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Black holes are some of the most mysterious and intriguing objects in the universe. They are usually found at the center of galaxies where their incredible gravitational pulls attract gasses, planets and stars. As this cosmic material spirals into black holes, large, flat accretion disks are created, which — due to the immense heat and forces exerted on the material — causes the disks to heat up and glow from blackbody radiation.
Incredibly, black holes end up only consuming a fraction (or less) of the gas and materials in these accretion discs. The rest is thrown in all directions into space. In more dramatic cases this excess material is ejected out into space at speeds that are so high the interstellar gases surrounding black holes are cleared away.
The clearing of interstellar gas around black holes means that the black holes will no longer have anything to consume and that no new stars can form in the regions surrounding the black holes — altering the structure of the galaxy. Recently, the European Space Agency’s (ESA) XMM-Newton X-ray observatory observed an average-sized black hole that is clearing the interstellar gas around it using its extreme “black hole wind” — which, before the XMM-Newton observations, had only ever been detected at extreme black holes featuring accretion disks that are at the limit of the amount of matter they can pull in.
“You might expect very fast winds if a fan was turned on to its highest setting. In the galaxy we studied, called Markarian 817, the fan was turned on at a lower power setting, but there were still incredibly energetic winds being generated,”Miranda Zak of University of Michigan is the lead author.
As mentioned, the black hole XMM-Newton observed is located at the center of a galaxy named Markarian 817 — an active spiral galaxy located approximately 430 million light-years away from Earth.
“It is very uncommon to observe ultra-fast winds, and even less common to detect winds that have enough energy to alter the character of their host galaxy. The fact that Markarian 817 produced these winds for around a year, while not being in a particularly active state, suggests that black holes may reshape their host galaxies much more than previously thought,”Elias Kammoun from Roma Tre University, Italy, is the co-author of this book and an astronomer.
The center of a galaxy that contains an active blackhole is called the active galactic centre. Active galactic centres emit a lot of high-energy, X-ray-like light because of the accretion disks, and other extremely bright and hot material, surrounding black holes.
When researchers used NASA’s Neil Gehrels Swift Observatory, or Swift, to observe Markarian 817’s active galactic center, they noticed activity seemingly ceased and the galactic center got unusually “quiet.” Zak recalls the team’s first observations of the galaxy with Swift, saying, “The X-ray signal was so faint that I was convinced I was doing something wrong!”
The Swift observations intrigued the team, so they enlisted the help of ESA’s X-ray XMM-Newton observatory. Data from XMM-Newton showed that the ultra-fast winds of gas and material being ejected from the Markarian 817 black hole were acting as a sort of shield and blocking X-ray light being emitted by the black hole and its accretion disk — explaining the seemingly quiet nature of the black hole. Later observations of the galactic center of Markarian 817 using NASA’s Nuclear Spectroscopic Telescope Array, or NuSTAR, X-ray telescope showed a result similar to that of XMM-Newton’s.
Additional analysis of the XMM-Newton data showed that the accretion disk of the Markarian 817 black hole created gusty storms that spread over the entire area of the accretion disk — an extreme contrast to the normal singular puffs of gas and material ejected by accretion disks. The wind around the Markarian black hole lasted for hundreds of years and consisted of three distinct components. Each component moved at a percentage speed of light. The black hole was ejecting winds that were extremely fast.
Scientists are able to better understand black holes, their galaxies and how they interact and influence each other with the XMM-Newton Markarian results. A lack of interstellar gas surrounding black holes due to extreme cosmic winds is not an uncommon phenomenon — there are several galaxies, including our own Milky Way — that appear to have large, empty regions at their galactic centers where very few to no new stars form. Extreme black hole winds may explain the empty region. However, this theory only holds if the black holes that generate the winds are active and have normal levels of activity.
ESA – XMM-Newton spots a black hole throwing a tantrum. This prevents the galaxy around the black hole from producing new stars. It gives us an insight into the co-evolution of black holes and galaxies. https://t.co/c4Dw4cg8Wh
— ESA XMM-Newton (@ESA_XMM) February 2, 2024
“Many outstanding problems in the study of black holes are a matter of achieving detections through long observations that stretch over many hours to catch important events. This highlights the prime importance of the XMM-Newton mission for the future. No other mission can deliver the combination of its high sensitivity and its ability to make long, uninterrupted observations,”Norbert Schrtel, XMM Newton project scientist.
Scientists will learn more about these empty regions, and how black holes interact with their surrounding galaxies, by using X-ray observatories like XMM Newton and IXPE.
(Lead image: Artist’s impression of Markarian 817’s black hole. Credit: ESA)
Original content by www.nasaspaceflight.com – “XMM-Newton observes black hole winds, provides insight into galaxy and black hole interactions”
Read the full article here https://www.nasaspaceflight.com/2024/02/markarian-817/