Measuring a black hole 660 million times as massive as our sun
It's about 660 million times as massive as our sun, and a cloud of gas circles it at about 1.1 million mph. Scientists think every massive galaxy, like the Milky Way, has a massive black hole at its center, Baker said. "The ubiquity of black holes is one indicator of the profound influence that they have on the formation of the galaxies in which they live," he said.
|NGC 1332, a galaxy with a black hole at its center whose mass has been measured at high precision by ALMA |
[Credit: Carnegie-Irvine Galaxy Survey]
Their groundbreaking observations, made with the revolutionary Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, were published in the Astrophysical Journal Letters. ALMA, the world's largest astronomical project, is a telescope with 66 radio antennas about 16,400 feet above sea level.
Black holes -- the most massive typically found at the centers of galaxies -- are so dense that their gravity pulls in anything that's close enough, including light, said Baker, an associate professor in the Astrophysics Group in Rutgers' Department of Physics and Astronomy. The department is in the School of Arts and Sciences.
A black hole can form after matter, often from an exploding star, condenses via gravity. Supermassive black holes at the centers of massive galaxies grow by swallowing gas, stars and other black holes. But, said Baker, "just because there's a black hole in your neighborhood, it does not act like a cosmic vacuum cleaner."
Stars can come close to a black hole, but as long as they're in stable orbits and moving fast enough, they won't enter the black hole, said Baker, who has been at Rutgers since 2006.
"The black hole at the center of the Milky Way, which is the biggest one in our own galaxy, is many thousands of light years away from us," he said. "We're not going to get sucked in."
Research suggests that the growth of galaxies and the growth of their black holes are coordinated. And if we want to understand how galaxies form and evolve, we need to understand supermassive black holes, Baker said.
Part of understanding supermassive black holes is measuring their exact masses. That lets scientists determine if a black hole is growing faster or slower than its galaxy. If black hole mass measurements are inaccurate, scientists can't draw any definitive conclusions, Baker said.
To measure NGC 1332's central black hole, scientists tapped ALMA's high-resolution observations of carbon monoxide emissions from a giant disc of cold gas orbiting the hole. They also measured the speed of the gas.
"This has been a very active area of research for the last 20 years, trying to characterize the masses of black holes at the centers of galaxies," said Baker, who began studying black holes as a graduate student. "This is a case where new instrumentation has allowed us to make an important new advance in terms of what we can say scientifically."
He and his coauthors recently submitted a proposal to use ALMA to observe other massive black holes. Use of ALMA is granted after an annual international competition of proposals, according to Baker.
Author: Todd B. Bates | Source: Rutgers University [May 05, 2016]