VOA科学技术2024--Scientists Learn More about Black Hole at Center of Our Galaxy（在线收听）

Scientists Learn More about Black Hole at Center of Our Galaxy

　　Researchers recently announced that they have found qualities of the main black hole in our Milky Way Galaxy that they did not know about before.

　　Black holes are very massive objects with gravity so strong that even light cannot escape them.

　　The space scientists said they found a strong and organized magnetic field around the black hole called Sagittarius A*. It is at the center of our galaxy 26,000 light years away.

　　Activity at the edge of the black hole is believed to have created the magnetic field. It is similar to activity surrounding the only other black hole ever imaged. That one is at the center of a nearby galaxy commonly called M87.

　　The researchers wondered if their finding suggests that strong magnetic fields might be a quality common to all black holes.

　　Black holes and jets

　　The magnetic field around the M87 black hole, called M87*, causes it to launch powerful jets of material into space, the researchers said. They added that while such jets have not yet been found near Sagittarius A*, they might exist and might be observable in the near future.

　　The researchers released the image showing the environment around Sagittarius A* in polarized light for the first time.

　　In a way, light behaves like a wave. Light waves can move in different directions. When light waves are restricted to one direction, or plane, the result is polarized light.

　　The latest image came from the Event Horizon Telescope (EHT). It is an international network of observatories working together to study radio waves connected with black holes. The EHT also provided the earlier image of the M87 black hole.

　　Sara Issaoun is with the Center for Astrophysics - Harvard & Smithsonian. Issaoun said scientists can "see" black holes: "By imaging polarized light from hot glowing gas near black holes, we are directly inferring the structure and strength of the magnetic fields..."

　　She said observing polarized light made the new study different: "Compared to the previous results, polarized light teaches us a lot more about the astrophysics, the properties of the gas, and mechanisms that take place as a black hole feeds."

　　A co-leader of the research, Issaoun said: "For a while, we've believed that magnetic fields play a key role in how black holes feed and eject matter in powerful jets."

　　"This new image...shows that strong and ordered magnetic fields are critical to how black holes interact with the gas and matter around them."

　　Angelo Ricarte is another researcher from the Center for Astrophysics who was involved with the study. Ricarte said: "The magnetic field appears to be organized into a spiral, similar to M87*. This magnetic field geometry implies that the black hole can power very efficient jets that shoot off into the galaxy,"

　　The M87 black hole has a mass 6 billion times that of our sun — much bigger than the one in our Milky Way. It ejects a powerful jet visible in all wavelengths of light.

　　The evidence for a jet flowing from Sagittarius A* is growing.

　　Ricarte said that researchers are hopeful about the prediction for a powerful jet in the Milky Way's black hole. As tools get better in the coming years, he said, researchers should be able to better understand the issue from the data.

　　The researchers' findings appeared recently in Astrophysical Journal Letters.

　　Words in This Story

　　light year –n. a measure equal to the distance light travels in space or 9.5 trillion kilometers

　　polarize – v. to restrict something, such as light waves, so that they only move in one direction or plane

　　mechanism – n. a process or system that is used to produce a particular result

　　eject – v. to push (something) out with force

　　critical – adj. extremely important

　　interact – v. to come together and have an effect on each other

　　spiral – n. a circular curving line that goes around a central point while getting closer to or farther away from it

　　imply – v. to include or involve (something) as a natural or necessary part

　　efficient – adj. capable of producing desired results without wasting materials, time, or energy

　　infer – v. to reach (a conclusion) based on known facts