Enlarge / Sandia National Labs' Z machine in action. (credit: Randy Montoya)

The old joke about the dinosaurs going extinct because they didn't have a space program may be overselling the need for one. It turns out you can probably divert some of the more threatening asteroids with nothing more than the products of a nuclear weapons program. But it doesn't work the way you probably think it does.

Obviously, nuclear weapons are great at destroying things, so why not asteroids? That won't work because a lot of the damage that nukes generate comes from the blast wave as it propagates through the atmosphere. And the environment around asteroids is notably short on atmosphere, so blast waves won't happen. But you can still use a nuclear weapon's radiation to vaporize part of the asteroid's surface, creating a very temporary, very hot atmosphere on one side of the asteroid. This should create enough pressure to deflect the asteroid's orbit, potentially causing it to fly safely past Earth.

But will it work? Some scientists at Sandia National Lab have decided to tackle a very cool question with one of the cooler bits of hardware on Earth: the Z machine, which can create a pulse of X-rays bright enough to vaporize rock. They estimate that a nuclear weapon can probably impart enough force to deflect asteroids as large as 4 kilometers across.

Enlarge / Artist's conception of a dark matter filament containing a galaxy with large jets. (Caltech noted that some details of this image were created using AI.) (credit: Martijn Oei (Caltech) / Dylan Nelson (IllustrisTNG Collaboration).)

The supermassive black holes that sit at the center of galaxies aren't just decorative. The intense radiation they emit when feeding helps drive away gas and dust that would otherwise form stars, providing feedback that limits the growth of the galaxy. But their influence may extend beyond the galaxy they inhabit. Many black holes produce jets and, in the case of supermassive versions, these jets can eject material entirely out of the galaxy.

Now, researchers are getting a clearer picture of just how far outside of the galaxy their influence can reach. A new study describes the largest-ever jets observed, extending across a total distance of 23 million light-years (seven megaparsecs). At those distances, the jets could easily send material into other galaxies and across the cosmic web of dark matter that structures the Universe.

Extreme jets

Jets are formed in the complex environment near a black hole. The intense heating of infalling material ionizes and heats it, creating electromagnetic fields that act as a natural particle accelerator. This creates jets of particles that travel at a substantial fraction of the speed of light. These will ultimately slam into nearby material, creating shockwaves that heat and accelerate that, too. Over time, this leads to large-scale, coordinated outflows of material, with the scale of the jet being proportional to a combination of the size of the black hole and the amount of material it is feeding on.

Enlarge / The eruptions that produced the dark mare on the lunar surface ended billions of years ago. (credit: NASA/GSFC/Arizona State University)

Signs of volcanic activity on the Moon can be viewed simply by looking up at the night-time sky: The large, dark plains called "maria" are the product of massive outbursts of volcanic material. But these were put in place relatively early in the Moon's history, with their formation ending roughly 3 billion years ago. Smaller-scale additions may have continued until roughly 2 billion years ago. Evidence of that activity includes samples obtained by China's Chang'e-5 lander.

But there are hints that small-scale volcanism continued until much more recent times. Observations from space have identified terrain that seems to be the product of eruptions, but only has a limited number of craters, suggesting a relatively young age. But there's considerable uncertainty about these deposits.

Now, further data from samples returned to Earth by the Chang’e-5 mission show clear evidence of volcanism that is truly recent in the context of the history of the Solar System. Small beads that formed during an eruption have been dated to just 125 million years ago.

Enlarge / High pressure ices near the crust are a feature of water-rich worlds.` (credit: Benoit Gougeon (University of Montreal))

The possibility that there is liquid water on an exoplanet’s surface usually flags it as “potentially habitable,” but the reality is that too much water might prevent life from taking hold.

“On Earth, the ocean is in contact with some rock. If we have too much water, it creates high-pressure ice underneath the ocean, which separates it from the planet’s rocky interior,” said Caroline Dorn, a geophysicist at ETH Zurich, Switzerland, who led new research in exoplanet interiors.

This high-pressure ice prevents minerals and chemical compounds from being exchanged between the rocks and the water. In theory, that should make the ocean barren and lifeless. But Dorn’s team argues that even exoplanets that have enough water to form such high-pressure ice can host life if the majority of the water is not stored in the surface oceans but is held much deeper in the planet’s core. The water in the core can’t sustain life—it’s not even in its molecular form there. But it means that a substantial fraction of a planet’s water isn’t on the surface, which makes the surface oceans a little more shallow and prevents high-pressure ice from forming at their bottom.

Enlarge / The Wow! signal, represented as "6EQUJ5," was discovered in 1977 by astronomer Jerry Ehman. (credit: Public domain)

An unusually bright burst of radio waves—dubbed the Wow! signal—discovered in the 1970s has baffled astronomers ever since, given the tantalizing possibility that it just might be from an alien civilization trying to communicate with us. A team of astronomers think they might have a better explanation, according to a preprint posted to the physics arXiv: clouds of atomic hydrogen that essentially act like a naturally occurring galactic maser, emitting a beam of intense microwave radiation when zapped by a flare from a passing magnetar.

