NASA’s Webb Observes Exoplanet Whose Composition Defies Explanation - UNIVERSE

Scientists using NASA’s James Webb Space Telescope have observed a rare type of exoplanet, or planet outside our solar system, whose atmospheric composition challenges our understanding of how it formed. 

Officially named PSR J2322-2650b, this Jupiter-mass object appears to have an exotic helium-and-carbon-dominated atmosphere unlike any ever seen before. Soot clouds likely float through the air, and deep within the planet, these carbon clouds can condense and form diamonds. How the planet came to be is a mystery. The paper appears Tuesday in The Astrophysical Journal Letters. 

“This was an absolute surprise,” said study co-author Peter Gao of the Carnegie Earth and Planets Laboratory in Washington. “I remember after we got the data down, our collective reaction was ‘What the heck is this?’ It's extremely different from what we expected.”

Image A: Exoplanet PSR J2322-2650b and Pulsar (Artist's Concept)

This artist’s concept shows what the exoplanet called PSR J2322-2650b (left) may look like as it orbits a rapidly spinning neutron star called a pulsar (right). Gravitational forces from the much heavier pulsar are pulling the Jupiter-mass world into a bizarre lemon shape.

Illustration: NASA, ESA, CSA, Ralf Crawford (STScI)

This planet-mass object was known to orbit a pulsar, a rapidly spinning neutron star. A pulsar emits beams of electromagnetic radiation at regular intervals typically ranging from milliseconds to seconds. These pulsing beams can only be seen when they are pointing directly toward Earth, much like beams from a lighthouse.  

This millisecond pulsar is expected to be emitting mostly gamma rays and other high energy particles, which are invisible to Webb’s infrared vision. Without a bright star in the way, scientists can study the planet in intricate detail across its whole orbit. 

“This system is unique because we are able to view the planet illuminated by its host star, but not see the host star at all,” said Maya Beleznay, a third-year PhD candidate at Stanford University in California who worked on modeling the shape of the planet and the geometry of its orbit. “So we get a really pristine spectrum. And we can study this system in more detail than normal exoplanets.” 

“The planet orbits a star that's completely bizarre — the mass of the Sun, but the size of a city,” said the University of Chicago’s Michael Zhang, the principal investigator on this study. “This is a new type of planet atmosphere that nobody has ever seen before. Instead of finding the normal molecules we expect to see on an exoplanet — like water, methane, and carbon dioxide — we saw molecular carbon, specifically C₃ and C_2.”

Molecular carbon is very unusual because at these temperatures, if there are any other types of atoms in the atmosphere, carbon will bind to them. (Temperatures on the planet range from 1,200 degrees Fahrenheit at the coldest points of the night side to 3,700 degrees Fahrenheit at the hottest points of the day side.) Molecular carbon is only dominant if there's almost no oxygen or nitrogen. Out of the approximately 150 planets that astronomers have studied inside and outside the solar system, no others have any detectable molecular carbon.

PSR J2322-2650b is extraordinarily close to its star, just 1 million miles away. In contrast, Earth’s distance from the Sun is about 100 million miles. Because of its extremely tight orbit, the exoplanet’s entire year — the time it takes to go around its star — is just 7.8 hours. Gravitational forces from the much heavier pulsar are pulling the Jupiter-mass planet into a bizarre lemon shape.

Image B: Exoplanet PSR J2322-2650b (Artist's Concept)

This artist’s concept shows what the exoplanet PSR J2322-2650b may look like. Gravitational forces from the much heavier pulsar it orbits are pulling the Jupiter-mass world into this bizarre lemon shape.

Illustration: NASA, ESA, CSA, Ralf Crawford (STScI)

Together, the star and exoplanet may be considered a “black widow” system, though not a typical example. Black widow systems are a rare type of double system where a rapidly spinning pulsar is paired with a small, low-mass stellar companion. In the past, material from the companion streamed onto the pulsar, causing the pulsar to spin faster over time, which powers a strong wind. That wind and radiation then bombard and evaporate the smaller and less massive companion. Like the spider for which it is named, the pulsar slowly consumes its unfortunate partner.

