Using data from the James Webb Space Telescope (JWST), astronomers have unraveled some of the atmospheric secrets of a bizarre, blisteringly hot world that has the consistency of marshmallow.
The extrasolar planet, or exoplanet, under the watchful infrared eye of the JWST, is WASP-17b, located around 1,300 light-years away. The exoplanet has a mass around 0.8 times that of Jupiter, but it is around twice as wide as the solar system's largest planet, giving it a "super-puff" consistency comparable to the Earth-based treat. WASP-17 b is so close to its parent star that it completes an orbit in under four Earth days, with this proximity also making the temperature of this "hot Jupiter" skyrocket.
Given the extreme conditions of this exoplanet, it is little wonder that its atmosphere is pretty unusual too. Using a new technique called transmission strings, a team of scientists mapped the contours of the atmosphere of WASP-17b. They found that the atmosphere is shaped like a ring with prominent "gems" rising from it.
"Planets are temperamental, their atmospheres complex and chaotic," team member Hannah Wakeford of the University of Bristol said in a statement. "The fact that all of these numbers came together and showed us this very structured, dynamical picture of this giant world over 1,000 light-years away was just really exciting."
Astronomers like WASP-17b so much they put a ring on it
WASP-17b is so close to its parent star that it is tidally locked, meaning one side permanently faces the star; its dayside is constantly bombarded with stellar radiation. In contrast, the planet also has a cooler nightside, which faces out into space in perpetuity.
By creating incredibly comprehensive 3D views of this exoplanet's atmosphere, researchers found that WASP-17b's atmosphere has a chemical composition and temperature that shift between dayside and nightside according to theory and modelling.
This was possible because the transmission strings technique tracked WASP-17b as it crossed or transited in front of its star, capturing the composition of light around the edge of the planet's atmosphere, or limb, from different angles. This method trumps standard approaches because traditional modelling only maps light as an average across the entire limb.
"Rather than assuming your atmosphere is a circle with the same radius all the way around, our technique allows you to pull out different distances from the center to the edge of the planet," Lili Alderson, of Cornell University, said. "We're able to go around the edge.
"So, we've gone from a ring to understanding where on the ring the gemstones are, so to speak."
The modelling showed just such a "gem," that occurs where hot winds from the planet reach the equator and the nightside of WASP-17b, the atmosphere of the cooler side inflates.
An illustration of the atmosphere of WASP-17b with "gems" rising from it. (Image credit: Robert Lea)
"Theory predicts that the morning and the evening sides should have a strong temperature difference, and WASP-17b fits really nicely in that trend – pretty much bang-on what we thought it would be," Alderson said.
The successful application of the transmission strings method is an exciting step forward in the modelling of the atmospheres of the over 6,000 worlds in NASA's exoplanet catalog.
"This is proof of concept that planets are, in fact, 3D objects, and that, consistently, as they go around their star, what we predict should be happening is happening," Alderson concluded. "To move beyond computational exercises and see it for real is a different matter."
The team's research was published on Wednesday (Oct.14) in the journal Nature Astronomy.
The "treble clef" galaxy cluster is an unusual source of radio waves, the Chandra X-ray observatory has found. (Image credit: X-ray: NASA/CXC/INAF-IRA/A. Botteon et al.; Infrared: UKIDSS-GPS ; Radio: ASTRON/LOFAR; Image processing: NASA/CXC/SAO/N. Wolk)
What looks like a neon pink treble clef floating out in space is actually a bizarre source of radio waves spotted deep in the cosmos.
What is it?
Scientists using NASA's Chandra X-ray Observatory have peered far out into space to look at strange radio waves coming from what they have nicknamed the "treble clef" because of its distinct shape, which looks a lot like the musical notation.
Using Chandra, as well as the German Extended RÖntgen Survey with an Imaging Telescope Array (eROSITA) X-ray telescope, researchers looking at this strange sight spotted a big cloud of blue gas, which we can see in this image, along with radio signals (seen here in bright pink). They think that this object is actually a huge galaxy cluster made up of two different clusters that are in the process of merging.
Why is it incredible?
The researchers think they may have gotten to the bottom of where these radio waves are coming from, they report in a new study.
The team thinks that the treble clef-shaped radio signals were created by an outburst from a supermassive black hole. They believe that this outburst pushed clouds of charged particles and magnetic fields away from the galaxy cluster's center, producing bright radio waves.
