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.
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File:SRG-eROSITA all-sky image.jpg
Created: 19 June 2020
• 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)