Star's Violent Death Could Reveal a Rare 'Missing Link' Black Hole

 

Black holes don't emit any light we can detect, but the dying stars they devour do. (NASA, ESA, Ralf Crawford/STScI)

A bright burst of light in a galaxy about 450 million light-years away showed a likely black hole that had just woken up to eat a passing star. This is not a very uncommon occurrence in and of itself.

The identify of the black hole in question—an elusive middleweight, or intermediate-mass black hole—is the sting in this specific tail. This mass range is so uncommon that it has presented a significant obstacle to our comprehension of the creation of supermassive black holes.

You see, there are typically two different mass regimes for black holes. On the one hand, there are stellar-mass black holes, which have masses up to around 100 times that of stars. A black hole is created when a huge star explodes as a supernova, leaving its core to collapse due to gravity.

Millions to billions of times the mass of the Sun is found in a supermassive black hole. These giants form a gravitational hub in the middle of galaxies. Astronomers are getting closer to understanding the enigma of how supermassive black holes form.

Growth from a stellar mass black hole seed is one potential route, but the main issue with this is that astronomers have discovered a startlingly small number of black holes between 100 and 1 million solar masses.  The universe should be dotted with things halfway through the black hole's trip from star mass to supermassive.

HLX-1 is located around 40,000 light-years from the center of its host galaxy. (NASA, ESA, CXC, Yi-Chi Chang/National Tsing Hua University)

 An X-ray source known as HLX-1 is useful in this situation.  Very bright X-rays have been observed coming from this object, which is situated in a nearby galaxy.  By 2012, it was 100 times brighter than when it first showed up in X-ray observations in 2009.  By 2023, it had dimmed once more.

The amazing thing about the light that an object emits when it is sucked up by a black hole is that it can reveal information about the size of the black hole. Though not at the level of a supermassive black hole, the light HLX-1 released was too brilliant to be a stellar-mass black hole.

An intermediate-mass object, between roughly 1,000 and 10,000 solar masses, waking up and snacking, is the best fit for the observed light and the changes it underwent, according to a team led by astronomer Yi-Chi Chang of the National Tsing Hua University in Taiwan. It is currently unknown if it was a one-time snack or an orbiting star that the black hole periodically consumes.

According to astronomer Roberto Soria of the Italian National Institute for Astrophysics, "we need to wait and see if it's flaring multiple times, or there was a beginning, there was a peak, and now it's just going to go down all the way until it disappears."

In any case, the finding is intriguing and adds to our understanding of the universe's most gravitationally intense objects.

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