When a white dwarf star gets too big after absorbing material from another nearby star, it explodes, sending a burst of light out into the universe in what is called a Type 1a supernova.
What scientists have not fully understood is the identity of the white dwarf's partner. Some have suggested that mergers between white dwarfs can lead to these explosions. But according to a new paper in the journal Science, the aged, puffy stars called red giants can also feed white dwarfs and cause supernovas.
Astrophysicists first caught sight of an unusual-looking supernova in January 2011. It was around 675 million light-years away in the constellation Lynx.
Until its telltale flashy burst, a future supernova is indistinguishable from other stars. "It's really not possible to look at them before they explode," said the paper's lead author, Benjamin Dilday, an astrophysicist at Las Cumbres Observatory Global Telescope Network in Goleta, Calif.
From the behavior of gas in the area after the explosion, Dilday and colleagues were able to deduce that their supernova had originally been a white dwarf orbiting a red giant.
Gas from the red giant had blown onto the white dwarf, repeatedly igniting its surface and causing explosions called novas. Eventually the star ignited at its center, leading to the supernova.
Astrophysicists use Type 1a supernovas, which are highly consistent in their brightness, as standard measures of distance in the universe. They help underpin the study of dark energy and how the universe expands.
Dilday hopes his work will help classify supernovas with greater precision. "If it's the case that different ways of making the supernova result in slightly different properties of the supernova, that would let us improve how we study cosmology," he said.
NEW YORK TIMES