IIA scientists detect emissions from novae in Andromeda galaxy

Bengaluru: Researchers from the Indian Institute of Astrophysics (IIA), Bengaluru, have detected ultraviolet emissions from 42 novae — a rare class of stellar explosions — and even captured four of them during their outburst phase.

Astronomers Judhajeet Basu, Krishnendu S, Sudhanshu Barway, Shatakshi Chamoli, and GC Anupama identified far-ultraviolet emissions from novae in the Andromeda Galaxy, the closest neighbour to the Milky Way. Novae are transient astronomical events where a star rapidly brightens and gradually fades.

Using archival data from the UV Imaging Telescope (UVIT) aboard Isro’s space-based multi-wavelength telescope, Astrosat, the team compiled a comprehensive catalogue of observations.

In close binary star systems, a white dwarf — the dense, hot remnant of a sun-like star — can pull matter from its companion star through a process called accretion. This matter forms an accretion disk around the white dwarf, emitting ultraviolet and blue light waves due to its extreme heat.

The accumulation of matter on the white dwarf eventually triggers runaway thermonuclear reactions, resulting in a nova eruption. These eruptions release intense light and enrich the galaxy’s chemical composition by dispersing material into the interstellar medium.

"The central region of Andromeda is quite bright, so we used advanced imaging techniques to uncover more novae. Both methods yielded identical results, confirming the authenticity of our findings,” said Sudhanshu Barway, a faculty member at IIA.

Judhajeet Basu highlighted the significance of their discovery: “This is the first time ultraviolet emissions from extragalactic novae in their dormant phase (quiescence) have been detected. While past observations captured outbursts, quiescent novae reveal features of the accretion disk, and some even show pre-eruption dips. The novae catalogued in this study can now aid other astronomers in refining their calculations.”