New method seen as powerful tool in studying stars
Newswise — COLUMBUS, Ohio – Astronomers have developed a powerful technique for identifying starspots, according to research presented this month at the 241st meeting of the American Astronomical Society.
Our sun is at times dotted with sunspots, cool dark regions on the stellar surface generated by strong magnetic fields, which suppress churning motions and impede the free escape of light. On other stars, these phenomena are called starspots, said Lyra Cao, lead author of the study and a graduate student in astronomy at The Ohio State University.
“Our study is the first to precisely characterize the spottiness of stars and use it to directly test theories of stellar magnetism,” said Cao. “This technique is so precise and broadly applicable that it can become a powerful new tool in the study of stellar physics.”
Use of the technique will soon allow Cao and her colleagues to release a catalog of starspot and magnetic field measurements for more than 700,000 stars – increasing the number of these measurements available to scientists by three orders of magnitude.
Since sunspots were first discovered in the 17th century, scientists have typically detected signatures of stellar magnetism indirectly, by looking at stars through different filters or detecting the modulation of spots in a star’s light curve. But by analyzing legacy high-resolution infrared spectra from the Sloan Digital Sky Survey, Cao was able to develop a technique for identifying starspots in 240 stars from two open star clusters, the Pleiades and M67.
The study showed that precision starspot measurements are a powerful new class of data which could help researchers understand how stellar magnetic fields work. Due to precision of the technique, Cao was also able to see how age and rotation affected the magnetic fields on these stars.
“It was lurking in plain sight: Within the spectrum, there was a cooler component corresponding to the starspot which was only visible in the infrared,” Cao said.
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As it turns out, younger stars can be enveloped in starspots – some of them more “spot” than star, with 80% of their surfaces covered. During her studies, Cao realized that these larger cooler regions may block so much light, it might have a measurable effect on these stars. Since the light must eventually escape, she said, the star compensates by expanding and cooling enough to make more surface area available for radiation.
Researchers also found that relying on classical methods to estimate the temperatures of these stars could be wrong by more than 100 degrees. Because scientists often rely on a star’s temperature when trying to estimate its size, astronomers could wrongly assume the radius of the star is smaller than it actually is.
“When this happens, you start seeing large changes in the stars’ structure, which can throw other important astronomical measurements off as well,” said Cao. As scientists use stellar parameters to understand our solar neighborhood and galaxy, and at times, the sizes and habitability prospects of nearby exoplanets, this method could dramatically improve researchers’ ability to test other scientific theories.
Additionally, researchers found a class of stars that are too active for standard theories to explain in the Pleiades cluster. According to Cao, these stars are not only magnetic and rife with starspots, but also overflowing with UV and X-ray radiation.
“You wouldn’t want to live around these stars,” said Cao. “But understanding why these stars are so active could change our models and criteria for exoplanetary habitability.” Further study of these unusual stars could hold the key for understanding why low mass stars are so active, the study notes.
“We can directly study the evolution of stellar magnetism in hundreds of thousands of stars with this new dataset, so we expect this will help develop key insights in our understanding of stars and planets,” said Cao.
Marc Pinsonneault, a professor of astronomy at Ohio State, co-authored the study. This work was supported by NASA.
Did James Webb Find Life on a Distant Planet Recently?
Recent findings from the James Webb Space Telescope suggest potential biosignatures on exoplanet K2-18b, including dimethyl sulfide, indicating possible microbial life, though further research is necessary.
James Webb Space Telescope mission observing universe. This image elements furnished by NASA
While the answer to that question is not a definitive “yes,” recent findings from the James Webb Space Telescope (JWST) are providing what scientists are calling the “strongest evidence yet” of potential life on an exoplanet, specifically K2-18b. This discovery opens a new frontier in our understanding of the universe and the possibility of life beyond Earth.
The Discovery
A dedicated team of astronomers recently utilized the powerful capabilities of the JWST to analyze the atmosphere of K2-18b, a super-Earth exoplanet located an incredible 124 light-years away from our planet. Their findings have revealed chemical signatures in the atmosphere that warrant further investigation.
The Biosignature
Among the intriguing detections was dimethyl sulfide (DMS) and potentially dimethyl disulfide (DMDS). These compounds are significant because, on Earth, they are predominantly produced by living organisms, with marine microbes being the primary source. The presence of these chemicals in K2-18b’s atmosphere suggests the potential for biological processes at work.
The Context
DMS is primarily emitted by marine phytoplankton, a crucial element of oceanic ecosystems. The detection of DMS in the atmosphere of K2-18b is interpreted as a potential indicator of microbial life, potentially thriving in an ocean on the planet. This tantalizing prospect encourages scientists to contemplate the types of ecosystems that could flourish far beyond Earth.
