Superluminous supernovae are the brightest explosions in the universe. In just a few months, a superluminal supernova can release as much energy as our Sun has in its entire lifetime. And at its peak, it can be as bright as the entire galaxy.
One of the best-studied superluminous supernovae (SLSNs) is SN 2006gy. Its origins were a mystery, but now Swedish and Japanese researchers say they have figured out what caused the explosion: a catastrophic interaction between the white dwarf and its massive partner.
SN 2006gy lies about 238 million light-years away in the constellation Perseus. It is located in the spiral galaxy NGC 1260. Discovered in 2006, as its name suggests, and has been studied by groups of astronomers using the Chandra X-ray Observatory, Keck Observatory and others.
When SN 2006gy was launched, Nathan Smith of the University of California, Berkeley led a team of astronomers from the University of California and the University of Texas at Austin.
“It was a truly monstrous explosion, a hundred times more energetic than a typical supernova,” Smith said.
This means that the exploding star was about 150 times larger than our Sun. We've never seen this before. '
These types of stars existed in the early universe, astronomers thought at the time. Thus, the evidence for this explosion has given astronomers a rare glimpse into one aspect of the early universe.
It wasn't just the SN 2006gy energy release that caught the eye. The SLSN displays some curious emission lines that have puzzled astronomers. Now the research team believes they have discovered what is behind SN 2006gy.
Their work is called 'Supernova Type Ia at the heart of the superluminal transient SN 2006gy'. It is published in the journal Science.
The team includes researchers from Stockholm University in Sweden and colleagues from Kyoto University, University of Tokyo and Hiroshima University.
How the brightness of SN 2006gy has changed over time. (NASA / CXC / UC Berkeley / N. Smith.)
The team saw iron ejection lines that appeared only a year after the supernova explosion. They explored several models to explain this phenomenon and settled on one.
'No one has compared the spectra from neutral iron, that is, the iron that all the electrons have retained, with the unidentified emission lines from SN 2006gy, because iron is usually ionized. We tried it and saw with excitement how line by line lined up in the same way as in the observed spectrum, ”says Anders Yerkstrand, Department of Astronomy at Stockholm University.
“It got even more exciting when it turned out that it took a very large amount of iron to draw the lines – at least a third of the Sun's mass – which outright ruled out some old scenarios and instead opened up a new one.”
According to the team's results, SN 2006gy is a double star. One star was a white dwarf the size of the Earth. The second was a massive, hydrogen-rich star that was as large as our entire solar system.
The large star was in later stages of evolution and expanded as new fuel was ignited. As it expanded, the white dwarf was pulled into the large star, spiraling toward the center.
Eventually, the white dwarf reached the center and became unstable. It then exploded as a Type Ia supernova.
Snapshot of SN 2006gy and its galaxy NGC 1260. (Fox et al. MNRAS, 2015)
This titanic collision produced SN 2006gy's extreme luminous flux.
“The fact that a Type Ia supernova appears to be behind SN 2006gy turns what most researchers believed,” says Anders Jerkstrand.
“The fact that a white dwarf can be in close orbit with a massive hydrogen-rich star and explode rapidly as it hits the center provides important new information for the theory of binary evolution and the conditions required for a white dwarf to explode.”
SN 2006gy was extremely bright.
At its peak, SN 2006gy was 570 billion times brighter than the Sun and 20 times brighter than the combined light emitted by the Milky Way.
This article was published by Universe Today.
Sources: Photo: Chandra X-ray Image of SN 2006gy. (NASA / CXC / UC Berkeley / N. Smith)
