BOSTON — A galactic pileup is underway 5 billion light-years from Earth. The colossal collision is spewing charged particles. And this fountain is huge. It’s jetting particles at nearly the speed of light some 2.5 million light-years into intergalactic space. One might think of the event as building a powerful particle accelerator — one up to a million times as strong as Earth’s mightiest (the Large Hadron Collider).
Astronomers reported the intergalactic fireworks at the American Astronomical Society meeting, here, on June 3. They observed the smashup in new images compiled by two telescopes. NASA’s Chandra X-ray Observatory, a satellite system, eyed the event from an altitude of 139,000 kilometers (86,500 miles) above Earth’s surface. A radio telescope, the Very Large Array, homed in on the collision from the ground. Its 27 antennas are splayed out across the New Mexico desert.
And the source of all the commotion? Four clusters of galaxies are crashing into each other. Together, they involve a mass equal to 3 million billion suns.
Galaxy clusters are the largest structures in the universe that are linked by gravity, notes Reinout van Weeren. He works at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. Large clusters can house thousands of galaxies. Astronomers think these built up over billions of years as smaller clusters merged.
The newly imaged jet sits at the heart of “the most complex cluster collision known,” van Weeren says. Chandra images show gas between the galaxies has been squeezed and heated to 100 million degrees Celsius. Radio maps from the Very Large Array reveal the particle fountain within the hot gas. That jet could provide information about how such large clusters are built.
galaxy A system of millions or billions of stars, together with gas and dust, held together by gravity.
galaxy cluster A group of galaxies held together by gravity. Galaxy clusters are the largest known objects in the universe.
intergalactic Between galaxies.
light-year The distance light travels in a 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.
particle accelerator (in physics) This massive machine revs up the motion of subatomic particles to great speed and then beams them at targets. Sometimes the beams are used to deliver radiation at a tissue for cancer treatment. Other times, scientists crash the particles into solid targets in hopes of breaking the particles into their building blocks.
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.