Caution
However, it is essential to approach these findings with the appropriate level of caution. While the presence of these compounds is compelling, scientists emphasize that this does not serve as definitive confirmation of life. Further observations and rigorous analyses are necessary to rule out other non-biological explanations for the presence of DMS and DMDS in K2-18b’s atmosphere.
Significance
This detection represents a significant leap forward in the ongoing quest to uncover extraterrestrial life. It is the first time scientists have successfully identified potential biosignatures on an exoplanet using advanced astronomical technology. This marks a pivotal moment in astrobiology, helping to narrow the focus of future exploration.
Future Research
The JWST will continue to play a vital role in studying K2-18b, as well as other exoplanets, in the relentless pursuit of knowledge about life in the cosmos. Ongoing research will seek to deepen our understanding and potentially corroborate these exciting initial findings.
In conclusion, while the James Webb Space Telescope has not definitively found life on K2-18b, the detection of biosignatures in its atmosphere represents a groundbreaking step in humanity’s exploration of worlds beyond our own. As scientists push forward, we stand on the brink of potentially transformative discoveries that could change our understanding of life in the universe. Stay tuned for further updates as we journey into the stars!
The science section of our news blog, STM Daily News, provides readers with captivating and up-to-date information on the latest scientific discoveries, breakthroughs, and innovations across various fields. We offer engaging and accessible content, ensuring that readers with different levels of scientific knowledge can stay informed. Whether it’s exploring advancements in medicine, astronomy, technology, or environmental sciences, our science section strives to shed light on the intriguing world of scientific exploration and its profound impact on our daily lives. From thought-provoking articles to informative interviews with experts in the field, STM Daily News Science offers a harmonious blend of factual reporting, analysis, and exploration, making it a go-to source for science enthusiasts and curious minds alike. https://stmdailynews.com/category/science/
An illustration of the exoplanet K2-18b, which some research suggests may be covered by deep oceans.
NASA, ESA, CSA, Joseph Olmsted (STScI)Daniel Apai, University of Arizona
A team of astronomers announced on April 16, 2025, that in the process of studying a planet around another star, they had found evidence for an unexpected atmospheric gas. On Earth, that gas – called dimethyl sulfide – is mostly produced by living organisms.
In April 2024, the James Webb Space Telescope stared at the host star of the planet K2-18b for nearly six hours. During that time, the orbiting planet passed in front of the star. Starlight filtered through its atmosphere, carrying the fingerprints of atmospheric molecules to the telescope.
JWST’s cameras can detect molecules in the atmosphere of a planet by looking at light that passed through that atmosphere.European Space Agency
By comparing those fingerprints to 20 different molecules that they would potentially expect to observe in the atmosphere, the astronomers concluded that the most probable match was a gas that, on Earth, is a good indicator of life.
I am an astronomer and astrobiologist who studies planets around other stars and their atmospheres. In my work, I try to understand which nearby planets may be suitable for life.
K2-18b, a mysterious world
To understand what this discovery means, let’s start with the bizarre world it was found in. The planet’s name is K2-18b, meaning it is the first planet in the 18th planetary system found by the extended NASA Kepler mission, K2. Astronomers assign the “b” label to the first planet in the system, not “a,” to avoid possible confusion with the star.
K2-18b is a little over 120 light-years from Earth – on a galactic scale, this world is practically in our backyard.
Although astronomers know very little about K2-18b, we do know that it is very unlike Earth. To start, it is about eight times more massive than Earth, and it has a volume that’s about 18 times larger. This means that it’s only about half as dense as Earth. In other words, it must have a lot of water, which isn’t very dense, or a very big atmosphere, which is even less dense.
Astronomers think that this world could either be a smaller version of our solar system’s ice giant Neptune, called a mini-Neptune, or perhaps a rocky planet with no water but a massive hydrogen atmosphere, called a gas dwarf.
Another option, as University of Cambridge astronomer Nikku Madhusudhan recently proposed, is that the planet is a “hycean world.”
That term means hydrogen-over-ocean, since astronomers predict that hycean worlds are planets with global oceans many times deeper than Earth’s oceans, and without any continents. These oceans are covered by massive hydrogen atmospheres that are thousands of miles high.
Astronomers do not know yet for certain that hycean worlds exist, but models for what those would look like match the limited data JWST and other telescopes have collected on K2-18b.
This is where the story becomes exciting. Mini-Neptunes and gas dwarfs are unlikely to be hospitable for life, because they probably don’t have liquid water, and their interior surfaces have enormous pressures. But a hycean planet would have a large and likely temperate ocean. So could the oceans of hycean worlds be habitable – or even inhabited?
