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All-sky surveys – visualizing our dynamic galaxy

Advances in all-sky surveys permit better visualization of the motions and dynamics inside our galaxy. And provide a better understanding of the evolution of the Milky Way.

X-ray all-sky surveys

As noted in this Space.com article, while “optical telescopes are much easier to design than X-ray telescopes … some of the most interesting objects in the Universe don’t emit light at visible wavelengths and therefore remain mostly hidden to optical telescopes.”

• Space.com > “German X-ray space telescope captures most complete map of black holes ever” by Tereza Pultarova (July 27, 2021) – eROSITA can see light from objects which took 7 billion years to reach its detectors.

(quote) The first science from the 2019 eROSITA space observatory [entire sky-survey] is here. … revealing more than 3 million newfound objects in less than two years. … Previous X-ray telescopes … such as ESA’s XMM Newton, or NASA’s Chandra X-ray Observatory, could only observe rather small sections of the sky [but deeply] in one go.

“For the first time, we have an X-ray telescope that can be used in very similar ways as the large field optical telescopes that we use today,” Merloni [mission’s senior scientist] said. “With eROSITA, we cover the entire sky very efficiently and can study large-scale structures, such as the entire Milky Way.”

… the catalogues contain information about 3 million sources of X-ray radiation — black holes, neutron stars and galaxy clusters. About 77% of those sources are distant black holes in other galaxies, 20% are neutron stars, stars and black holes in the Milky Way. The remaining 3% are galaxy clusters, he added.

Caption > The energetic universe as seen with the eROSITA X-ray telescope. The first eROSITA all-sky survey was conducted over a period of six months by letting the telescope rotate continuously, … To generate this image – in which the whole sky is projected onto an ellipse (so-called Aitoff projection) with the centre of the Milky Way in the middle and the body of the Galaxy running horizontally – photons have been colour-coded according to their energy … Piercing through this turbulent, hot diffuse medium, are hundreds of thousands of X-ray sources, which appear mostly white in the image, and uniformly distributed over the sky. Among them, distant active galactic nuclei (including a few emitting at a time when the Universe was less than one tenth of its current age) are visible as point sources, while clusters of galaxies reveal themselves as extended X-ray nebulosities. In total, about one million X-ray sources have been detected in the eROSITA all-sky image, …

Wiki image credits

Johannes Buchner
CC BY-SA 4.0
File:SRG-eROSITA all-sky image.jpg
Created: 19 June 2020

References

European Space Agency’s Gaia (2013)
European Southern Observatory’s ground-based Very Large Telescope
European Space Agency’s XMM Newton X-ray space observatory (1999)
Chandra X-ray Observatory (1999)

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