But in this case, the companion is officially considered an exoplanet, not a star. The International Astronomical Union defines an exoplanet as a celestial body below 13 Jupiter masses that orbits a star, brown dwarf, or stellar remnant, such as a pulsar.

Of the 6,000 known exoplanets, this is the only one reminiscent of a gas giant (with mass, radius, and temperature similar to a hot Jupiter) orbiting a pulsar. Only a handful of pulsars are known to have planets.

“Did this thing form like a normal planet? No, because the composition is entirely different,” said Zhang. “Did it form by stripping the outside of a star, like ‘normal’ black widow systems are formed? Probably not, because nuclear physics does not make pure carbon. It's very hard to imagine how you get this extremely carbon-enriched composition. It seems to rule out every known formation mechanism.”

Study co-author Roger Romani, of Stanford University and the Kavli Institute for Particle Astrophysics and Cosmology Institute, proposes one evocative phenomenon that could occur in the unique atmosphere. “As the companion cools down, the mixture of carbon and oxygen in the interior starts to crystallize,” said Romani. “Pure carbon crystals float to the top and get mixed into the helium, and that's what we see. But then something has to happen to keep the oxygen and nitrogen away. And that's where the mystery come in.

“But it's nice to not know everything,” said Romani. “I'm looking forward to learning more about the weirdness of this atmosphere. It's great to have a puzzle to go after.”

Video A: Exoplanet PSR J2322-2650b and Pulsar (Artist's Concept)

This animation shows an exotic exoplanet orbiting a distant pulsar, or rapidly rotating neutron star with radio pulses. The planet, which orbits about 1 million miles away from the pulsar, is stretched into a lemon shape by the pulsar’s strong gravitational tides.

Animation: NASA, ESA, CSA, Ralf Crawford (STScI)

With its infrared vision and exquisite sensitivity, this is a discovery only the Webb telescope could make. Its perch a million miles from Earth and its huge sunshield keep the instruments very cold, which is necessary for these observations. It is not possible to conduct this study from the ground.

The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).

To learn more about Webb, visit: https://science.nasa.gov/webb  

Source: NASA’s Webb Observes Exoplanet Whose Composition Defies Explanation - NASA Science   

Sea reptile's tooth shows that mosasaurs could live in freshwater - Biology Paleontology & Fossils

The Hell Creek Mosasaur, reconstruction by Christopher DiPiazza. Credit: Christopher DiPiazza

Mosasaurs, giant marine reptiles that existed more than 66 million years ago, lived not only in the sea but also in rivers. This is shown by new research based on analyses of a mosasaur tooth found in North Dakota and believed to belong to an animal that could reach a length of 11 meters.

Conducted by an international team of researchers led from Uppsala University, the study shows that mosasaurs adapted to riverine environments in the final million years before they became extinct.

The study is published in the journal BMC Zoology.

In 2022, paleontologists found a large tooth from a mosasaur in North Dakota. It was discovered in a fluvial deposit, together with a tooth from a Tyrannosaurus rex, and a crocodylian jawbone in an area known for remains of the duck-billed dinosaur Edmontosaurus.

The fact that land-dwelling dinosaurs, river-dwelling crocodylians and giant marine reptiles were found together raised the question: how did a mosasaur tooth end up in a river, when this reptile was assumed to live in the sea?

An international team of researchers from the United States, Sweden and the Netherlands has now answered the question using isotope analyses of the mosasaur's tooth enamel. 

Credit: Uppsala University

Isotopes show how they lived and what they ate

Since the mosasaur tooth, the T. rex tooth and the crocodylian jawbone are of similar age, around 66 million years old, the researchers were able to compare their chemical composition by means of isotope analyses.

