A black hole delivery system. Image Credit: X-ray: NASA/CXC/Swinburne Univ. of Technology/A. Graham et al.; Optical: NASA/ESA/STScI.

Astronomers See Small Galaxy Deliver Black Hole to Another Galaxy

The black hole at its center is estimated to contain a mass of between 60,000 and 100,000 Suns. Additionally, millions of stellar-mass black holes may exist throughout the galaxy, containing between five and thirty solar masses.

Observers may have seen a galaxy’s black hole delivery system in action. Astronomers believe that a smaller galaxy acts as a “cosmic pizza boy,” delivering a black hole into another, larger galaxy.

NASA’s Chandra X-ray Observatory and Hubble Space Telescope data have been used to show how another galaxy may have delivered a large black hole to spiral galaxy NGC 4424. NGC 4424 appears to have merged within the last half billion years due to its peculiar morphology. As a result of the lack of gas, star formation in the outer parts of the galaxy has completely ceased, while in the inner region, it is still occurring in a mild manner. In three billion years, NGC 4424 will most likely become a lenticular galaxy.

NGC 4424 is located about 54 million light-years from Earth in the Virgo galaxy cluster. The main panel shows a wide-field optical image of this galaxy in this previously released image, which is approximately 45,000 light-years wide.

The black hole at its center is estimated to contain a mass of between 60,000 and 100,000 Suns. Additionally, millions of stellar-mass black holes may exist throughout the galaxy, containing between five and thirty solar masses.

As shown in the accompanying image, NGC 4424 is viewed from a close-up perspective using Chandra X-ray data (blue) and Hubble infrared data (red) that has been adjusted to show fainter features hidden by the model.

The inset image measures 1,160 light-years across. According to the study’s authors, the elongated red object is a cluster of stars called “Nikhuli,” referring to a Tulini celebration in which a rich harvest is wished for. The cluster was named after the Sumi language of Nagaland in India. There is a point source of X-rays in the Chandra data.

According to the researchers, Nikhuli is the center of a small galaxy that has seen most of its stars stripped away in a collision with the larger galaxy NGC 4424. Its elongated shape is also due to gravitational forces as it falls towards NGC 4424’s center.

At present, Nikhuli is about 1,300 light-years from the center of NGC 4424, or 20 times closer than our planet is to its own black hole.

According to Chandra X-ray data, matter from Nikhuli may be falling towards a stellar-mass black hole. In a cluster the size of Nikhuli, these smaller black holes are expected to be rare, so they argue that these smaller black holes are more likely to result from material falling slowly onto a more massive black hole weighing between 40,000 and 150,000 Suns.

A black hole of this size is expected to be found at the center of NGC 4424. As a result, researchers have concluded that Nikhuli is, therefore, a delivery system for NGC 4424’s supply of black holes, bringing along a massive black hole in this case.

Assuming NGC 4424’s center contains a massive black hole, Nikhuli’s black hole should orbit it. In this scenario, the distance separating the two massive black holes would shrink until gravitational waves would be produced, merging them.

A paper describing these results appeared in the December 2021 issue of The Astrophysical Journal, and a preprint is available online.


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Written by Ivan Petricevic

I've been writing passionately about ancient civilizations, history, alien life, and various other subjects for more than eight years. You may have seen me appear on Discovery Channel's What On Earth series, History Channel's Ancient Aliens, and Gaia's Ancient Civilizations among others.

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