About 10 million light-years from Earth, a blurry galaxy called Mirach’s Ghost can help unravel a dark mystery: where the largest black holes in the universe came from. But this spooky galaxy has also deepened the mystery surrounding the birth of these objects.
A black hole is a singularity, a region in spacetime where matter has become too dense to sustain itself and collapsed to a formless point. Supermassive black holes (SMBH) are cosmic monsters that often weigh billions of times the mass of our sun, compared to the mass of heavy stars that form ordinary black holes. They sit at the centers of large galaxies, sucking up gas and whipping stars around with their enormous gravitational pulls. There is one in the middle of the Milky Way and an even larger one in the middle of the Virgo A galaxy astronomers have photographed. But it is still not clear how these mammoth objects were formed.
Physicists believe that there are two possibilities: Perhaps SMBH̵
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“The problem is that at least most black holes have grown significantly since birth and swallow clouds of gas and dust swirling around them,” said Timothy Davis, an astrophysicist at Cardiff University in Wales. “This makes them heavier and makes it difficult to determine the mass they started their lives with.”
So Davis and his colleagues were looking for the smallest SMBH they could find.
These small supermassives, he told Live Science, “have not had the chance to consume large amounts of material before,” [so in studying them we are] approach to reveal what SMBHs must have looked like when they were formed. “
The researchers studied SMBH at the center of the galaxy “Mirach’s Ghost” (so-called due to from Earth the galaxy looks like a revelation near the star Mirach) and uses a new technology to determine its mass.
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By relying on data from the Atacama Large Millimeter / Submillimeter Array (ALMA) in Chile, researchers measured the velocity of carbon monoxide gas as it swirled toward SMBH in the center of Mirach’s Ghost galaxy.
“Just like water going around a plug-hole, this gas goes faster and faster as it approaches the black hole,” Davis said.
The vortex is a product of the mass of the black hole, so the speed of the vortex – exactly measured – can tell scientists how much the black hole weighs. ALMA’s images, with a resolution of 1.5 light-years (very detailed for such a distant object), made it possible. This SMBH, they found, has a mass that is less than 1 million times our sun – a baby according to SMBH standards. Based on estimates of how much it has grown since it was born, it probably weighed less than 500,000 times the mass of our sun when it was born, Davis said.
This does not show that any of the origin stories are correct, the researchers found. But it suggests some balance against the model of direct collapse and completely excludes extreme versions of the theory of direct collapse. Some theories of direct collapse do not allow SMEs that are so small at all.
Still, the origin of black holes is a mystery. One problem: Other observations have shown that very large SMBHs were in their current form very soon after the Big Bang, defying our assumptions about how fast black holes can grow.
“We know of two main ways to make SMBHs, and none of them can make black holes of this size right away. Instead, they must have been born smaller and grown to these amazing sizes. It’s really hard to do, because there is a limit on how much a black hole can swallow during the available time since the universe was created, “said Davis.” Our work exacerbates this problem. We have shown that any mechanism that makes SMBHs allow them to have a mass that is less than 500,000 times the mass of our sun when they were born. “
Although it chooses the scales against the theory of direct collapse, none of the theories offer good explanations of where such a small SMBH could have come from. The final answer is likely to involve some significant changes to one of the models physicists currently have.
So now physicists know a little more about what young SMBHs look like. But they are still not sure where they came from. The essay describing the black hole in the center of Mirach’s Ghost was published today (July 14) in the journal Monthly Notices of the Royal Astronomical Society.
Originally published on Live Science.