U Scorpii
Recurrent nova system first seen in 1863
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U Scorpii (U Sco) is a recurrent nova system, one of 10 known recurring novae in the Milky Way galaxy.[5] Located near the northern edge of the constellation Scorpius it normally has a magnitude of 18, but reaches a magnitude of about 8 during outbursts. Outbursts have been observed in 1863, 1906, 1936, 1979, 1987, 1999,[6] 2010,[7] and 2022.
17.6 Min.[2]
| |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Scorpius |
| Right ascension | 16h 22m 30.78s[1] |
| Declination | −17° 52′ 42.8″[1] |
| Apparent magnitude (V) | 7.5 Max. 17.6 Min.[2] |
| Characteristics | |
| Spectral type | ? / White Dwarf |
| Variable type | Recurrent nova[2] |
| Astrometry | |
| Radial velocity (Rv) | 65[3] km/s |
| Proper motion (μ) | RA: −0.380±0.202[4] mas/yr Dec.: −7.591±0.144[4] mas/yr |
| Parallax (π) | −0.0945±0.1334 mas[4] |
| Distance | 19600+21000 −5300[2] pc |
| Other designations | |
| AAVSO 1616-17, Nova Sco 1863, BD−17 4554, 2MASS J16223079-1752431, Gaia DR2 6246188565119443072[3] | |
| Database references | |
| SIMBAD | data |
The 2010 outburst was predicted to occur April 2009 ± 1.0 year, based on observations during quiescence following the 1999 outburst.[8] The U Sco 2010 eruption faded by 1 magnitude in 1 day, and by 4 magnitudes in 6 days. By February 6 it was dimmer than magnitude 13. Between February 10–19, it was flickering around magnitude 14. The eruption ended on day 64, which is the fastest observed decline to quiescence of a recurring nova.[9] This eruption of U Sco became the best-observed nova event to its day, with 22,000 magnitudes accumulated.[9] Astronomers then predicted that another eruption of U Sco would occur in 2020±2. This prediction was correct: it brightened to +7.8 magnitude on 6 June 2022.[citation needed]
Originally identified as a nova in 1863 by English astronomer N.R. Pogson, U Scorpii was the third nova to be identified as recurrent, by American astronomer and historian of science Helen L. Thomas, in the years preceding World War II.[10][11]