Eta Carinae may be the most scary star in the galaxy.
Let me paint a picture for you. Eta Car is actually two stars, both called type O stars, which means they are far more massive, warm and luminous than the sun. The largest of the two, called Eta Carinae A, is a sample probably one hundred or more times the mass of the sun. It is one of the most luminous stars in the galaxy that propagates something like five million times the sun's energy.
Five. Million .
If the second star, A Car B, was turned off by itself, it would also be considered an animal, with about 50 times the sun's mass and glowing with a hundred light thousand suns. But besides Eta Car A it is actually hard to see at all.
A star is a balance between gravity trying to pull it together in the core, and the heat makes it grow. Eta Car A is so massive that nuclear fusion in its core runs at a furious pace, and the energy it generates is so large that it can hardly stick together. a slight increase in brightness would tear the star apart. In 1
Eta Car has been the subject of intense control for decades. An observatory that has been used many times to see it is the Hubble Space Telescope. Just in time for the 4th of July, this Hubble image of Eta Car is released:
Sacred cosmic pyrotechnics!
The Eta Car star is in the middle of all the clutter that is almost covered by the gas around it (if you have trouble seeing it, the eight sharply defined lines can be directed to it, it is diffraction tips caused by light into Hubble and bending around the metal angles with a mirror in place, see the footnote on this article). The two large gas bottles from the large eruption are obvious; we see them at an angle so that you are on the star's side towards us and the other on the other side.
There is a thick disk of material around the star and you can see a hint between it between the two lobes. The two stars make Eta Car circuits every five years, which is really fast. This tends to throw material out into the plane of the circuit, creating that disk. As Eta Car A eruptions, the material had a harder time plowing through the disc, so instead blowing up and down it in polar directions.
The red material surrounding the bubbles is nitrogen gas blown into the eruption as Good, slamming into material that is either previously drafted from the star or just the material that floats around near the star (Eta Car is in the ridiculous large Carina Nebula, which is thick with gas and dust). The shock waves generated as the material plows into the slower gas, spans it and causes it to glow.
What's so interesting about this new picture is the blue material. Astronomers took ultraviolet images to look for magnesium (which shines in the UV) ejected from the outbreak and they expected to be mixed with the nitrogen. Instead, they found it (shown in blue in the image) between the star and the shocked outer gas. They expected the area to be empty, but here it is loaded with very hot gas. It is unclear what that gas does there, but it was not seen before. This means that large outbreaks were even more energetic because it also had to throw out of this rapidly moving gas. It seems that Eta Car really was right on this side of going supernova back in the 1840s.
It's hard to overestimate how complicated everything is. When I was working on Hubble, we had a recurring program to observe Eta Car in a matter of months, and I did some work on the astronomer running the Ted Gold program to treat the spectra. They were a nightmare; There is so much energy in the gas that each atom shines in a phenomenal number of wavelengths. Worse, the different gas speeds are forging and changing the wavelengths of light, making it difficult to know which elements we are even looking at. One day, Ted printed a few dozen of the spectra on paper and tied them together in a really long spectrum on the wall outside the office. I used to see him stand there and look at it and shouted at the awful complexity he had chosen to loosen. I could hardly make heads or tails out of it.
Another thing: The whole star lets you see wider rays of light that flow out. It is light from Eta Car that leans past material in the bubbles; the lumps between gas and dust block lights, but the holes between the lumps sound through, illuminating the gas beyond.
In other words, they are crepuscular rays, as you sometimes see on cloudy days, especially near sunset. Unbelievable.
Finally – probably in less than a million years, maybe less – Eta Car will really explode, become a supernova. When it does, it will easily shine Venus in the southern hemisphere and will probably be bright enough to cast shadows. From 75 quadrillion kilometers away.
How is the for a four-year July fireworks?