Detecting DMS
In 2023, Madhusudhan and his colleagues used the James Webb Space Telescope’s short-wavelength infrared camera to inspect starlight that filtered through K2-18b’s atmosphere for the first time.
They found evidence for the presence of two simple carbon-bearing molecules – carbon monoxide and methane – and showed that the planet’s upper atmosphere lacked water vapor. This atmospheric composition supported, but did not prove, the idea that K2-18b could be a hycean world. In a hycean world, water would be trapped in the deeper and warmer atmosphere, closer to the oceans than the upper atmosphere probed by JWST observations.
Intriguingly, the data also showed an additional, very weak signal. The team found that this weak signal matched a gas called dimethyl sulfide, or DMS. On Earth, DMS is produced in large quantities by marine algae. It has very few, if any, nonbiological sources.
This signal made the initial detection exciting: on a planet that may have a massive ocean, there is likely a gas that is, on Earth, emitted by biological organisms.
K2-18b could have a deep ocean spanning the planet, and a hydrogen atmosphere.Amanda Smith, Nikku Madhusudhan (University of Cambridge), CC BY-SA
Scientists had a mixed response to this initial announcement. While the findings were exciting, some astronomers pointed out that the DMS signal seen was weak and that the hycean nature of K2-18b is very uncertain.
To address these concerns, Mashusudhan’s team turned JWST back to K2-18b a year later. This time, they used another camera on JWST that looks for another range of wavelengths of light. The new results – announced on April 16, 2025 – supported their initial findings.
These new data show a stronger – but still relatively weak – signal that the team attributes to DMS or a very similar molecule. The fact that the DMS signal showed up on another camera during another set of observations made the interpretation of DMS in the atmosphere stronger.
Madhusudhan’s team also presented a very detailed analysis of the uncertainties in the data and interpretation. In real-life measurements, there are always some uncertainties. They found that these uncertainties are unlikely to account for the signal in the data, further supporting the DMS interpretation. As an astronomer, I find that analysis exciting.
Is life out there?
Does this mean that scientists have found life on another world? Perhaps – but we still cannot be sure.
First, does K2-18b really have an ocean deep beneath its thick atmosphere? Astronomers should test this.
Second, is the signal seen in two cameras two years apart really from dimethyl sulfide? Scientists will need more sensitive measurements and more observations of the planet’s atmosphere to be sure.
Third, if it is indeed DMS, does this mean that there is life? This may be the most difficult question to answer. Life itself is not detectable with existing technology. Astronomers will need to evaluate and exclude all other potential options to build their confidence in this possibility.
The new measurements may lead researchers toward a historic discovery. However, important uncertainties remain. Astrobiologists will need a much deeper understanding of K2-18b and similar worlds before they can be confident in the presence of DMS and its interpretation as a signature of life.
Scientists around the world are already scrutinizing the published study and will work on new tests of the findings, since independent verification is at the heart of science.
Moving forward, K2-18b is going to be an important target for JWST, the world’s most sensitive telescope. JWST may soon observe other potential hycean worlds to see if the signal appears in the atmospheres of those planets, too.
With more data, these tentative conclusions may not stand the test of time. But for now, just the prospect that astronomers may have detected gasses emitted by an alien ecosystem that bubbled up in a dark, blue-hued alien ocean is an incredibly fascinating possibility.
Regardless of the true nature of K2-18b, the new results show how using the JWST to survey other worlds for clues of alien life will guarantee that the next years will be thrilling for astrobiologists.Daniel Apai, Associate Dean for Research and Professor of Astronomy and Planetary Sciences, University of Arizona
This article is republished from The Conversation under a Creative Commons license. Read the original article.
One of the most powerful objects in the universe is a radio quasar – a spinning black hole spraying out highly energetic particles. Come too close to one, and you’d get sucked in by its gravitational pull, or burn up from the intense heat surrounding it. But ironically, studying black holes and their jets can give researchers insight into where potentially habitable worlds might be in the universe.
As an astrophysicist, I’ve spent two decades modeling how black holes spin, how that creates jets, and how they affect the environment of space around them.
What are black holes?
Black holes are massive, astrophysical objects that use gravity to pull surrounding objects into them. Active black holes have a pancake-shaped structure around them called an accretion disk, which contains hot, electrically charged gas.
The plasma that makes up the accretion disk comes from farther out in the galaxy. When two galaxies collide and merge, gas is funneled into the central region of that merger. Some of that gas ends up getting close to the newly merged black hole and forms the accretion disk.
