Kiwi astronomers make ‘shockwaves’ discovery
A team of New Zealand astronomers has helped make a major astronomical breakthrough, observing for the first time an explosion 13,000 light years from Earth.
The University of Canterbury team joined research that has shown ‘‘shockwaves’’ from the nova explosion, rather than nuclear fusion, cause most brightness from these phenomena.
A nova, or stella nova – Latin for ‘‘new star’’ – is a sudden explosion on the surface of a white dwarf, which is the hot, burnt-out core of a star. It produces an incredible amount of energy and light, increasing the star’s brightness by thousands or even millions of times and appearing as a new star.
Team leader, associate professor in astronomy and director of the University of Canterbury Mt John Observatory, Karen Pollard, said novae are relatively common in the galaxy and understanding what makes them glow is important for understanding how stars evolve.
‘‘It’s a really good example of how observations from lots of different telescopes around the world and from telescopes in space . . . can give us a real insight into what these stars actually are.
‘‘The common theory is these stars have big thermo-nuclear fusion explosions occurring on the surface of these white dwarf stars, but the observations that our collaborations took showed that a lot of the light is actually output by shockwaves that are occurring from the explosion.’’
The team used Nasa’s spacebased telescopes and groundbased telescopes, including some at the Mt John Observatory in Tekapo, to observe the nova.
Pollard said this discovery was important for an observatory like Mt John as it showed the team was able to ‘‘collaborate with teams from all around the world‘‘.
The outburst originated from a star system discovered in March 2018 called V906 Carinae, which lies in the constellation Carina. The Tekapo-based team started observing the nova, which actually happened 13,000 years ago, soon after its discovery.
‘‘People would have been able to see it with their naked eyes if they knew which position in the sky to look,’’ Pollard said. ‘‘13,000 light years does seem like a long way away but .. we got such good observations of it from Mt John because it was a long way south and relatively bright.’’
Their results are documented in a new paper, co-written by Pollard, called Direct evidence for shock-powered optical emission in a nova published in April’s international journal Nature Astronomy.
Each nova explosion releases a total of 10,000 to 100,000 times the annual energy output of our sun.