When it comes to star sizes, there are dwarfs, there are giants, and there are supergiants.
And then there are hypergiants.
they are very big stars that live fast, die young, and go out with a big bang: Supernovae. And now we know before they leave that they also suffer from coughing: a massive explosion of clouds of dust that scream away at high speed, causing the star to change rapidly and deeply in it. the brightness.
If that’s familiar, yes, keep Betelgeuse in mind. We’ll get back to him.
But in this case we are talking about the VY star Canis Majoris (or VY CMa for short). This gloomy red hypergiant is about 4,000 light years away in the constellation Canis Major, the Big Dog (one of Orion’s hunting dogs). In this case, the constellation is appropriate: VY CMa is a big, long-gone star 2 billion kilometers wide.
For comparison, the sun is 1.4 million km across. VY CMa is over a thousand times larger. A. one thousand. Replace the sun with VY CMa and it would extend almost to Saturn’s orbit.
That would be too bad for the Earth. We would be inside. And because the star generates several hundred miles of solar energy, our planet would not last long there.
So this star is crushing in every direction. Stars like this do not last long, just a few million years, and as they age they generate so much light that they blow off their own surfaces, and the subject becomes that away with the intensity of the radiation from below. VY CMa may have started with as much as 40 times the mass of the sun, but it has already lost about half that. And this is where our story really begins.
The star ‘s observations show that it is emitting too much infrared light for a star of its kind, which is a strong indication that it is surrounded by dust. These are usually microscopic grains of rocky (silicate-loaded) or carbonaceous (sooty) material around the star (hence we call it circumellar, which is just a cool word). It is warmed by the light of the star so it shines in the infrared, causing overheating.
Very high views of VY CMa reveal this dust, and they also show that it is quite complex. The star is surrounded by knots, knobs, arcs, and scattered clouds. New ideas using Hubble, however, allowed astronomers to measure the speed at which this dust moves – much of it was emitted at tens of thousands of kilometers per hour. Fast. VY CMa does great things.
The beauty here is that they then measured the distance from the star to those different knobs and used that in conjunction with the distance to find the knobs back in time, to see when the eviction. What they found is really interesting … the age of the various bumps and other features show that they were blown off the star around 70, 120, 200, and 250 years ago.
Looking at historical scenes of the star, these moments go by at times with a great difference of brightness in the star, illuminating and shining with a great factor.
In other words, some physical device in the star caused it to erupt those huge clouds of dust, and those clouds then passed between us and the star, emitting it. The last big explosion was in the late 1800s, when the star fled. It used to be naked with eyes (almost) but after that explosion it diminished and has not clarified since.
And that’s so interesting because everyone’s favorite explosive star Betelgeuse had just gone through a terrific discount event at the end of 2019. For several months the star was shining at half its normal size, and astronomers are still arguing about what caused it. The two main controversies are cooling effects that let off its brightness, and the other – you managed – explosions of dust that blocked the star. I prefer the latter explanation; there is copious dust around Betelgeuse, and we know that he sometimes blows this stuff in big clouds. But a drop in temperature cannot yet be ruled out.
However, Betelgeuse is a real redhead. Lower mass, smaller, and not as light as VY CMa (which, after all, is one of the lightest stars in the entire galaxy), but very similar. If VY CMa is blowing off dust and dissipating, it then makes sense that the same could be going on with Big B.
There are other differences, some of which are important though. Betelgeuse is a constant variable star, undergoing dramatic changes in brightness on a one-year order due to physics advancing deep into the lower atmosphere. VY CMa is an irregular variant, and the changes in brightness take many years to complete, more likely due to the fact that things are going on in its very high atmosphere. So you have to be careful flipping from one star to another. But still, it’s an inspiring idea.
Stars like this really interest me. It’s hard to understand just how awesome they are with soul, how powerful, and how they live their lives. But they are essential for galactic evolution; they form heavy elements such as iron in their corrugations that are scattered throughout space when they explode. This stuff then goes into making new stars, new planets… and us. Literally, me and you.
The iron in your blood that was pumped through your body at one time was in the heart of an explosive star like VY CMa, which first pumped it into the galaxy. If that is not reason enough to study such stars, then nothing is.