However with an exemplary size of one, such claims could only be learned guesses, says Carl Rodriguez, an astrophysicist at Carnegie Mellon University.
Now data from LIGO’s latest catalog shows that black hole binaries are much less common than expected. In fact, the rate of melting black holes now observed could be “completely explained” by star clusters, according to a preview posted late last month by Rodriguez and his collaborators.
In addition, the new mergers enabled a new approach to the puzzle, where black holes come from. Despite their transient nature, black holes are very simple. Aside from mass and load, the only feature a black hole can have is spin – a measure of how fast it rotates. If a pair of black holes, and the stars from which they form, live their whole lives together, the constant pushing and pulling will line their spines. But if two black holes meet each other later in life, their spines are likely to be uneven.
After measuring the spin of the black holes in the LIGO data set, astronomers now suggest that the dynamic and isolated scenes are almost equally likely. There is no “one channel to govern all,” wrote University of Chicago astrophysicist Michael Zevin and collaborators in a recent press release describing many different paths that together can explain this new and growing population of black hole binaries.
“The simplest answer isn’t always the right one,” Zevin says. “It’s a more complicated landscape, and it’s certainly a bigger challenge. But I think it’s a more fun problem to deal with as well. “
LIGO and its sister observatory Virgo have grown more sensitive over time, meaning they can now see colliding black holes that are much farther from Earth and much further back in time. “We listen to a really big part of the universe, until the universe was much younger than it is today,” Fishbach says.
In a recent prepress, Fishbach and her collaborators found indications of differences in the types of black holes observed at different points in cosmic history. Especially heavier black holes appear to be more common earlier in the history of the universe.
This did not surprise many astrophysicists; they expect the first stars in the universe to be formed from huge clouds of hydrogen and helium, which would make them much larger than later stars. Black holes created by these stars must therefore also be huge.
But one thing is to predict what happened in the early universe, and another is to observe it. “You can really get used to it [black holes] as a trace of how the universe formed stars during cosmic time – and how the galaxies that make up those stars and star clusters are put together, “says Rodriguez.” And that becomes very cool. “
The study is a first step towards using large databases of black holes as a radical tool to explore the cosmos. Astronomers have created an astonishingly accurate model of how the universe evolved, known as Lambda-CDM. But no model is perfect. Gravitational waves offer a way to measure the universe completely independent of any other method in the history of cosmology, says Salvatore Vitale, an astrophysicist at the Massachusetts Institute of Technology. “If you get the same results, you’ll sleep better at night. If you don’t do that, that shows a possible misunderstanding. “