MacroCosmos mars-avril 2018

32 MARS-AVRIL 2018 CHRONIQUES DE L'ESPACE ted in the center of the galaxy, the expected address for such an object. The X-ray data also provide evi- dence that the supermassive black hole is embedded in a heavy veil of dust and gas. The results indicate that in the past, the supermassive black hole in J1354 appears to have consumed, or accreted, large amounts of gas while blasting off an outflow of high-energy particles. The outflow eventually switched off then turned back on about 100,000 years later. This is strong evidence that accre- ting black holes can switch their power output off and on again over timescales that are short compared to the 13.8-billion-year age of the universe. “We are seeing this object feast, burp, and nap, and then feast and burp once again, which theory had predicted,” said Julie Comer- ford of the University of Colorado (CU) at Boulder’s Department of As- trophysical and Space Science, who led the study. “Fortunately, we hap- pened to observe this galaxy at a time when we could clearly see evi- dence for both events.” So why did the black hole have two separate meals? The answer lies in Researchers catch supermassive black hole burping − twice by NASA/ESA A stronomers have caught a supermassive black hole in a distant galaxy snacking on gas and then “burping” — not once, but twice. The galaxy under study, called SDSS J1354+1327 (J1354 for short), is about 800 million light- years from Earth. The team used observations from NASA’s Hubble Space Telescope, the Chandra X-ray Observatory, as well as the W.M. Keck Observatory in Mauna Kea, Hawaii, and the Apache Point Ob- servatory (APO) near Sunspot, New Mexico. Chandra detected a bright, point- like source of X-ray emission from J1354, a telltale sign of the presence of a supermassive black hole mil- lions or billions of times more mas- sive than our Sun. The X-rays are produced by gas heated to millions of degrees by the enormous gravi- tational and magnetic forces near the black hole. Some of this gas will fall into the black hole, while a por- tion will be expelled in a powerful outflow of high-energy particles. By comparing X-ray images from Chandra and visible-light (optical) images from Hubble, the team de- termined that the black hole is loca- T his is an image of galaxy SDSS J1354 +1327 (lower center) and its companion ga- laxy SDSS J1354+1328 (upper right). The inset panel to the right is a four-color image that combines Hubble red, green and blue filtered exposures with Chandra X-ray observations colo- red purple. The Hubble image shows the nor- thern bubble of hot io- nized gas in the vicinity of a supermassive black hole. The black hole appears to have blasted out jets of bright light from gas it’s accreting from the com- panion galaxy. This happened twice in the past 100,000 years. While astronomers have predicted such objects can flicker on and off as a result of gas-fee- ding events, this is the first time one has convincingly been caught in the act. The galaxy pair is 800 mil- lion light-years from Earth. [NASA, ESA, and J. Comerford (University of Colorado-Boulder)] La version française de cette nouvelle n'est pas encore disponible.