It's often said that size does matter and now a new study reveals that black holes come in different sizes as well - small, medium and large - a discovery which may impact our understanding of them, especially their formation.

Our universe has uncountable number of black holes, and now Scientists may be a step closer to unraveling the mystery of this seemingly exotic phenomenon by recognizing a mid-size or intermediate-mass black hole for the first time.

For the unfamiliar, black holes are regions in space that contain dense mass and because its surface gravity is so strong, even light is unable to escape through it. Even though black holes are invisible, scientists can locate them by following their gravitational pull on other space objects. Astronomers estimate that there are over 100 million black holes in our Milky Way galaxy alone.

While scientists were familiar black holes in the universe that range from around 10 times to 100 times the mass of the Sun in our solar system, the detection of the mid-size black hole has been difficult until now.

Previously, astronomers were familiar with the existence of "stellar mass" (dozen times bigger than the sun) and supermassive (billion times bigger than our nearest star) black holes, two extremes, and believed them to be the only two sizes. However, these small- and large-size black holes are now joined by mid-size ones courtesy of the new finding.

Dheeraj Pasham, an astronomy graduate student, and a team of scientists at the University of Maryland (UMD) have found an object dubbed "X-1" in the galaxy Messier 82 (M82), which is 400 times the mass of the sun. The black hole is located around 12 million light-years away from the Earth.

The scientists observed X-1 nearly 800 times between 2004 and 2010, using NASA's Rossi X-Ray Timing Explorer (RXTE) satellite telescope. They recorded individual X-ray particles that were emitted by X-1. The astronomers also charted the wavelength and intensity of X-rays in each sequence and then analyzed the result.

"Objects in this range are the least expected of all black holes," says Richard Mushotzky, a UMD astronomy professor and the co-author of the latest study. "Astronomers have been asking, do these objects exist or do they not exist? What are their properties? Until now we have not had the data to answer these questions."

The researchers disclosed that while for several decades they were observing objects that could potentially be medium-size black holes, they were unable to measure the mass of these black holes at the time and, therefore, were uncertain about their size.

Study author Mushotzky opines that the latest discovery is significant as the newly-found black hole is the first that has been accurately and precisely measured.

The discovery is an exciting breakthrough for the scientific community as it provides the "missing piece" between stellar and supermassive black holes.

The study has been published in the online journal Nature.

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