Space

What are the little red dots deep in space?

Megan M Rogers — Tue, 27 Jan 2026 16:33:51 +0000

What are the little red dots deep in space? Megan M Rogers Tue, 01/27/2026 - 09:33

Colorado Arts and Sciences Magazine

CU researchers worked with an international team to uncover more about the mysterious objects detected by the James Webb Space Telescope.

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A 'generationally defining moment': 40 years later, NASA alum reflects on Challenger disaster

Amber Carlson — Mon, 26 Jan 2026 17:08:29 +0000

A 'generationally defining moment': 40 years later, NASA alum reflects on Challenger disaster Amber Carlson Mon, 01/26/2026 - 10:08

Amber Carlson

The Challenger space shuttle is transported to the launch pad in December 1985, about a month before the fateful launch. (Credit: NASA)

On Jan. 28, 1986, NASA’s Challenger space shuttle disintegrated 73 seconds after launching from the Kennedy Space Center. All seven crew members aboard, including CU ��ý�� alumnus Ellison Onizuka (AeroEngr ’69), tragically lost their lives.

David Klaus, professor emeritus from CU ��ý��’s Ann and H.J. Smead Department of Aerospace Engineering Sciences, started his career with NASA and was a shuttle launch control engineer at the time (although he did not work the Challenger mission).

CU ��ý�� Today spoke with Klaus about his memories of that day, the legacy of the crew and crucial lessons learned from the tragedy.

Where were you on the day of the Challenger incident?

NASA had plans to start launching Air Force payloads off the West Coast at Vandenberg Air Force Base in California in July of 1986. I was training to be on the Vandenberg launch team, and I would have been on the Challenger launch console, but I had just gone out to California for some work out there. So I was at the Vandenberg launch site when the Challenger launched from the Kennedy Space Center in Florida.

We happened to be sitting in the launch control center at Vandenberg. We pretty much saw what everybody else watching TV saw, although we could hear the comms loops. We could hear what was going on.

When did you realize that something was wrong?

All I saw was that infamous image with the solid rocket boosters going off in two directions. I was pretty new in the game at that point, so I didn't have a lot of insight. But I was sort of in disbelief at first. You don't really comprehend what you're seeing. It just doesn't look right. Something looks wrong. Your brain’s trying to process what's going on. But we realized pretty quickly that this was a bad event.

What caused the shuttle to break apart?

The actual root cause of the failure was the O-rings (gaskets) that keep the propellant pressure contained inside the two rockets. It was really cold in Florida that day, and my understanding is that the cold weather made the seals brittle. Because they were brittle, they allowed gas pressure to escape, and the escaping gas pressure is ultimately what caused the destruction of the vehicle.

The Challenger crew members are pictured in November 1985, about two months before the tragedy. Back row, from left: Ellison Onizuka, Sharon McAuliffe, Greg Jarvis and Judy Resnik. Front row, from left: Michael Smith, Dick Scobee and Ron McNair. (Credit: NASA)

What lessons were learned from the Challenger?

For every NASA mission, when something goes wrong or is unexpected, it gets documented as ‘lessons learned’, and you work to make sure it doesn't happen again. You either change operational requirements, or you change the design, or both.

After the Challenger accident, for example, NASA has had tighter weather criteria for launch. And they added heater strips around the O-ring joints on later flights as part of a redesign. So both operational and design changes were made.

It's a high-risk endeavor to start with, putting people into space. And I think it became very apparent at that point. The Challenger was the first in-flight fatal accident that had occurred in NASA's history. In the space domain, there are a lot of unknown unknowns, and those are the ones that can cause the biggest problem. But once they happen, they're not unknown anymore, and now you've got something you can design toward.

How do you view the legacy of the Challenger crew?

The Challenger incident was one of those generationally defining moments. It was a reminder that life is risky. If you're pushing the envelope, you accept the risks, and you do the best you can to mitigate those risks. But you can't ever make them go away. So the crew’s legacy was maybe a heightened awareness of the risk of space flight, but also the importance of continuing to go to space even when catastrophic events do occur.

