Hubble gasped at a dying star that echoed through a nearby galaxy: ScienceAlert

Hubble gasped at a dying star that echoed through a nearby galaxy: ScienceAlert

The last shrieks of light from a dying star have been preserved in a series of eerily beautiful images, which slowly reverberate through the cosmos.

The Hubble Space Telescope has captured in spectacular detail the flash of light that followed a massive star that went into supernova in 2016, as the glow spread out over a period of more than five years.

The resulting animation of stitched together images is a wealth of information about the evolution of dying stars and the dust surrounding the supernova in its own galaxy Centaurus A.

“A good everyday analogy is to imagine the finale of a fireworks show — a grenade’s bright burst of light at the end of the show will illuminate the smoke from previous grenades still hanging in the area,” says astronomer Stephen Lawrence from Hofstra University in the USA.

Animation of SN 2016_A_D_J with expanding light circles.
Time-lapse of the evolving light echoes of supernova SN 2016adj. (University College Dublin)

“By comparing a series of photos lasting several minutes, you could measure all sorts of information that isn’t directly related to the most recent explosion that lit up the scene, things like how many grenades had exploded before, how opaque the smoke is from a particular grenade, or how fast and in what direction the wind was blowing.”

Light echoes are a truly stunning phenomenon that can only be really seen from a distance. They occur when something produces a flash of light that radiates into space. If that light encounters a physical barrier, such as clouds of cosmic dust, it will reflect and arrive at a different time than the first eruption. It’s pretty much the same as a sound echo, but with light. We can use these light echoes to help map and understand spaceand the objects in it.

When a supernova was observed in 2016, astronomers noticed and repeatedly returned to the host galaxy, Centaurus A, more than 12 million light-years away, to see if they could detect changes over time. That perseverance paid off. Not only were they able to collect data on the fading light from the supernova, called SN 2016adjthey managed to capture its light echoes.

“The blast wave from this powerful supernova explosion is hurtling out at more than 10,000 kilometers (more than 6,200 miles) per second,” says astronomer Lluis Galbany of the Institute of Space Sciences in Spain.

“Before this blast wave, an intense flash of light is emitted from the supernova, and this is what causes the expanding rings that we can see in the images. Supernovas are important because these cosmic explosions produce many of the heavy elements, such as carbon, oxygen and iron, which makes up our galaxy, stars and planet.”

Centaurus A is a bit of an odd one out. It is classified as a elliptical galaxy, which are mostly smooth, oval-shaped galaxies with very little dust and very old stars. However, Centaurus A is very dusty, bursting with star formation and slightly distorted. These are all signs of a cosmically recent collision with another galaxy, whose effects have yet to fade.

It is thought that when the light from the supernova traveled to Earth, it would have encountered multiple dust clouds. From our position we would see this as a series of rings getting bigger. Four different light echoes were observed during the five-year observation period, representing four dust clouds, each large enough and dense enough to produce a light echo.

These light echoes allowed the researchers, led by astronomer Maximilian Stritzinger of Aarhus University in Denmark, to map the dust next to the supernova. Their analysis suggests that the dusty structures contain spaces filled with a material too low in density to produce an observable light echo.

While we’re pretty excited to fix our eyes on an image of JWST’s Centaurus A, which will cut through the dust to reveal the enigmatic heart of the galaxy, the research shows that there are some sightings that Hubble is still king of. Because Hubble has been in space for decades, it has been able to capture a multi-year observation that provides detailed information about the structure of another galaxy.

“The dataset is remarkable and allowed us to produce very impressive colored images and animations showing the evolution of the light echoes over a period of five years,” Stritzinger says:. “It’s a rarely seen phenomenon that was previously only documented in a handful of other supernovae.”

The research was published in The astrophysical diary letters.

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