Astronomers spot unusually synchronized star formation in ancient galaxy for 1st time

A galaxy on the left is boxed in white and enlarged on the right.
A close-up of the ancient NGC 1386 galaxy, where astronomers have discovered over 60 star clusters that formed in an unusually synchronized fashion, with more to come. (Image credit: ESO/ALMA (ESO/NAOJ/NRAO)/A. Prieto et al./Fornax Deep Survey)

Astronomers have spotted thousands of young stars huddled around the center of an ancient galaxy, all of which formed nearly simultaneously 4 million years ago. This observation marks the first time such synchronized star formation has been spotted in an old galaxy, and challenges the idea that star formation declines as galaxies age.

The newfound star clusters skirt the heart of NGC 1386, a spiral galaxy swirling roughly 53 million light-years from Earth in the constellation Eridanus. Researchers led by Almudena Prieto of Spain's Instituto de Astrofísica de Canarias identified 61 groups of young stars, which trace the 1 kiloparsec-wide blue ring seen in the image above, and found all of them sported similar masses, ages and sizes despite being spatially isolated.

"All of these clusters are distributed like pearls on a ring around the center of the galaxy," Prieto said in a recent news release. "Surprisingly they are all alike, which gives the idea that they were created at the same time, in a synchronized event."

Observations of the blue ring with the Hubble Space Telescope and the VLT Survey Telescope in Chile show the star clusters are fed by long filaments of gas and dust that ferry precious star-forming material — such as molecular hydrogen — from the galaxy's outer disk all the way to its center.

Related: Stare into the 'blood-soaked eyes' of 2 spooky galaxies in new Hubble, JWST images (video)

The researchers did not detect any companion galaxies swirling nearby NGC 1386, suggesting these filaments are likely the only source of star-forming material for the galaxy, according to another news release from the European Southern Observatory (ESO), which hosts the VLT Survey Telescope at its Paranal Observatory in Chile's Atacama Desert.

A side-by-side view of NGC 1386 in visible wavelengths (left), taken with the Hubble Space Telescope, and in radio (right), taken with the ALMA radio telescope. Both images highlight young star clusters where thousands of stars are being born. Dark wisps that are seen passing close to or ending in the star clusters are filaments ferrying star-forming material, such as molecular hydrogen.

A side-by-side view of NGC 1386 in visible wavelengths (left), taken with the Hubble Space Telescope, and in radio (right), taken with the ALMA radio telescope. Both images highlight young star clusters where thousands of stars are being born. Dark wisps that are seen passing close to or ending in the star clusters are filaments ferrying star-forming material, such as molecular hydrogen. (Image credit: HST/ ALMA. Composition: Gabriel Pérez Díaz (SMM, IAC))

These findings add to the growing body of recent evidence certain old galaxies are capable of host bursts of star formation, contrary to the majority of historical observations that have shown that the rate of star formation declines as galaxies age, suggesting their supplies of star-forming gas and dust shrinks. Despite its age, "this galaxy has organized itself to obtain the required supply from its outer zones, within its stellar disk," said Prieto.

"A major event in the disk may have caused the onset of cluster formation simultaneously in the ring," the researchers wrote in a paper published earlier this year in the Monthly Notices of the Royal Astronomical Society. That consequential event may have been a density wave that passed through the galaxy disk, which would have triggered the gas in its wake to compress and kickstart star formation.

Prieto and colleagues also detected a second ring around the center, depicted in the above image as golden, that traces roughly 70 identical pockets of gas, suggesting the galaxy is not finished forming stars yet. The team posits a second burst of similarly synchronized star formation is imminent, possibly in the next 5 million years or so.

"Even if old, NGC 1386 keeps rejuvenating itself," the ESO news release says.

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Sharmila Kuthunur
Space.com contributor

Sharmila Kuthunur is a Seattle-based science journalist covering astronomy, astrophysics and space exploration. Follow her on X @skuthunur.

  • Mikeshbike
    If the Galaxy is 53 million light years away light took 53 million years to get to us. So how do we know star formation was 4 million years ago?
    Reply
  • Unclear Engineer
    Mikeshbike said:
    If the Galaxy is 53 million light years away light took 53 million years to get to us. So how do we know star formation was 4 million years ago?
    That is just media mis-speak.

    What they mean is that it happened 57 million years ago, and we would have seen it happening 4 million years ago, if we were here then and had already developed the telescopes cited in the article.
    Reply
  • Mikeshbike
    Unclear Engineer said:
    That is just media mis-speak.

    What they mean is that it happened 57 million years ago, and we would have seen it happening 4 million years ago, if we were here then and had already developed the telescopes cited in the article.
    Thanks. I was trying to politely point out to the author their misspeak. You would hope technical writers would be more accurate for the non science literate readers. This is a small example of how mis information gets spread around. I think writers are in too much of a hurry to produce output that they don’t put themselves in the shoes of their readers. Thanks for the response!!
    Reply
  • Unclear Engineer
    You must have just joined us and missed the "X times the speed of sound" comparisons in some of the articles. What they do is divide some astronomical number like the speed of a star going around a black hole near the center of our galaxy (in mph) by the speed of sound in Earth's atmosphere at sea level (in mph). Sometimes they even use the mach number for the answer, which is the velocity divided by the LOCAL speed of sound, not the speed of sound somewhere else.

    So, they totally miss the concept that the speed of "sound" in the local vicinity of the astronomical phenomenon that they are describing is surely far different from the speed of sound we think of as "the sound barrier" here on Earth. Not to mention that the speed of compression waves in that vicinity might has some actual physical effects worth considering.

    The media authors seem to think that such comparisons are necessary to communicate the huge speed numbers. I just wish they would compare them to something that is not a variable that people do not understand, anyway. Maybe "X times the speed of satellites in low earth orbit"?
    Reply
  • Torbjorn Larsson
    Interesting confirmation of starbursts!

    Mikeshbike said:
    Thanks. I was trying to politely point out to the author their misspeak. You would hope technical writers would be more accurate for the non science literate readers. This is a small example of how mis information gets spread around. I think writers are in too much of a hurry to produce output that they don’t put themselves in the shoes of their readers.
    You are the one that misspeak, is inaccurate, try to spread misinformation around and are in too much of a hurry to read the paper or put yourself in the shoes of your astronomers by reading a number of papers previously.

    If you had taken the time to follow the link and read just the presented abstract it says clearly:

    The cluster ring formed simultaneously ∼4 Myr ago.
    By analogy, we propose that a density wave through the disc of this galaxy may have produced this gap in the central kpc. The CO filaments fragment into strings of dense, unresolved clouds with no evidence of a stellar counterpart. These clouds may be the sites of a future population of clusters in the ring. The free-fall time of these clouds, ∼10 Myr, is close to the orbital time of the CO ring. This coincidence could lead to a synchronous bursting ring, as is the case for the current ring.

    Now, as anyone with a smidgen interest in astronomy should now, their reference is "here and now" of the observatory. They can't possibly be tasked to translate the individual observations to each reference frame and back, unless they have to. So they don't.

    So if you really want to translate the given data to "it happened 53+4 = 57 million years ago", you can do it by yourself. But the 53 million year light travel distance is totally irrelevant to the dynamics of what we see.
    Reply