The James Webb Space Telescope has zoomed in on an ancient supernova, revealing fresh evidence that a crisis in cosmology called the Hubble tension isn't going anywhere soon.
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An ancient supernova from the early universe is magnified
and duplicated three times (circled dots) through the phenomenon of
gravitational lensing. (Image credit: NASA, ESA, CSA, STScI, B. Frye
(University of Arizona), R. Windhorst (Arizona State University), S. Cohen
(Arizona State University), J. D’Silva (University of Western Australia,
Perth), A. Koekemoer (Space Telescope Science Institute), J. Summers (Arizona
State University).) |
The James Webb Space Telescope (JWST) has discovered yet
another troubling sign that there's something very wrong with our model of the
universe.
Depending on which part of the universe astronomers measure,
the cosmos seems to be growing at different rates — a problem scientists call
the Hubble tension. Measurements taken from the distant, early universe show
that the expansion rate, called the Hubble constant, closely matches our best
current model of the universe, while those taken nearer to Earth threaten to
break it.
Now, a new study using the gravitationally-warped light of a
10.2 billion light-year distant supernova has revealed that the mystery could
be here to stay. The researchers released their findings in a series of papers
in The Astrophysical Journal. The Hubble tension calculations have also been
accepted for publication in the journal, and are posted in a paper on the
pre-print database arXiv.
"Our team's results are impactful: The Hubble constant
value matches other measurements in the local universe, and is somewhat in
tension with values obtained when the universe was young," co-author
Brenda Frye, an associate professor of astronomy at the University of Arizona
said in a statement.
Currently, there are two gold-standard methods for figuring
out the Hubble constant. The first involves poring over tiny fluctuations in
the cosmic microwave background, an ancient relic of the universe's first light
produced just 380,000 years after the Big Bang. This method enabled astronomers
to infer an expansion rate of roughly 67 kilometers per second per megaparsec
(km/s/Mpc), which closely matches predictions made by the standard model of
cosmology.
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A collection of some of the most recent measurements of the
Hubble constant. From left to right, the sources used to measure its value are:
The cosmic microwave background images by the European Space Agency's Planck
satellite; gravitational lensing and tip of the Red Giant Branch stars measured
by NASA's Hubble space telescope; and cepheid stars measured by the James Webb
space telescope (Image credit: Future) |
But the second method, measuring closer distances with
pulsating stars called Cepheid variables, contradicts this — returning a
puzzlingly high value of 73.2 km/s/Mpc. This discrepancy superficially may not
seem like much, but it's enough to completely contradict the predictions made
by the standard model. According to the model, a mysterious entity known as
dark energy is supposed to be driving the universe’s expansion at a constant
rate, but the new findings throw a wrench in this understanding.
In the new studies, astronomers pointed JWST's near-infrared
camera (NIRCam) at the galaxy cluster PLCK G165.7+67.0, also known as G16,
which is located 3.6 billion light-years from Earth. There, they spotted three
distinct points of light that came from a single type IA supernova whose light
had been both magnified and bent, or gravitationally lensed, by a galaxy in
front of it.
Type Ia supernovae occur when the material from one star
falls onto the embering husk of a dead star, known as a white dwarf, leading to
a gigantic thermonuclear explosion. These explosions are thought to always
happen at the same brightness, making them "standard candles" from
which astronomers can measure far-off distances and calculate the Hubble
constant.
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The evolution of the universe illustration seen with the Big
Bang event on the left and the present on the right. (Image credit: NASA / WMAP
Science Team) |
Follow-up observations made with the ground-based Multiple
Mirror Telescope and Large Binocular Telescope, both in Arizona, confirmed the
dots' point of origin.
By studying the time delays between the dots and plugging
them, alongside the supernova's distance, into various models of gravitational
lensing, the researchers produced a Hubble constant value of 75.4 km/s/Mpc,
plus 8.1 or minus 5.5 — flatly contradicting the standard model once more.
The calculation is unlikely to be the final word on the
tension, with other research groups pursuing their own lines of investigation
into the cosmic conundrum. For their part, the researchers behind the new
studies say that they will continue to gather vital clues from other exploding
stars found around the galaxy.