Looking back 40 years later, what stands out the most about the Challenger?

The technical lessons learned made me start thinking more about risk analysis. It's one thing to design a vehicle that can meet all the needs and do the job, but once you get to that point in the design process, you now go back and start looking at it and saying, ‘What can go wrong? What happens if it goes wrong, and what can we do about it if it does go wrong?’

The human aspect, of course, goes without saying. These were some pretty outstanding individuals, and their lives were tragically cut short. But on the other hand, I don't think they would have stepped aside. Everyone understood that there was risk. The degree of risk might have been debatable, but anytime you're launching people into space—anytime you're walking across the street, for that matter—there's a degree of risk that you accept in your life to do what you want to do.

David Klaus

If you were speaking to young engineers now, what would you want them to understand?

When you're the one designing the rockets or the habitats or any of the infrastructure, pay attention to the details. Don't take shortcuts. Try to think beyond just ‘Here's an answer that's good enough.’

Consider risk analysis from the very beginning of the design. Think about all the things that can go wrong and try to design something that is what we call either fault tolerant or redundant. So, if something breaks, can the system continue working? Or do you have another way that you can provide that function in place of the thing that broke?

Think about what needs to be done and break it down into the functions that have to be accomplished to make that happen. Then brainstorm different ideas—not just one solution, but as many as you can come up with. And then work to find an optimal balance of risk and complexity from that process.

CU ��ý�� Today regularly publishes Q&As with our faculty members weighing in on news topics through the lens of their scholarly expertise and research/creative work. The responses here reflect the knowledge and interpretations of the expert and should not be considered the university position on the issue. All publication content is subject to edits for clarity, brevity and university style guidelines.

A former NASA engineer and retired aerospace engineering professor reflects on lessons learned from the space shuttle tragedy.

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Leading hands-on Earth research planning for life on Mars

Megan M Rogers — Fri, 23 Jan 2026 20:08:16 +0000

Leading hands-on Earth research planning for life on Mars Megan M Rogers Fri, 01/23/2026 - 13:08

Ann and H.J. Smead Department of Aerospace Engineering Sciences

CU ��ý�� carried out major research at the Mars Desert Research Station, a facility that gives scientists and engineers the opportunity to conduct complex experiments in a Mars-simulation habitat.

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New study examines a gravitational wave mystery

Daniel William Strain — Wed, 07 Jan 2026 18:26:52 +0000

New study examines a gravitational wave mystery Daniel William… Wed, 01/07/2026 - 11:26

Daniel Strain

Image collected by the Hubble Space Telescope of an object called NGC 2623, which is made up of two galaxies in the final stages of merging together. (Credit: ESA/Hubble & NASA)

Scientists at the ��ý�� may have solved a pressing mystery about the universe’s gravitational wave background.

That’s the name for the ripples in space and time that move constantly through the cosmos and “jiggle us almost like Jell-O,” according to CU ��ý�� astrophysicist Julie Comerford.

The study, published recently in “The Astrophysical Journal,” reveals new insights into the evolution of the universe—namely, how smaller galaxies may have coalesced over billions of years to form larger and more complex galaxies like the Milky Way.

Comerford explained that, at any one time in the universe, countless galaxies are in the process of merging.

Each of those galaxies has an aptly named supermassive black hole at its center. As galaxies merge, these black holes spin around each other, whipping in circles until they eventually smack together. The resulting collisions create waves in space and time that are so subtle humans never feel them.

Artist's depiction of the gravitational wave background. (Credit: NANOGrav collaboration; Aurore Simonet)

“You can picture lots of people in a swimming pool,” said Comerford, lead author of the new study and professor in the Department of Astrophysical and Planetary Sciences at CU ��ý��. “They’re all creating their own waves, and the waves overlap. That’s what the gravitational wave background is like.”

In 2023, several international collaborations, including the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) experiment, reported that they had detected the gravitational wave background for the first time.

There was just one problem: Based on the groups’ measurements, those waves were much larger than scientists had estimated. No one knew why.

In the new study, Comerford and study co-author Joseph Simon, a former postdoctoral researcher at CU ��ý��, may have found the explanation.

