Huge 12 billion-year-old explosion in space has been spotted from Earth – and it could reveal secrets of the early universe
• Astronomers using a telescope in Texas have spotted the gamma-ray burst
• The rare explosion 12.1 billion light years away was caused by a supernova
• Gamma-ray bursts release more energy in seconds than the sun in its entire 10 billion-year lifetime
• Only a handful are thought to happen in a galaxy every few million years
• This particular event occurred not long after the Big Bang in cosmic terms
• It could give scientists ‘information about the early universe’ says Dr Kehoe
One of the biggest and hottest explosions in the universe – a rare event known as a gamma-ray burst (GRB) – has been spotted on camera.
And this particular event, caused by the enormous explosions of a star, occurred shortly after the Big Bang about 12.1 billion years ago.
The intense light recently reached Earth and it could give astronomers useful information about the conditions in the young universe.
Light from an explosion of a massive star at the end of its life 12.1 billion years ago reached Earth recently. An image of its peak afterglow, circled with blue and yellow, was captured by Southern Methodist University’s Rotse-IIIb telescope at McDonald Observatory, Fort Davis, Texas. A bright star sits on the left of the afterglow
Gamma-ray bursts are believed to be the catastrophic collapse of a star at the end of its life.
The observation was made by the telescope Rotse-IIIB at the McDonald Observatory in the Davis Mountains of West Texas, owned by the Southern Methodist University (SMU) in Dallas.
WHAT IS A GAMMA-RAY BURST?
A gamma ray burst occurs when a massive star dies and collapses, causing a huge explosion known as a supernova.
The remnant of this supernova is often a neutron star, quark star or black hole.
During the supernova a narrow beam of intense radiation known as a gamma-ray burst (GRB) is sometimes released from either pole of the star.
This burst can last anywhere from a few milliseconds to several minutes, with an ‘afterglow’ normally persisting after.
A GRB is incredibly powerful, typically releasing more energy in seconds than the sun will in its 10 billion-year lifetime.
A planet caught in one of these bursts would lose its atmosphere instantly and would be left a burnt cinder, astronomers say.
Scientists might be able to detect warning signs of an impending gamma ray burst but if a burst were headed for Earth there wouldn’t be anything anybody could do about it.
However, astronomers put the chances of that happening at around 1 in 10 million.
SMU physicists report that their telescope was the first on the ground to observe the burst, and to capture an image.
This particular explosion, first spotted back in April, was recorded as GRB 140419A by Nasa’s Gamma-ray Coordinates Network (GCN).
Gamma-ray bursts are not well understood by astronomers, but they are considered important, according to Farley Ferrante, a graduate student in SMU’s Department of Physics, who monitored the observations along with two astronomers in Turkey and Hawaii.
‘As Nasa points out, gamma-ray bursts are the most powerful explosions in the universe since the Big Bang,’ he said.
‘These bursts release more energy in 10 seconds than our Earth’s sun during its entire expected lifespan of 10 billion years.’
Some of these GRBs appear to be related to supernovae and correspond to the end-of-life of a massive star, said Dr Robert Kehoe, physics professor and leader of the SMU astronomy team.
‘Gamma-ray bursts may be particularly massive cousins to supernovae, or may correspond to cases in which the explosion ejecta are more beamed in our direction. By studying them, we learn about supernovae,’ Kehoe said.
SMU’s Rotse IIIb telescope (pictured) at the McDonald Observatory, Fort Davis, Texas had the earliest and brightest observation from the ground of a gamma-ray burst that occurred more than 12 billion years ago. The telescope is part of the Robotic Optical Transient Search Experiment
Scientists weren’t able to detect optical light from gamma-ray bursts until the late 1990s, when telescope technology improved.
Among all lights in the electromagnetic spectrum, gamma rays have the shortest wavelengths and are visible only using special detectors.
Gamma-ray bursts result from hot stars that measure as enormous as 50 solar masses.
The explosion occurs when the stars run out of fuel and collapse in on themselves, often forming black holes.
Outer layers detonate, shooting out material along the rotation axis in powerful, high-energy jets that include gamma radiation.
As the gamma radiation declines, the explosion produces an afterglow of visible optical light.
The light, in turn, fades very quickly, said Kehoe. Physicists calculate the distance of the explosion based on the shifting wavelength of the light, or redshift.
‘The optical light is visible for anywhere from a few seconds to a few hours,’ Kehoe said.
‘Sometimes optical telescopes can capture the spectra. This allows us to calculate the redshift of the light, which tells us how fast the light is moving away from us. This is an indirect indication of the distance from us.’
To put into context the age of the new gamma-ray burst discoveries, Kehoe and Ferrante point out that the Big Bang occurred 13.81 billion years ago.
GRB 140419A, meanwhile, exploded about 12.1 billion years ago, which is ‘only about one and a half billion years after the universe began,’ said Ferrante.
‘That is really old.’
A planet caught in the path of a gamma-ray bursts burst would lose its atmosphere instantly and would be left a burnt cinder, astronomers say (artist’s illustration shown). The chances of Earth being hit by one, which would apparently be almost undetectable, stands at around 1 in 10 million
Armed with images of the burst, astronomers can analyse the observational data to draw further conclusions about the structure of the early universe.
‘At the time of this gamma-ray burst’s explosion, the universe looked vastly different than it does now,’ Kehoe said.
‘It was an early stage of galaxy formation. There weren’t heavy elements to make Earth-like planets.
‘So this is a glimpse at the early universe. Observing gamma-ray bursts is important for gaining information about the early universe.’
The GRB’s brightness, regarded as being ‘of the 12th magnitude’, was also impressive; it was just 10 times dimmer than what can be seen through binoculars in the night sky and only 200 times dimmer than what the human eye can see.
‘The difference in brightness is about the same as between the brightest star you can see in the sky, and the dimmest you can see with the naked eye on a clear, dark night,’ Kehoe said.
‘Considering this thing was at the edge of the visible universe, that’s an extreme explosion. That was something big. Really big.’