The most distant, and therefore fastest rotating, disk galaxy ever discovered, could surprise astronomers and cast doubt on theories of galaxy evolution. Not only does this galaxy appear to exist too early in the universe to rotate strongly, but it also shows signs of spiral arms similar to highly evolved “modern” galaxies like our own Milky Way. It shows.
The galaxy, called REBELS-25, appears to date from just 700 million years after the Big Bang, a time when astronomers expect galaxies to have been small and messy. Living up to its name, this rebellious galaxy has bucked that trend by appearing orderly rather than chaotic.
REBELS-25 was discovered by a team of astronomers using the Atacama Large Millimeter/Submillimeter Array (ALMA), a network of 66 radio telescopes located in the Atacama Desert region of northern Chile.
“Our understanding of galaxy formation predicts that most early galaxies appear small and messy,” team member Jacqueline Hodge, an astronomer at Leiden University in the Netherlands, said in a statement.
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Modern galaxies like the Milky Way, which is 13.8 billion years old in the Universe, have developed unique shapes and features over billions of years, including their impressive spiral arms.
In the early universe, before organization was possible, astronomers expected to see galaxies that were messy and clumpy. These early galaxies are thought to have formed the shapes of modern galaxies over billions of years through a series of collisions and mergers, developing features such as disk shapes and spiral arms incredibly slowly. It is being
REBELS-25’s discovery, when the universe was only 5% of its current age, calls into question that timescale.
Research team leader Lucy Rowland (also from Leiden) said: “Seeing a galaxy so similar to our own Milky Way, with strong rotational dominance, is a sign of how galaxies in the early universe came to be in the order of today’s universe. “It challenges our understanding of how galaxies evolve into certain galaxies.” The university said in the same statement.
When astronomers first discovered REBELS-25 with ALMA, the galaxy was already considered attractive because it showed signs of rotation. However, this initial survey was not of sufficient resolution to confirm that this is indeed the most distant, strongly rotating galaxy ever observed.
To better understand the structure and motion of this early galaxy, the team continued their work with ALMA, but this time at higher resolution. This showed the gas in REBELS-25 moving toward and away from Earth. This is possible due to phenomena called blueshift and redshift.
As the light source moves toward Earth, the wavelengths of this light are compressed. This “shifts” the light towards the shorter wavelength “blue end” of the electromagnetic spectrum. Therefore, a light source moving towards us is “blueshifted”. Conversely, when a light source moves away from us, the wavelength of the light it emits is stretched and shifted toward the “red end” of the electromagnetic spectrum.
A new study confirms that REBELS-25 is a record-breaking galaxy, the earliest and most distant strongly rotating galaxy ever observed.
“ALMA is the only telescope in existence with the sensitivity and resolution to achieve this,” team member Lenske Smit of Liverpool John Moores University in the UK said in the same statement.
It appears that REBELS-25 has other surprises that have not yet been fully revealed. For example, early galaxies appear to have similar characteristics to the Milky Way galaxy, which was around 13.6 billion years old. These include an elongated “central bar” of stars, and it has even been suggested that they may have spiral arms. This makes REBELS-25 a new record as the most distant and oldest spiral galaxy ever observed. The current record holder is Cheers-2112, which was observed by the James Webb Space Telescope (JWST) when the universe was about 2.1 billion years old.
“Finding further evidence of a more evolved structure would be an interesting discovery, as this would be the most distant galaxy in which such a structure has been observed to date,” Roland concluded.
The team’s research has been accepted for publication in the Monthly Notices of the Royal Astronomical Society.