Using observations of real galaxies and computer simulations the team discovered something that researchers hadn’t accounted for: When a smaller supermassive black hole merges with a larger one, the smaller black hole seems to gain a lot of mass.

That extra mass makes a difference. Just like swimmers doing cannonballs in a pool, larger supermassive black holes produce larger gravitational waves.

“We had a prediction for what the gravitational wave background should be, and what NANOGrav found was larger than expected,” Comerford said. “It was a surprise and a fun new puzzle to figure out.”

Growth spurts

Supermassive black holes, like galaxies themselves, come in all sorts of sizes. Some of these celestial objects are truly humongous, with a mass equal to billions of Earth’s suns. Others are still big, but slightly less so, with a mass millions of times larger than the sun.

Julie Comerford

For years, many scientists studying the gravitational wave background didn’t believe those smaller black holes mattered, Comerford said. They were too little, the thinking went, to make a meaningful contribution to the gravitational wave background.

Comerford and Simon weren’t so sure.

In part, that’s because galaxy mergers can be messy affairs. When two galaxies come together, gas from those galaxies begins to funnel toward the supermassive black holes at their centers. This gas forms a doughnut-shaped cloud outside the black holes spiraling around each other. Some of that gas falls back into the black holes and makes them larger in the process.

But previous simulations suggested something surprising: The black holes in a merging pair may not grow at the same pace.

“The more massive black hole sits closer to the center of the doughnut where there isn’t much gas,” Comerford said. “The smaller black hole is further out, so it’s closer to where the gas is.”

The beginning

That difference in growth rates, or what the scientists call “preferential accretion,” could matter a lot.

In the current study, Comerford designed a detailed set of equations capturing the physics of how galaxies merge. The group then adjusted those equations to make smaller black holes grow 10% more than larger ones.

That single tweak was enough to make estimates of the gravitational wave background line up with measurements from the NANOGrav experiment.

“They start out little, but because the little ones grow the most, they shouldn’t be discounted,” Comerford said.

She noted that the study doesn’t completely solve the mystery: Her team has launched a new effort to observe real galaxies in the act of merging to see if their physics line up with what the simulations found.

The effort, she said, is part of a larger push to understand some of the most fundamental questions about the universe. That includes how “primordial” galaxies at the dawn of the universe, which were tiny and made up mostly of gas, may have built the gigantic black holes that exist today.

“I’ve spent my career studying supermassive black holes, and we don’t even know how they form,” Comerford said.

Ripples in space and time constantly churn through the universe, forming what's called the "gravitational wave background." A new study examines why these waves are so much bigger than scientists once predicted.

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LASP instruments target trip to the moon aboard NASA's Artemis IV mission

Megan M Rogers — Thu, 11 Dec 2025 16:00:06 +0000

LASP instruments target trip to the moon aboard NASA's Artemis IV mission Megan M Rogers Thu, 12/11/2025 - 09:00

Laboratory for Atmospheric and Space Physics

The Laboratory for Atmospheric and Space Physics has been awarded a $25 million NASA grant to develop instruments that will be deployed on the lunar surface by astronauts during the Artemis IV mission to the moon's south pole.

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Mars spacecraft observes comet from outside our solar system

Daniel William Strain — Mon, 08 Dec 2025 19:55:20 +0000

Mars spacecraft observes comet from outside our solar system Daniel William… Mon, 12/08/2025 - 12:55

Daniel Strain , Willow Reed

Artist's concept of NASA's MAVEN spacrcraft in orbit around Mars. (Credit: NASA/GSFC)

This summer, scientists spotted an incredibly rare visitor to Earth’s solar system—a comet, now known as 3I/ATLAS, that entered our solar system from the galaxy beyond and is zipping past the sun at a speed of about 137,000 miles per hour.

Now, a team of researchers from the ��ý�� has gotten an unprecedented opportunity to observe this visitor from interstellar space.

The team captured images of 3I/ATLAS over 10 days in September and October using NASA’s Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft, which is now orbiting Mars. The observations were part of a larger NASA effort to capture images of the comet from a fleet of spacecraft spread across the solar system.

