Supernova snaps: Astronomers capture ‘light echoes’ thanks to Hubble

28 Oct 2022

Image: © pongpinun/

Dublin-based astronomers were among those who captured the rings of light spreading from a supernova.

Some lucky astronomers managed to capture the after-effects of a star exploding using the Hubble Space Telescope.

When a star explodes it is known as a supernova. These explosions send an intense burst of light out in all directions. On rare occasions, rings of light spread out from the original supernova position in the months and years that follow.

This phenomenon is referred to as ‘light echoes’. Thanks to an international team of astronomers and the Hubble Space Telescope, we now have a clear picture of light echoes from a supernova.

The scientists who observed the light echoes were based in Dublin, New York, Barcelona, Aarhus and the German town of Garching.

They published their findings in The Astrophysical Journal Letters. They also merged the images into a short GIF. The animated image shows the supernova explosion at the very centre, followed by light rings which appeared when light from the explosion hit various layers of dust in the vicinity.

A light echo compilation of images turned into a gif by astronomers.

Light echoes around SN 2016adj. Image: Stritzinger et al

Lead scientist Prof Maximillian Stritzinger of Aarhus University, Denmark, said, “The dataset is remarkable and enabled us to produce very impressive coloured images and animations that exhibit the evolution of the light echoes over a five-year period. It is a rarely seen phenomenon previously only documented in a handful of other supernovae.”

The supernova studied, SN 2016adj, was first seen in 2016. It belongs to the well-known galaxy Centaurus A, which is situated between 10m and 16m lightyears from Earth.

For five-and-a-half years, the astronomers watched the area around SN 2016adj after it slowly faded away. The light echoes from the original supernova were very visible due to the dust lanes in Centaurus A.

The light echoes from the supernova meant that these dust lanes were illuminated enough for astronomers to examine their layout. The data suggests that they consist of columns of dust with large holes in between, resembling a chunk of Swiss cheese.

According to Stritzinger, activity in Centaurus A suggests that it has collided with another galaxy in the past.

He said elliptical galaxies like Centaurus A are “mostly quiet, dust-free and without younger stars prone to go off as supernovae”.

“Centaurus A is obviously different. It is a strong radioastronomical source and it contains prominent dust lanes with new stars forming within. This is a sign that it has ‘recently’ gobbled up another smaller spiral galaxy, and matters have not yet settled down, as it might in a couple of hundreds of millions of years. Observing the development of these light echoes will help us gain more insight into these violent galaxy collisions.”

Up to now, four distinct light echoes produced by four different sheets of dust have been observed. The team plans to follow up on the observations with the Hubble Space Telescope in the future.

Dr Morgan Fraser from University College Dublin’s School of Physics, who co-authored the study, highlighted the importance of Hubble’s historic data for this study.

“While the James Webb Space Telescope has drawn much attention, its predecessor Hubble continues to provide incredible images of the universe,” said Fraser. “HST has now been observing the sky for over three decades, so we can find things like this light echo that evolve slowly over many years.”

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Blathnaid O’Dea is Careers reporter at Silicon Republic