According to the scientists, following this bright outburst, there was likely an extreme collision between two galaxy clusters. This cosmic smash-up either compressed or somehow reenergized these charged particles to amplify the radio signal.
When we see beautiful images of objects in space such as this, they can seem just like peaceful, colorful, cosmic clouds. But when you look a bit deeper, these spectacular scenes can actually be evidence of violent, chaotic events.
Two leading space scientists say there is a need to redefine the edge of the solar system by presenting a theory which states that measurements of the Milky Way's gravitational field, including its dark matter, redraws the sun's frontier.
That theory was put forward by Jim Green, former NASA chief scientist and past director of the space agency's Planetary Science Division, along with Ed Belbruno, a professor of mathematics at Yeshiva University and a senior research associate at Princeton University.
The solar system's gravitational frontier extends to nearly 3.8 light-years from the sun, they contend, roughly 241,000 astronomical units (AU), a distance that brings the "edge" of the solar system to within the same scale as the separation between neighboring stars. The edge of our solar system may be defined not by a sharp boundary, but by a "complex dance among forces, energies and trajectories," they write. Green and Belbruno recently made their case in the August 2026 issue of the magazine ROOM - the Space Journal of Asgardia.
Slow moving objects
Moreover, this theory claims that the gravitationally stable Solar Lagrange points L1 and L2 could form a type of "portal" that could funnel future interstellar visitors such as the recent comet 3I/ATLAS into the solar system, perhaps allowing scientists to capture them for future study.
"Discovering the solar-galactic center L1 location is important since slow moving objects that enter this region can be captured by our sun and become part of our solar system," Green told Space.com. "Who knows if there may be a large captured rogue planet on its way into the solar system right now," he said.
Green said there's a need to look at these newly calculated L1 and L2 locations to see what could be found. He is now in discussion about making such observations with the New Horizons spacecraft team that explored Pluto in 2015 and is now operating in the outer heliosphere.
"Even accumulated dust in this region could verify many of the calculations we have made including the extent of the dark matter in our galaxy," said Green.
A diagram showing the Lagrange points L1 though L5. (Image credit: NASA Goddard Space Flight Center Scientific Visualization Studio)
Ballistic capture
"It's a really nice and significant result," Belbruno told Space.com. The ROOM article, written for a popular audience, draws from his August 2025 keynote lecture at the Niels Bohr Institute. Much of the theory also stems from Belbruno's work on permanent capture into the solar system and weak stability boundaries published in 2024 in the journal Celestial Mechanics and Dynamical Astronomy.
"This new work represents a new application of weak stability boundary theory, first applied in 1987 to find new routes to Earth's moon, using ballistic capture for spacecraft," Belbruno said. "Now, its application is substantially extended to ballistic capture into our solar system from interstellar space and in estimating the size of our solar system," he said.
Green and Belbruno point out that the very recent discovery of interstellar objects — such as interstellar comet 3I/ATLAS in 2025 — passing through our solar system on hyperbolic trajectories "has opened an entirely new window onto the material and processes shaping planetary systems across the galaxy."
Interstellar comet 3I/ATLAS as seen by the Hubble Space Telescope in August 2025 as it passed through our solar system. (Image credit: NASA/ESA/David Jewitt (UCLA)/ Image Processing: Joseph DePasquale (STScI))
Mastery of gravity
The article in ROOM adds some impactful ideas regarding potential distant alien civilizations.
"Interstellar travel requires a mastery of gravity, which an advanced extraterrestrial civilization might use to tour the galaxy, using portals created at Lagrange points for leverage, Green and Belbruno write.
"Remaining at these locations, they could observe the life within a stellar system with essentially no energy expenditure," the researchers add, "so perhaps we should be looking for large space stations at stellar L1 and L2 locations as a techno-signature of advanced intelligent life?"
How awesome would it be if the sun could take on a spooky green glow for Halloween? It turns out that scientists have discovered that our star may indeed go green, but only billions of years from now after its death — and only if it then starts eating planets like a cosmic zombie.
That's possible because scientists have discovered that white dwarfs, the type of stellar remnants sun-sized stars leave behind when they die, can actually take on a range of colors including green if they snack on their rocky planets like cosmic cannibals.
