The Hubble Space Telescope photographed a series of ghosts of quasars that existed in the past. They are seen as ethereal green objects in various forms and are the last effects of ancient quasars. These phenomena are very interesting from a scientific standpoint because they can provide information about the past of those galaxies, which were once very active.
An article published in the journal “Astronomy & Astrophysics” describes the results of a research carried out by combining the observations made with ESA’s Herschel and Planck space telescopes. The purpose was to find protoclusters, the precursors of today’s galaxy clusters seen in the distant past when the universe was only three billion years. This will help to understand how these huge groups of tens, hundreds and even thousands of galaxies formed and evolved.
A combined use of the Hubble and Chandra space telescopes allowed to conduct a study of dark matter and the results were described in an article published in the journal “Science”. Currently we have no instruments to directly detect dark matter so scientists have to study it indirectly through its effects, in this case on 72 galaxy clusters to study their behavior.