Most alien-signal searches listen to a narrow part of the radio spectrum, but astronomers are now testing higher frequencies that have barely been explored. A first search using archived ALMA telescope data found no alien signals, but it showed that existing observations can still be reused for SETI. Computer models suggest past surveys may have covered more than 6 million stars, far more than the roughly 288,000 previously counted. The search for alien radio signals has spent decades listening in a familiar part of the spectrum. A first-of-its-kind survey now suggests that unexplored higher frequencies could widen the hunt, while revealing how many stars may already have been examined without anyone realizing it. Most radio searches for extraterrestrial intelligence, or SETI, concentrate between 1.42 and 1.66 gigahertz. This quiet region is called the “water hole” because it lies between natural radio emissions from hydrogen and hydroxyl, the components of water. Astronomers have long considered it a logical meeting place for technologically advanced civilizations. Another society might recognize the same chemical landmarks and choose to transmit …

The Sun’s strongest space weather appears to stop suddenly at a specific point in each cycle. The number of sunspots at that moment may reveal how strong the following cycle will become. An early estimate suggests Solar Cycle 26 could be moderate, but a clearer prediction is still about two years away. The Sun does not ease quietly from one activity cycle into the next. Its most violent space weather appears to stop abruptly, and that sudden change may offer an unusually early glimpse of what comes next. A new forecasting method uses the number of sunspots present at this “switch-off” point to estimate the strength of the following solar cycle. Researchers say the approach could predict peak activity six or seven years in advance. Their first projection for Solar Cycle 26 points to a moderate cycle, with a peak sunspot number of about 100 to 120. That would make it similar to, or weaker than, the current Solar Cycle 25. The estimate remains highly uncertain. The switch-off point for Cycle 25 is still about …

NASA’s James Webb Space Telescope discovered Beta Pictoris d, a third giant planet orbiting the young star Beta Pictoris, 63 light-years from Earth. The system is now only the second known to contain at least three directly imaged planets. Astronomers identified the planet through its atmospheric “barcode,” including absorption patterns from carbon monoxide, methane and water vapor, rather than relying solely on a visible point of light hidden within the star’s bright debris disk. Beta Pictoris d is estimated to have two to four times Jupiter’s mass and may orbit more than 30 astronomical units from its star, placing it beyond Beta Pictoris b but inside the debris disk’s inner edge. The planet’s gravity may help explain gaps, clumps and other unusual structures in the disk. Its discovery also shows that spectroscopy can reveal planets concealed by dust and scattered starlight while simultaneously measuring their chemistry, temperature and motion. Beta Pictoris d spent years concealed inside one of the brightest debris disks astronomers know. NASA’s James Webb Space Telescope found it not as a clean …

Silver makes up only a minute fraction of the Sun, but its abundance carries clues about events that shaped the Milky Way. For years, measurements suggested that some of that silver was missing. Researchers at Uppsala University have now calculated that the Sun contains 55 percent more silver than previously estimated. Their result brings the solar value into much closer agreement with silver measured in chemically primitive meteorites. The difference arose from the way astronomers modeled the Sun’s atmosphere and the behavior of silver atoms within it. Earlier calculations assumed conditions that were simpler than the physical environment where sunlight forms. “The new knowledge about the sun’s composition is important for the understanding of other stars, planets and cosmic material, because the sun is one of astronomy’s key reference points,” said Sema Caliskan, who conducted the work during her doctoral studies at Uppsala University’s Department of Physics and Astronomy. Sunlight carries a chemical fingerprint Hydrogen and helium account for almost all the Sun’s mass. Heavier elements, including carbon, iron and silver, make up only about …

Nearly half a century after NASA’s Viking landers touched Mars, one question shadows their experiments: Did they miss life, or did they destroy it while trying to prove it was there? Dirk Schulze-Makuch, an astrobiologist at Technical University Berlin, has proposed that Viking’s life-detection tests may have exposed native Martian microbes to lethal amounts of liquid water. Organisms adapted to an extremely dry world, he argues, might not have survived the treatment intended to reveal their metabolism. “NASA may have unwittingly uncovered life on Mars nearly 50 years ago and accidentally destroyed it before understanding its significance,” Schulze-Makuch argues. The idea challenges the assumptions behind the 1976 mission. Viking 1 and Viking 2 carried four experiments designed to search Martian soil for organic compounds, metabolic activity and changes associated with living organisms. Four tests produced an uneven picture The Gas Chromatograph Mass Spectrometer heated soil samples, separated the released compounds and identified molecules by their mass signatures. It found no organic molecules, a result that strongly shaped the original conclusion that Mars was hostile to …

