WOH indeed ! To the left an actual image of another star in another galaxy, albeit one of the largest stars known, and the galaxy being in orbit of our own Milky Way at 'just' 160,000 light years from Earth.
To the right an artists impression.
The galaxy in question is the Large Magellanic Cloud, in the southern constellation of Dorado.
The star is in the upper section of this view, almost top middle.
The red star at the centre of this image is WOH G64, and is thought to be very close to going supernova, hence the interest and desire to image it, as while we have many good models of how stars die, we only get to witness the aftermath, so watching Betelgeuse and stars like this teach us a huge amount, validate our models or challenge them.
Source
(behind a pay wall sadly, but many other sources on this image)
The Andromeda Galaxy is the closest (non-dwarf) galaxy to our Milky Way, so much so there is evidence that suggests the material from our galaxy and Andromeda have already began the process of exchange, that dust and gas from the Milky Way or vice versa has made it to the other galaxy.
Additionally, it's so close, we can actually pick out individual stars within the galaxy, allowing us to track them on their path around the galaxy.
One such star was a rather large Red Giant, which appeared to dim over a period from 2016 then suddenly dramatically disappeared in 2023.
What the team think they may have witnessed was the first occurrence of a failed supernova, a star that is so large, that when it collapses, there's too much mass to create a neutron star, and it too collapses into a black hole, which then devours the star mass before it has a chance to cascade into a supernova.
JWST has taken a peep, and that study is still under way, but what JWST does show is an afterglow in IR, one that potentially is consistent with the material left over from the star forming an accretion disk and being devoured.
There are other possibilities, the great dimming of Betelgeuse was an example where dust and gas can be thrown out and temporarily obscure a star from view, or something similar can happen if a star merges with another, causing a huge amount of material to be ejected before it slowly clears up.
Either way, stellar blackholes are absolutely a thing, and no surprise it's so hard to catch one, when it simply quietly vanishes from view with little or no light show to confirm it.
Supernova are incredibly rare, from time to time we spot a distant one, but when we get one in a nearby galaxy or even our own, it's incredibly exciting for astronomers.
The last observed supernova in the Milky Way was in 1604, known as Kepler's supernova, which occurred 20,000 light years from Earth and got as bright as mag -2.5, it would have been the brightest star in the sky by some way (Sirius being -1.3), it is thought there may have been a few more since, but that they failed to become bright enough to the human eye having been concealed by dust and gas. It is thought this was a type 1A supernova.
SN1604 remnants
SN1987A occurred 150,000 light years from Earth but not in our Milky Way, but it's companion galaxy the Large Magellanic Clouds. Unlike SN1604, it was a type 2 supernova, a huge star that had collapsed having built up iron at it's core that it couldn't fuse, and when fusion energy stops pushing outwards, gravity wins ! The star collapsed.
Type 1 supernova come in a variety of flavours and are particularly interesting because they tend (Although not always) to explode with the same light output, allowing us to use these explosions to then predict the actual distance, or what we call Standard Candles in Astronomy.
SN2023ixf was similar to the SN1987a, a type 2 but at 20.87 million light years from Earth, it's close enough for us to observe. Much of those observations, especially in the past, were based on Radio output, and that should be useful in this new supernova, but many type 1a supernova's don't output much in the way of radio waves, and that's because of the way they occur.
Unlike type II. type 1a's occur in a tight binary partnership. One of the stars, maybe similar size to our Sun has died and become a white dwarf. Eventually it's companion also enters it's old age, expands and the white dwarf now starts pulling in huge amounts of hydrogen from the star's atmosphere, and increasing in mass.
Once it hits the Chandrasekhar limit of around 1.4 times the mass of our Sun, the weight of the white dwarf begins a second collapse, and goes supernova as it becomes a neutron star, often ejecting the old companion into space.
This is why many Type 1a supernova have similar brightness, because they explode only when they reach a point of collapse.
Credits for the title images go to @OkanaganAstro on Twitter who posted them when first spotted.
Other sources
New research shows that there are variations in how white dwarfs explode.
Supernova occur when a massive star (such as Betelgeuse) runs out of enough fusible material to maintain the thermal pressure pushing gravity back. The dramatic collapse crushes the core of the star so much, that even the atoms cannot survive, and a giant ball of neutrons forms a neutron star. Even larger and a black hole is formed ! But, discounting the exceptional cases where other objects are involved, why are the remnants so unique and different ?
Until recently, there was not much agreement on the internal processes, however a team of astrophysics' in the US believe they have created a computer model which goes somewhat to explaining the beautiful chaotic results of such stellar collapse.
“ These simulations have also revealed that turbulence results in an asymmetric explosion, where the star looks a bit like an hourglass. As the explosion pushes outward in one direction, matter keeps falling onto the core in another direction, fuelling the star’s explosion further. “
The atmosphere of the star is pulled towards the shrinking core, and fuses as it falls towards it, creating unimaginable amounts of energy that pushes out, but not in a uniform way, so there are still other areas where the atmosphere of the now dying star are continuing to fall towards the now near neutron based core.
Planetary nebula can take on more complex structures than just an orb of ejected gas. This particular nebula has quite a complex structure, with disk like structures and multiple shells, showing that sun like stars when they collapse into white dwarfs don’t always simply eject the stars atmosphere, the end can come in phases. Equally, the white dwarf is heavily on the blue side of the scale, making it a very hot 55,000′c at the surface (our Sun is 5,600′c in comparison).
White dwarfs despite no longer fusing are incredibly dense objects and the remaining carbon, oxygen is crushed to a ball not much larger than the Earth, yet holding a mass up to 1.4 times that of our Sun (depending on the mass of the star that collapsed). Such pressure actually heats up the remaining mass, however over time it does eventually begin to cool, just .. a very very long time ! So much so, no “black” dwarf has ever been found, but one 3,000′c is the coolest found so far.
From One Collapsing Star, Two Black Holes Form and Fuse
Black holes—massive objects in space with gravitational forces so strong that not even light can escape them—come in a variety of sizes. On the smaller end of the scale are the stellar-mass black holes that are formed during the deaths of stars. At the larger end are supermassive black holes, which contain up to one billion times the mass of our sun. Over billions of years, small black holes can slowly grow into the supermassive variety by taking on mass from their surroundings and also by merging with other black holes. But this slow process can't explain the problem of supermassive black holes existing in the early universe—such black holes would have formed less than one billion years after the Big Bang.
Now new findings by researchers at Caltech may help to test a model that solves this problem.
