The standard model for how galaxies formed in the early Universe predicted that the James Webb Space Telescope (JWST) would see faint signals from small, primitive galaxies. But the data does not support the popular hypothesis that invisible dark matter helped the first stars and galaxies to cluster together.
In contrast, the oldest galaxies are large and bright, consistent with an alternative theory of gravity, according to new research from Case Western Reserve University, published in The Astrophysical Journal.
The results cast doubt on astronomers’ understanding of the early universe.
“What the dark matter theory predicted is not what we see,” said Case Western Reserve astrophysicist Stacy McGaugh, whose work describes the formation of structure in the early Universe.
McGaugh, professor and director of astronomy at Case Western Reserve, said instead of dark matter, altered gravity may have played a role.
He says that a theory known as MOND, from Modified Newtonian Dynamics, predicted in 1998 that the formation of structure in the early Universe would have happened very quickly – much faster than the theory of cold dark matter, known as lambda, had predicted -CDM.
The results cast doubt on the understanding of the early Universe
JWST was designed to answer some of the biggest questions in the universe, such as how and when did stars and galaxies form? Until its launch in 2021, no telescope has been able to see so deep into the universe and so far back in time, he writes Phys.org.
Lambda-CDM predicts that galaxies formed by the gradual accretion of matter from small to larger structures, due to the additional gravity provided by the mass of dark matter.
“Astronomers invented dark matter to explain how we got from a very smooth early universe to the large galaxies with lots of empty space in between that we see today,” McGaugh said.
The small pieces assembled into larger and larger structures until galaxies were formed. JWST should be able to see these small precursor galaxies as faint light.
“The expectation was that every large galaxy we see in the nearby universe would have started from these tiny pieces,” he said.
Foretold over a quarter of a century ago
But even at increasing redshift—looking earlier and earlier in the universe’s evolution—the signals are larger and brighter than expected.
MOND predicted that the mass that becomes a galaxy rapidly assembles and initially expands outward with the rest of the universe.
The stronger force of gravity slows, then reverses the expansion, and the material collapses to form a galaxy. In this theory, there is no dark matter at all.
“The large, bright structures observed by JWST very early in the universe were predicted by MOND over a quarter of a century ago,” McGaugh said.
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Source: www.descopera.ro
