Black holes are not distinguished particularly. They can be so only in terms of one colour and one shape, which is black and a sphere.
The main difference between black holes is mass: some weigh about as much as a star like our Sun, while others weigh around a million times more. Stellar-mass black holes can be distributed throughout a galaxy. However, the really big ones have to be at the cores of galaxies-theyre called supermassive black holes.
Still, these super-massive giants are very tiny when viewed through a cosmic perspective, consisting of about only 1 percent of their host's mass in galaxy and reaching out only to a millionth of its width.
However, as we have only recently found out, it's a rather surprising relationship, between what actually happens in the environs of the black hole and the general shape of the entire galaxy that surrounds it. Our results appear in Nature Astronomy.
When black holes light up
Supermassive black holes are actually pretty rare. Our Milky Way galaxy has one at its center, referred to as Sagittarius A, and lots of other galaxies appear to contain a single supermassive black hole at their center.
In the right conditions, dust and gas falling toward these galactic cores can create a disk of hot material around the black hole. That "accretion disk" then goes on to produce a superheated jet of charged particles ejected from the black hole at mind-boggling velocities, close to the speed of light. This is a quasar when a supermassive black hole lights up in this way.
How to observe a quasar
To see quasar jets in some detail, we generally employ radio telescopes. Sometimes we even correlate our observations from more than one radio telescope placed at different locations on the Earth.
By means of an interferometric technique called very long baseline interferometry, we essentially make one telescope the size of the entire Earth. That behemoth eye is far finer than any individual telescope at resolving fine detail. As a result, we are able to discern objects and structures much smaller than we ever could with our naked eye; and we can do better than the James Webb Space Telescope.
This is the method behind the first "image" of a "black hole," released in 2019, showing the halo of light produced around the supermassive black hole hosted by galaxy M87.
Quasar jets that can be detected with very long baseline interferometry are millions of light years in length and are almost always in elliptical galaxies. The technique of very long baseline interferometry lets us observe them down to a few light years or so from their black hole of origin.
The direction of the jet near its source tells us about the orientation of the accretion disk, and so potentially the properties of the black hole itself .
Connecting to the host galaxy
A galaxy is a three-dimensional object, formed of hundreds of billions of stars.
But we see it to us in projection, either as an ellipse or a spiral. We can measure the shape of these galaxies by tracing the profile of starlight and may even measure the long axis and short axis of the two-dimensional shape.
We compare the direction of quasar jets with the direction of this shorter axis of the galaxy ellipse in our paper and find that they are pointing in roughly the same direction. That is a significantly more significant alignment than you would expect if they were randomly oriented.
This is surprisingly because this black hole is really tiny compared to the length of the jets that we measure, and in comparison to its host galaxy, it's hundreds of thousands or even millions of light years across.
But the really surprising thing is, from a size perspective of the object, it can influence or be influenced by its environment on such huge scales. We'd obviously expect to see the jet relate to the local environment, but not on the whole galaxy.
Galaxy formation
Does this say something about the mechanism for the formation of galaxies?
The best-known kind of galaxy is a spiral, but in some cases, they run into other spirals and end up forming elliptical galaxies. These three-dimensional egg-like things look like two-dimensional ellipses in the sky. The merger process can trigger quasar activity in ways we do not understand. As a consequence, nearly all quasar jets that can be detected using very long baseline interferometry are hosted in elliptical galaxies.
The mystery of our results is interpreted precisely. But it is significant in this context of the discovery by the James Webb Space Telescope of highly massive quasars, with a supermassive black hole inside them; much earlier than expected, on this universe's scale of times. Evidently, we should learn something new about how galaxies evolve and how black holes affect that process. (The Conversation) PY
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