Powerful transient radio flashes in the universe pop off randomly and appear to defy explanation, but astronomers have made a breakthrough in pinpointing the exact source of one of these fast radio bursts, known simply as "FRBs."
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Only a handful of FRBs have ever been positively identified by looking back through the data archives of radio telescopes. They may be extremely short lived, but they are so powerful that, for the briefest of moments, come from a phenomenon that can generate more energy than our sun can pump out for 10,000 years.
As dazzling as these events are, their apparently random nature (they seem to be generated well beyond our galaxy and appear anywhere in the sky) and extremely short (millisecond) burst makes follow-up observations nigh-on impossible. However, on Wednesday, astronomers using the Commonwealth Scientific and Industrial Research Organisation (CSIRO) radio telescopes in eastern Australia and the National Astronomical Observatory of Japan's Subaru telescope in Hawaii, announced a breakthrough.
Usually, FRBs are found months or even years after they've been detected by radio telescopes. By analyzing radio archives, the FRB signals can be teased out. Unfortunately, this method leaves no room for follow-up observations of the region of sky the signal was detected, leaving their origin a mystery. To rectify this, the international team set up an early warning system so that as soon as a signal is received, other observatories are alerted and are able to quickly zoom in on the region of sky where the FRB was detected.
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(This system is akin to the alert system between NASA's Swift space telescope that detects gamma-ray bursts, or GRBs, and ground-based observatories so rapid follow-up observations can zoom in on the energetic explosion.)
So, on April 18, 2015, the Australian 64-meter Parkes Radio Telescope detected an FRB flash and immediately notified the collaboration. Within 2 hours, the CSIRO Compact Array telescope, located 400 kilometers (250 miles) north of Parkes, slewed in the direction of where the pulse was spotted and was able to detect a radio emission from the blast site which lasted for 6 days before fading. Already astronomers had done something unprecedented; they had identified the location of a FRB and measured its radio afterglow.
Meanwhile, atop Mauna Kea in Hawaii, the Subaru telescope was able to begin its observing run, identifying the precise source of the FRB and radio afterglow. As the location of the April 18 FRB was known to a precision of 1,000 times better than previously discovered FRBs, Subaru made the groundbreaking discovery that this FRB originated inside a galaxy 6 billion light-years away.
What is particularly interesting is that, after further observations of this random galaxy, the researcher found it to be an old elliptical galaxy - the kind of galaxy where you wouldn't expect to see much in the way of star formation. This is the first indication that FRBs probably aren't generated by star formation processes.
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"This is not what we expected," said Simon Johnston, Head of Astrophysics at CSIRO and a member of the research team. "It might mean that the FRB resulted from, say, two neutron stars colliding rather than anything to do with recent star birth."
What's more, this observation was used as a tool to identify how much material the radio emission from the FRB traveled through, eventually reaching Earth 6 billion years later. And for this one event, it seems to exactly match our theoretical models as to the distribution of matter, including dark matter, in the universe.
"The good news is our observations and the model match - we have found the missing matter," said Evan Keane from the SKA Organisation, and lead author of the study published in the journal Nature. "It's the first time a fast radio burst has been used to conduct a cosmological measurement."
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It is hoped that, now a system is in place to make rapid and precise observations of FRBs, more FRBs can be used out to further refine cosmological models.
As for what generated this particular FRB, some production mechanisms have been ruled out and others have become more likely, but at least we know where it came from and what kind of galaxy produced it. But even better, astronomers estimate the universe sparkles with 10,000 FRBs throughout the entire sky every day - we just need more radio telescopes looking for them.