It’s three for the price of one. A trio of mysterious high-energy particles could all have the same source: active black holes embedded in galaxy clusters, researchers suggest January 22 in Nature Physics.

Scientists have been unable to figure out the origins of the three types of particles — gamma rays that give a background glow to the universe, cosmic neutrinos and ultrahigh energy cosmic rays. Each carries a huge amount of energy, from about a billion electron volts for a gamma ray to 100 billion billion electron volts for some cosmic rays.
Strangely, each particle type seems to contribute the same total amount of energy to the universe as the other two. That’s a clue that all three may be powered by the same engine, says physicist Kohta Murase of Penn State.

“We can explain the data of these three messengers with one single picture,” Murase says.

First, a black hole accelerates charged particles to extreme energies in a powerful jet (SN: 9/16/17, p. 16). These jets “are one of the most promising candidate sources of ultrahigh energy cosmic rays,” Murase says. The most energetic cosmic rays escape the jet and immediately plow through a sea of magnetized gas within the galaxy cluster.

Some rays escape the gas as well and zip towards Earth. But less energetic rays are trapped in the cluster for up to a billion years. There, they interact with the gas and create high-energy neutrinos that then escape the cluster.
Meanwhile, the cosmic rays that escaped travel through intergalactic space and interact with photons to produce the glow of gamma rays.

Murase and astrophysicist Ke Fang of the University of Maryland in College Park found that computer simulations of this scenario lined up with observations of how many cosmic rays, neutrinos and gamma rays reached Earth.

“It’s a nice piece of unification of many ideas,” says physicist Francis Halzen of the IceCube Neutrino Observatory in Antarctica, where the highest energy neutrinos have been observed.

There are other possible sources for the particles — for one, IceCube has already traced an especially high-energy neutrino to a single active black hole that may not be in a cluster (SN Online: 4/7/16). The observatory could eventually trace neutrinos back to galaxy clusters. “That’s the ultimate test,” Halzen says. “This could be tomorrow, could be God knows when.”

Knocking out an animal 15 times your size — no problem. A newly identified toxin in the venom of a tropical centipede helps the arthropod to overpower giant prey in about 30 seconds.

Insight into how this venom overwhelms lab mice could lead to an antidote for people who suffer excruciatingly painful, reportedly even fatal, centipede bites, an international research team reports the week of January 22 in Proceedings of the National Academy of Sciences.

In Hawaii, centipede bites account for about 400 emergency room visits a year, according to data from 2004 to 2008. The main threat there is Scolopendra subspinipes, an agile species almost as long as a human hand.
The subspecies S. subspinipes mutilans starred in studies at the Kunming Institute of Zoology in China and collaborating labs. Researchers there found a small peptide, now named “spooky toxin,” largely responsible for venom misery.

This toxin blocks a molecular channel that normally lets potassium flow through cell membranes. A huge amount of the biochemistry of staying alive involves potassium, so clogging some of what are called KCNQ channels caused mayhem in mice: slow and gasping breath, high blood pressure, frizzling nerve dysfunctions and so on. Administering the epilepsy drug retigabine opened the potassium channels and counteracted much of the toxin’s effects, raising hopes of a treatment for these bites.

Now there’s a way to tell if a drone is spying on someone.

Researchers have devised a method to tell what a drone is recording — without having to decrypt the video data that the device streams to the pilot’s smartphone. This technique, described January 9 at arXiv.org, could help military bases detect unwanted surveillance and civilians protect their privacy as more commercial drones take to the skies.

“People have already worked on detecting [the presence of] drones, but no one had solved the problem of, ‘Is the drone actually recording something in my direction?’” says Ahmad Javaid, a cybersecurity researcher at the University of Toledo in Ohio, who was not involved in the work.
Ben Nassi, a software engineer at Ben-Gurion University of the Negev in Israel, and colleagues realized that changing the appearance of objects in a drone’s field of view influences the stream of encrypted data the drone sends to its smartphone controller. That’s because the more pixels that change from one video frame to the next, the more data bits the drone sends per second. So rapidly switching the appearance of a person or house and seeing whether those alterations correspond to higher drone-to-phone Wi-Fi traffic can reveal whether a drone is snooping.