For stellar scientists, the colors of stars have always been indicative of their temperatures. Cool stars look orange, while stars like the sun look white, and the hottest stars glow pale blue. This is akin to a blacksmith's iron glowing red, then orange, then white-hot as it heats up. Researchers have always assumed that white dwarfs follow the same rule. However, new research suggests that these stellar corpses could glow in a range of colors including green, pink, cyan, yellow, and purple. That means the universe is far more colorful than we suspected.
"Most stars, including most white dwarfs, behave like 'perfect radiators,' so their color is set almost entirely by temperature. But nobody had really looked into what else might be possible for white dwarfs," team leader Mark Hollands of the University of Warwick said in a statement sent to Space.com.
"It turns out these incredibly dense stars caaaaan produce colors nobody expected, and some of them genuinely surprised me."
How white dwarfs break stellar color rules
White dwarfs get their name because when they were discovered, they appeared surprisingly hot and glowed white or pale blue. However, this new research suggests that this slightly bland and uniform appearance is because no white dwarf is close enough for Earthbound astronomers to see their true colors.
The key to the rainbow-like array of colors this team suggests white dwarfs could possess is their density. White dwarfs form when stars with a mass roughly that of the sun run out of fuel and can no longer support themselves against their own gravity, causing their cores to collapse. As a result, the matter that makes up white dwarfs is around the density of water, millions of times denser than the sun's surface, the photosphere.
In these conditions, elements like carbon, calcium, and sodium can interact with the surrounding dense helium plasma and absorb light across a wider range of colors than they would at lower densities. That shifts the colors of white dwarfs away from the white/light blue seen for a perfect radiator of heat.
Colour-accurate simulated images of white dwarfs. (Image credit: Mark Hollands/University of Warwick)
The researchers found that the colors of white dwarfs would fit into distinct groups tied to the individual chemical makeup of the stellar remnant's atmosphere.
White dwarfs abundant in carbon should be pink or purple, while those that have been enriched with debris from consumed asteroids and comets, and the remains of old planetary systems, would take a more yellow hue. Cooler white dwarfs with mixed hydrogen and helium atmospheres often would glow cyan or pale blue, caused as hydrogen molecules collide with helium atoms in their dense atmospheres.
One of the most striking examples of white dwarf coloration, however, would arise when one of these living dead stars starts feeding on the planets around it like a horror movie zombie.
Zombie white dwarfs go green
The researchers found that some dead star white dwarfs can go a little green around the gills after snacking on orbiting planets.
An example of this is WD J1330+6435, a cool white dwarf located around 326 light-years away, which has been accreting rocky material from a planetary companion. This has enriched its atmosphere with calcium, lithium, and sodium, and the team's model suggests this would have led WD J1330+6435 to adopt a green hue.
But unlike the green-tinged zombies of George Romero's classic Dawn of the Dead, there are no hordes of these green-faced cosmic zombies ... yet.
The researchers think that no other star, living or dead, has ever been credibly reported as green. That makes WD J1330+6435 the first known genuinely green star.
An illustration of a green star (Image credit: Robert Lea (created with Canva))
"The traces of sodium in the atmosphere of this white dwarf absorb the orange part of the spectrum, leaving behind a ghostly green glow," Hollands said. "Imagine standing on a planet and looking up at a green star. It feels like something out of science fiction."
Scientists see red
The team didn't just discover that a known white dwarf is the first-ever green star; they also discovered what could be the reddest star ever in the form of the white dwarf WD J1011+2845.
Located just 48 light-years from Earth, this white dwarf has a deep convection zone that carries carbon from its core to its surface. These carbon molecules distort light from the white dwarf, causing a deep salmon-pink glow unlike anything seen in any other star.
Enriched from below: The cool white dwarf WDJ0902+2010 has a deep convection zone within its helium dominated outer envelope. (Image credit: Mark A. Garlick/University of Warwick)
Despite this rainbow of white dwarfs, the team theorizes that white is still the most common color for these stellar corpses. Only five of the 151 white dwarfs within around 65 light-years of Earth have extraordinary coloring. Extrapolating this to the total population of white dwarfs, the team estimates that only one in 30 of these dead stars has an unusual color.
