Gravitational wave analysis hints at the way black hole pairs are formed
The movement of masses in the universe, such as stars in their orbits, gives rise to a kind of ripple of gravitational waves - a phenomenon that Albert Einstein predicted as early as 1916, with the development of the theory of general relativity. The first direct discovery of gravitational waves took place in 2015 and was one of the important confirmations of general relativity; The waves were picked up by the detectors as part of an international research to detect gravitational waves, after a technological development that lasted more than 25 years.
According to general relativity, gravitational waves are created by very fast motion of nearby systems in the gravitational field, such as stars, black holes and neutron stars (compressed stars, which are mostly made of neutrons). These systems, while mutually entangled, produce strong gravitational waves that can be measured from a distance of billions of light years, using very sensitive detectors.
Dr. Barak Zakai from the Department of Particle Physics and Astrophysics at the Weizmann Institute of Science, studies astrophysical phenomena using statistical tools and algorithms. "Gravitational waves are another way of looking at the universe," he says. "They are created from extreme processes such as the merging of black holes or neutron stars. In these processes, the emission of energy in gravitational waves is so strong that it causes the black holes to rapidly approach each other. Finally, they hit each other at a speed equal to about half the speed of light. As a result, they merge and release massive amounts of gravitational waves. In addition, gravitational waves penetrate through everything, there is no object that can absorb or deflect them, and they are not hidden by dust or gases. In short, they illuminate the universe for us in a different light and through them it is possible to decipher phenomena such as the formation of pairs of black holes and the heavy elements. Recording and measuring the signals of the gravitational waves with innovative detectors and examining their morphology, length and frequency reveal answers to various mysteries."
In their research, Dr. Zakai and his team analyze information produced by a detector called LIGO using advanced algorithms. This is how they detect gravitational waves that are not normally detected due to the noise in the instruments. "Detecting gravitational waves requires accurate and reliable knowledge of the changing properties of the noise in the device, and the algorithms we are developing manage to detect weak signals through the noise. This is how we found a mathematical correction that eliminates the effect of the change in the statistical properties of the noise, which makes it possible to discover additional gravitational waves."
In their latest study, which won a grant from the National Science Foundation, the researchers wanted to learn about the formation of pairs of black holes, the way they approach each other, collide and merge. "The rotation of the black holes causes the signals of the gravitational waves to be morphologically richer, due to periodic changes in their plane of motion. In order to discover and measure these phenomena, we search for and analyze the recorded and observed information using statistical tools and innovative algorithms that we are developing," explains Dr. Zakai.
Based on the analysis of the gravitational wave signals they did in their latest study, the researchers hypothesized that many pairs of black holes were formed within clusters (clusters) of millions of stars. There, following the interaction of three stars, they managed to collide and merge. "If the pairs of black holes are indeed formed in this way, we hypothesize that their mass is similar to the mass of a single black hole formed after the death of a star, and that the direction (rotation) of each of them is random with respect to the other and the plane of motion. These are phenomena that are still unknown in the known universe", concludes Dr. Zakai.
Life itself:
Dr. Barak Zakai, 35, married + three children, lives in Rehovot. In his free time he likes to play chess and ultimate frisbee.
More of the topic in Hayadan:
- Astrophysicists predict the strength of gravitational waves from merging supermassive black holes
- Two gravitational wave events within 10 days: black holes have been discovered that eat neutron stars - "like Pac-Man"
- Researchers have retrospectively identified another event of gravitational waves from colliding neutron stars
- For the first time, gravitational waves and light waves were discovered from the same event - the merger of two neutron stars
- "With the LIGO upgrade we will be able to discover dozens of gravitational wave events per year"
