image 20-March-2019 07:53:31

Active galaxies to measure cosmic expansion

Date: 28 January 2019
Satellite: XMM-Newton
Copyright: ESA (artist's impression and composition); NASA/ESA/Hubble (background galaxies); CC BY-SA 3.0 IGO

Artist's impression of quasars, the cores of galaxies where an active supermassive black hole is pulling in matter from its surroundings at very intense rates, located at increasingly larger distances from us.

As material falls onto the black hole, it forms a swirling disc that radiates in visible and ultraviolet light; this light, in turn, heats up nearby electrons, generating X-rays. The relation between the ultraviolet and X-ray brightness of quasars can be used to estimate the distance to these sources – something that is notoriously tricky in astronomy – and, ultimately, to probe the expansion history of the Universe.

A team of astronomers has applied this method to a large sample of quasars observed by ESA's XMM-Newton to investigate the history of our cosmos up to 12 billion years ago, finding there might be more to the early expansion of the Universe than predicted by the standard model of cosmology.

 
This work is licensed under a Creative Commons Attribution-ShareAlike 3.0 IGO License. Creative Commons License


Last Update: 28 January 2019

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