Astrophysicists made history last year when they detected gravitational waves – the elusive ripples in space-time that were first theorized by Albert Einstein as part of his theory of general relativity in 1916. Early efforts failed to pinpoint the visible light component of the chaotic event that triggered the waves. But now data from NASA's Fermi telescope has reduced the search area by around two-thirds, which will help scientists understand more about the nature of the event and improve their systems for detecting future gravitational wave events.
Detected on September 14, 2015 by the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) team, the disturbance to the very fabric of space-time was produced by two massive black holes, each about 30 times the mass of the sun, which collided some 1.3 billion years ago. It's been heralded as confirmed physical proof, at last, that Einstein's theory was correct – that gravity is inextricably interwoven with matter and energy, and that an exciting new era of astronomical observation awaits.
But pinpointing the origins of the waves has not been easy. LIGO scientists narrowed it down to an arc of sky spanning approximately 600 square degrees. It's a little like searching for a specific needle located somewhere in the United States. NASA's Fermi Gamma-ray Space Telescope has further reduced the search area to just 200 square degrees, however.
This comes thanks to analysis of a brief, weak burst of high-energy light that hit Fermi's Gamma-ray Burst Monitor (GBM) less than half a second after LIGO detected the event. An international team of scientists has calculated that the Fermi measurements have less than 0.2 percent chance of being random fluctuations (because they happened so close to the merger), though some astronomers remain unconvinced because they expected the gas needed to generate x-ray or gamma-ray signals to have been swept up by the twin black holes long before the collision.
The bad news is that the burst occurred at a high angle to the GBM detectors, which reduced Fermi's ability to pinpoint the incident, but the good news is that Earth blocked much of the burst from Fermi's detection. See the video below for a visualization of how Fermi can reduce the search area.