"One in thirty might not sound like a huge fraction, but across the entire population of white dwarfs in the universe, that is still a lot of oddly colored stars out there," Boris Gänsicke, Department of Physics, University of Warwick, said. "Yet if we take the median across a representative population of white dwarfs, we found that the average white dwarf really is white."
NASA is accelerating the development of three helicopters that will be deployed into the sky above Mars after a voyage aboard NASA's Space Reactor‑1 Freedom spacecraft.
Slated for launch in 2028, SR-1 Freedom is the first fission nuclear-powered interplanetary spacecraft and is assigned the duty of dropping off the SkyFall entry capsule loaded with the trio of aerial vehicles at the Red Planet. SR-1's trajectory will deliver the SkyFall helicopters in Mars' northern hemisphere during the planet's spring season to avoid dust storms.
SkyFall is based on the success of the first aerial craft to float about the Red Planet, Ingenuity, which flew over 70 missions at Jezero Crater before it finally broke a rotor. It was designed to fly five. The SkyFall mission will consist of three identical helicopters to be deployed by an entry vehicle in the atmosphere, let loose at roughly under a mile (3,300 feet or 1,000 meters) above Mars, with each of the craft landing independently.
Regions of interest
The SkyFall mission is to conduct investigations that address objectives relevant for science and preparing for human exploration of Mars. Anticipated flights of the vehicles will travel outside of the landing ellipse to regions of interest within a broader exploration zone.
However, there are further science-focused flight paths and regions that have yet to be determined. NASA intends for the SkyFall helicopters to go to multiple regions of scientific interest on Mars.
NASA's Mars Exploration Program, along with the SkyFall project at the Jet Propulsion Laboratory (JPL), will work together to pick those "why and where" paths to navigate.
A first workshop on potential landing sites for the SkyFall mission and adjacent exploration zones of high scientific value is slated for early next year. And as always, sites and zones on Mars for the choppers means satisfying engineering constraints imposed by the project and spacecraft design.
Given the rapid development cadence of the SkyFall mission, decisions are to be fast-paced, but are geared to maximizing science value of the endeavor.
What Mars researchers are after will be a ranked list of potential landing sites that will be studied in more detail by the SkyFall project and science community, prior to a second workshop to be held in late 2027.
Notional flight trajectories
On the table are potential science value and notional flight trajectories of individual landing sites given the capabilities and payload of the SkyFall helicopters.
Landing site selection will occur after the back-to-back landing site workshops next year, said Matthew Golombek, SkyFall Project Scientist at JPL.
"The project has identified a design reference landing site that targets subsurface water ice deposits with glacial/periglacial terrains," Golombek told Space.com.
Given their deployment, how much real estate will the aerial vessel assault study?
Golombek said that the helicopters are capable of flying one to two kilometers every other sol, so flight traverses of 125 miles to a little over 185 miles (200-300 kilometers) are possible.
"The helicopters are designed to last 6 months, with a goal of one Earth year and each can fly every other sol so multiple flights are expected," Golombek added.
Thanks to the success of the Perseverance rover's unleashing of the Ingenuity rotorcraft, Golombek said that there are a host of lessons learned, as well as engineering additions to be made to the set of SkyFall vehicles.
An illustration of NASA's nuclear-powered SR-1 Freedom spacecraft that will transport the agency's SkyFall helicopters to Mars. (Image credit: NEMES LASZLO/SCIENCE PHOTO LIBRARY/Getty Images/NASA)
Nominal payload
"Although the helicopters are slightly larger than Ingenuity, they are being designed to operate in exactly the same way, so all of the experience with Ingenuity operations will be directly relevant," said Golombek.
The nominal payload to be toted around the Red Planet will be identical for all three helicopters, consisting of five instruments, plus engineering navigation cameras. Those instruments are to investigate the subsurface structure of Mars, the geomorphology and geology of surface terrains, as well as look at the meteorology of the atmosphere and the radiation environment.
Although there is no dedicated hardware to directly measure winds, the helicopters themselves can serve as on-the-spot wind sensors, even shifting to "Balloon Mode," whereby a helicopter will drift in the background wind.
Radar love
Each low-flying helicopter is outfitted with a ground penetrating radar (GPR) instrument, one that can detect layering in the near surface, at depths unobservable by orbital radar.
Those layers could be assembled from rocky material, buried ice, or combinations of the two. Detection of near-surface ice is of interest both scientifically as well as in support of future human expeditions to Mars.
