- 4523
- DISTANT GALAXIES
- with ancient explosions? - The
James Webb Space Telescope has spotted a supernova dating to just 1.8 billion
years after the Big Bang, as well as 80 others in the early universe. The
ancient explosions could help scientists figure out the mysteries of how the
universe evolved.
----------------------------- 4523 - DISTANT GALAXIES - with ancient explosions?
- (Also see
#4521 - Early Universe and #4522
- Earliest stars)
-------
-
- The
Webb Telescope has discovered the oldest and most distant supernova ever
seen. It is a stellar explosion that
took place when the universe was just 1.8 billion years old.
-
- The ancient starburst was uncovered among
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 transient objects, as their
brightness changes over time. This makes the new batch of distant star
explosions especially exciting, as studying them could provide key insights
into unresolved questions of how the early universe grew.
-
- There are two main categories of supernova:
core collapse and thermonuclear runaway supernovae. Explosions in the first category occur when
stars with masses at least eight times bigger than our sun run out of fuel and
collapse in on themselves, before expanding outward again in a gigantic
explosion.
-
- The second, known as “type Ia supernovae”,
occur when two stars, one of which is the collapsed husk of a star called a
white dwarf, spiral toward each other. This causes the white dwarf to strip
hydrogen from the star it is spiraling around, creating a runaway reaction that
ends in a gigantic thermonuclear explosion.
-
- Type Ia supernovae are of particular
interest to astrophysicists because their explosions are thought to always be
the same brightness, making them "standard candles" from which
astronomers can measure far-off distances and work out the expansion rate of
the universe, known as the “Hubble constant”.
-
- But attempts to measure the Hubble constant
using these standard candles and other methods have produced an alarming
discrepancy. The universe appears to be
expanding at different rates depending on where we look. This problem, known as
the “Hubble tension”, has cast major doubt over the standard model of cosmology
and has made finding standard candles across the universe's lifetime a major
task for astronomers.
-
- The researchers found the ancient supernovae
using data from the “JWST Advanced Deep Extragalactic Survey” (JADES). The
survey was made by taking multiple images of the same patch of the sky at
year-long intervals. By looking at the new points of light that appeared or
faded across successive images, the researchers identified the supernovae, some
of which were “type Ia” blasts.
-
- Now that they've identified the extremely
distant star explosions, the researchers will study them more closely to
determine their metal content and their exact distances. Doing so should help the scientists
understand the stars the blasts came from, as well as the conditions of the
"pre-teen" universe they occurred in.
-
- This is really our first sample of what the
high-redshift [distant] universe looks like for transient science. Astronomers are trying to identify whether
distant supernovas are fundamentally different from or very much like what we
see in the nearby universe.
-
-
July 8, 2024 DISTANT
GALAXIES - with ancient explosions? 4523
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--------------------- --- Tuesday, July 9, 2024
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