As previously reported, the Wow! signal was detected on August 18, 1977, by The Ohio State University Radio Observatory, known as “Big Ear.” Astronomy professor Jerry Ehman was analyzing Big Ear data in the form of printouts that, to the untrained eye, looked like someone had simply smashed the number row of a typewriter with a preference for lower digits. Numbers and letters in the Big Ear data indicated, essentially, the intensity of the electromagnetic signal picked up by the telescope over time, starting at ones and moving up to letters in the double digits (A was 10, B was 11, and so on). Most of the page was covered in ones and twos, with a stray six or seven sprinkled in.

But that day, Ehman found an anomaly: 6EQUJ5 (sometimes misinterpreted as a message encoded in the radio signal). This signal had started out at an intensity of six—already an outlier on the page—climbed to E, then Q, peaked at U—the highest power signal Big Ear had ever seen—then decreased again. Ehman circled the sequence in red pen and wrote “Wow!” next to it. The signal appeared to be coming from the direction of the Sagittarius constellation, and the entire signal lasted for about 72 seconds. Alas, SETI researchers have never been able to detect the so-called “Wow! Signal” again, despite many tries with radio telescopes around the world.

Enlarge / Artist's rendition of the LADEE mission above the lunar surface. (credit: NASA/ Dana Berry)

The Moon may not have much of an atmosphere, mostly because of its weak gravitational field (whether it had a substantial atmosphere billions of years ago is debatable). But it is thought to presently be maintaining its tenuous atmosphere—also known as an exosphere—because of meteorite impacts.

Space rocks have been bombarding the Moon for its 4.5-billion-year existence. Researchers from MIT and the University of Chicago have now found that lunar soil samples collected by astronauts during the Apollo era show evidence that meteorites, from hulking meteors to micrometeoroids no bigger than specks of dust, have launched a steady flow of atoms into the exosphere.

Though some of these atoms escape into space and others fall back to the surface, those that do remain above the Moon create a thin atmosphere that keeps being replenished as more meteorites crash into the surface.

Enlarge / A naked-eye sunspot group on May 11, 2024. There are typically 40,000 to 50,000 sunspots observed in ~11-year solar cycles. (credit: E. T. H. Teague)

A team of Japanese and Belgian astronomers has re-examined the sunspot drawings made by 17th century astronomer Johannes Kepler with modern analytical techniques. By doing so, they resolved a long-standing mystery about solar cycles during that period, according to a recent paper published in The Astrophysical Journal Letters.

Precisely who first observed sunspots was a matter of heated debate in the early 17th century. We now know that ancient Chinese astronomers between 364 and 28 BCE observed these features and included them in their official records. A Benedictine monk in 807 thought he'd observed Mercury passing in front of the Sun when, in reality, he had witnessed a sunspot; similar mistaken interpretations were also common in the 12th century. (An English monk made the first known drawings of sunspots in December 1128.)

English astronomer Thomas Harriot made the first telescope observations of sunspots in late 1610 and recorded them in his notebooks, as did Galileo around the same time, although the latter did not publish a scientific paper on sunspots (accompanied by sketches) until 1613. Galileo also argued that the spots were not, as some believed, solar satellites but more like clouds in the atmosphere or the surface of the Sun. But he was not the first to suggest this; that credit belongs to Dutch astronomer Johannes Fabricus, who published his scientific treatise on sunspots in 1611.

Enlarge / Some of the galaxies in the JADES images. (credit: NASA, ESA, CSA, M. Zamani)

One of the things that the James Webb Space Telescope was designed to do was look at some of the earliest objects in the Universe. And it has already succeeded spectacularly, imaging galaxies as they existed just 250 million years after the Big Bang. But these galaxies were small, compact, and similar in scope to what we'd consider a dwarf galaxy today, which made it difficult to determine what was producing their light: stars or an actively feeding supermassive black hole at their core.

This week, Nature is publishing confirmation that some additional galaxies we've imaged also date back to just 300 million years after the Big Bang. Critically, one of them is bright and relatively large, allowing us to infer that most of its light was coming from a halo of stars surrounding its core, rather than originating in the same area as the central black hole. The finding implies that it formed through a continuing burst of star formation that started just 200 million years after the Big Bang.

Age checks

The galaxies at issue here were first imaged during the JADES (JWST Advanced Deep Extragalactic Survey) imaging program, which includes part of the area imaged for the Hubble Ultra Deep Field. Initially, old galaxies were identified by using a combination of filters on one of Webb's infrared imaging cameras.

