The European Space Agency’s (ESA) XMM-Newton X-ray Mission has revealed the latest edition of their 2XMM catalogue.
The newest edition of this cosmic compendium contains 42,000 new entries, sending the total to over a quarter of a million x-ray sources. This extensive trove of information and knowledge will allow scientists to further probe the workings of the Universe.
The mission, launched in 1999, was not initially meant to produce this data. XMM-Newton makes over 600 observations each year, but at any given time the object under study takes up only a small portion of the total field of view - just under 30 arc minutes (imagine an area about the size of the full Moon).
So, to make things more efficient, the search for additional x-ray sources is simultaneously carried out, with the data being accumulated in the 2XMM catalogue for future reference. On average, an extra 70 sources additional to the main object of interest are found.
“We are getting 40,000 new detections a year. The vast majority of those - 98 per cent of them - are completely unknown; they’ve never been detected before with x-rays,” said Professor Mike Watson, leader of the XMM-Newton Survey Science Centre (SSC) based at the University of Leicester. Watson’s team compiled the catalogue. “With a serendipitous catalogue, surprises are always possible,” explained XMM-Newton Project Scientist Norbert Schartel.
Some interesting and unexpected finds have shown this was good practice. In 2009, a variable hyper-luminous x-ray source was noted. At 500 solar masses, i.e. 500 times the mass of the sun, it shows all the signs of being an intermediate-mass black hole; the missing link between stellar-mass and super-massive black holes. While it is accepted that stellar-mass black holes are formed by massive stars at the end of their lifetimes, the formation process for super-massive black holes is still unclear. One school of thought suggests the mergers of intermediate-mass black holes. This XMM-Newton detection was the first solid evidence that such an intermediate class exists.
Another surprise in the cosmic ‘party bag’ was the find, in the year 2008, of the most massive galaxy cluster found in the distant Universe. At approximately 5 × 1014 solar masses, this galaxy cluster equalled the combined mass of over a thousand large galaxies. The discovery also shed some light on the evidence for dark energy, which is what scientists believe could be the cause of the observed expansion of the Universe.
Schartel said: “The 2XMM catalogue is still, even after 10 years, producing exciting new results. It is also a key catalogue for future missions to optimise their target choices for future research. So catalogues such as this have a legacy that goes much further into the future than just current research”.
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