Subsurface ice not only preserves a record of past Martian climate but also serves as a "high-priority environment" that might have served as a habitat of past…or Martian life resident today.
NASA's SkyFall Mars helicopters will use cape-like ground penetrating radar (GPR) instruments to look under the Red Planet's surface. (Image credit: NASA/JPL-Caltech)
SkyFall maneuver
AeroVironment of Arlington, Virginia is partnering with JPL, selected last August to co-design and co-manufacture the SkyFall helicopters. They too are building on their experience as co‑developers of NASA's Ingenuity Mars helicopter that made those 72 flights at Jezero Crater on Mars.
"Now, with SkyFall, we're taking AV's high‑volume uncrewed systems mindset into planetary exploration and showing that Mars helicopters can be built as a repeatable product line, not a one‑off delivery," said Jeff Rodrian, Head of MacCready Works, AV's advanced research and development organization.
A special "SkyFall maneuver" is to be utilized in deploying the three aerial craft. They will be released directly from the carrier spacecraft into the Martian atmosphere, where they separate, deploy, descend, and land under their own power.
"By eliminating the need for a single-use lander stage or a host rover (as Ingenuity required with Perseverance), this approach significantly reduces the technical and financial risk of getting to the Martian surface," explains an AeroVironment statement.
NASA's SkyFall mission to Mars will release of a trio of helicopters on the Red Planet, if all goes to plan. (Image credit: NASA/JPL-Caltech)
Mountains of data
"Just like here on Earth, Mars helicopters can cover distance quickly and can go places that might be impossible to reach by ground," said Will Pomerantz, Head of Space Ventures at AeroVironment.
The science community may guide these helicopters to locations, Pomerantz said, where the ground penetrating radar can map out the specific spots of ice below the martian surface.
"The three SkyFall helicopters are going to show us parts of Mars we've never seen before and return mountains of data for scientists to pore over," said Pomerantz.
An illustration of AeroVironment's new "Skyfall" helicopter concept that could deploy six scouts to Mars. (Image credit: AeroVironment)
An illustration of AeroVironment's new "Skyfall" helicopter concept that could deploy six scouts to Mars. (Image credit: AeroVironment)
A new image from the Mars Express spacecraft reveals windblown ridges known as yardangs, seen here as wrinkled sections on the left and right sides of the image. (Image credit: ESA/DLR/FU Berlin)
A new image from the European Space Agency's Mars Express spacecraft reveals the powerful erosive forces that have shaped and re-shaped the surface of the Red Planet over long periods of geological time.
What is it?
This new Mars Express image captures Amazonis Mensa, a large, flat mountain on the Red Planet that offers planetary scientists a glimpse into the many factors that can sculpt a world's surface.
In this photograph, several features stand out to help illustrate this. Easiest to make out are the large round craters created by ancient impacts on the surface of Mars. However, many of these craters have been at least partially filled by lava flowing across the surface of the Red Planet around three billion years ago, according a statement from the European Space Agency (ESA) accompanying the image.
More interestingly, rippled structures known as yardangs can be seen to the left and right sides of the image. These ridges "form as loose sand particles are whipped up by wind and deployed a little like a cosmic sandblaster," according to ESA.
In the image, the two groups of yardangs ripple across the Martian surface in two different directions. This is because Amazonis Mensa acts as a windbreak, pushing material blown by winds in separate orientations.
Why is it incredible?
For over 20 years, Mars Express has been providing scientists with an unparalleled look at the Martian surface, helping us better understand the forces that have shaped the Red Planet over eons.
You can tell a lot about how a child will age by looking at their parents, and it turns out that this could be true for planetary systems, too. Scientists have performed cosmic genealogy on planetary systems in the Milky Way, finding two distinct families that influence the evolution and fate of these systems.
The study team, led by researchers at the Italian National Institute for Astrophysics (INAF), studied 300 of the best-understood multiplanet systems of the over 1,000 that astronomers have discovered in the Milky Way.
The team's research clarifies how the environments around infant stars directly affect planetary fates and, in turn, the survival of extrasolar planets, or exoplanets, that are potentially capable of hosting life. That could be crucial as astronomers search for life beyond the solar system, pointing them to systems with potentially habitable planets like Earth.
