Astronomical three-dimensional models can be ridiculously complex. They can range from black holes through which light cannot escape to the literal size of the universe and everything in between. However, not every object has received the attention required to create a complete model of it, so we can officially add another highly complex model to our list. University of Arizona astronomers have created a model of VY Canis Majoris, a red hypergiant that may be the largest star in the Milky Way. And they’ll use that model to predict how it’ll die.
Recently, there has been some discussion about how red hypergiants die. Astronomers initially assumed they simply exploded into a supernova, as so many other stars do. However, more recent data show a significant lack of supernovae in comparison to what would be expected if red hypergiants themselves exploded in this manner.
The current consensus is that they are more likely to collide into a black hole, which is much more difficult to observe directly than the previously proposed supernovae. It is unclear what exactly the characteristics of stars that would evolve into black holes are, and it would be helpful to have a model to find out.
Enter the University of Arizona team. They chose VY Canis Majoris as a good stand-in for the type of red hypergiants they wanted to learn more about. The star itself is massive, ranging in size from 10,000 to 15,000 AU, which means it would be 10,000 to 15,000 times farther away from the sun than the Earth is today. It’s also only 3,009 light-years away from Earth. Observers are drawn to VY Canis Majoris, which is located in the southern constellation Canis Major.
Its sheer size and proximity to our solar system make it an excellent candidate for observation. Astronomers can see the breathtaking complexity of what the star’s surface actually looks like with good observational data.
Mass loss is a fundamental process in the death of a star. Typically, this occurs when gas and dust are blown evenly out of the photosphere of a star. However, there are massive features on VY Canis Majoris that are similar to Earth’s coronal arcs but a billion times more massive.
The UA researchers used ALMA time to collect radio signals of the material ejected into space as a result of these eruptions. That material, which includes sulphur dioxide, silicon dioxide, and sodium chloride, would allow them to detect the speed at which it moves rather than just the presence of other ejecta like dust. To get the correct information, they had to align all 48 ALMA dishes and collect over a terabyte of data.
Processing all of the collected data can be difficult, and they are still working on some of it. Nonetheless, they had enough information to present to the American Astronomical Society in mid-June. When they have more data, they will be able to describe a more accurate model of one of the galaxy’s largest stars. And someday, far in the future, when VY Canis Majoris finally, officially dies, that model of what will happen to a red hypergiant might just get a chance to be tested.