Tycho G
Star in the constellation Cassiopeia
From Wikipedia, the free encyclopedia
Tycho G has been proposed as the surviving binary companion star of the SN 1572 supernova event. The star is located about 6,500±1,300 light-years away in the constellation Cassiopeia. It is a subgiant, similar to the Sun in temperature, but more evolved and luminous.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Cassiopeia |
| Right ascension | 00h 25m 23.59578s[1] |
| Declination | +64° 08′ 02.0297″[1] |
| Apparent magnitude (V) | 18.71[2] |
| Characteristics | |
| Evolutionary stage | subgiant[3] |
| Spectral type | G0/1 IV[3] |
| Astrometry | |
| Radial velocity (Rv) | −79.22[2] km/s |
| Proper motion (μ) | RA: −2.50[2] mas/yr Dec.: −4.22[2] mas/yr |
| Parallax (π) | 0.5189±0.0993 mas[1] |
| Distance | approx. 6,000 ly (approx. 1,900 pc) |
| Details | |
| Mass | 1.0[3] M☉ |
| Radius | 1.32–2.63[3] R☉ |
| Luminosity | 1.9–7.6[3] L☉ |
| Surface gravity (log g) | 4.0[2] cgs |
| Temperature | 6,025[2] K |
| Metallicity | −0.13[2] |
| Rotational velocity (v sin i) | < 6[2] km/s |
| Age | 5.7[2] Gyr |
| Other designations | |
| Tycho G, 2MASS J00252358+6408019 | |
| Database references | |
| SIMBAD | data |
Origin of the name
The supernova SN 1572 is often called "Tycho's supernova", named after Tycho Brahe who observed the "new star" in 1572. The postfix "G" originates from the candidate companion stars considered in a 2004 study, labelled Tycho A to Tycho V.[4]
Evidence for companion hypothesis
Tycho G is travelling away from us at nearly 80 km/s, much faster than the mean velocity of other stars in its stellar neighbourhood. It matches the properties of some models for the pre-supernova star system, although other studies exclude it.[5]