If you make a list of the largest stars ever discovered in our galaxy, VY Big Dog would be in the top ten, if not the top five. Located at a distance of more than 3,800 light-years from Earth in the Big Dog constellation, this bloated red hypergiant contains as much mass as 40 of our Suns. Indeed, if VY of the Bolshoi were swapped with our Sun, its outer layers would extend far beyond the orbit of Jupiter.
But VY Big Dog does not have long to be in this Universe. She is approaching the final stage of her starry life, throwing a huge amount of materials into space. Using a high-contrast spectropolarimetric receiver for observing SPHERE exoplanets (Spectro-Polarimetric High-contrast Exoplanet REsearch instrument) mounted on the Very Large Telescope (abbr. VLT) in Chile, astronomers were able to directly observe how the light from VY Canis Polarized and polarized clouds of dust and gas are dropped from an aging star. Every year, VY Big Dog loses weight equivalent to 30 Earths. Much of this debris is rather large particles, large enough to be bogged down in the outer radiation pressure of an expanding star and even survive a supernova.
“Massive stars live a short life,” said Peter Scicluna of the Academy Sinica Institute of Astronomy and Astrophysics in Taiwan and lead author of a new article to be published in Astronomy & Astrophysics. “When they grow old, they start to lose a lot of mass. In the past, we could only theorize how it happens. But now, thanks to new data from SPHERE, we have found large dust particles around this hypergiant. They are large enough to be pushed by strong radiation pressure star, which explains the rapid mass loss of the star. "
The death of VY Big Dog will happen in the near future by cosmic standards, but up to this point a few hundred thousand light years away. When this happens, it will be amazing. Looking from Earth VY Big Dog will be as bright as the full moon.