Galaxies that shouldn’t exist keep being discovered by JWST

A bright red speck appears against the backdrop of a space photo, but astronomers say it shouldn’t be there.

But there it is. Published today in the journal Nature, an international research team led by Karl Glazebrook from Swinburne University of Technology in Melbourne says the light reaching Earth from this galaxy – named JWST-7329 – is 11.5 billion years old and comes from an ancient assembly of stars that likely formed 13bn years ago.

It doesn’t make sense because it’s been thought until now there wasn’t enough dark matter in the early universe to prompt their formation.

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JWST-7329: a rare massive galaxy that formed very early in the Universe. Credit: Supplied

Current understanding of what grows a galaxy suggests that dark matter halos, which are fields of invisible material in space, coalesce and collect stars and galaxies within their structure.

It’s only because of the JWST that the team has been able to clarify what the red speck was. In 7 years of long observations using the ground-based Keck (Hawaii, US) and Very Large Telescopes (Chile) all they could see was a faint red smudge.

“NASA’s James Webb Space Telescope, it’s been such an incredible thing. I’ve been wanting it for the last 30 years and it’s delivering on all those dreams we’ve had,” Glazebrook tells Cosmos.

“This is something we’ve been working on over the years: deeper and deeper surveys looking for the oldest and most massive galaxies that formed.

“We did the calculations of how old it is and it’s way beyond the bounds of what’s reasonable to form in the cold dark matter dominated universe. It’s really a huge puzzle.

“I hope it points to the revision of how dark matter halos assemble and how galaxies are made.”

Not the first ‘impossible galaxy’, not the last either

As impossible as galaxy ZF-UDS-732 is, it’s not the first so-called “impossible galaxy” to be spotted.

Earlier this month, a team led by Arizona State University (ASU) researchers found a dwarf galaxy – named PEARLSDG – in a region of space 98 million light years away expected to house, well, nothing much.

An isolated dwarf galaxy should either continue making new stars or interact with another nearby galaxy. PEARLSDG does neither.

“These types of isolated quiescent dwarf galaxies haven’t really been seen before except for relatively few cases. They are not really expected to exist given our current understanding of galaxy evolution, so the fact that we see this object helps us improve our theories for galaxy formation,” said ASU research scientist Tim Carleton, who led the team that found PEARLSDG.

“Generally, dwarf galaxies that are out there by themselves are continuing to form new stars.”

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