Supernova light fantastic – the dead stars that light up the universe

Posted on: 08 October 2019

An international collaboration of scientists including Kate Maguire, from Trinity’s School of Physics, has made a startling discovery about supernovae – the brilliant points of light that result when stars explode at the end of their lives.

Supernovae can briefly outshine entire galaxies and radiate more energy than our sun will in its entire lifetime. They’re also the primary source of heavy elements in the universe. As a result, scientists have good reason to try to understand as much as they can about them.

It turns out that Type Ia supernovae – which occur following the death of one star that was orbiting another – experience long plateaus of up to a year in their light curves post-death, rather than fizzling out fast after their final acts.

This discovery was completely unexpected based on prior knowledge and is outlined in a paper published in leading international journal Nature Astronomy.

Type Ia supernovae were key in the discovery of the Accelerating Universe that was awarded the Nobel Prize in Physics in 2011. Despite their important role in that discovery, their use in measuring the basic cosmological properties of the universe has been limited by how precisely we understand how the stars explode.

The new research was led by Or Graur at the Center for Astrophysics | Harvard & Smithsonian, who said: “Most supernova research is conducted in the weeks or months immediately following an explosion, but we wanted to see how light curves behave at late times, around 500 to 1,000 days after explosion.”

Kate Maguire, Assistant Professor in Trinity’s School of Physics, added:

These new observations are very exciting as they reveal that many Type Ia supernovae just stop declining as expected at late times and stay bright for up to a year.

To better understand the surprising behaviour of these supernovae, Professor Maguire went to one of the European Southern Observatory’s flagship telescopes – the Very Large Telescope (VLT) in Chile – to take a deeper look at what was going on. Her work was crucial in constraining potential reasons for the slowdown in the light curves.

Her data were combined with observations from the Hubble Space Telescope obtained by co-author, Adam Riess, of The Johns Hopkins University and the Space Telescope Science Institute. Riess won the Nobel Prize in Physics in 2011.

It was by combining these two sets of data that allowed the scientists to obtain a more consistent picture of this long plateau in the light curves.

Professor Maguire added:

These results go against what we had previously thought we understood about the complex processes going on during these massive explosions.

It’s very important to understand this in more detail so that Type Ia supernovae can continue to be used to understand the fundamental properties of our universe.

In addition to Graur, Maguire and Riess, the study involved the scientists Arturo Avelino, Harvard Smithsonian; Russell Ryan, Space Telescope Science Institute; Matt Nicholl, University of Edinburgh; Luke Shingles, Queen’s University Belfast; Ivo R. Seitenzahl, University of New South Wales; and, Robert Fisher, University of Massachusetts Dartmouth.

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