The Milky Way may not always have faced the same direction. New simulations suggest its stellar disc could have swung through space by more than 90 degrees after an ancient collision, helping explain why the galaxy’s surrounding halo turns so slowly. Most stars in the Milky Way, including the Sun, occupy its flat spiral disc. Far beyond that structure lies a much larger stellar halo. It contains relatively few stars, many of which formed inside smaller galaxies before mergers drew them into the Milky Way. A Durham University team examined 25 Milky Way-like galaxies in the Auriga suite of cosmological simulations. These models followed galactic growth across billions of years, including collisions, mergers and changes in stellar motion. The galaxies with the slowest rotating stellar haloes shared two traits. Each had experienced a major head-on merger, and each had undergone what astronomers call a disc flip. A galaxy can change its direction A disc flip occurs when a galaxy’s stellar disc changes orientation by more than 90 degrees. Its overall plane turns enough that stars …

Dark matter appears to hold galaxies together, yet it has never shown itself directly. A new theory suggests the missing substance may owe its elusive behavior to the geometry of a hidden fifth dimension. The framework, developed at the University of Sheffield and published in Physical Review D, connects two major ideas in fundamental physics: dark matter and extra dimensions. It proposes that dark matter particles and force-carrying dark photons occupy an additional dimension beyond the four dimensions people experience. The shape of that dimension could arrange the particles’ masses in a precise relationship. That alignment would produce a resonance, greatly strengthening dark matter interactions under particular conditions. The effect resembles a musical instrument vibrating strongly when it encounters the right note. In this case, however, the resonance would involve particles whose masses naturally fall into step. Geometry could replace artificial tuning Dark matter has never been detected directly, but its gravitational influence appears across the universe. Galaxies rotate as though they contain far more matter than astronomers can see, while clusters and large cosmic …

A rocky planet about 49 light-years from Earth appears to have held onto an atmosphere, despite orbiting a red dwarf capable of stripping gases into space. The evidence comes from helium escaping high above the planet, LHS 1140 b. The detection marks the clearest atmospheric signal yet from a rocky planet in the habitable zone of another star. That region allows temperatures that could support liquid water, although the observations do not establish that water or life exists there. “This is the first time anyone has found an atmosphere on a rocky planet in the habitable zone of another star,” Cherubim said. Atmospheres can regulate climate, shield a surface from damaging radiation and allow liquid water to persist. Yet astronomers have struggled to determine whether small, rocky planets around red dwarfs can retain them for billions of years. A nearby super-Earth offered a rare target LHS 1140 b circles its star every 24.7 days. It has 5.6 times Earth’s mass and a radius about 1.7 times larger than Earth’s. Those measurements are consistent with a …

The Milky Way and Andromeda have appeared locked on a destructive course for decades. Now, thousands of simulations suggest their collision is not destiny, but a contest between gravity, uncertain measurements and two smaller neighboring galaxies. Astronomers have known for a century that Andromeda is moving toward the Milky Way. Because the two spiral galaxies dominate the Local Group, which contains about 100 smaller galaxies, their approach became one of astronomy’s most familiar forecasts. The standard account held that the pair would collide in five billion years. Gravity would distort both galaxies and eventually combine them into a large elliptical system sometimes nicknamed “Milkomeda.” A forecast built from 50,000 possible futures A team led by Till Sawala of the University of Helsinki modeled the Milky Way, Andromeda, the Triangulum galaxy M33 and the Large Magellanic Cloud. The team used measurements from the Hubble Space Telescope and the European Space Agency’s Gaia mission. The observations track galactic positions and motion across the sky. Such sideways motion is exceptionally difficult to measure at galactic distances. Even small …

The Big Bang may not mark the absolute beginning of everything. A controversial cosmological model instead treats it as a boundary, with our universe on one side and a time-reversed anti-universe on the other. The proposal, developed by Neil Turok, Latham Boyle and colleagues from the Perimeter Institute, begins with a simple fact about the early cosmos. Soon after the Big Bang, space appears to have been flat, radiation dominated and governed by the standard Friedmann–Robertson–Walker description. Its small density fluctuations were nearly scale invariant and Gaussian, with no detected primordial vector or tensor disturbances. Inflation has long served as the leading explanation for those conditions. It proposes that the universe passed through a burst of accelerated expansion before the hot, radiation-filled phase familiar to cosmologists. Turok and Boyle argue that another possibility deserves attention. Instead of adding an earlier inflationary stage, they extend the equations across the Big Bang and impose CPT symmetry, a central principle in physics. A universe reflected through the Big Bang CPT symmetry combines three transformations. Charge conjugation swaps matter …