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03/28/2024 08:08:43 pm

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ALMA Sets Standard for Measuring the Mass of Black Holes

Measuring the supermassive black hole at the center of NGC 1332.

(Photo : A. Barth (UC Irvine), ALMA (NRAO/ESO/NAOJ); NASA/ESA Hubble; Carnegie-Irvine Galaxy Survey) Hubble sees a silhouetted disk surrounding the black hole. ALMA sees a bright spinning disk in radio wavelengths. The red part of the disk is cold gas moving away from the Earth while the blue is gas spinning toward us.

In a feat of incredible science, a team of astronomers determined the actual mass of a supermassive black hole 73 million light years from Earth using ALMA, the most powerful telescope in the world, and a lot of smarts.

Observations taken with the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile led a team of astronomers to conclude the black hole at the center of the elliptical galaxy NGC 1332 has a mass 660 million times greater than our Sun, give or take 10 percent.

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While heavier than the black hole at the center of our Milky Way galaxy, the mass of the NGC 1332 black hole pales in comparison to largest black holes known to exist.

Other studies about NGC 1332 using ground- and space-based telescopes estimated the mass of this black hole at 500 million to 1.5 billion times the mass of the Sun.

The astronomers, whose work was published in the Astrophysical Journal Letters, figured out the mass of the NGC 1332 black hole by measuring the strength of its gravitational pull on the stars and clouds of gas milling around it.

Their work gives the most accurate mass measurements to date for a black hole outside our galaxy. It helps develop a standard for measuring these terrifying anomalies.

The team led by Aaron Barth, an astronomer at the University of California, Irvine and lead author of the paper, used ALMA to measure the speed of carbon monoxide gas orbiting around the black hole at the center of NGC 1332.

Barth said measuring the mass of a black hole accurately is very challenging, even with the most powerful telescopes on Earth or in space.

"ALMA has the revolutionary ability to observe discs of cold gas around supermassive black holes at small enough scales that we can clearly distinguish the black hole's influence on the disc's rotational speed," he pointed out.

ALMA is an astronomical interferometer of radio telescopes consisting of 66 12 meter and 7 meter diameter radio telescopes observing the universe at millimeter and submillimeter wavelengths. ALMA is the most expensive ground based telescope in the world. 

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