Milky Way’s Black Hole Gave Off a Burst 300 Years Ago

Our Milky Way’s black hole is quiet – too quiet – some astronomers might say. But according to a team of Japanese astronomers, the supermassive black hole at the heart of our galaxy might be just as active as those in other galaxies, it’s just taking a little break. Their evidence? The echoes from a massive outburst that occurred 300 years ago.

The astronomers found evidence of the outburst using ESA’s XMM-Newton space telescope, as well as NASA and Japanese X-ray satellites. And it helps solve the mystery about why the Milky Way’s black hole is so quiet. Even though it contains 4 million times the mass of our Sun, it emits a fraction of the radiation coming from other galactic black holes.

“We have wondered why the Milky Way’s black hole appears to be a slumbering giant,” says team leader Tatsuya Inui of Kyoto University in Japan. “But now we realize that the black hole was far more active in the past. Perhaps it’s just resting after a major outburst.”

The team gathered their observations from 1994 to 2005. They watched how clouds of gas near the central black hole brightened and dimmed in X-ray light as pulses of radiation swept past. These are echoes, visible long after the black hole has gone quiet again.

One large gas cloud is known as Sagittarius B2, and it’s located 300 light-years away from the central black hole. In other words, radiation reflecting off of Sagittarius B2 must have come from the black hole 300 years previously.

By watching the region for more than 10 years, the astronomers were able to watch an event wash across the cloud. Approximately 300 years ago, the black hole unleashed a flare that made it a million times brighter than it is today.

It’s hard to explain how the black hole could vary in its radiation output so greatly. It’s possible that a supernova in the region plowed gas and dust into the vicinity of the black hole. This led to a temporary feeding frenzy that awoke the black hole and produced the great flare.

Original Source: ESA News Release

New Chandra Image Is Eye Candy

This picture is too gorgeous not to share it. A new Chandra X-ray telescope image shows a beautiful, dense region of massive stars in the Centaurus constellation. It almost appears as though someone threw a handful of colored candies out into space. Known as Westerlund 2, this star cluster has been a mysterious region of our galaxy, filled with dust and gas that have obscured our vision of what lies inside. But new X-ray observations with Chandra have revealed some of the hottest, brightest and most massive known stars, and this is now regarded as one of the most interesting star clusters in the Milky Way galaxy.

About 20,000 light years from Earth, Westerlund 2 is a young star cluster with an estimated age of about one or two million years. An extremely massive double star system called WR20a is visible in the image, the bright yellow point just below and to the right of the cluster’s center. This system contains stars with whopping masses of 82 and 83 times that of the Sun. The dense streams of matter steadily ejected by these two massive stars, called stellar winds, collide with each other and produce large amounts of X-ray emissions. But alas, no chocolate candies.

This collision is seen at different angles as the stars orbit around each other every 3.7 days.

Several other bright X-ray sources may also show evidence for collisions between winds in massive binary systems.

The Chandra image of Westerlund 2 shows low energy X-rays in red, intermediate energy X-rays in green and high energy X-rays in blue. This is an area that is incredibly dense with massive stars, and bright with X-rays.

Image is 8.4 arc minutes across and was taken by the Chandra Advanced CCD Imaging Spectrometer, which can study temperature variations from x-ray sources.

Download this image for your desktop here.

Original News Source: Chandra Photo Album