The James Webb Space Telescope has discovered the oldest and most distant supernova ever observed – a stellar explosion that occurred when the universe was only 1.8 billion years old.
The ancient star was discovered among 80 others in a sky that is about the width of a grain of rice held at arm’s length from our view on Earth.
Supernovae are transient objects because their brightness changes over time. This makes the new batch of distant star explosions particularly exciting, as studying them could provide key insights into the unresolved questions of how the early universe grew. The scientists presented their findings on June 10 244th Meeting of the American Astronomical Society in Madison, Wisconsin.
“Essentially, we’re opening a new window into the transient universe,” Matej Siebertan astronomer who conducts spectroscopic analysis of supernovae, he said in a statement. “Historically, whenever we’ve done that, we’ve found extremely exciting things — things we didn’t expect.”
There are two main categories of supernovae: core collapse and thermonuclear runaway supernovae.
Outbursts in the first category occur when stars with masses at least eight times that of our Sun run out of fuel and collapse in on themselves before expanding outward again in a gigantic explosion.
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The other, known as Type Ia supernovae, occurs when two stars—one of which is the collapsed shell of a star called a white dwarf—spiral toward each other. This causes the white dwarf to undress hydrogen from the star it spirals around, creating a runaway that ends in a gigantic thermonuclear explosion.
Type Ia supernovae are of particular interest to astrophysicists because their explosions are thought to always have the same brightness, making them “standard candles” from which astronomers can measure distant distances and calculate the expansion rate of the universe, known as Hubble’s constant.
But attempts to measure the Hubble constant using these standard candles and other methods have thrown up a disturbing contradiction—the universe appears to be expanding at different rates depending on where we look. This problem, known as the Hubble tension, cast great doubt on the standard model of cosmology and made the search for standard candles throughout the universe a major task for astronomers.
Scientists found ancient supernovae using data from the JWST Advanced Deep Extragalactic Survey (JADES). The survey was conducted by taking multiple images of the same spot in the sky at yearly intervals. By looking at new points of light that appeared or disappeared in successive images, scientists identified supernovae, some of which were Type Ia explosions.
Now that they have identified extremely distant star explosions, scientists will study them more closely to determine their metal content and their exact distances. They say this should help scientists understand the stars from which the explosions came, as well as the conditions of the “pre-teen” universe in which they occurred.
“This is really our first sample of what is at high redshift [distant] the universe appears to be for transitional science,” Justin Pierre, an astronomer on the JADES team, said in a statement. “We’re trying to find out if distant supernovae are fundamentally different from what we see in the nearby universe, or if they’re very similar.”