"The fundamental question we started from was: What determines the characteristics of planetary systems as we see them today? Are they established at birth or sculpted by evolution over time? The truth, in the end, turned out to lie somewhere in the middle," team member and INAF researcher Diego Turrini said in a statement sent to Space.com.
"Our results show that there is a genetic link between planetary systems and their stars, and that, depending on the star around which they are born, this link also determines their fate," Turrini added.
What is the genetic code of a planetary system?
The first "family" the scientists identified consists of wide, massive systems, often with total masses between two and 10 times that of our own solar system. The planets in these systems orbit stars more massive than the sun with lower concentrations of elements heavier than hydrogen and helium (which astronomers somewhat confusingly call metals) than seen in our star.
The second family is more compact and lower-mass systems. The members of this family are composed of planets with comparable masses and sizes, a so-called "peas-in-a-pod" configuration. They orbit stars with mass and metallicity equal to or lower than those of the sun, with orbits that are usually much tighter than those of Mercury, the closest planet to the sun.
One of the "genes" Turrini and colleagues selected to sort planetary systems into families was the deviations that planets make from orbiting their star in the same circular plane. That, in turn, reveals a family history of violent gravitational instability caused by events like giant collisions and planetary ejections.
Violent events were common for the first family, but much less so for the second group of planetary systems, the researchers found. They determined that the number of these turbulent events a planetary system experiences can be linked to even modest variations in the environment in which planets form. These variations arise due to different properties of the parent star of those systems.
Thus, the nature of the star in these systems doesn't just fundamentally change the formation of planets in their systems; it influences the system's future evolution, determining whether it will be characterized by phases of marked instability and giant impacts.
An illustration shows two planets colliding. Such collisions may be more common around certain types of stars (Image credit: Robert Lea (created with Canva))
"The main difficulty during the data analysis was determining whether the two families of planetary systems were real or just an illusion created by the technological limits of current observational techniques," said team member Camilla Danielski, of the University of Valencia in Spain.
"At the end of the path, it became clear that selection effects acted as the tip of the iceberg, revealing the existence of much deeper structural diversities between these systems," Danielski said.
The scientists tested their conclusions by running simulations of planetary system evolution, all of which began with different conditions.
"The scenarios that best reproduce the dynamical properties of the family of wide and massive systems are those in which the systems are unstable from birth," said research supervisor and INAF researcher Danae Polychroni. "The greater abundance of material from which planets form around their host stars causes them to be born too large, preventing the system from remaining stable."
The team's research was published on Tuesday (Oct. 13) in the journal Nature Astronomy.
Now you see them, now you don't. Scientists have discovered that some of the universe's most powerful explosions, hypernovas, may not happen at all.
These explosions, known as hypernovas, were first proposed to explain unusual stars in the halo of our galaxy, the Milky Way, and in a neighboring dwarf galaxy. It was suggested that these stars could only form from the debris of an explosion 10 times more powerful than the 'average' supernovas.
The team behind these new findings suggests that ordinary supernovas could actually account for these stars when the uneven or non-spherical way they fling out matter is considered.
"If we look at a supernova today, the star's materials are not spread evenly. Oxygen might predominantly fly in one direction, sulphur in another. New stars might form from a mix of pieces of the supernova, not its overall mix of elements," team leader Anmol Aggarwal of University College London (UCL) said in a statement. "We developed mathematical models that took account of this and found in all cases that stars with a very unusual mix of ingredients were most likely formed from ordinary supernovas.
"All the evidence we see for hypernovae is suddenly gone."
Hypernova vs. supernova: What's the difference?
Supernovas occur when massive stars run out of fuel for nuclear fusion, effectively ending their lives. This results in the star's core collapsing, sending shockwaves rippling through its outer layers, causing explosions we call supernovas.
Hypernovas are proposed to occur in a similar way, but for an even more massive and rapidly spinning star. This results in a vastly more energetic explosion.
When supernovas or hypernovas happen, they fling elements that the dying star has forged throughout its lifetime into their surrounding cosmic environments. These elements eventually become the building blocks of the next generation of stars.
That means analyzing the chemical signatures of stars can tell stellar scientists about their family histories.
