Most massive star known

What to remember

Some 163,000 light-years away, in the Large Magellanic Cloud, the star R136a1 is thought to have around 291 times the mass of the Sun. No known star is more massive, or more luminous: it shines around 7.2 million times brighter than the Sun.

It is a Wolf-Rayet star of spectral type WN5h, at the centre of R136, the central concentration of stars in the large open cluster NGC 2070, in the Tarantula Nebula (30 Doradus). The cluster can be seen from the far southern sky with binoculars or a small telescope, at magnitude 7.25, but R136a1 itself is 100 times fainter than the cluster and can only be resolved with speckle interferometry.

The figure comes with a wide margin: plus or minus 46 solar masses, and the mass was estimated from stellar evolution models. Most masses of such very massive stars are inferred from theory and difficult measurements of temperature and luminosity, so they may be revised. Another estimate puts it between 170 and 230 solar masses.