Melnick 42 is a massive blue supergiant star in the Tarantula Nebula in the Large Magellanic Cloud located in the constellation Dorado. Although it is only 21 times the size of the sun, its high temperature of 47,300 K makes it one of the most luminous stars of the Tarantula Nebula at 3,600,000 L☉. It is less than two parsecs from the centre of the R136 cluster, although that is well outside the central core.
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Dorado |
| Right ascension | 05h 38m 42.12s[1] |
| Declination | −69° 05′ 55.19″[1] |
| Apparent magnitude (V) | 12.78[1] |
| Characteristics | |
| Spectral type | O2If*[2] |
| B−V color index | +0.08[3] |
| Astrometry | |
| Radial velocity (Rv) | 173[4] km/s |
| Distance | 163,000 ly (49,970[5] pc) |
| Absolute magnitude (MV) | −7.4[3] |
| Details | |
| Mass | 189[3] M☉ |
| Radius | 21.1[6] R☉ |
| Luminosity | 3,600,000[3] L☉ |
| Surface gravity (log g) | 3.90[7] cgs |
| Temperature | 47,300[3] K |
| Rotational velocity (v sin i) | 240[7] km/s |
| Age | ~1 million[8] years |
| Other designations | |
MK42, Brey 77, BAT99 105, 2MASS J05384212-6905552 | |
| Database references | |
| SIMBAD | data |
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Mk 42 was originally classified as spectral type WN when it was discovered, then as O3 If. When the slash stars were defined it was given the spectral type O3 If*/WN6. Finally, the introduction of the spectral class O2 and the refinement of slash star classifications led to it being tagged as O2 If*. Although it is given a supergiant luminosity class, it is effectively a main sequence star still burning hydrogen in its core. It is thought to be less than a million years old.[8]