by Lee Billings

May 13, 2026

from ScientificAmerican Website

 

 

Lee Billings

is a science journalist specializing in astronomy, physics, planetary science, and spaceflight and is senior desk editor for physical science at Scientific American. He is author of a critically acclaimed book, Five Billion Years of Solitude: The Search for Life Among the Stars, which in 2014 won a Science Communication Award from the American Institute of Physics. In addition to his work for Scientific American, Billings's writing has appeared in the New York Times, the Wall Street Journal, the Boston Globe, Wired, New Scientist, Popular Science and many other publications. Billings joined Scientific American in 2014 and previously worked as a staff editor at SEED magazine. He holds a B.A. in journalism from the University of Minnesota.

 

 

 

 


Galaxy cluster MACS J0416.1-2403 (MACS0416)

magnifies the light from more distant background galaxies

through gravitational lensing.
NASA/ESA/CSA/STScI/J.

Diego/Instituto de Física de Cantabria/

J. D'Silva/University of Western Australia/

A. Koekemoer/STScI/

J. Summers/Arizona State University/

R. Windhorst/Arizona State University/

H. Yan/University of Missouri
 

 


 Seen just 800 million years

after the Big Bang,

an object called LAP1-B

is a galactic building block

that seems to hold some of

the first stars to ever shine...




It's a discovery so rich with mind-bending ideas that it seems straight from science fiction:

using humanity's biggest off-world observatory to focus on a tiny, faraway arc of light magnified by a quirk of spacetime, astronomers have glimpsed a faint galaxy as it was 13 billion years ago, when it was brimming with dark matter - as well as what may be fresh remains from the universe's earliest, strangest stars.

The small, faraway galaxy is named LAP1-B, the observatory is NASA's James Webb Space Telescope (JWST), and the strange stars would have been what astronomers call "Population III" stars - titanic suns that burned bright and died young close to the dawn of time.

Such stars are the key quarry that JWST was designed for - stellar orbs composed of the pristine, primordial hydrogen and helium gas that was summoned into being by the Big Bang.

 

These stars are not quite the stuff that most cosmologists' dreams are made of, but rather the sources for the atoms that made cosmologists themselves.

The oxygen in your lungs, the iron in your blood, the calcium in your bones, the carbon in your cells, and even the silicon in your smartphone can all be traced back to Population III stars, which blasted out heavy-metal cosmic fertilizer (astronomers call all heavier-than-helium elements "metals") upon their explosive deaths.

The debris from their demise coalesced to form subsequent stellar generations - Population II and Population I stars - plus planets and 'eventually' people...

That's the creation story astronomers tell themselves, anyway.

 

The trouble with proving all of its details has been that these first stars are so distant in space and time, even the mighty JWST has yet to directly, definitively see them.

 

Instead telltale hints of their existence primarily show up in studies of galaxies that are big and bright enough for JWST to see clear across the universe.

 

Rather than gathering Population III stars' light, JWST so far has only inferred their presence in such places via incandescent fogs that are eerily lit from within by the first stars' intense radiation.

LAP1-B is different. It's a wisp of glowing gas nestled in a pool of invisible dark matter, a cosmic "fossil" seen a mere 800 million years after the Big Bang.

 

Yet it closely resembles the swarms of "ultrafaint dwarf galaxies" (UFDs) astronomers find near our Milky Way.

 

Cosmologists suspect that, in the early universe, such objects were like puzzle pieces, assembling into bigger galaxies:

the UFDs we see around us today are part of a larger population of leftover scraps scattered throughout the cosmos that never found a larger home.

JWST's ability to see LAP1-B at all is only because of the galaxy's fortuitous placement behind a cosmic behemoth called MACS J0416.1-2403, a giant galaxy cluster so immense its mass warps spacetime to create a "gravitational lens" that boosts LAP1-B's feeble light 100-fold.

Ironically, this boost is so great that JWST, custom-built for the task of finding things like LAP1-B, wasn't needed to discover it.

 

Instead the object was first announced in 2020 from data gathered with a ground-based facility, the European Southern Observatory's Very Large Telescope in Paranal, Chile, which had been following up on earlier Hubble Space Telescope studies of MACS0416.

 

Subsequent studies with JWST have progressively revealed more about this mysterious object.

 

The latest, published in Nature today, strengthens the case that LAP1-B is an early cosmic puzzle piece packed with material freshly manufactured by dying Population III stars.

 

 


A false-color image of a portion of the MACS0416 galaxy cluster

 as seen at multiple infrared wavelengths by NASA's James Webb Space Telescope (JWST).

The "cosmic fossil" LAP1-B - a small, faint background galaxy magnified into view

by the gravitational lensing of MACS0416 - appears as a faint arc of light in a zoomed-in inset image.

LAP1-B is thought to contain relics of the universe's first generation of stars.

Orange bars around LAP1-B denote slits used for JWST's spectroscopic measurements of the galaxy.
"An Ultra-faint, Chemically Primitive Galaxy Forming in the Reionization Era"

by Kimihiko Nakajima et al.

 

"LAP1-B shows us the 'first generation' of element production," says the study's lead author Kimihiko Nakajima, an astronomer at Kanazawa University in Japan.

 

"We see a galaxy that has just inherited its first batch of heavy elements from the very first stars to ever shine.

 

It tells us that these tiny, dark-matter-filled galaxies were the fundamental building blocks of the universe, and we have finally caught the moment they first blinked into existence."

These key insights arise from JWST's ability to perform spectroscopy on LAP1-B, spreading the tiny galaxy's light into a rainbowlike spectrum of colors:

the specific mix of colors can reveal an object's chemical composition.

Reading this chemical "barcode," Nakajima and his colleagues found LAP1-B's gas is mostly pure hydrogen and helium from the Big Bang, with meager traces of oxygen presumably pumped out by the first generation of stars.

 

The data also show a surprising surfeit of carbon - a sign, Nakajima says,

of Population III stars ending their life in a "weak" supernova, as predicted by some theoretical models.

This would involve the stars ejecting their carbon-rich outer layers while oxygen-rich inner layers get swallowed by a newly formed black hole at their core.

The data further reveal that the galaxy's gas is glowing from high-energy radiation, consistent with predicted Population III emissions.

 

Yet the actual stars remained undetected in JWST's instruments, allowing the team to set an upper limit on their number:

LAP1-B contains no more than about 3,300 solar masses of stars (the Milky Way, by comparison, contains about 100 billion solar masses).

If it had more than that, JWST should've seen the stars' glow.

 

Meanwhile the tiny galaxy's gas is swirling so fast that it would fly apart if it wasn't held together in the gravitational grip of a sprawling cloud of dark matter.

All this, Nakajima says, makes LAP1-B,

"exactly what we expect for the ancestors of the ultrafaint dwarfs we see today.

 

Until now, we only saw these fossils in their 'final' state - old and quiet. LAP1-B has turned a theoretical 'missing link' into a physical reality we can now measure and analyze."

Independent experts view the result with cautious optimism, noting the uncertainties associated with studying spectra from such a strange object across such vast distances.

"I do think this is a compelling object," says Roberto Maiolino, an astronomer at the University of Cambridge, who uses JWST to study early galaxies.

 

"LAP1-B may indeed be tracing the transition between the earliest pristine stellar populations and the regime of chemically enriched galaxies."

Evan Kirby, an astronomer studying the chemistry of dwarf galaxies at the University of Notre Dame, agrees.

"This is the galaxy that chemical evolution experts have wanted JWST to find," he says.

The team's interpretations of LAP1-B, however,

"will need corroboration by future observations and other research groups."

Eros Vanzella, an astronomer at the National Institute for Astrophysics in Italy, who has previously studied LAP1-B with JWST and led the team that first discovered the galaxy, finds these latest results vindicating - and promising.

"I'm very happy to see that our first claim on [LAP1-B's] very low metallicity is confirmed with deeper spectroscopic observations," he says, adding that direct detection of the tiny galaxy's starlight might yet be possible through even deeper observations with JWST.

 

"The story of this remarkable source is far from over."