Image of the comet 3I/ATLAS taken by MAVEN in October 2025. (Credit: NASA/Goddard/LASP/CU ��ý��)

Map of 3I/ATLAS's trajectory through the solar system. (Credit: NASA)

“This is the biggest and brightest object from outside our solar system that’s ever been observed,” said Shannon Curry, a planetary scientist at the Laboratory for Atmospheric and Space Physics (LASP) at CU ��ý�� who leads the MAVEN mission. “The idea that we could be observing it at this level of detail is really incredible.”

She’s not alone in her excitement: 3I/ATLAS is only the third comet or similar icy body researchers have ever seen flying through solar system from interstellar space.

The comet, which scientists estimate could measure as much as 3.5 miles across, will make its closest brush with Earth on Dec. 19. It will pass within 167 million miles of our planet—too far to see with the naked eye.

NASA released MAVEN’s images, along with data from other spacecraft, in November. The MAVEN team is still analyzing these data, but they may yield a treasure trove of information about 3I/ATLAS, including some of the main ingredients that make up the comet.

“It comes from somewhere else, and that’s why we’re so excited about it,” said Nicky Fox, associate administrator for NASA’s Science Mission Directorate, in a Nov. 19 media event. “It’s only the third time that we’ve been able to identify and track something coming from outside our own solar system.”

A view from Mars

Curry noted that MAVEN was never designed to observe objects like comets.

The spacecraft launched in 2014 to study the upper atmosphere of Mars. But in fall 2025, it was in the right time and place to see 3I/ATLAS.

On Oct. 3, the comet passed Mars at a distance of roughly 18.6 million miles. At the time, Earth was on the other side of the sun from Mars, blocking our planet’s view of 3I/ATLAS.

A team at Lockheed Martin in Colorado, which operates MAVEN, positioned the spacecraft so that it was pointing in the comet’s direction. The researchers then began collecting images using an instrument called the Imaging Ultraviolet Spectrometer (IUVS), designed by a team from LASP.

“Our engineering teams enjoy a challenge, and our spacecraft are incredibly versatile, allowing us to support science far beyond the spacecrafts’ initial mission profiles,” said Sandy Freund, mission operations manager for Deep Space Exploration at Lockheed Martin.

Image taken by MAVEN of 3I/ATLAS showing hydrogen emitted from different sources: the comet (dim spot on the far left), hydrogen from Mars (bright emission on the right), and hydrogen flowing through our solar system between the planets (dim emission in the middle). (Credit: NASA/Goddard/LASP/CU ��ý��)

A comet from beyond

The resulting images show a bright object pummeling through space surrounded by a haze of gas and dust—almost like a fuzzy dandelion ball in space.

They may not look like much on the surface, but these pixels carry a wealth of information about the comet.

Image taken of 3I/ATLAS by the Hubble Space Telescope in July 2025. (Credit: NASA, ESA, David Jewitt/UCLA; Image Processing: Joseph DePasquale/STScI)

“There was a lot of adrenaline when the data came down and we saw what we’d captured,” said Justin Deighan, a research scientist at LASP and deputy principal investigator for MAVEN. “Every measurement we can make of this comet is precious and helps to open up new understanding of interstellar objects.”

Curry explained that 3I/ATLAS is made up mostly of ice. As the comet flies through the solar system, radiation from the sun cooks off some of that ice. In the process, 3I/ATLAS emits water through hydrogen and oxygen in various forms into space.

These elements become part of the comet’s coma, or the wide halo of wispy gases and dust that surround its body.

MAVEN’s images will allow scientists to identify many of the ingredients in that halo—bringing researchers as close as they can to traveling to 3I/ATLAS and seeing what it’s made of. It’s the only spacecraft capable of measuring how fast the comet is losing water to space, Curry said.

She added that, despite speculation among some people that 3I/ATLAS could be an alien spacecraft, data from multiple NASA instruments show that it’s clearly a comet.

“Everything about this object tells us it’s a comet,” she said. “There’s nothing to indicate that its trajectory, size and evolution could be produced in any other way.”