Black holes and their disks can rotate, and when they do, they drag space and time with them – a concept that’s mind-boggling and very hard to grasp conceptually. But black holes are important to study because they produce enormous amounts of energy that can influence galaxies.
How energetic a black hole is depends on different factors, such as the mass of the black hole, whether it rotates rapidly, and whether lots of material falls onto it. Mergers fuel the most energetic black holes, but not all black holes are fed by gas from a merger. In spiral galaxies, for example, less gas tends to fall into the center, and the central black hole tends to have less energy.
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One of the ways they generate energy is through what scientists call “jets” of highly energetic particles. A black hole can pull in magnetic fields and energetic particles surrounding it, and then as the black hole rotates, the magnetic fields twist into a jet that sprays out highly energetic particles.
Magnetic fields twist around the black hole as it rotates to store energy – kind of like when you pull and twist a rubber band. When you release the rubber band, it snaps forward. Similarly, the magnetic fields release their energy by producing these jets.
The accretion disk around a black hole can form a jet of hot, energetic particles surrounded by magnetic field lines. NASA, ESA, and A. Feild (STScI), CC BY
These jets can speed up or suppress the formation of stars in a galaxy, depending on how the energy is released into the black hole’s host galaxy.
Rotating black holes
Some black holes, however, rotate in a different direction than the accretion disk around them. This phenomenon is called counterrotation, and some studies my colleagues and I have conducted suggest that it’s a key feature governing the behavior of one of the most powerful kinds of objects in the universe: the radio quasar.
You can imagine the black hole as a rotating sphere, and the accretion disk as a disk with a hole in the center. The black hole sits in that center hole and rotates one way, while the accretion disk rotates the other way.
This counterrotation forces the black hole to spin down and eventually up again in the other direction, called corotation. Imagine a basketball that spins one way, but you keep tapping it to rotate in the other. The tapping will spin the basketball down. If you continue to tap in the opposite direction, it will eventually spin up and rotate in the other direction. The accretion disk does the same thing.
Since the jets tap into the black hole’s rotational energy, they are powerful only when the black hole is spinning rapidly. The change from counterrotation to corotation takes at least 100 million years. Many initially counterrotating black holes take billions of years to become rapidly spinning corotating black holes.
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So, these black holes would produce powerful jets both early and later in their lifetimes, with an interlude in the middle where the jets are either weak or nonexistent.
When the black hole spins in counterrotation with respect to its accretion disk, that motion produces strong jets that push molecules in the surrounding gas close together, which leads to the formation of stars.
But later, in corotation, the jet tilts. This tilt makes it so that the jet impinges directly on the gas, heating it up and inhibiting star formation. In addition to that, the jet also sprays X-rays across the galaxy. Cosmic X-rays are bad for life because they can harm organic tissue.
For life to thrive, it most likely needs a planet with a habitable ecosystem, and clouds of hot gas saturated with X-rays don’t contain such planets. So, astronomers can instead look for galaxies without a tilted jet coming from its black hole. This idea is key to understanding where intelligence could potentially have emerged and matured in the universe.
Black holes as a guide
By early 2022, I had built a black hole model to use as a guide. It could point out environments with the right kind of black holes to produce the greatest number of planets without spraying them with X-rays. Life in such environments could emerge to its full potential. https://www.youtube.com/embed/b7mTVX9IE0s?wmode=transparent&start=0 Looking at black holes and their role in star formation could help scientists predict when and where life was most likely to form.
Where are such conditions present? The answer is low-density environments where galaxies had merged about 11 billion years ago.
These environments had black holes whose powerful jets enhanced the rate of star formation, but they never experienced a bout of tilted jets in corotation. In short, my model suggested that theoretically, the most advanced extraterrestrial civilization would have likely emerged on the cosmic scene far away and billions of years ago.
The science section of our news blog STM Daily News provides readers with captivating and up-to-date information on the latest scientific discoveries, breakthroughs, and innovations across various fields. We offer engaging and accessible content, ensuring that readers with different levels of scientific knowledge can stay informed. Whether it’s exploring advancements in medicine, astronomy, technology, or environmental sciences, our science section strives to shed light on the intriguing world of scientific exploration and its profound impact on our daily lives. From thought-provoking articles to informative interviews with experts in the field, STM Daily News Science offers a harmonious blend of factual reporting, analysis, and exploration, making it a go-to source for science enthusiasts and curious minds alike. https://stmdailynews.com/category/science/
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Daniel Apai, Associate Dean for Research and Professor of Astronomy and Planetary Sciences, University of Arizona
This article is republished from The Conversation under a Creative Commons license. Read the original article.
