The entire surface of the inner core, or small patches of it, may be swelling and contracting.
WASHINGTON, D.C. — Earth's inner core, a solid metal ball gyrating within the molten outer core, may be both slowing down and changing shape.

Recent analyses of earthquake waves have suggested that around 15 years ago, the inner core's rotation may have slowed so much that it appeared to pause or reverse direction relative to the surface. But a new analysis suggests something more must be changing at Earth's center.

The most probable explanation is that the inner core is not only rotating differently — its surface is probably also morphing, geophysicist John Vidale of the University of Southern California in Los Angeles reported December 9 at a meeting of the American Geophysical Union. The finding could help resolve a long-standing debate over what is changing at the inner core.

No instrument can physically probe Earth's core. So, researchers study it using seismic waves from earthquakes. Scientists typically use quakes that occur in the South Sandwich Islands near Antarctica, which repose on the opposite side of the planet from instrument arrays in Alaska. The earthquake waves travel through the planet like sonar waves through water, with some passing through the inner core on their way to Alaska. Instruments there then record the waves as squiggly signatures called waveforms, which contain information about what the waves encountered on their journey through Earth.

Astronomers analyzing archival images from JWST have discovered an unexpectedly vast population of the smallest asteroids ever seen in the asteroid belt between Mars and Jupiter.
Astronomers analyzing archival images from the James Webb Space Telescope (JWST) have discovered an unexpectedly vast population of the smallest asteroids ever seen in the asteroid belt between Mars and Jupiter. The finding could lead to better tracking of the tiny but powerful space rocks that are likely to approach Earth.

The newfound asteroids range in size from that of a bus to several stadiums — tiny compared to the massive space rock that wiped out most dinosaurs, but they nevertheless pack a significant punch. Only a decade ago an asteroid just tens of meters in size took everyone by surprise when it exploded over Chelyabinsk, Russia, and released 30 times more energy than the atomic bomb detonated over Hiroshima in WWII.

These so-called "decameter" asteroids collide with Earth 10,000 times more frequently than their larger counterparts, but their small size makes it challenging for surveys to detect them well in advance.

In recent years, a team of astronomers including Julien de Wit, an associate professor of planetary science at MIT, has been testing a computationally-intensive method to identify passing asteroids in telescope images of faraway stars.

By applying this method to thousands of JWST images of the host star in about 40 light-years distant TRAPPIST-1 system, which is the best-studied planetary system beyond our own, the researchers found eight previously known and 138 new decameter asteroids in the main asteroid belt. Among them, six appear to have been gravitationally nudged by nearby planets into trajectories that will bring them close to Earth. An early, unedited release of the findings was published Dec. 9 in the journal Nature.

"We thought we would just detect a few new objects, but we detected so many more than expected — especially small ones," de Wit said in a statement. "It is a sign that we are probing a new population regime."

For the first time, the NASA/ESA/CSA James Webb Space Telescope has detected and "weighed" a galaxy that not only existed about 600 million years after the Big Bang, but also has a mass that is similar to what our Milky Way galaxy's mass might have been at the same stage of development.

Other galaxies Webb has detected at this period in the history of the universe are significantly more massive. Nicknamed the Firefly Sparkle, this galaxy is gleaming with star clusters — 10 in all — each of which researchers examined in great detail. Their work is published in Nature.

"I didn't think it would be possible to resolve a galaxy that existed so early in the universe into so many distinct components, let alone find that its mass is similar to our own galaxy's when it was in the process of forming," said Lamiya Mowla, co-lead author of the paper and an assistant professor at Wellesley College in Massachusetts. "There is so much going on inside this tiny galaxy, including so many different phases of star formation."

There is no question that the sun is a temperamental star, as this year's unusually strong solar storms show. Some of them led to remarkable auroras even at low latitudes. But can our star become even more furious?

Evidence of the most violent solar "tantrums" can be found in prehistoric tree trunks and in samples of millennia-old glacial ice. However, from these indirect sources, the frequency of superflares cannot be determined. And direct measurements of the amount of radiation reaching the Earth from the sun have only been available since the beginning of the space age.

Another way to learn about our sun's long-term behavior is to turn to the stars, as is the approach of a new study. The work is published in the journal Science.

Several brief flashes on the lunar surface were captured from Earth.
As we approach the peak of the Geminid meteor shower overnight on Friday (Dec. 13), the skies are beginning to light up with impressive meteors striking Earth's atmosphere. But Earth isn't the only target; the moon is regularly bombarded with such meteors, and Daichi Fujii, the curator of the Hiratsuka City Museum in Japan, has captured some of the most recent collisions.

Fujii documented meteor impacts on the moon on Dec. 6, Dec. 7 and twice on Dec. 8, 2024, using cameras set to monitor Earth's nearest neighbor. You can view some of his lunar impact videos (as well as some impressive fireballs) on his X account.

"There was another lunar impact flash tonight. I filmed it at 360fps from my home at 22:34:35 on December 8, 2024 (slow playback) and was able to confirm it with multiple telescopes. Bright meteors and fireballs have been appearing every day, but lunar impact flashes have also been captured one after another," Fujii wrote in a post on X on Dec. 8.

