The research offers a new way to discover black holes from the early universe. The research was published today (Wednesday) in the prestigious journal Nature
A new study at Tel Aviv University suggests that, contrary to conventional scientific belief, the black holes created by the first stars heated the gas throughout the universe at a late period and left a clear signal that observers can detect using radio waves.
The article, which is published tonight (February 5, 2014 at 20:00, Israel time) in the journal Nature, is signed by Dr. Anastasia Fialkov from Tel Aviv University and "Ecole Normale Supérieure" in Paris, Prof. Renan Barkana from the School of Physics and Astronomy at Tel Aviv University and Dr. Eli Visbal from Columbia and Harvard Universities in the USA.
"One of the fascinating fields in astronomy is the study of the era of the formation of the first stars," explains Prof. Barkana. "Since the universe was then full of hydrogen atoms, the most promising way to observe this era is by measuring radio waves from the early universe, since the radiation of hydrogen has a wavelength of 21 cm - which falls in the range of radio waves."
Astronomers study our distant history, billions of years into the distant past. Unlike archaeologists, who can only examine remnants of the past, astronomers can see the distant past directly as it is. The light from distant objects reaches us after a long time, and we see these objects as they appeared when they emitted the light. As a result, if astronomers look far enough, with the help of powerful telescopes they can see the first stars just as they were in the early universe. Therefore, the new discovery, according to which the cosmic heating happened later, raises the possibility that it will not be necessary to look so far down the path to see this cosmic event, and it will be easier to discover it than first thought.
Among other things, the discovery of cosmic heating will make it possible to study the early black holes, because the heating was caused by black holes in binary systems. These systems were formed from binary (double) stars where the more massive star ended its life in a supernova explosion leaving a black hole in its place. Later, gas from the second star in the system is drawn to the black hole, torn apart under its enormous gravitational force and emits high-energy radiation - X-rays (X-rays). This radiation reaches far away, and researchers believe that it reheated the gas in the universe, after it had time to cool as a result of the expansion of the universe. The innovation in the current study is the heating delay.
"Until now, it was thought that the heating occurred very early," says Prof. Barkana, "but we discovered that this accepted picture depends on the exact energy of the heating X-rays. Observations conducted in recent years show that black holes in binary systems emit radiation at extremely high energies - which changes expectations about cosmic heating. We received a new prediction for an early period (when the universe was only 400 million years old) when we expected to see uniform radio waves in the sky emitted from the primordial hydrogen gas."
So far, several international groups of observers have built and started operating new arrays of radio telescopes, with the aim of discovering the radio waves from hydrogen in the early universe. These arrays were designed under the assumption that cosmic heating occurred too early for us to see, so it was thought that the telescopes would only be able to look for a later cosmic event, when radiation from stars broke up the hydrogen atoms in the spaces between galaxies. The new discovery overturns the accepted assumption, and raises the possibility that these radio arrays will also detect signs of the gas being heated by the early black holes.
7 תגובות
To someone
Basically you are right, even before collapsing into a black hole the massive star pulled material from its partner. But at that stage the fall of the material and its impact on the face of the star is not a catastrophic event (because the face of the star is at a radius where the force of gravity is still relatively weak). After the collapse, the material falls down a deeper potential well, accelerates, heats up greatly from friction and thus emits X-rays.
To someone
to your question Another possible explanation is that the double star of the black hole was formed only after an explosion
The super nova, from the cloud of material ejected by the supernova. Therefore before that it did not exist as a separate star but was part of the star that exploded.
Hawking's theory seems profound to me, if I misunderstood. I am impressed by the low height I am that he is one of the greatest experts on the subject of black holes, and even the dialog you held in a series of 2-3 articles was clear.
The fact that there is no publication of a theory, either that will come later or that it is difficult for him to translate insights into mathematics due to physical limitations.
I found the article even though it's $22 in NATURE does not distribute the link. Thank you for considering a section of the public that is more academic and wants to see what is done in other disciplines. In the last two weeks you have dealt with an article by Hawking, who is the only professor in the world who was allowed to publish an article without a theory. At his young age, he finds it difficult to translate his lofty ideas into mathematics. In addition, the article that explains from information theory the formation of the universe from nothing. The article on reducing dementia in diabetic mice. An article about Saranak winning the Wolf Prize on a useful topic for Dr. Nachmani's articles.
Someone it happens because they slowly get closer to each other. So instead of mating (which would have happened if it were 2 suns) the black hole drinks the white sun.
"Subsequently, gas from the second star in the system is drawn to the black hole, torn apart under its enormous gravity and emits radiation at high energies"
I didn't understand, why did it happen only after the sun became a black hole? After all, the mass of the black hole (and therefore also its gravitational force) is exactly equal to that of the sun before it collapsed into a black hole, so why, being still a sun, did it not forcibly tear the gas from the other star? What has changed in terms of the gravitational force it exerts on the star?
You still haven't found out about the early universe. This is a prediction.
And I don't see what's so dramatic about it. It is not something as grandiose as the headlines scream.