The analysis, carried out at the Vrije Universiteit (VU) in Amsterdam, studied the ratio between different isotopes of the elements oxygen, strontium and carbon. The mosasaur teeth contained more of the lighter oxygen isotope (¹⁶O) than is usually seen in marine mosasaurs, indicating that they lived in freshwater. The ratio between different strontium isotopes also suggests a freshwater habitat.

"Carbon isotopes in teeth generally reflect what the animal ate. Many mosasaurs have low ¹³C values because they dive deep. The mosasaur tooth found with the T. rex tooth, on the other hand, has a higher ¹³C value than all known mosasaurs, dinosaurs and crocodiles, suggesting that it did not dive deep and may sometimes have fed on drowned dinosaurs," says Melanie During, one of the study's corresponding authors.

"The isotope signatures indicated that this mosasaur had inhabited this freshwater riverine environment. When we looked at two additional mosasaur teeth found at nearby, slightly older, sites in North Dakota, we saw similar freshwater signatures. These analyses show that mosasaurs lived in riverine environments in the final million years before going extinct," says During.

The mosasaur tooth that was found in 2022 in the Bismarck Area, North Dakota. Credit: Melanie During

When seas became rivers

The discovery sheds light on an interesting chapter in Earth's history. The influx of freshwater into the Western Interior Seaway, an inland sea that then stretched from north to south across today's prairies and divided North America in two, increased over time. This gradually transformed the sea water from saltwater to brackish water and eventually to mostly freshwater, rather like in the Gulf of Bothnia.

The authors believe that this led to the formation of a "halocline," in which a layer of freshwater sat on top of heavier saltwater. This theory is borne out by isotope analyses.

"For comparison with the mosasaur teeth, we also measured fossils from other marine animals and found a clear difference. All gill-breathing animals had isotope signatures linking them to brackish or salty water, while all lung-breathing animals lacked such signatures. This shows that mosasaurs, which needed to come to the surface to breathe, inhabited the upper freshwater layer and not the lower layer where the water was more saline," says Per Ahlberg, co-author of the study and promotor of Dr. During.

Adapted to new living conditions

The researchers argue that the mosasaur teeth analyzed clearly came from individuals that were adapted to these changing environments. Such a transition is not an unknown phenomenon among large predators.

"Unlike the complex adaptation required to move from freshwater to marine habitats, the reverse adaptation is generally simpler," says During.

Modern examples of such adaptation can be seen in river dolphins, which live in freshwater rivers despite being descended from marine ancestors.

The estuarine crocodile, known in Australia as the saltwater crocodile, is another example. It moves freely between freshwater rivers and the open sea, hunting in both environments depending on what prey is available.

Could be as big as a bus

Mosasaur fossils are abundant in North American, European and African marine deposits that are 98–66 million years old. However, they are only rarely found in North Dakota, which makes the new discovery particularly noteworthy. The size of the tooth testifies to an impressive creature that could grow up to 11 meters long, about the size of a bus.

This estimate is corroborated by a handful of mosasaur bones found earlier at a nearby site in North Dakota. The tooth comes from a prognathodontine mosasaur, though the genus cannot be determined with certainty.

Mosasaurs of the genus Prognathodon, closely related to the animal that lost this tooth, had bulky heads with sturdy jaws and teeth. They are widely regarded as opportunistic predators that posed a significant threat to other large aquatic animals.

"The size means that the animal would rival the largest killer whales, making it an extraordinary predator to encounter in riverine environments not previously associated with such giant marine reptiles," says Ahlberg.

The study was conducted by researchers from Uppsala University in collaboration with Eastern West Virginia Community and Technical College, Moorefield, West Virginia, Vrije Universiteit Amsterdam and the North Dakota Geological Survey.

The article is based on a chapter of Melanie During's thesis, which she presented at Uppsala University in November 2024.

Provided by Uppsala University 

by Uppsala University

edited by Sadie Harley, reviewed by Robert Egan 

Source: Sea reptile's tooth shows that mosasaurs could live in freshwater