Occasional flashes light up Venus’ shroud of clouds. Previous analyses have hinted that the bursts of light could be lightning in the hellish world’s atmosphere. But a new study suggests most of the flashes may be nothing more than the brief yet brilliant blazes of meteors.

With upcoming missions planned for Venus, scientists are eager to figure out the light’s origin (SN: 6/2/21). If the flashes are lightning, the electrical phenomenon could pose risks to future probes dropping through the Venusian atmosphere or carried by balloons for extended periods in the planet’s clouds, says Claire Blaske, a planetary scientist now at Stanford University. Small meteors that burn up in the atmosphere, however, wouldn’t pose much of a danger.

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Previous landers on Venus have often detected electromagnetic static similar to the type picked up on AM radio and caused by lightning during thunderstorms on Earth, Blaske says. And orbiters and Earth-based telescopes have discerned brief, bright flashes in the atmosphere.

But the static and optical flashes have never been detected simultaneously, Blaske says. And, notes Paul Byrne, a planetary scientist at Washington University in St. Louis who was not involved in the study, “it’s not clear there is the potential for lightning on Venus” given how little is known about the dynamics of its atmosphere.

Blaske, then at Arizona State University in Tempe, and her colleagues wondered whether meteors could be masquerading as lightning on Venus. Two surveys counted the flashes of light: one by a telescope on Arizona’s Mount Bigelow and one by instruments aboard Japan’s Akatsuki orbiter (SN: 12/8/15).

Given that data, there are probably between 10,000 and 100,000 of these flashes each year, the researchers report in the September Journal of Geophysical Research: Planets.

That may seem like too many flashes to all be caused by meteors. After all, Venus is a slightly smaller cosmic target than Earth. But meteors there will be substantially brighter — and thus more noticeable — because they are traveling faster on average: The space rocks zip through Venus’ atmosphere at about 25 kilometers per second, compared with 20.3 kilometers per second for meteoroids entering Earth’s atmosphere. In part, that’s because Venus is traveling around the sun faster than Earth is.

Overall, these factors and others led Blaske and her colleagues to conclude that meteors could be numerous enough to account for most, if not all, of the flashes expected to occur in Venus’ atmosphere.

The team’s analysis “is convincing and does a nice job of establishing a plausible explanation for these flashes,” Byrne says. Future observations that simultaneously measure the flashes and electromagnetic static on Venus could help resolve the mystery. But other big questions remain. For example, it’s unknown whether Venus might experience a form of lightning, or other type of electrical discharge, in its carbon dioxide–rich atmosphere that isn’t accompanied by flashes of light but could still pose a risk to probes. More

Deploying a telescope in space is one thing. Making two of them deep under the sea is a task in a league of its own.

On a ship bobbing in the Mediterranean Sea, physicists — not typically known for their sea legs — brave weeklong voyages and rough waters, working around the clock to deploy the telescopes’ detectors.

The telescopes are designed to detect not light, but neutrinos. These subatomic particles are spewed at high energies from mysterious, unidentified realms of space. But such high-energy neutrinos are so rare, and so stealthy, that the detectors that study them must be enormous. So scientists are outfitting a cubic kilometer of the Mediterranean with light-collecting devices designed to snag them. More

McKenzie Prillaman is a science and health journalist based in Washington, DC. She holds a bachelor’s degree in neuroscience from the University of Virginia and a master’s degree in science communication from the University of California, Santa Cruz. She was the spring 2023 intern at Science News. More

If you want to be a successful star by making the minimum possible effort, aim for a surface temperature about a quarter of the sun’s. This is the temperature that a new study says separates red dwarf stars, which shine for a long time, from failed stars known as brown dwarfs.

It’s often hard to distinguish between red and brown dwarfs, because when young they both look the same: red and dim. But only red dwarfs are born with enough mass to sustain the same nuclear reactions that power stars like the sun. In contrast, brown dwarfs glow red primarily from the heat of their birth, but then their nuclear activity sputters out, causing them to cool and fade. Now astrophysicists Dino Hsu and Adam Burgasser at the University of California, San Diego and their colleagues have discerned the dividing line between the two types by exploiting how they move through space.

When a star is born, it revolves around the Milky Way’s center on a fairly circular orbit. Over time, though, gravitational tugs from giant gas clouds, spiral arms and other stars toss the stars to and fro. These perturbations make the stars’ orbits around the galactic center more and more elliptical. Thus, the orbital paths of stars can reveal their approximate age.

Most red dwarfs are fairly old; their predicted lifetimes are far longer than the current age of the universe. But because brown dwarfs cool and fade, any that are still warm are young. Thus, on average, red dwarfs should follow more elliptical orbits around the galaxy than young brown dwarfs do.

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In the new study, Hsu’s team analyzed 172 red and brown dwarfs of different spectral types, classifications based on the objects’ spectra that correlate with their surface temperatures. The researchers found that a sharp break in stellar motions separates warmer objects, which on average have more elliptical orbits and are older, from cooler ones, which on average have more circular orbits and are younger. This break appears at a spectral type between L4 and L6, corresponding to a surface temperature of about 1200° to 1400° Celsius (1,500 to 1,700 kelvins) — a fraction of the sun’s surface temperature of about 5500°C (5,800 K) — the team reports July 5 at arXiv.org.

Above this critical temperature, the dim suns are a mix of long-lived red dwarfs and young brown dwarfs. Below this temperature, though, “it’s all brown dwarfs,” Hsu says. These are the failed stars that are fated to fizzle out. The study will appear in a future issue of the Astrophysical Journal Supplement Series.

This new method for detecting the temperature boundary between red and brown dwarfs is intriguing, but the result is tentative, says Trent Dupuy, an astronomer at the University of Edinburgh who was not involved in the work. “It’s right around where you would expect,” he says. Dupuy says additional red and brown dwarfs should be observed to verify the finding.

Hsu agrees: “We need a more complete sample.” Expanding the sample will be both easy and hard. On the positive side, red dwarfs abound, outnumbering all other stellar types put together, and brown dwarfs are also common. On the negative side, though, red and brown dwarfs are faint. That makes measuring their Doppler shifts, which reveal how fast the objects move toward or away from Earth, a challenge. But knowing this motion is essential for calculating a star’s orbital path around the galaxy. More

An outburst from the super magnetic remains of a star suggests similar eruptions are behind some of the most powerful explosions in the universe. More