Latest news with #JiwonJesseHan
WIRED
25-02-2025
- Science
- WIRED
Something Unexpected Is Spewing Stars Into the Milky Way
Feb 25, 2025 1:05 PM Fast-moving stars in the Milky Way indicate there could be a supermassive black hole in the neighboring Large Magellanic Cloud—something that has never been detected in a smaller galaxy. The Large Magellanic Cloud. Photograph: NASA New research from a team at the Harvard Center for Astrophysics suggests that the Large Magellanic Cloud, a dwarf galaxy neighboring the Milky Way, hosts a gravitational structure hundreds of thousands of times the mass of the sun: a potential supermassive black hole. The most widely accepted theory of galactic evolution holds that supermassive black holes are found only in the largest galaxies, such as the Milky Way. Until now, there was no reason to imagine that a small cluster like the Large Magellanic Cloud could host one. When x-ray telescopes or observatories have been trained on smaller clusters like the Large Magellanic Cloud, they have found no signatures associated with black hole activity. But then came the hypervelocity stars. For nearly 20 years, astronomers have spotted fast-traveling stars with enough acceleration to be ejected from their own galaxies. While a traditional star moves at about 100 kilometers per second, a hypervelocity star travels up to 10 times faster. Experts think such stars appear by being 'catapulted outward' by a supermassive gravitational structure under the Hills mechanism—which is where a binary star system interacts with a black hole, with one star captured by the black hole and the other flung away from it. Within the Milky Way itself there are hypervelocity stars that probably originated here. Studies suggest they were accelerated by Sagittarius A*, the supermassive black hole at the center of the galaxy. But at least 21 hypervelocity stars detected are consistent with being ejected by a supermassive black hole but cannot be linked to the intrinsic activity of the Milky Way. In the team's simulations, it's plausible that these stars are instead originating from the Large Magellanic Cloud. For the team, led by Jiwon Jesse Han, this is one of the first major pieces of evidence for the presence of a supermassive black hole in our neighboring dwarf galaxy. According to the team's initial calculations, this black hole structure could be between 251,000 and 1 million solar masses. Its average mass would be 600,000 times the size of the sun. The study—which is currently in preprint but is to be published in The Astrophysical Journal—used data from the European Space Agency's Gaia mission, whose purpose is to map millions of stars to calculate their motion. There could, of course, be other explanations for the phenomenon. Stars escaping from their galaxies could also originate from a supernova or any other energetic mechanism powerful enough to eject them. The paper's authors explain, however, that this does not appear to be the case with the hypervelocity stars that seem to come from the Large Magellanic Cloud. The Large Magellanic Cloud is an irregularly shaped galaxy orbiting the Milky Way, along with other dwarf star clusters, such as Sagittarius, Carina, or Draco. It is 163,000 light-years from Earth and has a diameter of approximately 14,000 light-years. Astronomers believe that in the distant future—in about 2.4 billion years—the Large Magellanic Cloud and the Milky Way will merge into a single larger cluster, along with other larger structures, such as the Andromeda galaxy. Experts believe that the merger process will be slow and, on a planetary scale, will not pose any problems. This story originally appeared on WIRED en Español and has been translated from Spanish.
Yahoo
14-02-2025
- Science
- Yahoo
A Supermassive Black Hole Is on a Collision Course With The Milky Way
A Milky Way collision with a supermassive black hole might be closer than we thought. Hidden deep in the Large Magellanic Cloud dwarf galaxy that orbits the Milky Way on an ever-closing loop, signs of a massive invisible object clocking in at around 600,000 times the mass of the Sun have been detected. Since the Large Magellanic Cloud will one day collide with our own galaxy, that means the black hole is also destined to come crashing in. What's even more interesting is that the black hole falls into a mass regime rarely seen, under a million times the mass of the Sun. If its existence can be confirmed, it gives us a new datapoint for understanding how black holes grow from star-sized masses to chunky monsters equivalent to not just millions but billions of Suns' worth of mass. The discovery, led by astrophysicist Jiwon Jesse Han of the Harvard & Smithsonian Center for Astrophysics (CfA), has been submitted to The Astrophysical Journal, and is currently available on preprint server arXiv. Black holes can actually be pretty difficult to spot. Unless they're actively slurping up matter, a process that produces blazing light as the material is super-heated by friction and gravity, they emit no radiation we can detect. That means scientists have to get tricky, and one of their tricks is to look for stars that are moving around in a way that can be explained no other way. The primary method of doing this is to measure for unusual orbits. It was by carefully studying orbits in the center of the Milky Way, for example, that astronomers confirmed the existence and mass of Sagittarius A*, the supermassive black hole at the center of the Milky Way (it's about 4.3 million solar masses, if you're interested). Han and his colleagues did not look for orbits, however. Instead, their research focused on another type of stellar motion: the hypervelocity star, anomalous objects that travel much faster than the average speed of other stars in their galaxy – so fast, they could even make a break for intergalactic space. There are a number of these daredevil stars zooming through the galactic halo, destination unknown. The way these stars are accelerated led the researchers to the notion that they might lead us to hidden black holes. That acceleration kick is known as the Hills mechanism, a three-body interaction between a black hole and two stars. Eventually, the gravitational dance will lead to a member of this triplet being forcefully yeeted across space at hypervelocity. The recently retired Gaia space telescope spent several years in space mapping the objects of the Milky Way, including their positions in three-dimensional space (which is harder than you'd think), as well as their motions and velocities. Armed with Gaia data, the researchers made a new analysis of 21 hypervelocity stars in the galaxy's outer halo that are consistent with the Hills mechanism. These stars are all of the B subtype, huge and hot, with relatively short lives, which means their high-speed journeys through space have to have been relatively short too. This analysis involved tracking back the stars' velocity and motion to their point of origin, carefully ruling our other possible acceleration scenarios. They were able to confidently trace 16 stars. Seven of them originated close to Sgr A*, at the center of the Milky Way. The remaining nine stars, however, appear to have come from the Large Magellanic Cloud. And together, they suggest ejection via the Hills Mechanism by an object that weighs around 600,000 solar masses – a hidden black hole lurking therein. The Large Magellanic Cloud currently orbits the Milky Way at a distance of around 160,000 light-years. Its long, slow fall into our galaxy is not a straightforward affair, but an ongoing dance; a recent estimate puts the encounter at around 2 billion years away. Once the two galaxies are merged, the supermassive hole in the Large Magellanic Cloud – if black hole there is – will make its way to the galactic center, where it will eventually, after many more eons, merge with Sgr A* to make an even bigger black hole. Astronomers believe that this is one way that black holes can grow from relatively small sizes to even bigger ones. It would be so incredible to see that process slowly taking place, right here in our own galaxy – even if we're not going to be around to see the finale. Future research, the team hopes, will help them confirm the existence and determine the properties of their fascinating new discovery. The research, submitted to The Astrophysical Journal, is available on arXiv. Astronomers Discover Nearby Alien World That May Sustain Life NASA Announces Return Date For Astronauts Trapped on ISS Record-Breaking Neutrino From Deep Space Spotted by Undersea Telescope
