For decades, astronomers thought rings were something only giant planets had. That changed in 2013, when a small, dark body orbiting between Saturn and Uranus passed in front of a star and blinked twice on either side of the main event, revealing two narrow rings around an object barely 250 kilometers across. “It was a surprise,” says Pablo Santos-Sanz, an astronomer at the Instituto de Astrofísica de Andalucía in Granada, Spain. Ever since, the question has been what such rings are made of and how long they can last.

In a recent study, Santos-Sanz and his colleagues used the James Webb Space Telescope to watch the same body, now known as Chariklo, pass in front of a background star again. They found one of its rings had grown denser and the other had almost vanished. We don’t know exactly why.

Shadowing a star

The technique behind the observation is simple. “We predict when a Solar System object passes in front of a star,” Santos-Sanz said. The starlight dims for a moment, and the shape of that dip reveals the size, shape, and surroundings of the object that caused it. “This is particularly challenging for minor bodies, and more challenging for distant minor bodies,” he said.

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It’s a regrettable reality that there is never enough time to cover all the interesting scientific stories we come across. So every month, we highlight a handful of the best stories that nearly slipped through the cracks. August’s list includes the discovery of a new celestial object astronomers have dubbed a "black hole star"; breaking down plastics with microbes and turning them into edible cookies; how whale calls are connected to Einstein's special theory of relativity; and how avocado tree flowers switch sex during the day, among other highlights.

Discovery of a "black hole star"

Credit: Rohan Naidu (University of Hawai'i)

In 2024, astronomers combing through datasets taken by the James Webb Space Telescope noticed hundreds of mysterious little red dots lurking therein, believed to be baby quasars. They existed when the Universe was just a few hundred million years old. One such object in particular captured scientists' interest: a red dot that was extremely red and very bright, but whose properties didn't fit with any known astrophysical object. Astronomers have now concluded that the little red dot is a "black hole star," so named because it is the size of a large star but produces far more energy than would be possible via nuclear fusion—energy comparable to what an active black hole would produce.

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Sgr A* is the name we've given to the supermassive black hole that sits at the center of the Milky Way. We've known about its presence since the 1970s but only managed to image it within the past few years. In the intervening time, most of our understanding of the object was obtained by watching a group of stars that orbit the black hole, helping us get a good estimate of its mass and size. In essence, those stars acted as instruments that let us peer into an environment we couldn't study any other way.

In Wednesday's issue of Nature, researchers describe a recently discovered star that is on an extremely eccentric orbit that takes it closer to Sgr A* than anything we've previously identified. It gets so close that it may help us get our first measurements of the spin of the black hole.

Reading the spin

There's an entire population of stars that orbit relatively close to Sgr A*. We can estimate their mass based on their brightness and spectral features. Using their masses and a reconstruction of their orbits using several years of data, we can figure out just how supermassive Sgr A* is (nearly 10³⁷ kilograms).

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A walk down the tarmac at the National Air and Space Museum of France is guaranteed to thrill aviation enthusiasts. Several civilian and military aircraft of the past and the present are showcased in this museum, located at the Paris-Le Bourget airport. One of them is the legendary Concorde F-WTSS 001 prototype, the sight of which should give goosebumps to science enthusiasts as well.

That’s because right behind its long nose is a painted map that traces the path of a June 1973 total solar eclipse across Africa. It’s there on the Concorde 001 prototype because a group of eight scientists set a new world record of observing a total solar eclipse for 74 minutes by flying this aircraft at more than twice the speed of sound.

To put this figure into context, the maximum duration of totality on the ground is around 7.5 minutes when an eclipse is observed in the equatorial regions. For the upcoming solar eclipse of August 12, which can be seen from parts of Europe, the maximum duration of totality from the ground will be slightly more than two minutes.

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Wherever two fluids slide past each other at different speeds, the boundary between them buckles, then curls, then rolls up into vortexes. It’s called the Kelvin-Helmholtz instability, and the physics behind it was worked out in the late 1860s. We know this instability explains why wind causes ripples on the surface of water and clouds shear into a row of curves.

For decades scientists argued the same thing must be happening with plasma on the surface of the Sun, and yet nobody had been able to confirm it. Now, a team led by David Kuridze and Friedrich Wöger of the National Solar Observatory reports that Kelvin-Helmholtz instabilities are not just visible on the Sun, but they’re ubiquitous. Their new study proposes that this may change the way we think about how heat, mass, and magnetic energy move through the Sun's atmosphere.

Telescope’s test drive

The reason plasma whirlpools on the Sun stayed hidden for so long is rather trivial: They are very small. Their scale sits below what telescopes with mirrors smaller than 2 meters can resolve. For most of the history of solar physics, that has ruled out every telescope on Earth. This changed when the US National Science Foundation opened the Daniel K. Inouye Solar Telescope, a 4-meter instrument in Hawaii and the largest solar telescope in the world. The telescope entered its operational phase back in November 2021.

