Biggest star in the known universe is tearing itself apart as it dies

Astronomers believe that they're seeing the last dying 'gasps' of the biggest star in the known universe, as it blows off its outer layers in preparation for a massive supernova explosion.

Roughly 16,000 light years away, there's a cluster of hundreds of thousands of stars called Westerlund 1, and within this crowded region of space is a 'red hypergiant' star called Westerlund 1-26 (W26), which is quite likely the largest star in the known universe. Most giant stars are thousands to millions of times bigger than our sun. However, you could fit a billion or more stars like our sun in these hypergiants, and likely still have room to spare. To get a feel for just how truly immense these stars are, check out this short Discovery Channel video from a couple of years ago:

The video is great for giving the visual comparison, but it isn't perfect. It might just be due to an update in the size of the star since 2011, but VY Canis Majoris is actually closer to 3 billion times the size of our sun. Also, it's no longer considered to be the largest we've ever discovered. That title now falls to Westerlund 1-26. At the very least, it's just slightly bigger than VY Canis Majoris, at around 3.5 billion times the size of our sun. However, it could be as large as 16.5 billion times the size of our sun.

Astronomers at the European Southern Observatory also recently found something else to set W26 apart from other stars. Using the Very Large Telescope Survey Telescope, they've discovered a huge cloud of glowing hydrogen gas surrounding this colossus — something very rarely found around these hypergiant stars. In fact, the only other nebula they've seen like it is around a star called SN1987A, which we saw go supernova in 1987. This is a big hint that what they're seeing here is W26 blowing off its outer layers and it may be on the verge of exploding, not just as a supernova, but possibly a hypernova.

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Studying W26 over the next while should give astronomers added insight on what goes on during these massive stellar explosions, but what will be truly spectacular is actually seeing the hypernova happen.

The Westerlund-1 star cluster is located in the constellation Ara, deep in the southern hemisphere, and it never gets above the horizon for places like Canada, northern Europe or Russia. So, when W26 finally does go hypernova, those of us that live that far north will miss seeing it with our own eyes, but maybe that might be a good time to plan a vacation in some nice southern destination.

(Image courtesy: ESO/VPHAS+ Survey/N. Wright)

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