Astronomers detect new type of brightest cosmic explosion

The newly found explosion is so powerful that it produced brightness comparable to hundreds of billions of Suns.
Mrigakshi Dixit
Representational image of a cosmic explosion
Representational image of a cosmic explosion


The vast and continuously expanding nature of our universe implies that there is a high probability that our current knowledge and documentation of it represent only a small fraction of the whole picture. And there are millions of new cosmic events and objects waiting to be discovered. 

Scientists have now discovered an unusual type of star explosion that is exceptionally luminous and outshines the majority of known supernovae. 

For the unversed, a supernova is a dazzling stellar explosion that occurs in the final stages of a massive star's life cycle. It is one of the most energetic events in the universe. During a supernova, the star briefly outshines an entire galaxy, and it can emit as much energy in a matter of seconds as our Sun will emit over its entire lifetime.

Shockingly, the newly found explosion is so powerful that it produced brightness comparable to hundreds of billions of Suns. 

Astronomers from the Queen’s University Belfast state that this stellar explosion could represent a whole new class of cosmic events. 

“We’ve been hunting for the most powerful cosmic explosions for over a decade, and this is one of the brightest we’ve ever seen,” said Matt Nicholl from the School of Mathematics and Physics at Queen’s, in an official release. 

The detection of brightest cosmic event  

The ATLAS network of robotic telescopes distributed over Hawaii, Chile, and South Africa was the first to detect this explosion, named AT2022aedm. Every night, this massive network works collectively to scan the whole visible sky for any transient objects, or the ones that quickly change in brightness.

Soon after the initial detection, the team conducted additional observations using the New Technology Telescope in Chile, along with other powerful observatories of the world.

Extensive observations confirmed that this explosion appears to be quite unique from the other known supernova explosions. 

The data from the subsequent observations also revealed that the explosion faded and cooled relatively faster than anticipated. 

Nicholl added: “Usually, with a very luminous supernova, it will have faded to maybe half of its peak brightness within a month. In the same amount of time, AT2022aedm faded to less than one percent of its peak – it basically disappeared!” 

The location where this stellar explosion occurred was also unexpected. 

“Our data showed that this event happened in a massive, red galaxy two billion light years away. These galaxies contain billions of stars like our Sun, but they shouldn’t have any stars big enough to end up as a supernova,” said Shubham Srivastav, also from Queen’s. 

This explosion belongs to a new class: Luminous Fast Coolers

The comprehensive data set gathered for AT2022aedm demonstrates that these are new types of cosmic events. 

Nicholl mentions: “The exquisite data set that we have obtained rules out this being another supernova. The most plausible explanation seems to be a black hole colliding with a star.”

“We have named this new class of sources “Luminous Fast Coolers” or LFCs. This is partly to do with how bright they are and how fast they fade and cool,” Nicholl added. 

Following confirmation of the brightest explosion ever detected, the researchers searched archive data to find similar kinds of events that may have happened in the past. 

Surprisingly, there were only two cosmic occurrences with some similar properties as this newly detected one. These were detected through the ROTSE and ZTF surveys conducted in 2009 and 2020, respectively. 

This new finding has opened up a whole new area of cosmic research to identify and analyze more of these explosions, as well as what causes them to be so luminous. 

“If we find more LFCs, especially in the more local Universe, we should be able to test this scenario. Collisions are more likely in dense star clusters, so we can look for these at the sites of the explosions,” concluded Nicholl. 

The study results were reported in The Astrophysical Journal Letters.

Study abstract:

We present the discovery and extensive follow-up of a remarkable fast-evolving optical transient, AT 2022aedm, detected by the Asteroid Terrestrial impact Last Alert Survey (ATLAS). In the ATLAS oband, AT 2022aedm exhibited a rise time of 9 ± 1 days, reaching a luminous peak with Mg ≈ −22 mag. It faded by 2 mag in the g band during the next 15 days. These timescales are consistent with other rapidly evolving transients, though the luminosity is extreme. Most surprisingly, the host galaxy is a massive elliptical with negligible current star formation. Radio and X-ray observations rule out a relativistic AT 2018cow–like explosion. A spectrum in the first few days after explosion showed short-lived He ii emission resembling young core-collapse supernovae, but obvious broad supernova features never developed; later spectra showed only a fast-cooling continuum and narrow, blueshifted absorption lines, possibly arising in a wind with v ≈ 2700 km s−1. We identify two further transients in the literature (Dougie in particular, as well as AT 2020bot) that share similarities in their luminosities, timescales, color evolution, and largely featureless spectra and propose that these may constitute a new class of transients: luminous fast coolers.

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