#Repost @nasachandraxray with @get_repost ・・・ News: Dark energy may be getting stronger with time! If confirmed, it could mean that we need to re-examine our basic understanding of the history & structure of the Universe! A new study using data from NASA’s Chandra X-ray Observatory and ESA’s XMM-Newton suggests that dark energy may have varied over cosmic time. This artist's illustration helps explain how astronomers tracked the effects of dark energy to about one billion years after the Big Bang by determining the distances to quasars, rapidly growing black holes that shine extremely brightly. Discovered about 20 years ago by measuring the distances to exploded stars called supernovas, dark energy is a proposed type of force, or energy, that permeates all space and causes the expansion of the Universe to accelerate. Using this method, scientists tracked the effects of dark energy out to about 9 billion years ago. The latest result stems from the development of a new method to determine distances to about 1,598 quasars, which allows the researchers to measure dark energy's effects from the early Universe through to the present day. Two of the most distant quasars studied are shown in Chandra images in the insets. The new technique uses ultraviolet (UV) and X-ray data to estimate quasar distances. In quasars, a disk of matter around the supermassive black hole in the center of a galaxy produces UV light (illustrated in blue). Some of the UV photons collide with electrons in a cloud of hot gas (shown in yellow) above and below the disk. These collisions can boost the energy of the UV light up to X-ray energies. This interaction causes a correlation between the amounts of observed UV and X-ray radiation. This correlation depends on the luminosity of the quasar, which is the amount of radiation it produces. Using this technique the quasars become standard candles, as implied by the illustration, showing quasars with the same luminosity at different distances from Earth. Once the luminosity is known, the distance to the quasars can be calculated. This is because the observed amount of radiation from quasars converted into standard candles depend on their distanc https://www.instagram.com/p/BtP3uF4A1a5/?utm_source=ig_tumblr_share&igshid=1uxd8yg3inj5u
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