A few times a year, Nasa's Swift telescope detects intense flashes of energy coming from deep space.
The flashes are short-duration gamma-ray bursts (SGRBs) and the explosions that cause them "release, in just a fraction of a second, the same amount of energy that [our] Sun puts out in a million years," says Nial Tanvir of the University of Leicester.
Now for the first time, a "kilonova" associated with these gamma-ray bursts has been observed by the Hubble Space Telescope in infrared light.
[pullquote source="Nial Tanvir, University of Leicester] "We don't get many opportunities to look at these things," says Tanvir, the lead author on a paper [link url="http://www.nature.com/nature/journal/vnfv/ncurrent/full/nature12505.html"]published in Nature[/link"]Explosive events of that power nearly always involves a black hole[/pullquote] of kilonova observations made in June and July 2013.
The paper confirms predictions that kilonovae are more visible in infrared, and should pave the way for more detailed observations of future kilonovae.
More importantly, perhaps, these gamma-ray bursts and kilonova could one-day play a key part in testing Einstein's Theory of General Relativity with cosmic gravitational waves.
Insanely high-energy events in the Universe are almost inevitably tied to those incredible and mysterious objects known as black holes. "Explosive events of that power [...] nearly always involve a black hole," notes Tanvir.
In the case of SGRBs, we're talking about the creation of a black hole through the violent collision of two neutron stars.
Containing up to three times the entire mass of the Sun in a ball only 20 kilometres in diameter, neutron stars are the dying remnants of massive stars after they have exploded in a supernova.
They are unimaginably dense, so when you have the rare case of two neutron stars orbiting each other in a binary system, the fun really begins.
Their orbits slowly decay and the two stars inexorably circle closer and closer, eventually meeting in a final embrace. The energy released when they collide explodes out in short, sharp jets of gamma rays, followed by dense, radioactive stellar material ejected in the explosion, the kilonova flash. In the explosion on 4 June, the gamma ray burst was 100 billion times brighter than the kilonova flash that followed.
In any one galaxy, these events occur once every million years or so, says Tanvir. But across the Universe, five or six are detected each year.
A few percent of the neutron stars' mass is ejected in the explosion, "a few tens of Jupiters," estimates Tanvir. Research released in June this year, which used visible and near-infrared measurements of kilonovae, suggested that these neutron star collisions could be how gold and other heavy elements are created in the Universe -- yes, the same dying embrace that creates black holes and intense gamma ray bursts also showers the Universe with gold. "The fabric of spacetime wobbles when you have binary systems like neutrons," says Tanvir, hinting at why these binary neutron star systems and their blinging catastrophic deaths could hold the key to measuring cosmic gravitational waves. "These [binary] systems might be the first places you would detect gravitational waves," he says. Gravitational waves are ripples in space time that are predicted by Einstein's Theory of General Relativity. They are difficult to detect because gravity is, counterintuitively, so weak (think about it, if gravity is so strong, then why does a simple fridge magnet overpower it and remain on your fridge?).
Orbiting neutron stars are exactly the kind of intense gravitational environments where the ripples would be strongest.
Short-duration gamma ray bursts and kilonovae are like beacons -- they say to astronomers, look over here, it's a binary neutron star system.
With this benchmark, researchers will be able to target their search for gravitational waves and, importantly, measure how far away the source of the waves is, thereby helping us understand how they propagate through space-time.
Colliding neutron stars, black holes, the creation of gold, and gravitational waves -- yes, short-term gamma-ray bursts may just be the most interesting things in the Universe.
This article was originally published by WIRED UK
