An object thought to a faraway galaxy is actually the youngest and brightest supernova remnant in the Milky Way, according to a new study.
The team led, by Bryan Gaensler from the University of Sydney, published their findings in the latest edition of The Astrophysical Journal Letters.
The object, known as G350.1-0.3, was first discovered in the 1980s, but its irregular shape led astronomers to believe it was a background galaxy.
According to co-author and University of Sydney Ph.D. student Anant Tanna, Gaensler thought the object's brightness and spectral index was too similar to that of a supernova, than that of a faraway galaxy.
"He said 'let's have a look at this in X-rays and check to see whether it is a galaxy or a supernova remnant'," said Tanna.
The team used data from the European Space Agency's orbiting X-ray observatory XMM-Newton to analyze the object.
When they examined G350.1-0.3 they concluded it is an irregularly-shaped supernova remnant.
"Given the information obtained from the X-ray observation it's pretty much definite that this is a supernova remnant," Tanna said.
To explain its shape, the team looked at radio surveys and discovered that G350.1-0.3 had exploded next to a dense cloud of gas about 15,000 light years from Earth.
The cloud prevented the blast from expanding evenly in all directions, resulting in an example of a rare kind of misshapen supernova remnant.
"The large cloud explains why it is such an unusual shape, because the shock wave is expanding into a very unhomogeneous environment," Tanna said.
According to Tanna, G350.1-0.3 is incredibly small and young in astronomical terms, only eight light-years across and about 1000 years old.
"Only a handful of such young supernova remnants are known. So even having one more is important," Tanna said. "It may turn out that many of the youngest supernova remnants have these strange shapes. The hunt is now on to find more."
Tanna believes G350.1-0.3 will help astronomers better understand the evolution of supernova and their parent stars.
"Young supernova help astronomers trace back through the life of a supernova remnant, back to when there was an actual star was there," Tanner said. "They can then work out what type of star it was and have a better understanding of what kinds of stars explode and how certain remnants form."
Tanner defends the astronomers who misclassified the supernova as a background galaxy two decades ago.
"Had we been in those people's position with the same data, we would have made the same conclusion," Tanna said. "It's not that they were wrong, it's just that new information allows us to develop or rule out theories."
This is not the first time that Gaensler has corrected the astronomical text books.
In February, he led a team that concluded that our home galaxy -- the Milky Way- - is 12,000 light-years thick when seen edge-on, not 6000, as previously thought.
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