Also known as Virgo A or NGC 4486, M87 is the brightest object in the Virgo cluster of galaxies, the largest gravitationally bound type of structure in the universe. It came to fame in April 2019 after scientists from EHT released the first image of a black hole in its center. Led by the EHT multi wavelength working group, a study published in Astronomy and Astrophysics Journal presents the data from the second EHT observational campaign conducted in April 2018, involving over 25 terrestrial and orbital telescopes. The authors report the first observation of a high-energy gamma-ray flare in over a decade from the supermassive black hole M87, based on nearly simultaneous spectra of the galaxy spanning the broadest wavelength range ever collected.

"We were lucky to detect a gamma-ray flare from M87 during this Event Horizon Telescope's multi-wavelength campaign. This marks the first gamma-ray flaring event observed in this source in over a decade, allowing us to precisely constrain the size of the region responsible for the observed gamma-ray emission. Observations — both recent ones with a more sensitive EHT array and those planned for the coming years — will provide invaluable insights and an extraordinary opportunity to study the physics surrounding M87's supermassive black hole. These efforts promise to shed light on the disk-jet connection and uncover the origins and mechanisms behind the gamma-ray photon emission." says Giacomo Principe, one of the paper coordinators, a researcher at the University of Trieste associated with INAF and INFN. The article has been accepted for publication in Astronomy & Astrophysics.

The relativistic jet examined by the researchers is surprising in its extent, reaching sizes that exceed the black hole's event horizon by tens of millions of times (7 orders of magnitude) - akin to the difference between the size of a bacterium and the largest known blue whale.

The first pictures of the new-born baby that flashed up on our family chat showed a charming, surprised-looking face with wide, slate-grey eyes - similar in shape to his father's brown eyes, but closer in colour to his mother's green. By his second birthday, however, the pictures revealed he had become a happy toddler with eyes the same dark brown shade as his father's, with all trace of the dark grey of those early photographs gone.

We might think of our eye colour as one of our defining physical traits, as personal to us as the shape of our nose or how much our ears stick out. It is a trait that can often leave a lasting impression on us too - eye colour can even influence how trustworthy we find someone.

But, surprisingly, our eye colour doesn't always remain constant throughout our lives - in fact, a wide range of external influences can change it, from injury to infection and sun damage. And sometimes the change appears to happen spontaneously.

A new view of archival Webb telescope data reveals small asteroids in the main asteroid belt are more numerous than we thought.

Astronomers have uncovered an unexpectedly large population of small main-belt asteroids thanks to a new analysis of images from the James Webb Space Telescope. The finding could change calculations of the impact rate on Earth from such bodies, which range from house-size to the size of a stadium.

These are by far the smallest objects ever imaged so far away. Artem Burdanov (MIT) and colleagues applied a computationally intensive shift-and-stack method to Webb's archival images. From the telescope's sensitive infrared detectors, the team was able to accurately determine the sizes of small objects, ranging from about 10 to 500 meters (30 to 1,600 feet) across. An early release of their results appears in Nature.

Larger main-belt asteroids, whose orbits are between those of Mars and Jupiter, tend to remain in relatively stable orbits. However, gravitational interactions more frequently perturb smaller ones, which may enter the inner solar system to become potential impactors. The high number of small objects now found in the main belt — more than an order of magnitude greater than expected — could affect calculations of the frequency of such impacts.

The James Webb Space Telescope's brand-new image of the Sombrero Galaxy casts this city of stars in a new light — mid-infrared light, to be precise — and reveals clumps of dust in a mottled outer ring.

The Sombrero galaxy is so named because, in visible light images, lying nearly edge-on to us, it bears an uncanny resemblance to a sombrero hat, with its wide rim and bulging center. In this new image taken by JWST's Mid-Infrared Instrument (MIRI), which can peer through clouds of gas and warm dust, those classic hallmarks of the Sombrero have vanished, replaced by a lumpy ring of dust around a gap that houses the bright core where a supermassive black hole lurks.

Located about 31 million light-years away in the constellation Virgo, the Sombrero (catalogued as Messier 104 and NGC 4594) is the most massive spiral galaxy within 100 million light-years of us. The total mass of all the Sombrero's stars amounts to 260 billion solar masses, nearly five times greater than all the stars in our Milky Way galaxy.

The mini-moon 2024 PT5, which has been orbiting Earth for two months and is likely a chunk of the moon, will now drift away from our planet in an orbit around the sun.

A mini-moon that has been orbiting Earth for the past two months will peel away from our planet's orbit today (Nov. 25) as it prepares for a decades-long jaunt through the solar system.

The bus-size asteroid, known as 2024 PT5, is currently 2 million miles (3.2 million kilometers) from Earth and has begun to move away from our planet as it is overcome by the sun's gravity.

The space rock was spotted by the Asteroid Terrestrial-Impact Last Alert System (ATLAS) on Aug. 7 and snared by Earth's gravity on Sept. 29, making one complete orbit of our planet before now being snatched away by the sun. Objects that temporarily orbit Earth as natural satellites are known as mini-moons.