Curry sees the new observations as a testament to the MAVEN scientists and engineers and the spacecraft itself—which has been collecting invaluable scientific information at Mars since 2014

“You the MAVEN team show up to do science and can still produce exciting and groundbreaking results no matter what the challenges are,” she said. “That demonstrates the inherent value of an observatory like MAVEN.”

The MAVEN mission is part of NASA’s Mars Exploration Program portfolio. MAVEN’s principal investigator is based at the Laboratory for Atmospheric and Space Physics (LASP) at the ��ý��, which is also responsible for managing science operations and public outreach and communications. NASA’s Goddard Space Flight Center in Greenbelt, Maryland, manages the MAVEN mission. Lockheed Martin Space built the spacecraft and is responsible for mission operations. NASA’s Jet Propulsion Laboratory in Southern California provides navigation and Deep Space Network support.

In July 2025, scientists spotted a comet speeding into our solar system from the galaxy beyond. Researchers from CU ��ý�� have gotten an unprecedented opportunity to capture images of this interstellar visitor.

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New research on flares from a hot-tempered star could inform search for habitable planets

Daniel William Strain — Thu, 04 Dec 2025 22:27:50 +0000

New research on flares from a hot-tempered star could inform search for habitable planets Daniel William… Thu, 12/04/2025 - 15:27

Daniel Strain

Artist's concept of a planet called TRAPPIST-1d passing in front of the star TRAPPIST-1. (Credit: NASA, ESA, CSA, Joseph Olmsted/STScI)

Like a toddler right before naptime, TRAPPIST-1 is a small yet moody star. This little star, which sits in the constellation Aquarius about 40 light-years from Earth, spits out bursts of energy known as “flares” about six times a day.

New research led by CU ��ý�� takes the deepest look yet at the physics behind TRAPPIST-1’s celestial temper tantrums. The team’s findings could help scientists search for habitable planets beyond Earth’s solar system.

The researchers used observations from NASA’s James Webb Space Telescope and computer simulations, or “models,” to understand how TRAPPIST-1 produces its flares—first building up magnetic energy, then releasing it to kick off a chain of events that launches radiation deep into space. The results could help scientists unravel how the star has shaped its nearby planets, potentially in drastic ways.

The team published its findings Nov. 20 in “The Astrophysical Journal Letters.”

Artist's depiction of TRAPPIST-1 with its seven Earth-like planets in orbit. In a Goldilocks situation, the innermost planets are likely too hot to host liquid water, while the outermost planets are too cold. (Credit: NASA/JPL-Caltech)

Artist's concept of the planet TRAPPIST-1e, which may carry hints of an Earth-like atmosphere. (Credit: NASA)

“We think that the innermost TRAPPIST-1 planets are just bare, denuded rocks because the star has blown away their atmospheres,” said Ward Howard, lead author of the new study and a NASA Sagan Fellow in the Department of Astrophysical and Planetary Sciences (APS) at CU ��ý��.

It’s a highlight for the little star, which has attracted a lot of attention from scientists in recent years.

TRAPPIST-1 has less than 10% the mass of the sun and is only a bit larger than the planet Jupiter. But it also hosts seven Earth-sized planets, three of which lie in what researchers call the “habitable zone”—a region of space that may have just the right temperatures for liquid water to form on the surface of a planet.

There’s just one big problem: Scientists have struggled to get a good look at those planets because of the star’s volatile activity.

“When scientists had just started observing TRAPPIST-1, we hadn’t anticipated the majority of our transits would be obstructed by these large flares,” Howard said.

The challenge of studying flares

Studying a flare is a bit like investigating the scene of a crime. Scientists can see the aftermath of a flare—in this case, a big flash. The Webb telescope, for example, records how much infrared radiation, or heat, a star releases during a flare.

But that same space telescope can’t tell you whodunnit.

Howard said that all stars, from TRAPPIST-1 to our own sun, are surrounded by magnetic fields. These magnetic fields twist and bend, forming something that looks like a bowl of noodles. They also shape the plasma, an ultra-hot gas made up of charged particles, in a star’s outer atmosphere.

