Until now, dark matter was known only in the form of clouds of size at least with the galaxy. Now, however, astronomers figured out that she can get together in smaller clumps. It is important to determine the nature of the mysterious substance.
Recall that dark matter is an unknown substance, whose existence is known only through its gravity. The pull of dark matter affects the movement of entire galaxies of stars and star clusters within them. Astronomers have calculated that stars and gas in virtually every galaxy is immersed in a huge cloud of dark matter, which is much more than ordinary matter.
Most scientists believe that this substance is composed of yet undiscovered particles, the nature of which have various assumptions. The most popular model is cold dark matter. The word “cold” here means that these particles move with velocities much smaller than speed of light. Theorists calculated that in this case the dark matter under its own gravity will be collected in clumps of different sizes, from a few tens of tons to hundreds of thousands of the masses of the milky Way.
However, even the most detailed maps of the distribution of dark matter is still applied to a large (at least in the galaxy) clusters. Observations more modest “clumps” – a task at the limit of technical capabilities.
But there is a small accumulation of dark matter at all? Until today it was impossible to exclude that the answer is no, because they were simply never seen again. In this regard, experts are not discounting an alternative model of hot dark matter. In this theory the particles of the mysterious substance are moving at relativistic speeds and gravity under force to form only the largest blobs.
Images of quasars, many times repeated gravitational lens.Photo NASA, ESA, A. Nierenberg (JPL), T. Treu (UCLA).
However, tnow astronomers have found clusters of dark matter, inferior to the milky Way mass in the tens and hundreds of thousands of times. This is a record figure and a strong argument in favor of the model of cold dark matter.
“Previously, astronomers have already conducted additional observational tests of theories of dark matter, but our [work] provides the most convincing evidence of the presence of small clusters, cold dark matter. By combining the latest theoretical predictions, statistical tools and new observations of Hubble, we now have a much more reliable result than previously possible,” says co-author Anna Nirenberg (Anna Nierenberg) from laboratory of jet movement of NASA.
the Authors used an unusual technique. Data from the surveys SDSS and DES, they chose eight quasars whose radiation falls down the gravitational lensing. This means that the galaxy, located in the light path of the quasar distorts its rays its attraction, working as a lens.
the image of each of the studied quasars through galaxy lens added three doubles, like in space announced four brand of the same quasar. This is a known but fairly rare effect. Because its occurrence requires that the quasar, a galaxy-lens and the observer was located almost on the same line.
Selected quasars located about 10 billion light years from Earth. Lingirie their galaxy is much closer: about two billion light-years.
With the help of Hubble, the authors carefully studied the result of lensing in the infrared range. They were interested in the distortion introduced by the image, the gravity of clumps of dark matter.
a schematic Diagram illustrating the principle of gravitational lensing. Translation Of “News.Science.”Illustration by NASA, ESA, D. Player (STScI).
“Imagine that each of these eight galaxies is a giant magnifying glassklom, explains study co-author Daniel Gilman (Daniel Gilman), University of California, Los Angeles. – Small accumulations of dark matter act like small cracks in the magnifying glass, changing the brightness and position of the four images of the quasar compared to what you would expect to see if the glass will be smooth.”
Using sophisticated computer models, astronomers have deduced from the images the contribution of small clumps of dark matter located in the path of infrared rays. By the way, judging by the mass of these clouds of dark matter, they do not contain stars, so to detect them by conventional methods according to the movement of celestial bodies – would not have been.
the Team presented their results at the 235th meeting of the American astronomical society (AAS 235th Meeting) in Honolulu, Hawaii.
By the way, earlier “News.Science” (nauka.vesti.ru) wrote that the Land can be wrapped in a “hair” of dark matter. We talked about how to use the stars to measure the rate of this substance.