Scientists Probe Mysteries at the Heart of the Milky Way Galaxy

First Posted: Oct 14, 2014 12:00 PM EDT

Scientists have long wondered whether matter is falling into the massive black hole in the center of our Milky Way galaxy, or being ejected from it. Now, scientists are searching for an answer.

In this case, researchers analyzed images collected by the Russian spacecraft RadioAstron. This spacecraft was launched into orbit in July 2011 with several missions, one of which was to investigate the scattering of pulsars by interstellar gas. In this case, the scientists took a closer look at Sagittarisu A-Star (A*), the source that marks the Milky Way's central black hole.

This central black hole, which contains the equivalent of four million solar masses, is visible from the gas around it. In addition, the wavelengths that make Sagittarius A* visible are scattered by interstellar gas along the line of sight the same way that light is scattered by fog on Earth.

With further observations, the researchers spotted lumps and anomalies in the image of Sagittarius A*. This, in particular, revealed a bit more about the central black hole.

"I was quite surprised to find that the effect of scattering produced images with small lumps in the overall smooth image," said Carl Gwinn, one of the researchers, in a news release. "We call these substructure. Some previous theories had predicted similar effects in the 1980s, and a quite controversial observation in the 1970s had hinted at their presence."

The scientists conducted further theoretical research in order to learn a bit more about substructure. They drew inferences about the scattering properties from observations at longer wavelengths. From these, the scientists extrapolated the properties to one centimeter and used it to make a rough estimate of the size of the source.

In fact, the scientists managed to directly confirm these indirect inferences about the size of Sagittarius A* with observations. They were also able to provide new information about fluctuations in the interstellar gas that cause scattering.

"There are different ways of interpreting observations of the scattering, and we showed that one of them is right and the others are wrong," said Yuri Kovalev, co-investigator in the new study. "This will be important for future research on the gas near this black hole. This work is a good example of the synergy between different modern research infrastructures, technologies and science ideas."

The findings are published in Astrophysical Journal Letters.

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