ARI PhD student observes a newly discovered Classical Nova eruption in Barnard's Galaxy

NGC 6822 "Barnard's Galaxy" (Credit: ESO)

A UK-US team, led by ARI PhD student Mike Healy have discovered and investigated a Classical Nova eruption in the nearby “Barnard’s Galaxy”. These observations utilised many different telescopes, including the ARI’s own Liverpool Telescope and the Neil Gehrels Swift Observatory. This work has recently been published in Monthly Notices of the Royal Astronomical Society.

Novae are huge nuclear explosions that occur every 1,000-100,000 years on the surface of white dwarfs – the dense extinguished cores of stars that were once like our own Sun. But unlike our Sun, these white dwarfs are in binary systems and accumulate material from their nearby stellar companion. This is made possible by the fact that the two stars orbit around one another at distances much smaller than the orbit of Mercury. Once enough material accumulates onto the white dwarf, a series of runaway nuclear reactions occurs, just like a hydrogen-bomb – the nova explosion. 

Mike Healy, the lead author explains, “Novae are one evolutionary path towards Type Ia supernovae. Gaining a better understanding of these systems will help us towards answering the big cosmological questions”.

At the peak of their eruption, novae are extremely luminous, up to 100,000 times brighter than the Sun. This allows astronomers to see them at great distances, and even within other galaxies. Barnard’s Galaxy is an irregularly shaped low-mass galaxy that is similar in size to the Small Magellanic Cloud. It is about 1,600,000 light years away and is one of around 50 galaxies that make up the ‘Local Group’.

This nova eruption is the second nova discovered in Barnard’s Galaxy, but the first to be studied in great detail. The observations hint that the nova may belong to the recently uncovered ‘faint and fast’ sub-class; novae that evolve very rapidly but are fainter than one expects. These `faint and fast’ novae are perhaps associated with ‘recurrent novae’, systems that erupt every 100 years or less. It is difficult to say whether this nova is recurrent or not, since only one eruption from this system has been seen so far.

Mike Healy adds, “AT 2017fvz is a very fast fading nova. It took only 10 days to become ten times dimmer compared to when it was at its brightest. This might mean that the system responsible for this nova eruption contains a hot and massive white dwarf."

Mike Healy, originally from Ormskirk, just north of Liverpool, earned his undergraduate degree in Applied Mathematics from the University of Liverpool. He was also one of the first students to graduate from the Astrophysics MSc Distance Learning programme at the ARI. Mike is now a second year PhD student working on rapidly recurring novae, and is supervised by Dr Matt Darnley.