Artist's impression of a hypernova, generating 2 gamma-ray jets. (Image credit: NASA/JPL-CALTECH)
"Just before a star goes supernova, it has layers like an onion, with heavier elements at the center and lighter ones further out. Our model looks at how much material from each layer or each region would be needed to fit the observed star," Ralph Schoenrich of Mullard Space Science Laboratory at UCL said. "We still don’t know how well the supernova material gets mixed before it forms new stars. That is despite decades of work in this area. Our research suggests some mixing goes on, but incomplete mixing.
"We need to take this into account in our models of how chemicals evolve in galaxies and of how the interstellar medium works."
The team began their investigation by observing four stars that are suspected to have been forged from material ejected in a hypernova explosion. Three of those stars were more likely to have been created after supernovas, the team concluded.
An artist's impression of the dust surrounding a red giant star. (Image credit: Anna Mayall )
The scientists then studied a single red giant star in the halo of the Milky Way with an odd chemical composition, including an overabundance of heavy elements like silver and uranium. These are too heavy to be forged in the cores of all but the most massive stars, the kind of stars that go hypernova.
Such elements could also be created when two massive and dense stellar remnants called neutron stars collide and merge. However, this star doesn't have certain other heavy elements that would be present after a neutron star collision.
This team considered the origins of this star using a model of the Milky Way that has been rapidly enriched with elements heavier than hydrogen and helium, which astronomers call metals, via the death of the first generation of stars.
The rapid speed at which the star spins and the fact it exists at the outskirts of the Milky Way led the team to conclude that this star escaped a metal-poor dwarf galaxy and was eventually dragged into our galaxy. The event that created it, they concluded, was the combination of a neutron star merger and an ordinary supernova.
No hypernova required. An asymmetrical supernova would be enough, the scientists found.
The location of Earth's geographic poles has changed several times over the past 320 million years in a process known as true polar wander, according to measurements of ancient flooding brought about by sea level changes resulting from our planet's crust shifting relative to Earth's spin axis.
Such a shift can affect climate, both on local scales and globally, as regions that were by the poles find themselves moving down to lower latitudes and vice versa. This can then affect atmospheric circulation patterns, which affect climate across the world.
The changes would have affected the environments in which life developed and evolved, from the age of the dinosaurs through to some of our oldest primate ancestors.
True polar wander is not the same as a change in the rotational axis of the Earth. Currently, Earth spins at an angle of 23.4 degrees relative to the plane of its orbit around the sun, and this rotational axis can vary periodically over tens of thousands of years as a result of the Milankovitch cycles caused by the gravitational pull of the sun and planets.
True polar wander is different. Here, the angle of Earth's spin axis does not change relative to its orbital plane. Instead, Earth's crust and mantle shift relative to that rotational axis. This is because Earth is not perfectly spherical. Instead, it is oblate, with Earth's rotation causing the equator to bulge out and the poles to slightly flatten. Because Earth is not spherical, it has multiple axes of inertia, the largest one being aligned with the rotational axis.
These axes need to be balanced to prevent Earth's rotation from becoming chaotic. However, plate tectonics and indeed the Milankovitch cycles can upset that balance of mass, for example by causing more continental crust to congregate in one hemisphere than another.
To rebalance things, Earth's crust and mantle must become decoupled from our planet's core, which stays aligned with the rotational axis. In physical terms, if there is more continental crust in one hemisphere, the crust and mantle might rotate in that direction relative to the rotational axis and the Earth's core in order to balance itself. This sees the geographical locations of the poles change, hence the name 'true polar wander'.
Currently, true polar wander takes place at a rate of 10 centimeters (4 inches) per year, but figuring out when and how fast true polar wander has occurred in the past is not without its difficulties, not least since plate tectonics can mask and even mimic the signal of true polar wander.
Previous studies relied on paleomagnetism, the study of residual magnetic traces in ancient rocks, since the orientation of those magnetic traces would have varied depending upon where that rock was located relative to Earth's magnetic field. Alas, it's not a terribly accurate means of measuring true polar wander and scientists arrived at substantially different conclusions using this technique.
Nevertheless, based on paleomagnetism, scientists had concluded that true polar wander had been negligible, or slow to proceed, in the distant past. However, new results from researchers at the Centre for Planetary Habitability at the University of Oslo in Norway, led by Mathew Domeier, have shown this not to be the case.
