![]() “If you’re going to see neutrinos, it has to be from a very, very powerful beast, otherwise you wouldn’t see them at all.” “It makes sense – it cannot be a wimpy blazar,” says Paolo Padovani of the European Southern Observatory. TXS 0506+056 is among the brightest blazars in the gamma-ray sky, which is remarkable given that it lives roughly four billion light-years away, and means that it is a prime candidate for producing very high-energy cosmic rays. “Blazars are some of the most powerful astrophysical sources in the universe,” says Princeton University’s Maria Petropoulou. As it snacks on nearby gas and dust, the black hole produces a jet of extremely energetic particles, which just happens to be pointed in Earth’s direction. Those gamma rays came from a giant elliptical galaxy called TXS 0506+056 that contains a churning supermassive black hole at its core. Jedidah Isler, the first African-American woman to receive a Ph.D in astrophysics from Yale, takes the stage to talk about her love for black holes and her passion to support women of color in the sciences. That included a barrage of highly energetic gamma rays, which the space-based Fermi Gamma-Ray Space Telescope detected. Tucked into that patch of northern sky, a large, faraway object called a blazar had shaken itself awake and started hurling energetic particles into the void. ![]() When scientists retraced this neutrino’s path, it led them to a spot on the sky near the constellation Orion, a location where, nearly simultaneously, several telescopes had spotted a massive cosmic flare. The hit triggered an alert notifying neutrino-hunting astronomers that the chase was on. It packed a whopping 290 TeV of energy- nearly 50 times more powerful than the most energetic proton beams running at the Large Hadron Collider. Then, on September 22, 2017, a single neutrino traveling at nearly the speed of light zinged through Earth and set off IceCube’s detectors. But they’ve been frustratingly hard to pin on a single celestial object, offering scientists only some hints about where their sources might lie. Since 2013, several extremely energetic neutrinos (some whimsically named after Sesame Street characters) have burrowed through the polar ice and registered on IceCube’s sensors. IceCube, which occupies a cubic kilometer of ice beneath the Amundsen-Scott South Pole Station, uses 5,160 light sensors designed to detect the small flashes of light produced when cosmic neutrinos speeding through Earth do interact with atomic nuclei in the ice. Trillions of solar neutrinos are passing through you right now. Since neutrinos interact only very weakly with other types of matter, even detecting them is no simple feat. Photograph courtesy NASA/JPL-Caltech/ESA/Harvard-Smithsonian CfA Located about 12 million light-years away in the Ursa Major constellation, M81 is among the brightest of the galaxies visible by telescope from Earth. Previously, scientists had discovered neutrinos coming from the sun and from nearby supernova remnants, but neither of those sources is powerful enough to sling the most energetic of cosmic particles toward Earth.Ī composite image of the Messier 81 (M81) galaxy shows what astronomers call a "grand design" spiral galaxy, where each of its arms curls all the way down into its center. The results are reported today in three papers appearing in Science and the Monthly Notices of the Royal Astronomical Society. ![]() "It’s exciting, no doubt, to have finally nailed the cosmic accelerator,” says the University of Wisconsin-Madison’s Francis Halzen, lead scientist with IceCube. ![]() The find adds to an emerging era in astronomy when particles other than just photons can be used to study and reveal the cosmos. Leading that charge is the IceCube Neutrino Observatory in Antarctica, which-along with a few of its friends-has at last traced a handful of energetic cosmic neutrinos to a galaxy far, far away. That’s why now, the hunt has focused on neutrinos, chargeless and nearly massless particles that can be reliably traced back to their source. Most cosmic rays, though, have an electrical charge, and their paths get bent by the magnetic fields scattered throughout space, making it difficult to follow their footsteps home. Since then, scientists have been hunting for the astrophysical accelerators responsible for hurling the most tremendously energetic of these particles across the cosmos. In the early 1900s, physicist Victor Hess discovered that Earth is being constantly bombarded by energetic particles coming from outer space, which we now call cosmic rays. A flash of light detected about a mile below the South Pole likely solves a century-old cosmic mystery-and potentially opens up a new kind of astronomy involving ghostly subatomic particles called neutrinos. ![]()
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