Recently, the first time-lapse images of a thermonuclear fireball blasting out of a nova star have been captured by the astronomers.
An international team of researchers worked together to map the nova eruption, a baby brother to a supernova explosion. The study is published in the Nature journal.
Professor Peter Tuthill of the University of Sydney’s Institute for Astronomy stated that, “Although novae often play second fiddle in the popular imagination to their more famous big cousins – the supernovae – they are a truly remarkable celestial phenomenon.”
When a striking, compact star known as white dwarf shreds the matter from a nearby companion star with its intense gravitational field, Novae happen.
The white dwarf frequently sucks hydrogen from its partner, forming an ocean on its surface similar to the little stellar mosquito . After forming about as much mass as the entire planet Saturn, the pressure reaches a critical point, then bang!
Professor Tuthill said, “The stellar surface turns into one titanic hydrogen bomb throwing a fireball out into space and pushing a previously faint, murky star system into eminence as a nova in our night skies.”
However, the rage of the expansion is breathtaking, surrounding an area the size of the Earth’s orbit within a day, and passing Jupiter’s orbit in less than two weeks. In spite of the massive size of the fireball, at the remotest distance to this star of 15000 light years, it took very special technology to be able to image it at all.”
The team of researchers collaborated with the Georgia State University scientists, running the Centre for High Angular Resolution Astronomy (CHARA) array in Southern California, in order to make the fine measurements necessary to map the event.
Dr. Vicente Maestro, also of the University of Sydney, said, “The technical challenge posed requires the magnification equivalent to watching a flower in my Spanish hometown of Algeciras open out from here in Sydney, a distance of 12,000 kms away.”
The array took the first pictures of a nova at the early fireball stage from one that exploded in the Delphinus constellation last year, from Earth’s point of view. In reality, the star went nova 15,000 years ago, but the star is 14,800 light years from our Sun so we only spotted it last August.
However, the observations were quite clear and showed how the structure of the ejected material evolves as the gas expands and then cools. This study eventually reveals that, this expansion is more complicated than the simple models formerly predicted.
As per the first observation, the fireball was roughly the size of Earth’s orbit. When last measured, 43 days after detonation, it had expanded nearly 20-fold at a velocity of more than 600 kms per second to nearly the size of Neptune’s orbit, the outermost planet of our Solar System.
But, the explosion was not exactly circular, instead the fireball had a slightly elliptical shape. The researchers also found that the outer layers of the eruption became more diffuse and transparent as the fireball expanded. Just after a month, the researchers observed a brightening in the cooler, outer layers, potentially caused by the formation of dust grains that spew light at infrared wavelengths.
Dr Theo ten Brummelaar of Georgia State University stated that, “The recent information enable us to study in detail exactly how the fireball evolves as the gas expands and cools. It seems like the ride is a lot more complex and jarring for the gas than the simple models used previously would have predicted.”
Perhaps most shockingly, the astronomers discovered that regardless of the rage of the detonation on the white dwarf’s surface, the star itself emerges almost intact, leaving it free to start the whole process all over again.
