New observations from the Space Photo James Webb Space Telescope of the star cluster NGC 346 are providing groundbreaking insights into the origins of planetary formation in the early universe—revealing when, where, and how these cosmic worlds first took shape.
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Space Photo of the Week: Webb & Hubble Team Up to Unravel ‘Impossible’ Planet Mystery
Webb’s Stunning Space Photo of NGC 346 Sheds Light on an Ancient Cosmic Mystery
What it is: A breathtaking open star cluster known as NGC 346
Where it is: 210,000 light-years away in the constellation Tucana
When it was shared: December 16, 2024
Astronomers have long been puzzled by an unexpected discovery: a massive exoplanet that seemed far too old to exist. But thanks to the powerful James Webb Space Telescope (JWST), scientists are finally unraveling the mystery of how planets formed in the early universe.
More than two decades ago, the Hubble Space Telescope spotted the universe’s oldest known planet—a world so ancient that it shouldn’t have existed, at least according to what scientists believed at the time. Traditionally, planetary formation requires elements like carbon and iron, which are forged in the fiery deaths of stars. Since the early universe lacked these heavier elements, astronomers assumed that planets couldn’t have formed so soon after the Big Bang.
Yet, in 2003, Hubble detected a massive planet orbiting a star in the ancient M4 globular cluster, a system about 13 billion years old and located roughly 5,600 light-years away. This discovery challenged the long-held belief that planets couldn’t form without a significant presence of heavy elements.
Now, JWST has turned its powerful infrared gaze toward NGC 346, a young but metal-poor star cluster, to study its planet-forming regions. This groundbreaking research suggests that planetary formation may have begun far earlier than previously believed—reshaping our understanding of how and when planets emerge in the vast cosmic timeline.
With each new image and discovery, Webb continues to rewrite the story of our universe, proving that even the most “impossible” planets may have been forming long before we ever imagined.
Webb Confirms Hubble’s Clues About Ancient Planet Formation
To unlock the secrets of the early universe, astronomers turn to cosmic “proxies”—objects that share key characteristics with ancient galaxies. One such proxy is NGC 346, a vibrant star-forming region nestled within the Small Magellanic Cloud (SMC), a dwarf galaxy orbiting the Milky Way. Like the primordial galaxies of the early universe Space Photo, the SMC is rich in hydrogen and helium but lacks heavier elements like carbon and iron.
When astronomers aimed the Hubble Space Telescope at NGC 346, they made a surprising discovery: planet-forming disks around young stars seemed to persist for an astonishing 20 to 30 million years—nearly 10 times longer than theoretical models had predicted. However, the evidence was faint, leaving scientists eager for more definitive proof.
In 2023, the James Webb Space Telescope (JWST) stepped in to solve the mystery. Using the Near Infrared Spectrograph (NIRSpec) and Mid-Infrared Instrument (MIRI), Webb delivered the clearest evidence yet that these long-lived planet-forming disks truly exist in NGC 346.
Published on December 16, 2024, in The Astrophysical Journal, the findings confirm Hubble’s observations and suggest an intriguing possibility: the absence of heavier elements might actually slow down the process of disk dispersal, allowing planets more time to take shape. Another theory proposes that the initial gas clouds giving birth to these stars may be larger than expected, resulting in more massive and long-lived disks.
By studying regions like NGC 346, astronomers are piecing together a clearer picture of how planets formed in the universe’s earliest days—challenging long-standing assumptions and proving once again that the cosmos still has many secrets left to unveil.