Has the Hubble telescope been programmed?

Only visible to Hubble: the space telescope finds the most distant double quasars

The aging Hubble Space Telescope has once again proven its scientific value and imaged two pairs of supermassive black holes that are further away than any other known double quasars. The telescope has imaged the two pairs in their state about 10 billion years ago, when they were each about 10,000 light years apart. The double find is like a needle in a haystack, explains Yue Shen of the University of Illinois, who led the analysis. He and his team opted for a new strategy that has turned out to be extremely promising.

To be told apart only for Hubble

Quasars are the active nuclei of distant galaxies that shine immensely brightly because matter falls into their central supermassive black holes and is heated enormously in the process. They are therefore among the brightest objects in the universe and often shine much brighter than their galaxies. In the current case, too, Hubble was only able to image the quasars, but not the associated galaxies. At the same time, however, they are so close that both pairs would have appeared as individual quasars to earth-based telescopes, the scientists explain. When their light set out on the long journey, quasars were much more common than they are today, they add. That is why much more should wait for their discovery in the firmament.

As the US space agency NASA is now explaining, a celestial atlas was first searched for particularly promising quasars for the find. Thanks to ESA's revolutionary Gaia space telescope, they would then have narrowed the list further: Although the distant objects in its perspective would not move, a flicker could indicate that there are two objects. In this way, four candidates were identified, and Hubble was then assigned. The space telescope found what it was looking for in at least 50 percent of these. Follow-up observations confirmed the findings, even if there was a low probability that it was only one quasar that was imaged twice

A census of the double quasars

The researchers now want to expand their method and thus compile an overview of the double quasars in the early universe. They assume that roughly one in every 1000 quasars there actually consists of two quasars. Double quasars could also better understand the collisions of galaxies in the early universe, as well as the formation of the supermassive black holes, which still raise a number of questions. A few billion years after the Big Bang, both processes were significantly more frequent than they are now. The current work was in the trade magazine Nature Astronomy released.


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