When two black holes get close, what are the chances they will meet and emit gravitational waves?
Right in the center of our galaxy – the Milky Way – sits a supermassive black hole weighing several million of our suns. Prof. Tal Alexander
of the Faculty of Physics was part of that discovery. Currently, he is investigating what happens to bodies when they get close to such enormous black holes.
A small black hole is the remnant of a star that was bigger than our sun, until it exploded as a huge supernova. In the process, the star ejected most of its material, but its core collapsed inward. At some point, the gravity of this core became so great that not even light could escape.
Even though this star can’t be seen, the effects of its gravity on its neighbors are hard to ignore.
Such small black holes can grow by sucking in whatever is in their immediate vicinity. Alexander is trying to understand what is taking place in the dense crowd of nearby stars that are under the influence of the supermassive black hole’s gravitational pull. Recently, he and collaborators developed a new mathematical model to examine what happens when a small black hole approaches a large black hole.
Alexander: “We found, to our surprise, that the two black holes are not only attracted to each other, as we expected, but are also repelled. We are now investigating how this affects the chances they will meet, coalesce and emit gravitational waves. Such waves were predicted by Einstein a century ago, but still remain to be discovered.”
Suggesting a covered wagon, the form immediately arouses expectations in the traveler or wanderer. But this covered wagon stands on metal legs that will never roll. The wagon, with its sly wink of promise, creates a powerful attraction, pulling in the curious to be swallowed up, only their legs peeking out from under the wagon’s body. What happens to those who enter? Does time pass with the same speed inside as it does outside? What lures people into the maw of the covered wagon?
Shay Id Alony, b. Israel, 1974, lives and works in Tel Aviv. He is the recipient of the 2009 Young Artist Prize awarded by the Israel Ministry of Science, Culture and Sport. His work has been displayed in the Tel Aviv Art Biennale, a number of biennales for video art installation and in various museums in Israel.