The James Webb Space Telescope may have just found its first supernova

Astronomers spotted something unusual happening in a distant galaxy in recent images from the James Webb Space Telescope – something that wasn’t there when Hubble last looked at the same galaxy.

“We suspect it’s a supernova”, astronomer mike engerser of the Space Telescope Science Institute (STScI) tells Reverse. Finding short-lived cosmic events like supernovae isn’t what Webb was designed to do, but the newly operational space telescope appears to be full of surprises. And this one could open the door to researching the agony of the universe’s first generations of massive stars.

What’s new – Engesser and his colleagues say the bright object is likely the first supernova spotted by the Webb Telescope. It’s extremely bright compared to the rest of the galaxy, for one thing. And Webb observed the galaxy, called SDSS.J141930.11+5251593, twice, five days apart; the object faded, just slightly, over those five days – classic supernova behavior.

“We would need more time-series data to make a decision, but the data we have is consistent with a supernova, so it’s a very good candidate,” says Engesser.

This series of images shows the same set of galaxies – first seen by Hubble, then by Webb. In the lower right corner, an image shows the differences in brightness between the two images. Can you spot the supernova?STScI

The galaxy, whose unwieldy astronomical name we won’t repeat, is between 3 and 4 billion light-years away, so astronomers are seeing the slowly fading light from an explosion that happened there. 3 to 4 billion years old. The actual death of a star takes a fraction of a second, but the resulting fireball takes days to grow and clear, then gradually fades over the next few months. It’s a snap in astronomical time, so it’s pure luck that Webb spotted this supernova shortly after its brightness peaked.

“First, it’s exciting because we’ve shown that we’re able to find and detect new transients with Webb, which JWST isn’t designed to do,” says Engesser. “But that’s one of the things that we show we’re capable of doing on an ad hoc basis.”

Even as versatile as it is, Webb isn’t the kind of telescope astronomers typically use to search for short-lived objects like supernovae. Much of this work is done by ground-based telescopes here on Earth, which image large swaths of the sky each night.

Webb, on the other hand, looks much, much deeper into smaller patches of sky. The telescope’s first deep-field image, released July 12, covers an area of ​​sky you could cover with a grain of sand held at arm’s length.

“So the actual probability of you finding a transient in the field you’re looking at is quite low – or at least we thought it would be low,” says Engesser. “But as you’ve probably heard, every JWST field is a deep field at this point, so there are galaxies everywhere, and now we’re thinking, oh, we might have a really good chance of detecting supernovae all the time. .”

Here’s the background — Ground-based telescopes that typically search for supernovae take images of the same large areas of sky every few nights. Their data processing software compares each new image to previous images of the same area, looking for anything that might have changed.

To do the same with space telescopes, Engesser and his colleague compared new data from Webb’s NIRCam instrument to Hubble images of the same area. They used software to look for any differences that could reveal what astronomers call “transients”, objects that appear, disappear, brighten or darken on a timescale that we can actually see in real time. .

This is how the team found the supernova. This is also how they located a supernova that burst into life in 2013. Astronomers were familiar with this one, called 2013 EJ, but its once-bright fireball has long since faded too far for most telescopes to see. can see her.

“There are a lot of questions about this particular object and what kind of star it was and its surroundings – like how dusty is it? It looks like it’s very dusty,” says Engesser.

Because supernovae tend to fade within months, astronomers typically don’t see their much later stages, which could offer more clues about the type of star that exploded, as well as the physics of this stellar explosion. Webb’s deep insight into the universe could make it easier to track the aftermath of a supernova like 2013 EJ, even many years later.

SN 2013EJ as seen by the Virtual Telescope Project.Virtual Telescope Project

“So observing this now with Webb is actually really cool as a way to investigate the super-late environment around large, bright supernovae like this,” says Engesser. “We’re getting new information that we couldn’t get before.”

Engesser calls the two detections — the newly discovered supernova and the fading one scientists had lost sight of — proof of concept. He and his colleagues are part of the Transient Science @ Space Telescope research team, led by astrophysicist Ori Fox at STScI. Fox’s team wants to use Webb to search for supernovae in the oldest and most distant galaxies in the universe, the kind that even Hubble has trouble seeing.

“If we can detect new things, it allows us to do these kind of very quick opportunity propositions, where we detect something and then we can say, ‘Okay, cut everything else off. We want to watch this thing now’ “Once you have a nice repertoire [of supernovae] built, we can say, “Okay, it’s actually really helpful for us to have these time-sensitive observations of super redshift supernovae.”

Why is it important – Ancient and distant supernovae could help astronomers better understand the very fabric of the universe and how it stretches and expands over time. Most physicists now agree that the universe is expanding and that this expansion is accelerating; that’s thanks to a 1998 study that used a specific type of supernova to help measure distances between objects in the cosmos. These supernovae, called Type Ia supernovae, occur when a white dwarf star in a binary star system steals (or accumulates) so much material from its companion star that the greedy white dwarf collapses under its own mass.

Since Type Ia supernovae always have the same luminosity, astronomers can measure the luminosity of a supernova in order to calculate how far away it and its host galaxy are. Astronomers call objects with known brightness “standard candles.”

“By looking at the redshift of these supernovae, you can measure how fast they are moving away from you, as well as how far away they are,” says Engesser. “So one of the things we want to be able to do with Webb is detect very high redshift supernovae to further constrain the cosmological nature of the universe and how it evolves over time.”

The oldest supernovae in the universe also contain clues to the short life and violent death of the first generation of very massive stars in the universe. These ancient giant stars may have been very different from the giant stars of the nearby, recent universe that we are more familiar with.

“We think the stars of the first few million years would have been mostly, almost entirely, hydrogen and helium, as opposed to the kinds of stars we have now. They would have been massive – 200 to 300 times the mass of our Sun, and they would definitely have been living some sort of ‘live fast, die young’ lifestyle,” says Engesser. “Seeing these types of explosions is something that we haven’t really done yet.”

And after – Engesser and his team have not yet decided to re-examine the supernova they discovered.

“Supernovae in the grand scheme of things are actually quite common,” he says. “This supernova is interesting in that Webb was the first to find it, which is incredible. That in itself might not be very interesting. We’re still figuring out whether or not we want to make observations. tracking this thing.”

If astronomers decide to study their newly discovered supernova further, it might answer some specific questions. Watching how the light from the supernova fades over time could reveal what type of supernova – like Type Ia – Engesser and his colleagues found. Measuring the spectra of light from the supernova could reveal what chemical elements made up the parent star, and therefore what type of star exploded so violently.

But in the meantime, Engesser and his colleagues are focused on finding more transient bright spots in Webb’s profound views of the universe.

This story was updated on July 28, 2022 to include the last five paragraphs.

Leave a Comment