Nassi’s team tested this idea by covering a house window with a smart film that could switch between transparent and nearly opaque, and aiming a drone with a video camera at the window from 40 meters away. Every two seconds, the researchers either flickered the smart film back and forth or left it transparent. They pointed a radio frequency scanner at the drone to intercept its outgoing Wi-Fi signals and found that its traffic spiked whenever the smart film flickered.

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For people without such radio equipment, it’s also possible to intercept Wi-Fi signals with a laptop or computer with a wireless card, says Simon Birnbach, a computer scientist at the University of Oxford not involved in the work.

In another test, a drone recorded someone wearing a strand of LED lights from about 20 meters’ distance. At five-second intervals, the person either flipped the LED lights on and off, or left them off. The drone camera’s data stream peaked whenever the LED lights flickered.

This strategy to discern a drone camera’s target is “a very cool idea,” says Thomas Ristenpart, a computer scientist at Cornell University not involved in the work. But the researchers need to test whether the method works in a wider range of settings and find ways to alter a drone’s view without cumbersome equipment, he says. “I don’t think anyone is going to want to wear a [light-up] shirt on the off chance a drone may fly by.”

Javaid agrees that this prototype system must be made more user-friendly to achieve widespread use. For home security, he imagines a small device stuck to a window that flashes a light and intercepts a drone’s Wi-Fi signals whenever it detects one nearby. The device could alert the homeowner if a drone is found scoping out the house.

Still, identifying a nosy drone may not always be enough to know who’s flying it. “It’s sort of the equivalent of knowing that an unmarked van pulled up and waited outside of your house,” says Drew Davidson, a computer scientist at Tala Security, Inc. in Dallas, who was not involved in the study. “Better to know than not, but not exactly enough for the police to find a suspect.”

Something is giving small, pristine stars extra lithium. A dozen newly discovered stars contain more of the element than astronomers can explain.

Some of the newfound stars are earlier in their life cycles than stars previously found with too much lithium, researchers report in the Jan. 10 Astrophysical Journal Letters. Finding young lithium-rich stars could help explain where the extra material comes from without having to tinker with well-accepted stellar evolution rules.

The first stars in the Milky Way formed from the hydrogen, helium and small amounts of lithium that were produced in the Big Bang, so most of this ancient cohort have low lithium levels at the surface (SN: 11/14/15, p. 12). As the stars age, they usually lose even more.
Mysteriously, some aging stars have unusually high amounts of lithium. About a dozen red giant stars — the end-of-life stage for a sunlike star — have been spotted over the last few decades with extra lithium at their surfaces. It’s not enough lithium to explain a different cosmic conundrum, in which the universe overall seems to have a lot less lithium than it should (SN: 10/18/14, p. 15). But it’s enough to confuse astronomers. Red giants usually dredge up material that is light on lithium from their cores, making their surfaces look even more depleted in the element.

Finding lithium-enriched red giants “is not expected from standard models of low-mass star evolution, which is usually regarded as a relatively well-established field in astrophysics,” says astronomer Wako Aoki of the National Astronomical Observatory of Japan in Tokyo. A red giant with lots of lithium must have had a huge amount of lithium in its former life, or imply a tweak is needed to some fundamental rule of stellar evolution.

Aoki and his colleagues used the Subaru Telescope in Hawaii to find the 12 new lithium-rich stars, all about 0.8 times the mass of the sun. Five of the stars seem to be relatively early in their life cycles — a little older than regular sunlike stars but a little younger than red giants.
That suggests lithium-rich stars somehow picked up the extra lithium early in their lives, though it’s not clear from where. The stars could have stolen material from companion stars, or eaten unfortunate planets (SN: 5/19/01, p. 310). But there are reasons to think they did neither — for one thing, they don’t have an excess of any other elements.

“This is a mystery,” Aoki says.

Further complicating the picture is the possibility that the five youngish stars could be red giants after all, thanks to uncertainties in the measurements of their sizes, says astronomer Evan Kirby of Caltech. Future surveys should check stars that are definitely in the same stage of life as the sun.

Still, the new results are “tantalizing,” Kirby says. “It’s a puzzle that’s been around for almost 40 years now, and so far there’s no explanation that has satisfying observational support.”