Stephenson 2-18
Stephenson 2-18 (St2-18, also known as Stephenson 2 DFK 1 and RSGC2-18)[3] is a red supergiant (RSG) or red hypergiant (RHG) star. It is close to, and a possible member of, the open cluster Stephenson 2. It is about 6,000 parsecs (20,000 ly) away from Earth in the constellation of Scutum and is one of the largest known stars.
 Dense starfield around the red supergiant star St2-18 (brightest star in the image) as seen from the 2MASS astronomical survey. The picture was published in 2003. Credit: Université de Strasbourg/CNRS | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Scutum |
| Right ascension | 18h 39m 02.3709s |
| Declination | -06° 05′ 10.5357″ |
| Characteristics | |
| Evolutionary stage | Red supergiant |
| Spectral type | ~M6[1] |
| Apparent magnitude (G) | 15.2631±0.0092 |
| Apparent magnitude (J) | 7.150 |
| Apparent magnitude (H) | 4.698 |
| Apparent magnitude (K) | 2.9 |
| Astrometry | |
| Proper motion (μ) | RA: −3.045±0.511 mas/yr Dec.: −5.950±0.480 mas/yr |
| Parallax (π) | −0.0081 ± 0.3120 mas |
| Distance | 19,560 ly (6,000 pc) |
| Details | |
| Radius | 2,150 R☉ |
| Luminosity | 90,000–440,000; 630,000[2] L☉ |
| Temperature | 3,200 K |
| Other designations | |
| Database references | |
| SIMBAD | data |
It is also possibly one of the most luminous of its type, if it is a member of the cluster. It is estimated to have a radius of 2,150 times that of the Sun,[4] and a volume 10 billion times that of the Sun, however these parameters are unreliable and it is likely not a member of Stephenson 2.[4][5]
This star has a spectral type of M6,[1] which is pretty unusual for a supergiant star (below the Hayashi limit) and corresponds to its cool temperature of 3,200 Kelvin.[4]
The clear single image of stephenson 2-18 was first taken in the year 2007 using 2MASS All-Sky Survey camera from Cerro Tololo Inter-American observatory in Chile.[6]
Stephenson 2-18 Media
The Australia Telescope Compact Array was used to derive Stephenson 2 DFK 1's 2012 bolometric luminosity and effective temperature estimates.
Stephenson 2 DFK 1 seen by Pan-STARRS DR1
References
- ↑ 1.0 1.1 Negueruela, I.. The population of M-type supergiants in the starburst cluster Stephenson 2. Eas Publications Series 60 (2013). p. 279–285. doi:10.1051/eas/1360032.
- ↑ Humphreys, Roberta M.. Exploring the Mass-loss Histories of the Red Supergiants. The Astronomical Journal 160 (3) (2020). p. 145. doi:10.3847/1538-3881/abab15.
- ↑ Stephenson, C. B.. A possible new and very remote galactic cluster. The Astronomical Journal 99 (June 1990). p. 1867. doi:10.1086/115464.
- ↑ 4.0 4.1 4.2 Fok, Thomas K. T.. Maser Observations of Westerlund 1 and Comprehensive Considerations on Maser Properties of Red Supergiants Associated with Massive Clusters. The Astrophysical Journal 760 (1) (2012-11-05). p. 65. doi:10.1088/0004-637x/760/1/65.
- ↑ Humphreys, Roberta M.. Exploring the Mass-loss Histories of the Red Supergiants*. The Astronomical Journal 160 (3) (2020-09-01). p. 145. doi:10.3847/1538-3881/abab15.
- ↑ Stephenson 2-18: Everything About This Largest Star - Planets Order (in en-US) (2023-05-29). Retrieved 2023-10-07.