Scorpius X-1
| Observation data Epoch J2000.0 Equinox J2000.0 | |
|---|---|
| Constellation | Scorpius |
| Right ascension | 16h 19m 55.0693s |
| Declination | −15° 38′ 24.018″ |
| Apparent magnitude (V) | 12.40 |
| Characteristics | |
| Spectral type | M4-M5V |
| Variable type | X-ray binary |
| Astrometry | |
| Proper motion (μ) | RA: −7.185 mas/yr Dec.: −12.332 mas/yr |
| Parallax (π) | 0.4297±0.0220 mas |
| Distance | 7,600 ± 400 ly (2,300 ± 100 pc) |
| Orbit | |
| Period (P) | 0.7873114(5) days |
| Semi-major axis (a) | 4.37 R☉ |
| Inclination (i) | 25–34° |
| Semi-amplitude (K1) (primary) | 74.9±0.5 km/s |
| Details | |
| Optical star | |
| Mass | 0.40 M☉ |
| Radius | 1.25 R☉ |
| Luminosity | 0.114 L☉ |
| Temperature | 2,500–3,050 K |
| Neutron star | |
| Mass | 1.4 M☉ |
| Radius | 15–20 km |
| Temperature | (3–5)×107 K |
| Other designations | |
| V818 Sco, H 1620-15, RE J1619-153, XSS J16204-1536, 2U 1617-15, 4U 1617-15 | |
| Database references | |
| SIMBAD | data |
Scorpius X-1 is a low-mass X-ray binary located roughly 9,000 light years away in the constellation Scorpius. Scorpius X-1 was the first extrasolar X-ray source discovered, and, aside from the Sun, it is the strongest apparent non-transient source of X-rays in the sky.