For astronomers, in particular, learning about Sagittarius A* is important because it provides insights into the formation of our galaxy and black holes themselves. Image credit: X-ray: NASA/UMass/D.Wang et al., IR: NASA/STScI | › Full image and caption Why They're Importantīlack holes hold allure for everyone from young children to professional astronomers. The inset shows Sgr A* in X-rays only, covering a region half a light year wide. It was made by combining X-ray images from NASA's Chandra X-ray Observatory (blue) and infrared images from the agency's Hubble Space Telescope (red and yellow). This image shows the center of the Milky Way galaxy along with a closer view of Sagittarius A*. Scientists are uncertain how supermassive black holes form, but one theory is that they result from the combining of stellar-mass black holes. Supermassive black holes contain between a million and a billion times as much mass as a stellar-mass black hole. (Some of the mass was converted to energy and about nine solar masses were radiated away as gravitational waves.) The Laser Interferometer Gravitational Wave Observatory, or LIGO, funded by the National Science Foundation, detected the merger of two stellar-mass black holes with masses 65 and 85 times that of our Sun forming an intermediate-mass black hole of 142 solar masses. NASA’s Chandra X-ray Observatory has identified several intermediate-mass black hole candidates by observing X-rays emitted by the gas surrounding the black hole. Until recently, the existence of intermediate-mass black holes had only been theorized. Intermediate-mass black holes have masses between about 100 and 100,000 times that of our Sun. If the star’s mass is more than about 25 times that of our Sun, a stellar-mass black hole can form. Once the fuel in the core of a high-mass star has completely burned out, the star collapses, sometimes producing a supernova explosion that releases an enormous amount of energy, detectable across the electromagnetic spectrum. Image credit: NASA/CXC/M.Weiss | › Full image and caption This gas forms a disk of hot gas around the black hole, and the wind is driven off this disk. The strong gravity of the black hole, on the left, is pulling gas away from a companion star on the right. This illustration shows a binary system containing a stellar-mass black hole called IGR J17091-3624. The outflow of energy from the central regions of the star provides the pressure necessary to keep the star from collapsing under its own weight. Stars are fueled by the nuclear fusion of hydrogen, which forms helium and other elements deep in their interiors. They comprise one of the possible endpoints of the lives of high-mass stars. Stellar-mass black holes are found throughout our Milky Way galaxy and have masses less than about 100 times that of our Sun. There are three different types of black holes, categorized by their size: stellar-mass, intermediate-mass, and supermassive black holes. Scientists know how some types of black holes form, yet the formation of others is a mystery. We can surmise a lot about the origin of black holes from their size. Black holes come in various sizes and can exist throughout space. In fact, a black hole contains a great amount of matter packed into a relatively small space. Contrary to their name’s implication, black holes are not empty. Because not even light can escape, a black hole is literally black. Matter and radiation fall in, but they can’t get out. A black hole’s outer edge, called its event horizon, defines the spherical boundary where the velocity needed to escape exceeds the speed of light. A black hole is a location in space with a gravitational pull so strong that nothing, not even light, can escape it.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |