James Webb Space Telescope spots dark matter halo within rare Einstein cross

Astronomers are pulling back the curtain on two of the universe’s biggest mysteries: how planets are born and how invisible matter shapes galaxies. Thanks to the James Webb Space Telescope (JWST) and a rare gravitational lensing event, researchers are getting clearer views of cosmic structures than ever before.

For decades, scientists have tried to understand how planets grow in disks of gas and dust circling young stars. These protoplanetary disks are where the building blocks of worlds, moons, and asteroids first come together. A recent study used JWST’s Mid-Infrared Instrument (MIRI) to examine carbon monoxide gas in several of these disks with unprecedented detail.

Carbon monoxide, though simple, is a vital tracer of chemistry in these disks. Its abundance and isotopic variations reveal how elements move between gas and ice, offering hints about what forming planets might inherit. JWST detected more than a hundred individual CO lines in some systems, separating them with enough clarity to measure temperatures, densities, and gas movement down to a few kilometers per second.

The study targeted four very different disks—AS 209, DR Tau, HD 163296, and SR 21. Each one told a unique story. AS 209 showed strong, widespread CO signatures, while HD 163296 displayed the hottest gas, reaching nearly 1,000 Kelvin. DR Tau revealed turbulent conditions likely linked to its star’s active accretion, and SR 21 stood out for weaker signals, suggesting much of its inner gas had already been cleared, possibly by forming planets.

The data confirmed that these disks are not static leftovers from star formation. Instead, they actively process their chemistry. Ratios of carbon isotopes varied, pointing to processes like selective photodissociation, where ultraviolet radiation preferentially breaks apart rarer isotopologues. In some cases, the ratios deviated significantly from what is seen in the broader interstellar medium, meaning planets born in these systems may carry unique chemical fingerprints.

The velocity maps created by JWST were just as revealing. In AS 209 and HD 163296, gas rotated in neat Keplerian patterns, hinting at stable disk structures. In DR Tau, though, chaotic motions suggested winds or turbulence were shaping the inner regions. SR 21’s depleted inner disk fit with the idea of transition disks, where planets or other processes have carved out gaps.

This precision is a leap forward compared to earlier missions like Spitzer, which lacked either the resolution or sensitivity for such fine details. JWST, with its sharp instruments and space-based vantage point, is turning broad surveys into molecule-by-molecule analyses of planet-forming environments.

Carbon and oxygen are essential for planetary atmospheres and life-supporting chemistry. By mapping CO in protoplanetary disks, astronomers can predict whether future planets may be carbon-rich or carbon-poor. A disk low in CO might produce planets with leaner atmospheres, while one that holds onto carbon could yield planets with thicker, carbon-heavy envelopes.

These findings also connect to icy bodies in the outer disk. At colder distances from a star, CO freezes onto grains, eventually becoming part of comets or icy planets. Understanding how much of this molecule remains in gas versus ice form gives scientists a blueprint of how elements distribute throughout a system during planet formation.

While JWST revealed hidden chemistry close to young stars, another discovery offered a look at something even more mysterious: dark matter. Dark matter makes up most of the universe’s mass, yet it cannot be seen directly. Its presence is revealed only through gravity.

An international team of astronomers recently studied a distant galaxy called HerS-3. Using the Northern Extended Millimeter Array (NOEMA) in the French Alps and the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, they saw something puzzling. Light from the galaxy appeared as five images instead of the usual four expected in an “Einstein Cross,” a phenomenon where foreground galaxies bend light into a cross-shaped pattern.

Pierre Cox, a French astronomer and the study’s lead author, recalled the surprise: “It looked like a cross, and there was this image in the center. I knew I had never seen that before.”

Rutgers University astrophysicist, Charles Keeton, agreed that something unusual was happening. “You can’t get a fifth image in the center unless something unusual is going on with the mass that’s bending the light,” he said.

Through detailed computer modeling, Keeton and graduate student Lana Eid found that the visible galaxies alone could not explain the strange pattern. Only by adding a massive, unseen halo of dark matter to their models did the math line up with reality.

“We tried every reasonable configuration using just the visible galaxies, and none of them worked,” Keeton said. “The only way to make the math and the physics line up was to add a dark matter halo. That’s the power of modeling. It helps reveal what you can’t see.”

This invisible halo not only explained the fifth image but also magnified the background galaxy, letting astronomers study it in unprecedented detail. “This system is like a natural laboratory,” Cox explained. “We can study both the distant galaxy and the invisible matter that’s bending its light.”

The discovery required instruments spread across the globe and the dedication of scientists working across continents. Eid described the collaboration as a highlight of her doctoral journey. “Collaborating across continents and time zones taught me the value of diverse expertise and research styles in fully understanding a new discovery,” she said.

Future observations may reveal even more, such as gas outflows predicted by the team’s models. If confirmed, these will strengthen the case for their explanation. If not, scientists will revise their understanding, a process Keeton welcomed: “If we look and don’t see it, we’ll have to go back to the drawing board. That’s how science works.”

The two breakthroughs highlight how modern astronomy is rewriting our understanding of the universe. JWST’s insights into protoplanetary disks help scientists predict the kinds of planets and atmospheres that may form around distant stars, paving the way for interpreting exoplanet data in the years ahead.

The gravitational lensing discovery demonstrates how dark matter, though invisible, can be mapped and studied with precision, improving models of galaxy formation.

Together, these studies provide powerful tools for exploring the origins of planets and the hidden forces shaping the cosmos.

Research findings are available online in the journal The Astrophysical Journal.

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