Christopher Intaliata: this is Scientific american60 seconds of science, my name is Christopher Intagliata.
There are black holes everywhere in the universe. But where are they hiding? Well, it’s a little hard to say.
Priya Natarajan: Our current list of black holes is still very incomplete.
Ingria Tower: Yale astronomer Priya Natarajan said that black holes pose unique challenges for those who count.
Natarajan: These are dark objects with such peculiar characteristics that you will never be able to directly image them like we image galaxies. Therefore, we must infer their existence indirectly.
Ingria Tower: Natarajan and her colleagues Recent forecast There may be a large number of previously undiscovered supermassive black holes wandering around the galaxy. But, as the name suggests, supermassive black holes are very large—which makes them easier to detect than relatively small black holes of the same kind: so-called stellar black holes, whose masses are closer to our sun.
Natarajan: If you have a black hole of stellar mass, it does not have the same “charm”. So detecting them is tricky.
Ingria Tower: European researchers now claim to have accidentally discovered these unexpected treasure troves of stellar mass black holes in a fluffy star cluster called Palomar 5.
Mark Giles: In the paper, we call it a Rosetta Stone.
Ingria Tower: Mark Gieles is an astrophysicist at the University of Barcelona and the Catalan Institute for Research and Advanced Studies.
He said that Palomar 5 is known for its spectacular star trails, and in the past 11.5 billion years, it has been full of stars ejected from star clusters. But these traces proved to be a key clue that led Gilles and his team to a large group of black holes.
You see, astronomers set out to determine how these trajectories were formed. To do this, they ran more than three dozen computer simulations in which they allowed black holes of different configurations to occupy hundreds of thousands of stars over a period of about 11 billion years.
Giles: Each of these models will run for weeks to months. They run on special hardware, such as graphics cards, GPUs-essentially what you use to play games.
Ingria Tower: Hopefully, one of those models will spit out something similar to today’s Palomar 5. In the end, someone did it.
Giles: We see that the star is removed very effectively, because the black hole basically pushes the star away from the center.
Ingria Tower: The model explains the star trails. But this also suggests that Palomar 5 may have more than 100 black holes-which is three times the number of black holes that astronomers expect to find there.Details appear in the log Natural astronomy. [Mark Gieles et al., A supra-massive population of stellar-mass black holes in the globular cluster Palomar 5]
Natarajan of Yale University says this work provides another investigative tool for black hole hunters.
Natarajan: This is another indirect feature of the existence of these latent black holes.
Ingria Tower: This also hints at how much we might lose in other star clusters such as Pal 5.
Natarajan: If globular clusters like Pal 5 are further scattered with black holes, basically this inventory will explode.
Ingria Tower: In other words, our current black hole census seems to have some important loopholes.
thanks for listening.for Scientific american60 seconds of science, my name is Christopher Intagliata.
[The above text is a transcript of this podcast.]