Domeier's team looked through the geological record to track how sea level has changed across millions of years. True polar wander would bring about an identifiable pattern in sea-level changes as the oceans reacted in response to changes in the mass distribution of the planet. The sea level changes would be equal but opposite between hemispheres — sea level rises on one side of one hemisphere would be matched by rises on the other side of the opposite hemisphere, creating a 'quadrupolar' effect.
By using statistical modeling on maps of sea level changes across intervals of 10 million years, Domeier's team identified four periods of true polar wander: in the early Jurassic period 190—200 million years ago, the late Jurassic — early Cretaceous period 140—150 million years ago, during the mid-Cretaceous 90—100 million years ago and from the Oligocene period 30 million years ago through to the Miocene 20 million years ago.
The results show that, contrary to established opinion, true polar wander can happen in bursts that are relatively fast on geological timescales, with the results showing that during the episodes of true polar wander the Earth's surface shifted by as much as 0.6 degrees per million years relative to the spin axis. This is slow by human standards, but fairly fast on geological timescales, certainly quicker than plate tectonics.
Domeier's team were also able to rule out a suspected case of true polar wander around 300 million years ago when the last great supercontinent, Pangea, migrated northwards. It turns out that Pangea's movements were entirely due to plate tectonics.
The findings were published on Oct. 1 in the journal Science.
Hydrogen may be the most common element in the cosmos, but scientists could use it to do something unique: uncover the nature of dark energy, the mysterious force driving the accelerating expansion of the universe.
This new line of dark energy investigation comes from the fact that researchers have determined that the CHIME (Canadian Hydrogen Intensity Mapping Experiment) project can detect the faint radio glow of hydrogen from the universe's distant past.
Not only does this represent a faster and much less expensive way to investigate dark energy, but it is a major milestone for CHIME. The instrument was specifically devised to investigate dark energy and its pervasive influence.
"This is a completely new technique for probing the cosmos, delivered by an instrument that was conceived and built by Canadians," CHIME principal investigator Mark Halpern of the University of British Columbia said in a statement. "It's a bold new step in the global cosmology program and a Canadian success story."
Why is dark energy so problematic?
Dark energy is the mysterious force that is accelerating the expansion of the universe. It is so problematic for scientists because it started acting on the fabric of space only after the expansion triggered by the Big Bang had halted.
That's akin to pushing a child on a swing, watching it stop, and then seeing the swing start up again without a push. And, not only that, but the swing starts oscillating faster and faster. Consider scientists akin to very worried parents, who would really like to know where this ghostly push came from and how it is going to proceed.
Just as, if the push on the swing continues, the child could end up in the bushes, or in orbit, the strengthening of dark energy could result in the cold death of the cosmos, or even a "Big Rip" scenario that sees space shredded. Alternatively, if it weakens and allows gravity to reassert dominance, then the universe could collapse back in on itself, resulting in a "Big Crunch" ending that sees the cosmos compressed back into a singularity, as it was at the beginning of time.
Dark energy is now the dominant element of the universe, accounting for 68% of the universe's matter-energy budget. It's little wonder that scientists are very keen to know what this mysterious force is.
The universe's matter-energy budget showing the dominance of dark energy (Image credit: Robert Lea (created with Canva))
So how can hydrogen help the investigation of dark energy?
"Hydrogen is the most common element in the universe and the raw material from which stars form," team member Arnab Chakraborty of the University of Toronto said. "Its faint radio emission acts like a cosmic tracer, revealing how matter is distributed across space."
Previously, CHIME could map the distribution of hydrogen in the early universe but only by cross-correlating its observations with galaxy survey data from other telescopes, operations that cost millions of dollars and can only focus on regions of the universe dense enough to form stars. CHIME has now shown it can map the radio glow of hydrogen all on its own.
Indeed, the team has already begun making steps in this direction using just a tiny fraction of existing CHIME data. Using 94 nights of observations from 2019, they detected a hydrogen signal from when the universe was just 5 billion years old.
"Our data indicate that roughly 2% of the hydrogen in the universe was in neutral atomic form at this time, broadly consistent with other measurements," team member Shabbir Shaikh of Arizona State University said. "By measuring how that hydrogen is distributed and clustered, CHIME gives us a new way to test our understanding of how galaxies form and evolve."
CHIME has now collected seven years of data, and using this, the team is hoping to probe the distribution of hydrogen back to 3 billion years after the Big Bang.
