary. However, these temperatures yield a luminosity over a million times that of the sun, uncomfortably close to the Eddington luminosity for each star, and it is suspected the actual temperatures are slightly lower. [6]
Sagittarius A*, abbreviated Sgr A*, is the supermassive black hole at the Galactic Center of the Milky Way. It is located near the border of the constellations Sagittarius and Scorpius, about 5.6° south of the ecliptic, visually close to the Butterfly Cluster (M6) and Lambda Scorpii.
The red-giant branch (RGB), sometimes called the first giant branch, is the portion of the giant branch before helium ignition occurs in the course of stellar evolution. It is a stage that follows the main sequence for low- to intermediate-mass stars. Red-giant-branch stars have an inert helium core surrounded by a shell of hydrogen fusing via the CNO cycle. They are K- and M-class stars much larger and more luminous than main-sequence stars of the same temperature.
Delta Velorum is a triple star system in the southern constellation of Vela, near the border with Carina, and is part of the False Cross. Based on parallax measurements, it is approximately 80.6 light-years from the Sun. It is one of the stars that at times lies near the south celestial pole due to precession.
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.
GCIRS 13E is an infrared and radio object near the Galactic Center. It is believed to be a cluster of hot massive stars, possibly containing an intermediate-mass black hole (IMBH) at its center.
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.
S2, also known as S0–2, is a star in the star cluster close to the supermassive black hole Sagittarius A* (Sgr A*), orbiting it with a period of 16.0518 years, a semi-major axis of about 970 au, and a pericenter distance of 17 light hours – an orbit with a period only about 30% longer than that of Jupiter around the Sun, but coming no closer than about four times the distance of Neptune from the Sun. The mass when the star first formed is estimated by the European Southern Observatory (ESO) to have been approximately 14 M☉. Based on its spectral type, it probably has a mass of 10 to 15 solar masses.
AB7, also known as SMC WR7, is a binary star in the Small Magellanic Cloud. A Wolf–Rayet star and a supergiant companion of spectral type O orbit in a period of 19.56 days. The system is surrounded by a ring-shaped nebula known as a bubble nebula.
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.
HD 15558 is a massive O-type multiple star system in Cassiopeia and is specifically in our galaxy's Heart Nebula in open cluster IC 1805. The primary is a very massive star with 152 M☉ and 660,000 L☉.
HP Lyrae is a variable star in the constellation Lyra, with a visual magnitude varying between 10.2 and 10.8. It is likely to be an RV Tauri variable, an unstable post-AGB star losing mass before becoming a white dwarf.
AB8, also known as SMC WR8, is a binary star in the Small Magellanic Cloud (SMC). A Wolf-Rayet star and a main sequence companion of spectral type O orbit in a period of 16.638 days. It is one of only nine known WO stars, the only Wolf-Rayet star in the SMC not on the nitrogen sequence, and the only Wolf-Rayet star in the SMC outside the main bar.
TV Geminorum is a variable red supergiant in the constellation Gemini. Its visual magnitude varies from 6.3 to 7.5.
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.
BP Crucis is an X-ray binary system containing a blue hypergiant and a pulsar.
HD 143183 is a red supergiant variable star of spectral type M3Ia in constellation Norma. It is a member of the Norma OB1 association, at a distance of about 2 kiloparsecs. It is one of the most luminous red supergiants with a luminosity over 100,000 times greater than the Sun (L☉), and is as well one of the largest stars with a radius more than a thousand times that of the Sun (R☉). Older studies frequently calculated higher luminosities and radii. It has an estimated mass loss rate of 5×10−5 M☉ per year and has been once described as a cool hypergiant. It is surrounded by a dozen early-type stars and a circumstellar nebula which extends 0.12 parsecs (0.39 ly).
V752 Centauri is multiple star system and variable star in the constellation of Centaurus. An eclipsing binary, its apparent magnitude has a maximum of 9.10, dimming to 9.66 during primary eclipse and 9.61 during secondary eclipse. Its variability was discovered by Howard Bond in 1970. From parallax measurements by the Gaia spacecraft, the system is located at a distance of 410 light-years from Earth.
GCIRS 7 is a red supergiant located in the Galactic Center. It is very bright and is one of the largest stars currently discovered, with a size about 960 solar radii. If placed in the Solar System, its photosphere would nearly engulf the orbit of Jupiter.
The Sagittarius A* cluster is the cluster of stars in close orbit around Sagittarius A*, the supermassive black hole at the center of the Milky Way. The individual stars are often listed as "S-stars", but their names and IDs are not formalized, and stars can have different numbers in different catalogues.
CV Serpentis is a binary star system in the equatorial constellation of Serpens. It is a detached eclipsing binary with an orbital period of 29.7 days. The system includes a Wolf–Rayet (WR) star with the identifier WR 113. The system is located at a distance of approximately 6,700 light years from the Sun based on parallax measurements. It is a member of the Serpens OB2 association of co-moving stars.