Supernova 2016adj – Hubble Captures Rare Light Echoes

By James Anderson •  Updated: 10/29/22 •  5 min read

Supernovas, or star explosions, release an intense burst of light in all directions. Rarely, from the original supernova position, rings of light or “light echoes” spread out in the months and years that follow.

As described in a recent paper based on observations made with the Hubble Space Telescope, astronomers were able to capture images of supernova light echoes, which had only been seen before in a small number of other supernovae.

“The data set 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,”

said lead scientist Professor Maximillian Stritzinger of Aarhus University.

supernova SN 2016adj

Colored images of the light echo associated with SN 2016adj. The dashed line highlights the position of the main light echo ring as it expands from the position of the supernova from 300 to 580 days post-explosion, along with a prevalent dust lane. The dust lane extends from east-northeast to west-southwest direction and clearly obscures both portions of the light echo and the background stars.
Credits: ICE-IEEC, UCD, Aarhus University, Hofstra University, European Southern Observatory.

Even though the James Webb Space Telescope has received a lot of attention, Hubble Space Telescope (HST) is still producing many excellent images of the cosmos.

“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,”

said co-author and astrophysicist Dr. Morgan Fraser, University College Dublin School of Physics.

Supernova Blastwave

The strong 2016adj supernova explosion is sending a blast wave outward at a speed of more than 10,000 kilometres per second. The bright flash of light that the supernova released prior to this blastwave is what is causing the expanding rings that can be seen in the images.

The HST images were combined to create a brief gif video that first showed the supernova explosion at the very centre, then light rings that appeared when light from the explosion hit different layers of dust nearby.

“Supernovae are of interest as these cosmic explosions produce many of the heavy elements such as carbon, oxygen and iron, which make up our galaxy, stars and our planet,”

explained co-author Dr. Lluis Galbany, of the Institute of Space Sciences, Barcelona.

Supernova SN 2016adj

supernova SN 2016adj

Host-subtracted F555W-band HST image of SN 2016adj on +1991 days, with the positions of LE1, LE2, LE3, and LE4 highlighted by colored rings and labeled. Credit: The Astrophysical Journal Letters (2022).

The supernova SN 2016adj, which is located in the well-known galaxy Centaurus A and is 10 to 16 million light years away from Earth, was first observed in 2016. Over the course of five and a half years, astronomers observed the area around the supernova as it slowly dissipated.

There are many dust lanes in Centaurus A, and as the supernova’s outward spreading light hit these dusty areas over time, it lit them up farther and farther away from the supernova’s original position, producing a series of expanding emission rings known as light echoes.

Changes in these rings over time have given scientists a chance to study how the dust lanes in the part of the galaxy near the explosion are set up. According to the data, they appear to be made up of dust columns with sizable gaps between them, resembling a slice of Swiss cheese.

Centaurus A is a huge elliptical galaxy. The majority of these are dust-free, quiet, and devoid of younger stars that could explode as supernovae, but Centaurus A is unique. It has prominent dust lanes where new stars are forming, and it is a strong source for radio astronomy.

“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,”

said Stritzinger.

A Spectrum of Light Echoes?

Four distinct light echoes produced by four different dust sheets have so far been seen. The SN 2016adj data set shows the earliest detection of light echo emission from a supernova.

While earlier light echoes captured by HST, like SN 2014J, started only hundreds of days after the explosion, the team was able to measure these emissions 50 days after the star’s explosion. These are also the first light echoes discovered in the vicinity of a type Ic supernova.

The team plans to keep making observations with the HST in the future in the hopes that more light rings will show up. Also, it might be possible to capture the spectrum of the light echoes, which would show the spectrum of the supernova underneath.


Maximilian D. Stritzinger et al, Hubble Space Telescope Reveals Spectacular Light Echoes Associated with the Stripped-envelope Supernova 2016adj in the Iconic Dust Lane of Centaurus A, The Astrophysical Journal Letters, 939 L8

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