Credit: ESO/VPHAS+ Survey/N. Wright
This new picture from the VLT Survey Telescope (VST) at ESO's Paranal
Observatory shows the remarkable super star cluster Westerlund 1 (eso1034).
This exceptionally bright cluster lies about 16 000 light-years from
Earth in the southern constellation of Ara (The Altar). It contains
hundreds of very massive and brilliant stars, all of which are just a
few million years old — babies by stellar standards. But our view of
this cluster is hampered by gas and dust that prevents most of the
visible light from the cluster's stars from getting to Earth.
Now, astronomers studying images of Westerlund 1 from a new survey of the southern skies [1] have spotted something unexpected in this cluster. Around one of the stars — known as W26, a red supergiant
and possibly the biggest star known— they have discovered clouds of
glowing hydrogen gas, shown as green features in this new image.
Such glowing clouds around massive stars are very rare, and are even
rarer around a red supergiant— this is the first ionised nebula
discovered around such a star. W26 itself would be too cool to make the
gas glow; the astronomers speculate that the source of the ionising
radiation may be either hot blue stars elsewhere in the cluster, or
possibly a fainter, but much hotter, companion star to W26.
W26 will eventually explode as a supernova.
The nebula that surrounds it is very similar to the nebula surrounding
SN1987A, the remnants of a star that went supernova in 1987 [2].
SN1987A was the closest observed supernova to Earth since 1604, and as
such it gave astronomers a chance to explore the properties of these
explosions. Studying objects like this new nebula around W26 will help
astronomers to understand the mass loss processes around these massive
stars, which eventually lead to their explosive demise.
Notes
[1] This picture forms part of a detailed public
survey of a large part of the Milky Way called VPHAS+ that is using the
power of the VST to search for new objects such as young stars and
planetary nebulae. A spectacular recent picture of the Prawn Nebula was made using observations from the same survey.
[2] This nebula is thought to have surrounded SN1987A’s progenitor star since before it went supernova.
Links
Source: ESO