Sometimes those magnetic fields can get a little too twisted. When that happens, the fields snap, and a beam of electrons hurtles through the star’s atmosphere. That beam is the culprit behind a flare.

“Those beams will continue down into the stellar atmosphere where they smack into the plasma and heat it up,” Howard said. “And once you have a nice hot plasma, it glows.”

To solve the mystery of TRAPPIST-1’s flares, Howard and his colleagues analyzed data from six flares collected by the Webb telescope in 2022 and 2023.

The researchers turned to a new grid of models that describe the physics of flares developed by Adam Kowalski, an associate professor in APS who is also a co-author of the current study.

The models use a series of complex equations to, essentially, wind back time for these flares. If the researchers spot a flare coming from TRAPPIST-1, they can use the models to predict what kind of electron beam kicked off that flare in the first place.

Wimpy flares

Knowing about those electron beams may open up a range of opportunities for scientists studying TRAPPIST-1, Howard said.

For a start, his team discovered that TRAPPIST-1’s flares seem to be surprisingly weak. Most flares from similar stars, by comparison, are produced by electron beams about 10 times stronger.

“These flares were a little wimpier than we expected,” Howard said.

He added that the same electron beams that produce the infrared light seen by Webb also generate a wide range of other kind of radiation—from visible light to ultraviolet radiation and powerful X-rays. The group’s research will allow scientists to explore that full range of radiation coming from TRAPPIST-1’s flares. This information could help researchers understand how these events might alter the atmospheric chemistry of nearby planets.

Scientists suspect that one of the planets in TRAPPIST-1’s habitable zone, named TRAPPIST-1e, may carry a hint of an Earth-like atmosphere—a possible sign of habitability.

“If we can simulate these events using a computer model, we can reverse engineer how a flare might influence the radiation environment around each of these planets,” Howard said.

Co-authors of the new study include researchers at the University of Chicago; Johns Hopkins University; Max Planck Institute for Solar System Research; Massachusetts Institute of Technology; University of Oxford; and Université de Montréal.

A new study takes a close look at TRAPPIST-1, a little star roughly 40 light-years from our sun that hosts seven Earth-sized planets.

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Postdoc working on AI for astronauts

Megan M Rogers — Wed, 03 Dec 2025 16:32:39 +0000

Postdoc working on AI for astronauts Megan M Rogers Wed, 12/03/2025 - 09:32

Ann and H.J. Smead Department of Aerospace Engineering Sciences

Ulubilge Ulusoy is advancing the science of artificial intelligence to help astronauts on future missions to Mars.

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A new possibility for life: Study suggests ancient skies rained down ingredients

Yvaine Ye — Mon, 01 Dec 2025 18:09:45 +0000

A new possibility for life: Study suggests ancient skies rained down ingredients Yvaine Ye Mon, 12/01/2025 - 11:09

Yvaine Ye

Earth’s atmosphere might have contributed to the origin of life more than previously thought.

In a study published Dec. 1 in the "Proceedings of the National Academy of Sciences," CU ��ý�� researchers and collaborators reveal that billions of years ago, the planet’s early sky might have been producing sulfur-containing molecules that were essential ingredients for life.

The finding challenges a long-held theory that these sulfur molecules emerged only after life had already formed.

“Our study could help us understand the evolution of life at its earliest stages,” said first author Nate Reed, a postdoctoral fellow at NASA, who conducted the work as a postdoctoral researcher in the Department of Chemistry and the Cooperative Institute for Research in Environmental Sciences (CIRES) at CU ��ý��.

Nate Reed and Ellie Browne (Credit: Patrick Campbell/CU ��ý��)

Just like carbon, sulfur is an essential element found in all life forms, from single-cell bacteria to humans. It is part of some amino acids, which are the building blocks of protein.

While the young Earth’s atmosphere contained sulfur elements, scientists had long thought that organic sulfur compounds, or biomolecules like amino acids, emerged later as a product of the living system.

In previous simulations of early Earth, scientists either failed to detect meaningful amounts of sulfur biomolecules before life existed, or created the molecules only under specialized conditions that were unlikely to be widespread on this planet.

