BAT99-98

BAT99-98 is a Wolf–Rayet star in the Large Magellanic Cloud, situated inside NGC 2070 near the R136 cluster within the Tarantula Nebula (30 Doradus). It ranks among the most massive stars known and is close to being one of the most luminous.

In 1978, Jorge Melnick surveyed the 30 Doradus region and identified six new Wolf–Rayet stars, all of the WN sequence. The survey targeted stars brighter than apparent magnitude 14 within two arcminutes of the nebula’s center. The star now called BAT99-98 was labeled Mel J, with a magnitude of 13.5 and a spectral type of WN5. The following year, thirteen new Wolf–Rayet stars in the Large Magellanic Cloud were reported, including Mel J, which was numbered 12 and designated AB12 (or LMC AB12 to distinguish it from AB stars in the Small Magellanic Cloud).

Melnick later studied stars in NGC 2070 again, giving BAT99-98 the number 49 and reclassifying its spectral type as WN7. Neither AB12 nor Mel J is widely used today, though "Melnick 49" appears occasionally. More commonly, LMC Wolf–Rayet stars are referred to by R (Radcliffe Observatory) numbers, Brey (Breysacher catalogue) numbers, or BAT99 numbers.

Characteristics

BAT99-98 lies near the R136 cluster and shares similar mass–luminosity properties with the cluster’s massive stars. It is estimated to have held a certain mass at birth and has since lost a substantial amount.

It sheds mass through a stellar wind moving at a high speed. The star has a surface temperature and luminosity that place it among the brightest, but much of its light is ultraviolet and invisible to humans, making it 141,000 times brighter than the Sun visually. It is now classified as WN6, and models suggest it is 7.5 million years old.

Fate

The star’s fate depends on its mass loss. Stars this massive are thought unable to lose enough mass to avoid a catastrophic end. The outcome could be a supernova, hypernova, gamma-ray burst, or perhaps almost no visible explosion, leaving behind a black hole or neutron star.

The exact result hinges on the timing and amount of mass loss, with current models not fully matching observed stars. Most massive stars in the Local Group are expected to produce Type Ib or Ic supernovae, sometimes with a gamma-ray burst, and leave a black hole. For some exceptionally massive stars, a pair-instability supernova may occur, leaving no remnant at all.