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It’s a regrettable reality that there is never enough time to cover all the interesting scientific stories we come across. So every month, we highlight a handful of the best stories that nearly slipped through the cracks. July’s list includes outfitting cyborg cockroaches with a tiny diving suit for navigating flooded terrain; confirmation that a Medici duke died of malaria, not poisoning; the best evidence to date that Betelgeuse is orbited by a companion star; and evidence that some ancient Egyptian princesses were skilled archers.

Sacrificial Incan boy died of blunt force trauma

Credit: Administrative Archive, Regional Museum of Iquique–CORMUDESI

It's known that the Incas practiced a human sacrifice ritual known as Capachoca, in which children were offered to the mountains and believed to become divine themselves, serving as intermediaries with the gods. This often involved pilgrimages to the remote sacrificial sites, with colonial accounts describing strangulation, asphyxiation, and blunt force trauma as the most common methods of sacrifice. Archaeologists have reanalyzed the remains of one such victim and concluded the boy died from blunt force trauma, rather than freezing to death as previously believed. They described their findings in a paper published in the journal Science Advances.

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Most of the gas in the Universe is a mixture of hydrogen and helium. It's thought that the initial atmospheres of most planets also start out that way. However, over billions of years, as planets evolve, the composition of their atmospheres may shift. Hydrogen can react with other chemicals, and both it and helium can be lost to space. Venus, Earth, and Mars are thought to have second atmospheres, with their original hydrogen/helium envelopes having been lost and/or transformed.

The dynamics of loss are complicated. Lighter elements are lost more easily, but hydrogen can be protected by being incorporated into molecules like methane and ammonia. The gravity of the body can help retain some molecules, and a magnetic field can limit radiation's ability to blast material out of the atmosphere. Proximity to a star will matter too, both because of the radiation it produces and because it can heat the atmosphere and expand it to where gravity's influence is less substantial.

Given all these complications, it can be difficult to know what to expect to find on exoplanets. But a study in Wednesday's issue of Nature describes observations of helium being lost from the atmosphere of an exoplanet orbiting the star LHS 1140, about 50 light-years away. Based on the rate at which the helium is being lost, we can infer something about the remaining atmosphere.

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WD 1856 b is the only confirmed case of a planet that survived the death of a Sun-like star. It’s a Jupiter-size world orbiting a white dwarf—the burned-out remnant of a Sun-like star. Now, a team of astronomers has used the James Webb Space Telescope to take a closer look at this planet for the first time, and what they found makes an already strange system even stranger.

A feeding frenzy

WD 1856 b was an accidental discovery. Astronomers pointed the TESS observatory at a sample of roughly 2,000 white dwarfs in 2020. These stars are the remains of a Sun-like star that have already gone through a red-giant phase, leaving behind an Earth-size body that’s primarily composed of elements like carbon and oxygen. The TESS team was searching for small objects like comets or asteroids that might transit across the face of these dead stars.

What they found in the WD 1856 system was a gas giant. “As soon as they looked at it, they said, okay, that’s weird,” said Christopher O’Connor, a theoretical astrophysicist at Cornell University and co-author of the recent Nature study on WD 1856 b.

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Earth is the only planet we know of with buoyant, silica-rich continents. But, despite decades of research, geologists still don't agree on how they formed. "The continents started appearing around about four billion years ago—that's the oldest continental rock we know about,” said Tim Johnson, a geologist at Curtin University in Perth, Australia. “The Earth is four and a half billion years old, so why they started appearing then is unknown, as is the mechanism to make that continental crust."

Johnson and his colleagues are now arguing that the formation of continents on Earth was caused largely by an intense, sustained barrage of asteroid impacts that kept the early crust hot and thin enough to make buoyant continents possible. In short, the lands we live on are here because of ancient bombardment from space.

Plates and plumes

The problem with studying the formation of continents is that the geological evidence of this process is almost gone. The oldest known continental-type rocks crystallized around 4.03 billion years ago, right at the end of the Hadean eon (the earliest era in Earth’s history, spanning the first 500 million years of its existence). Rare basaltic rocks date back about 4.2 billion years, and a handful of the oldest zircon crystals push the record back to 4.4 billion years. Beyond that, there's hardly anything else. So, scientists looking into the origin of continents had to rely largely on educated guesses. “There are huge debates about what was going on in the early Earth, because the data is so scarce,” Johnson said.

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Having a computer strapped to my face for 40 minutes was one reason to feel a little sweaty. But the tour of the Universe I had just received in virtual reality—including visits to the near vicinity of the Sun, the giant black hole at the center of our galaxy, and a hellscape of an exoplanet 41 light-years distant—provided another excuse for sensing some heat.

Smithsonian Starstruck: An Immersive Experience is a 40-minute astronomy walk-through. It debuted in Washington, DC, in May with solo adult tickets now ranging from $29 to $35 and group tickets for four or more starting at $18 each (all now discounted by 15 percent); it will also open in Denver, Orlando, Florida, and San Antonio, Texas, later this year. I stopped by on a Monday in June to take it in.

After some onboarding that included setting such preferences as closed captioning and signing a waiver, I had enough time to sit on a bench next to the exhibit space (which has hosted other VR experiences) to enjoy watching another attendee with a VR headset blurt out, “Oh my God!”

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