In the first all-sky map produced by the eROSITA X-ray telescope, one of two instruments aboard Russia’s Spektr-RG orbital observatory, astronomers have discovered an astonishing new detail: a large-scale bubble structure below the plane of the Milky Way that occupies a significant portion of the Southern Sky.
As scientists explain, a similar structure in the Northern Sky has been known for a long time. For many years it was believed that it arose as a result of a supernova explosion close to the Sun tens or hundreds of thousands of years ago.
However, according to the Space Research Institute of the Russian Academy of Sciences, the discovered structures form an “hourglass” when taken together.
What are the large-scale bubbles in the Milky Way?
The bubbles detected by the telescope are structures of hot gas on either side of the Galactic disk. They are clearly visible in the all-sky X-ray survey. Scientists suggest that the unusual rounded structures arose, most likely, due to shock waves caused by a powerful burst of activity in the center of our galaxy tens of millions of years ago.
“They were caused by the ejection of matter due to the activity of a supermassive black hole in the center of our Galaxy or a giant burst of star formation in the gas of the central part of the Galaxy,” scientists say.
The gas bubbles were detected thanks to the high sensitivity and good spectral and angular resolution of the eROSITA telescope, which scans the entire sky every six months. An analysis of the data obtained showed that the energy required for the formation of these bubbles is equal to the power of 100 thousand supernovae, and the sizes of both structures are comparable to the dimensions of the entire Milky Way Galaxy.
What is the importance of this discovery?
According to scientists, the discovery of these bubbles will help to understand the circulation of matter in and around the Milky Way, as well as in other galaxies that we cannot observe with such a degree of detail due to the enormous distance to them.
As Yevgeny Churazov, Academician of the Space Research Institute of the Russian Academy of Sciences, notes, the size of the bubbles and the temperature of the gas makes it possible to judge only the total released energy and approximately the time scale.
Researcher of the Astronomical Institute. Sternberg, Vladimir Surdin, in a conversation with RBC, noted that the presence of bubbles suggests that several tens of thousands of years ago, the black hole in the center of the Galaxy “was not quite so quiet”. It could have thrown out into space huge streams of energy that heated the gas in the southern northern part of the Galaxy to such an extent that it still cannot cool down.
According to the scientific director of the eROSITA project Peter Predel, the boundaries of the bubbles within the Milky Way are most likely traces of shock waves caused by a powerful release of energy from the center of our Galaxy into its halo (secondary glow around a light source).
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Sources:
• Predehl, P., Sunyaev, R., Becker, W., Brunner, H., Burenin, R., Bykov, A., . . . Wilms, J. (2020, December 09). Detection of large-scale X-ray bubbles in the Milky Way halo.
• Starr, M. (n.d.). Astronomers Detect Giant X-Ray Bubbles Expanding Above And Below The Galactic Plane. Retrieved December 11, 2020
• Спектр-РГ обнаружил крупномасштабные пузыри горячего газа в гало Млечного Пути.