Enlarge / A jet of particles moving at nearly light-speed emerges from a massive star in this artist’s concept of the BOAT. (credit: NASA's Goddard Space Flight Center Conceptual Image Lab)

Scientists have been all aflutter since several space-based detectors picked up a powerful gamma-ray burst (GRB) in October 2022—a burst so energetic that astronomers nicknamed it the BOAT (Brightest Of All Time). Now an international team of astronomers has analyzed an unusual energy peak detected by NASA's Fermi Gamma-ray Space Telescope and concluded that it was an emission spectra, according to a new paper published in the journal Science. Per the authors, it's the first high-confidence emission line ever seen in 50 years of studying GRBs.

As reported previously, gamma-ray bursts are extremely high-energy explosions in distant galaxies lasting between mere milliseconds to several hours. There are two classes of gamma-ray bursts. Most (70 percent) are long bursts lasting more than two seconds, often with a bright afterglow. These are usually linked to galaxies with rapid star formation. Astronomers think that long bursts are tied to the deaths of massive stars collapsing to form a neutron star or black hole (or, alternatively, a newly formed magnetar). The baby black hole would produce jets of highly energetic particles moving near the speed of light, powerful enough to pierce through the remains of the progenitor star, emitting X-rays and gamma rays.

Those gamma-ray bursts lasting less than two seconds (about 30 percent) are deemed short bursts, usually emitting from regions with very little star formation. Astronomers think these gamma-ray bursts are the result of mergers between two neutron stars, or a neutron star merging with a black hole, comprising a "kilonova." That hypothesis was confirmed in 2017 when the LIGO collaboration picked up the gravitational wave signal of two neutron stars merging, accompanied by the powerful gamma-ray bursts associated with a kilonova.

Enlarge / Artist's illustration of the Chandra X-ray Observatory. (credit: NASA/MSFC)

NASA launched the Chandra X-ray Observatory 25 years ago this week, opening a new eye on the Universe and giving astronomers vision into unimaginably violent cosmic environments like exploding stars and black holes. But Chandra's mission may soon end as NASA's science division faces a nearly billion-dollar budget shortfall.

NASA says it can no longer afford to fund Chandra at the levels it has since the telescope launched in 1999. The agency has a diminished budget for science missions this year, and the reductions may continue next year due to government spending caps in a deal reached between Congress and the Biden administration last year to suspend the federal debt ceiling.

Congress and the White House have prioritized funding for NASA's human spaceflight programs, primarily the rockets, spacecraft, landers, spacesuits, and rovers needed for the Artemis program to return astronauts to the Moon. Meanwhile, the funding level for NASA's science mission directorate has dropped.

Enlarge / Image of Epsilon Indi A at two wavelengths, with the position of its host star indicated by an asterisk. (credit: T. Müller (MPIA/HdA), E. Matthews (MPIA))

We have a couple of techniques that allow us to infer the presence of an exoplanet based on its effects on the light coming from its host star. But there's an alternative approach that sometimes works: image them directly. It's much more limited, since the planet has to be pretty big and orbiting far away enough from its star to avoid having light coming from the planet swamped by the far more intense starlight.

Still, it has been done. Massive exoplanets have been captured relatively shortly after their formation, when the heat generated by the collapse of material into the planet causes them to glow in the infrared. But the Webb telescope is far more sensitive than any infrared observatory we've ever built, and it has managed to image a relatively nearby exoplanet that's roughly as old as the ones in our Solar System.

Looking directly at a planet

What do you need to directly image a planet that's orbiting a star light-years away? The first thing is a bit of hardware called a coronagraph attached to your telescope. This is responsible for blocking the light from the star the planet is orbiting; without it, that light will swamp any other sources in the exosolar system. Even with a good coronagraph, you need the planets to be orbiting at a significant distance from the star so that they're cleanly separated from the signal being blocked by the coronagraph.

Enlarge / Renditions of a possible composition of LHS 1140 b, with a patch of ocean on the side facing its host star. Earth is included at right for scale. (credit: BENOIT GOUGEON, UNIVERSITÉ DE MONTRÉAL)

Of all the potential super-Earths—terrestrial exoplanets more massive than Earth—out there, an exoplanet orbiting a star only 40 light-years away from us in the constellation Cetus might be the most similar to have been found so far.

Exoplanet LHS 1140 b was assumed to be a mini-Neptune when it was first discovered by NASA’s James Webb Space Telescope toward the end of 2023. After analyzing data from those observations, a team of researchers, led by astronomer Charles Cadieux, of Université de Montréal, suggest that LHS 1140 b is more likely to be a super-Earth.

If this planet is an alternate version of our own, its relative proximity to its cool red dwarf star means it would most likely be a gargantuan snowball or a mostly frozen body with a substellar (region closest to its star) ocean that makes it look like a cosmic eyeball. It is now thought to be the exoplanet with the best chance for liquid water on its surface, and so might even be habitable.