As a result, when the James Webb Space Telescope detected dimethyl sulfide, an organic sulfur compound produced by marine algae on Earth, on another planet called K2-18b, many thought it was a possible sign of life on other planets.

But in previous work, Reed and the study’s senior author, Ellie Browne, a chemistry professor and a CIRES fellow, successfully created dimethyl sulfide in their lab using only light and common atmospheric gases. This suggested that this molecule could arise in places void of life.

This time, Browne, Reed and their team set off to see what early Earth’s sky could have contributed. They shone light on a gas mixture containing methane, carbon dioxide, hydrogen sulfide and nitrogen to simulate Earth’s atmosphere before life emerged.

Sulfur is a difficult element to work with in the lab, according to Browne. It tends to stick to all equipment, and in the atmosphere, sulfur molecules tend to exist at very low concentrations compared to CO2 and nitrogen. “You have to have equipment that can measure incredibly tiny quantities of the products,” she added.

Ellie Browne (Credit: Patrick Campbell/CU ��ý��)

Using a highly sensitive mass spectrometry instrument that can identify and measure different chemical compounds, Browne’s team found that the early Earth simulation produced a whole suite of sulfur biomolecules, including the amino acids cysteine and taurine, as well as coenzyme M, a compound critical for metabolism.

When the team scaled their lab results to calculate how much cysteine an entire atmosphere could produce, they found that the early Earth’s sky might have brought cysteine to supply about one octillion—one followed by 27 zeros—cells. Currently, Earth boasts about one nonillion—one followed by 30 zeros—cells.

“While it’s not as many as what’s present now, that was still a lot of cysteine in an environment without life. It might be enough for a budding global ecosystem, where life is just getting started,” Reed said.

The team said these biomolecules formed in Earth’s atmosphere might have fallen onto the ground or oceans with rain, helping to get life started.

“Life probably required some very specialized conditions to get started, like near volcanoes or hydrothermal vents with complex chemistry,” Browne said. “We used to think life had to start completely from scratch, but our results suggest some of these more complex molecules were already widespread under non-specialized conditions, which might have made it a little easier for life to get going.”

A CU ��ý��-led study finds that Earth's early atmosphere could have produced key sulfur biomolecules essential for life, challenging long-held assumptions.

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An artist’s interpretation of young Earth, with haze built up in the atmosphere. (Credit: NASA’s Goddard Space Flight Center/Francis Reddy)

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An artist’s interpretation of young Earth, with haze built up in the atmosphere. (Credit: NASA’s Goddard Space Flight Center/Francis Reddy)

Close brush with 2 hot stars millions of years ago left a mark just beyond our solar system

Daniel William Strain — Mon, 01 Dec 2025 17:43:28 +0000

Close brush with 2 hot stars millions of years ago left a mark just beyond our solar system Daniel William… Mon, 12/01/2025 - 10:43

Daniel Strain

Nearly 4.5 million years ago, two large, hot stars brushed tantalizingly close to Earth’s sun. They left behind a trace in the clouds of gas and dust that swirl just beyond our solar system—almost like the scent of perfume after someone has left the room.

That’s one finding from new research led by Michael Shull, an astrophysicist at CU ��ý��, and published Nov. 24 in The Astrophysical Journal.

The study sheds new light on the details of Earth’s neighborhood in space.

Earth’s solar system is surrounded by what scientists call the “local interstellar clouds.” These wispy clumps of gas and dust are made up mostly of hydrogen and helium atoms and stretch about 30 light-years, or roughly 175 trillion miles, from end to end.

Map of the local interstellar clouds just outside Earth's solar system, with blue arrows showing in what directions these clouds are moving. The yellow arrow indicates the direction of the sun's own motion. (Credit: NASA/Adler/U. Chicago/Wesleyan; https://svs.gsfc.nasa.gov/10906)

The constellation Canis Major seen in the night sky. Beta Canis Majoris sits at the end of the dog's "front leg," while Epsilon Canis Majoris is at the end of the "rear leg." (Credit: CC image by Till Credner via Wikimedia Commons)

Zoom past that and our sun exists in a region of the galaxy known as the “local hot bubble,” where gas and dust are relatively scarce.

