![]() There are three main matter components to consider: galaxies, hot intracluster gas found between galaxies, and dark matter. But only because there is dark matter as well as ordinary matter. G is the gravitational constant and M and R are the cluster mass and characteristic radius, respectively.Ī lot of mass in a confined region – how about large groups of clusters and galaxies? It turns out we need of order 1000 galaxies for a rich cluster and this will do the trick. GM/R, simple Newtonian mechanics, is sufficient no general relativistic calculation is needed at this point. The potential energy of the gravitational field is proportional to the amount of matter (total mass) coalesced into a region and inversely proportional to the characteristic scale of that region. So how can we produce gas hot enough to give off X-Rays by this mechanism? Gravity, and lots of it. One eV converts to 11,605 degrees Kelvin (or we can just say Kelvins).Ĭhandra X-ray Observatory prior to launch in the Space Shuttle Columbia in 1999. A gas with a temperature of 10 million degrees will give off approximately 1 kiloVolt X-rays (hereafter we use the KeV abbreviation), and a gas with a temperature of 100 million degrees will radiate 10 KeV X-rays. ![]() We talk about the temperature of such an ionized gas, and that is proportional to the square of the average speed of the electrons. The speed at which the electrons are moving around determines how energetic the produced photons will be. As electrons fly around near ions (protons and helium nuclei primarily) their mutual electromagnetic attraction will result in some of the electrons’ kinetic energy being transferred to radiation. That is, the electrons will be stripped from the nuclei and move about freely. A gas which is hot enough to give off X-rays will be ionized. Bremsstrahlung is a German word meaning ‘decelerated radiation’. One of the main mechanisms for X-ray production in the universe is known as thermal bremsstrahlung. How does dark matter result in X-rays being produced? Indirectly, as a consequence of its gravitational effects. Schematic of grazing incidence mirrors used in the Chandra X-ray Observatory. X-ray telescopes use the principle of grazing incidence reflection the X-rays impinge at shallow angles onto gold or iridium-coated metallic surfaces and are reflected to the focal plane and the detector electronics. X-rays are absorbed in the Earth’s atmosphere, so today X-ray astronomy is performed from orbiting satellites. This gave me the wonderful opportunity to work in the control rooms at the NASA Johnson Space Center in Houston. One major project was a solar X-Ray telescope mounted in SkyLab, America’s first space station. ![]() At a later date, I worked part-time at AS&E, as we called it, while in graduate school. The energy associated with these X-rays is typically around an order of magnitude less than those zapped into your mouth when you visit the dentist.Īround 50 years ago scientists at American Science and Engineering flew the first imaging X-ray telescope on a small rocket. One of the most significant methods by which we detect the presence of dark matter is through the use of X-ray telescopes. Don’t ask, but they took 3 digital X-Rays.
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