Massive Black Hole in Satellite Galaxy Displaces Stars into Milky Way

A significant discovery has emerged regarding a massive black hole located in the largest satellite galaxy of the Milky Way, which appears to be ejecting hypervelocity stars into our galaxy. This finding comes from a research team at the Harvard & Smithsonian Center for Astrophysics, which is currently undergoing peer review.

The team studied a selection of 16 hypervelocity stars racing through the Milky Way. They identified that only seven of these stars were accelerated to such high speeds within the galactic center. The remaining nine are believed to originate from the Large Magellanic Cloud (LMC) and are linked to a black hole that is much more massive than previously estimated.

Hypervelocity stars, or HVS, are defined as stars moving significantly faster than the escape velocity of their surrounding area. One mechanism for their formation is the Hills mechanism, where a binary star system is disrupted by a black hole, causing one of the stars to be expelled at speeds exceeding 1,000 kilometers per second. The research group focused on a limited number of these stars at the outskirts of the Milky Way. By analyzing some of their characteristics, the team was able to determine the extent of their acceleration in the LMC and estimate the mass of the black hole responsible.

The researchers conclude that the ratio of hypervelocity stars originating from the neighboring galaxy compared to those from the Milky Way can only be explained by the presence of a supermassive black hole hidden within the LMC. Their calculations suggest this black hole could have a mass of approximately 600,000 solar masses. While this is smaller than the 4.3 million solar masses of Sagittarius A*, the supermassive black hole at the center of the Milky Way, it is still significantly larger than previously thought.

The research adds another piece to the puzzle regarding the LMC, which has about 10% of the mass of the Milky Way. There remains uncertainty about whether it is orbiting the Milky Way or merely passing by. Recently, another research team noted that the LMC has retained enough gas for star formation despite what they termed a "catastrophic interaction" with the Milky Way, largely due to its relatively large size. If it had been smaller, it may have only contained an aging population of red stars alongside a hefty black hole at its core.