milton keynes, Astronomers succeeded in taking the first direct image of a black hole in 2019. The luminous material in a black hole made it possible to image it, but many black holes are virtually impossible to detect. Now it looks like another team using the Hubble Space Telescope has finally found something no one had seen before: a black hole that’s completely invisible. The research, which has been posted online and submitted for publication in the Astrophysical Journal, is yet to be reviewed.
Black holes are those that remain after massive stars collapse and their cores collapse. They are incredibly dense, the gravity is so strong that nothing, including light, can escape from them. Astronomers are keen to study black holes because they can tell us a lot about the way stars die. By measuring the mass of black holes, we can know what was going on in the last moments of stars, when their cores were collapsing and their outer layers were disintegrating.
It may seem that black holes are invisible by definition – in fact they have earned this name because of their ability to block light. But we can still detect the way he treats the objects around him with his strong gravity. Hundreds of tiny black holes have been discovered by the way they interact with other stars.
There are two different approaches to this kind of identification. In “X-ray binary stars” – in which a star and a black hole orbiting a common center produce X-rays – a black hole’s gravitational field can pull material from its orbiting companion star. Is. That material surrounds the black hole and in doing so gets heated by friction. The hot material glows brightly in X-ray light, making the black hole visible, although the star later merges into the black hole and disappears.
You can even detect pairs of black holes as they merge, emitting a brief flash of gravitational waves before collapsing inside each other. There are also many rogue black holes that are roaming in space without having anything to do with anything, however – they are difficult to detect. This is a problem, because if we cannot detect individual black holes, we cannot know how they formed and how the stars died, after which they came into existence.
new dark horizons
To discover such an invisible black hole, the team of scientists had to combine two different types of observations over many years. This method was useful and proved to be a new way to find isolated black holes that were previously missing.
Einstein’s General Theory of Relativity predicted that when light passed through large objects, they would bend it. This means that any light passing too close to an invisible black hole – but not close enough to get inside it – will be twisted in the same way that light passing through a lens is twisted. This is called gravitational lensing, and can be seen when an object ahead is in the same line with a rear object, bending its light. This method has been used to study everything from clusters of galaxies to planets around other stars.
The authors of this new research combined two types of gravitational lensing observations in their search for black holes. Due to this, they saw light in a distant star, which suddenly increased before becoming normal. During this time, he could not see the object ahead, increasing the size of the object behind through the process of gravitational lensing. However, it suggested that the object could be a single black hole, something that had never been seen before. The problem was that it could also have been a faint star.
Much work was needed to determine whether it was a black hole or a faint star, and this is where other types of gravitational lensing observations came in handy. The authors repeatedly took pictures with Hubble for six years to measure how far the star had moved. Because his light was deflected.
Ultimately, this gave them the opportunity to calculate the mass and distance of the object that caused the lensing effect. They found that it is about seven times the mass of our Sun, located about 5,000 light-years away, which seems far away but is actually relatively close. A star whose size is such that it should be visible to us close. Since we cannot see it, he concluded that it must be a separate black hole.
It is not easy to make so many observations with an observatory like Hubble. Binoculars are very popular and there is a lot of competition for its time. And given the difficulty of verifying such an object, you might think that the chances of finding more of them are not very good.
Fortunately, we are at the beginning of a revolution in astronomy. This has been made possible with a new generation of facilities, including the ongoing Gaia Survey, and the upcoming Vera Rubin Observatory and the Nancy Grace Roman Space Telescope, all of which will repeatedly measure large parts of the sky with unprecedented detail.
This is going to be huge for all areas of astronomy. With regular, high-precision measurements of such a large part of the sky, we can collectively examine things that change over a very short period of time. We’ll study things as diverse as asteroids, the bursting stars known as supernovae, and planets around other stars in new ways. When it comes to the discovery of an invisible black hole, this means that instead of celebrating the discovery of just one, we may soon discover so many more that it becomes routine. It will also help us to know what we do not know about the formation of black holes after the extinction of stars. After all, hiding the invisible black hole of the Milky Way is going to be difficult now.
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