t change much. But an exploding supernova appears for only a short time and then disappears. That explosion will appear at a different time in each of those four parts of the Einstein cross. Scientists can measure the time delay between the appearance of the supernova in each of the images to get clues about gravity and the mass of the galaxy (or galaxy cluster) creating the lens.
“It’s very rare to get something like this,” Ebeling says. “The timing was just perfect.”
Kelly thinks the first two images of the supernova actually arrived in 1964 and 1995, but “we missed it.” Thanks to the time delay, the image will appear one more time, giving astronomers a replay of the supernova. But Kelly can’t say when.
“Nothing like this has ever happened before,” he says. “So it’s hard to know exactly what will happen.”
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astronomy The area of science that deals with celestial objects, space and the physical universe as a whole. People who work in this field are called astronomers.
Einstein cross Albert Einstein’s General Theory of Relativity, in 1915, proposed that gravity can bend light. This bending can create an optical illusion — the image of the same distant light source, repeated four times in a “cross-like” pattern. It takes a very massive object or community of objects to do this.
galaxy A massive group of stars bound together by gravity. Galaxies, which each typically include between 10 million and 100 trillion stars, also include clouds of gas, dust and the remnants of exploded stars.
galaxy cluster A group of galaxies held together by gravity. Galaxy clusters are the largest known objects in the universe.
gravitational lensing The distortion of space and time by an intense gravitational force, such as what can be exerted by clusters of galaxies — the most massive things in the universe.
gravity The force that attracts anything with mass, or bulk, toward any other thing with mass. The more mass that something has, the greater its gravity.
lens (in physics) A transparent material that can either focus or spread out parallel rays of light as they pass through it.
light-year The distance light travels in one year, about 9.48 trillion kilometers (almost 6 trillion miles). To get some idea of this length, imagine a rope long enough to wrap around the Earth. It would be a little over 40,000 kilometers (24,900 miles) long. Lay it out straight. Now lay another 236 million more that are the same length, end-to-end, right after the first. The total distance they now span would equal one light-year.
mass A number that shows how much an object resists speeding up and slowing down — basically a measure of how much matter that object is made from.
star Thebasic building block from which galaxies are made. Stars develop when gravity compacts clouds of gas. When they become dense enough to sustain nuclear-fusion reactions, stars will emit light and sometimes other forms of electromagnetic radiation. The sun is our closest star.
supernova (plural: supernovae or supernovas) A massive star that suddenly increases greatly in brightness because of a catastrophic explosion that ejects most of its mass.
telescope Usually a light-collecting instrument that makes distant objects appear nearer through the use of lenses or a combination of curved mirrors and lenses. Some, however, collect radio emissions (energy from a different portion of the electromagnetic spectrum) through a network of antennas.
J. Raloff. “Picture This: Smiley face in space!” Science News for Students. February 9, 2015.
C. Crockett. “Dead star makes a lens for its companion.” Science News for Students. April 22, 2014.
S. Ornes. “An invisible cosmic bridge.” Science News for Students. July 23, 2012.
S. Ornes. “The dark side of the universe.” Science News for Students. April 26, 2011.
Original Journal Source: P.L. Kelly et al. “Multiple images of a highly magnified supernova formed by an early-type cluster galaxy lens.” Science. Vol. 347, p. 1123, March 6, 2015. doi: 10.1126/science.aaa3350.