Many objects in the Milky Way prick the imagination: be it Saturn’s rings, the mystical shapes created from the primordial gas clouds, the strange exoplanets that careen around their stars at hyper speeds, or even our very own moon. However, VY Canis Majoris generally tops the list.

Situated in the constellation Canis Major, about 3,900 light years from earth, this star is the largest hypergiant we know of. This stellar titan was first observed over 200 years ago, and for many years afterwards it was suspected that it was part of a binary system. Because VY CMa is similar to what are known as Wolf-Rayet stars, it is surrounded by a large nebulae of complex arcs and filaments, meaning it was difficult for Astronomers to view the star effectively through the interstellar gas and dust clouds. After extensive studies were undertaken by the Hubble Space Telescope, it was confirmed in 1998 that there is no companion star. It is so huge that, if it was to replace our Sun here in the Solar System, its surface would stretch out beyond Saturn’s orbit. Furthermore, it takes over 8 HOURS for photons to travel from one side of the star to the other.

Hypergiants like VY Canis Majoris are so massive that they devour themselves at exponential rates. The amount of energy our Sun emits in year is equal to what a hypergiant would release in the matter of just 6 seconds. Although, these enormous levels of activity means that their lives are only measurable in *millions* of years (by comparison, our Sun is a pretty ‘normal’ star, and will live for about 10 *billion* years). But as well as burning up their fuel quickly, they also throw out billions of tons of gas and matter in violent explosions and outbursts – this further shortens the life of the star. It is believed that VY Canis Majoris has already shed half of its original mass, and could literally reach hypernovae at any time, but some astronomers believe that the star has the capability to last nearly another 100,000 years.

Hypernovae are a rare form of supernova, producing enough energy that they easily equal 100 regular supernovae. The core collapse of the star is so fast that the gamma rays produced can decompose the nuclei of elements such as iron inside the star. As neutrinos escape, the process is accelerated and protons and electrons are squeezed together to produce more neutrons and neutrinos – because the core now consists of almost no electrons, the neutrons/nuclei can pack together closer and closer until they can go no tighter. In a regular supernova this extremely dense ball could become a neutron star or a pulsar, but the unusually high mass of VY Canis Majoris (or a similar hypergiant) would result in the formation of a rogue stellar-mass black hole… with an explosion of gamma rays that has the ability to wipe out any cellular life in nearby solar systems. Luckily for us, we aren’t at risk from these rare and deadly objects. In fact, there are only a little more than 10 hypergiants recorded out of the 100 billion other stars present in the Milky way.

Breakdown of a hypernova.

On the positive side, the explosion of a hypergiant has the potential to condense clouds and increase proto-star formation within nearby nebulae or dust clouds. The spectacle would also shine so brightly that we would be able to see it during daytime here on earth! In an average sized galaxy a supernova occurs about every 50 years, and this means many have been recorded by our early and late ancestors. The last of which, was recorded by the famed astronomer, Johannes Kepler in 1604.

As for VY Canis Majoris, we can only wait and see what happens… But it is a perfect example of how the same laws of physics we live by can create almost unbelievable objects of wonder (as well as death and destruction – but that doesn’t matter because it’s awesome!)


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