Shull noted that understanding these features is important because they may have influenced the evolution of life on Earth over millions of years.

“The fact that the sun is inside this set of clouds that can shield us from that ionizing radiation may be an important piece of what makes Earth habitable today,” said Shull, professor emeritus in the Department of Astrophysical and Planetary Sciences at CU ��ý��.

In the new research, he and his colleagues used a series of equations, or models, to catalogue the forces that have shaped our corner of the galaxy over time.

The group examined two stars in particular: Epsilon Canis Majoris, sometimes called Adhara, and Beta Canis Majoris, or Mirzam.

Today, these stars sit in the front and rear legs of the constellation Canis Major, or the “Great Dog.” Based on the team’s calculations, they likely charged past our sun around 4.4 million years ago at a distance of 30 to 35 light-years, a close brush in cosmic terms.

In the process, those stars, which are much hotter than the sun, emitted powerful ultraviolet radiation. That radiation “ionized” the local clouds, stripping electrons from the hydrogen and helium atoms and leaving them with a positive charge—a mark that scientists can still see today.

“If you think back 4.4 million years, these two stars would have been anywhere from four to six times brighter than Sirius is today, far and away the brightest stars in the sky,” Shull said.

Jigsaw puzzle

The research drills down on a mystery that has confounded scientists for decades.

When researchers first began peering at the region of space beyond our solar system decades ago, including with the Hubble Space Telescope, they discovered something strange: Around 20% of the hydrogen atoms and 40% of the helium atoms in the local clouds had been ionized—the amount of ionized helium, in particular, seemed unusually high.

In the current study, Shull and his colleagues set out to inventory the celestial phenomena that may have contributed to that ionization.

The team wound back time to simulate what Earth’s neighborhood was like millions of years ago—a difficult task, in part because the sun is barreling through the local gas in the galaxy at a speed of 58,000 miles per hour.

“It’s kind of a jigsaw puzzle where all the different pieces are moving,” Shull said. “The sun is moving. Stars are racing away from us. The clouds are drifting away.”

The group reports that at least six sources may have helped to ionize the clouds around our solar system. They include three small white dwarf stars. The hot bubble itself may also have played a role.

Shull explained that this void in space was likely created by 10 to 20 stars going supernova—a bit like blowing bubbles into a glass of milk. Those explosions heated up gas within the hot bubble. These hot gases continue to churn out ultraviolet and X-ray radiation today, which bakes the clouds around Earth’s solar system.

Feeling the heat

Epsilon and Beta Canis Majoris likely contributed just as much to the ionization of the sun’s local clouds as the hot gas in the local bubble.

These stars, which today sit more than 400 light-years from Earth, are B-stars, which tend to live fast and hard. Epsilon and Beta Canis Majoris will only burn for 20 million years at most. They are about 13 times more massive than our sun and blaze at about 38,000 and 45,000 degrees Fahrenheit—making the sun, at roughly 10,000 degrees Fahrenheit, look chilly in comparison.

Shull noted that the ionization of the local clouds will likely disappear over millions of years as those positively charged atoms pick up stray electrons in space.

Epsilon and Beta Canis Majoris themselves don’t have much time. Shull estimates that these stars will likely spend the last of their fuel and go supernova in the next few million years.

They won’t pose any danger to Earth, Shull said, but will produce an impressive light show—if anyone is around to see it.

“A supernova blowing up that close will light up the sky,” he said. “It’ll be very, very bright but far enough away that it won’t be lethal.”

Co-authors of the new study include Rachel Curran at the University of North Carolina; Michael Topping at the University of Arizona; and Jonathan Slavin at the Harvard and Smithsonian Center for Astrophysics.

Roughly 4.5 million years ago, two stars known as Epsilon and Beta Canis Majoris flew past Earth's sun at a distance of about 30 to 35 light-years. In the process, they altered the chemistry of what scientists call the "local interstellar clouds."

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