Pasham is an alum of IIT Bombay.
By The American Bazaar Staff
WASHINGTON, DC: A new study by an Indian American researcher Dheeraj Pasham, who is a University of Maryland post-doctoral student, and an alum of IIT Bombay, has discovered that black holes, that awesome entity in space that can swallow planets the size of earth like candy, comes in surprisingly three sizes: small, medium and extra large.
Astronomers have studied many black holes at either size extreme — “stellar-mass” black holes, which are a few dozen times as weighty as the sun, and supermassive black holes, which can contain millions or billions of times the mass of the sun and lurk at the heart of most, if not all, galaxies, reported Space.com.
Researchers have spotted hints of much rarer medium-size black holes, which harbor between 100 and several hundred thousand solar masses. But it’s tough to weigh these objects definitively — so tough that their existence has been a matter of debate.
But Pasham’s study has measured an intermediate black hole’s mass with unprecedented precision. A black hole in the nearby galaxy M82 weighs in at 428 solar masses, give or take a hundred suns or so, and that came out on August 17 in the journal Nature.
Black holes famously gobble up anything that gets too close, including light. But that doesn’t mean astronomers can’t see them; bright X-ray light streams from the superhot disk of material spiraling into a black hole’s mouth, said the Space report.
About 15 years ago, NASA’s Chandra X-ray Observatory spacecraft spotted such emissions coming from a source in the galaxy M82, which lies about 12 million light-years away from Earth. For a long time, Mushotzky and some other scientists suspected that the object, called M82 X-1, was a medium-size black hole. But those suspicions were tough to confirm.
Pasham took a closer look at M82 X-1. He and his team studied observations made from 2004 to 2010 by NASA’s Rossi X-ray Timing Explorer (RXTE) satellite, which ceased operations in 2012.
The RXTE data revealed a pair of repeating oscillations in M82 X-1’s X-ray emissions. These oscillations occurred 5.1 times per second and 3.3 times per second, respectively — a ratio of three to two. This fact allowed the team to determine the black hole’s mass.
“In essence, [the] frequency of these 3:2 ratio oscillations scales inverse[ly] with black hole mass,” Pasham told Space.com via email. “Simply put, if the black hole is small, the orbital periods at the innermost circular orbit are shorter, but if the black hole is big, the orbital periods are longer (smaller frequencies).”
The researchers calculated M82 X-1’s mass at 428 suns, plus or minus 105 solar masses.
Pasham finished his Ph.D. in Astronomy, from the University of Maryland, College Park, Maryland, in 2014, from where he also obtained his M.S in Astronomy. His thesis was titled ‘X-ray time and spectral variability as probes of ultraluminous X-ray sources.’ He graduated from the Indian Institute of Technology, Bombay, with a degree in B. Tech, Aerospace Engineering, in 2008.