The James Webb Space Telescope has discovered the oldest and most distant supernova ever observed: a stellar explosion that occurred when the universe was just 1.8 billion years old.
The ancient fireworks explosion was discovered along with 80 others in a patch of sky that, from our perspective on Earth, is about the width of a grain of rice held at arm’s length.
Supernovae are temporary objects because their brightness changes over time. This makes the new series of distant star explosions particularly exciting, because studying them could provide important insights into unresolved questions about how the early universe grew. The researchers presented their findings on June 10 at the 244th Meeting of the American Astronomical Society in Madison, Wisconsin.
“We are essentially opening a new window into the ephemeral universe,” Matthew Siebertan astronomer who leads the spectroscopic analysis of supernovae, 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: nuclear collapse and thermonuclear runaway supernovae.
Explosions in the first category occur when stars with a mass at least eight times greater than our sun run out of fuel and collapse, before expanding outward again in a gigantic explosion.
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The second, known as Type Ia supernovae, occurs when two stars – one of which is the collapsed shell of a star called a white dwarf – spin towards each other. This causes the white dwarf to strip hydrogen From the star it spins, causing a runaway reaction that ends in a giant 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 the Hubble constant.
But attempts to measure Hubble’s constant using these standard candles and other methods have turned up an alarming discrepancy: The universe appears to be expanding at different rates depending on where we look. This problem, known as the Hubble Voltage, has cast major doubt on the Standard Model of cosmology and has made finding standard candles throughout the life of the universe a major task for astronomers.
The researchers found the ancient supernova using data from the JWST Advanced Deep Extragalactic Survey (JADES). The research was carried out by taking multiple images of the same patch of sky at annual intervals. By looking at the new points of light that appeared or faded in successive images, the researchers identified the supernovae, some of which were Type Ia explosions.
Now that they have identified the extremely distant star explosions, the researchers will study them more closely to determine their metal content and their exact distances. They say this should help scientists understand the stars the explosions came from, as well as the conditions of the “pre-teen” universe in which they occurred.
“This is really our first example of what high redshift is [distant] universe looks like to ephemeral science,” Justin Pierel, an astronomer on the JADES team, said in the statement. ‘We are trying to determine whether distant supernovae are fundamentally different from or very similar to what we see in the nearby universe.’