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    A map of 14 million galaxies and quasars deepens a dark energy mystery

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    ANAHEIM, Calif. — Change is in the air. New data strengthen a hint that dark energy, long thought to be constant force in the universe, might change over time.Dark energy explains the observation that the universe’s expansion rate is accelerating. But its origins are unknown. It’s typically expected to have constant density across the billions of years of the universe’s history. So when researchers from the Dark Energy Spectroscopic Instrument, or DESI, reported in 2024 that dark energy might vary over time based on their first year of data, it shook cosmology to its core.

    Many scientists expected that the standard picture would prevail with additional data from DESI. But that hasn’t happened. Instead, with three years of DESI data, the preference for a changing, or dynamical dark energy has grown. More

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      The nearest single star to Earth has four small planets

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      The nearest single star to the sun, Barnard’s star, has a brood of planets all its own. The red dwarf star, about six light-years from Earth, hosts four close-in planets each about two to three times the mass of Mars, astronomers report in the March 20 Astrophysical Journal Letters.

      “Barnard’s star has a long history of claimed detections, but none of them could be confirmed for a long time,” says astronomer Ritvik Basant of the University of Chicago. “It’s pretty exciting to know what’s orbiting the nearest stars.” More

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      New baby pictures of the universe deepen a cosmic mystery

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      The clearest pictures yet of the newborn cosmos strengthen the prevailing model of the universe but deepen a mystery about its expansion rate.

      Measurements of this rate, known as the Hubble constant, have produced conflicting results. Cosmologists hoped that new data from the Atacama Cosmology Telescope in Chile, which examines the oldest light in the universe, would clear things up and possibly reveal physics that diverges from the standard model of cosmology. But those results, announced March 18 in a webinar, only affirmed that model. More

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      A new iron compound hints ‘primordial’ helium hides in Earth’s core

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      Scientists have coaxed one of the universe’s most stubborn elements into a new compound.

      Formed under intense pressures, the newly discovered compound packs helium atoms into crystalline iron, researchers report February 25 in Physical Review Letters. The compound joins a short list of materials that incorporate the normally unreactive element and suggests that helium from the early solar system could be stored in the iron that makes up Earth’s core.

      Helium is one of the least reactive elements on the periodic table. Like the other noble gases, helium doesn’t gain or lose electrons easily and so does not normally form chemical compounds. But under extremely high pressures, helium can interact with a few other elements, including nitrogen and sodium — and now iron, research shows.

      An iron-helium compound, shown here in artificial color using a technique called secondary ion mass spectrometry, forms under high temperature and pressure. Blue and black areas mark the background, while the orange and red area represents the sample. ©2025 Hirose et al. CC-BY-ND

      To make the new iron compound, physicist Kei Hirose of the University of Tokyo and his colleagues squeezed iron and helium together in a diamond anvil cell, a high-pressure device that subjected the elements to pressures greater than 50,000 Earth atmospheres and temperatures above 1,000 degrees Celsius. This compression formed crystals containing both iron and helium.

      The volume of the crystal formed was larger than that of a crystal of pure iron at the same pressure, the team found. The researchers attributed this increase to helium ions packing into interstitial sites, the tiny spaces between iron atoms in the crystal. But the helium atoms don’t bond directly to iron — they’re too unreactive, even at extreme conditions. More

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      Uranus emits more heat than previously thought

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      Uranus emits more energy than it gets from the sun, two new studies report — a discovery that contradicts findings from the venerable Voyager spacecraft.

      When Voyager 2 sped past Uranus on January 24, 1986, the spacecraft detected no significant excess heat from the planet, making it seemingly unique among the sun’s giant worlds. However, new observations from space- and ground-based telescopes reveal that Uranus does in fact radiate more energy than sunlight provides, two research teams report in work submitted to arXiv.org in late February. More

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      Juno reveals dozens of lava lakes on Jupiter’s moon Io

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      Jupiter’s moon Io, the most volcanically active body in the solar system, is littered with hundreds of erupting volcanoes. High-resolution images now reveal several dozen lava lakes, researchers report in the February Journal of Geophysical Research: Planets. These lakes are far larger than their analogs on Earth, and their structure sheds light on how magma moves beneath the surface of Io. 

      Io’s volcanism — probably present over the moon’s entire 4.6-billion-year existence — was discovered when the Voyager spacecraft flew by in 1979. The volcanic activity is caused by the intense gravitational pulls of Jupiter and nearby moons, which deform Io by tens of meters. “This squeezing is heating the body,” says Alessandro Mura, a planetary scientist at Italy’s National Institute for Astrophysics in Rome. More

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      The Milky Way’s black hole is constantly bubbling

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      The black hole at the Milky Way’s heart neither slumbers nor sleeps. Instead, the ring of plasma surrounding it flickers constantly, punctuated by superbright flares, observations show.

      Astronomers used the James Webb Space Telescope to observe Sgr A* and its disk for hours at a time over the course of a year, from April 2023 through April 2024. These were the longest continuous observations yet of our galaxy’s central supermassive black hole.

      The telescope revealed a “constant bubbling” in the disk’s light that changed every few seconds or minutes, says astrophysicist Farhad Yusef-Zadeh of Northwestern University in Evanston, Ill. A few times a day, and seemingly at random, the disk would emit a blindingly bright flare, Yusef-Zadeh and colleagues report in the Feb. 20 Astrophysical Journal Letters. More

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      Citizen scientists make cosmic discoveries with a global telescope network

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      In January in Monterrey, Mexico, Iván Venzor was one of only a dozen people in the world to glimpse a potential Jupiter-sized planet crossing in front of a distant star.

      It happened too fast to see by eye — just a seconds-long flicker of light — but Venzor’s backyard telescope recorded the data, allowing him to verify the event with researchers. “I’m having dinner with my family, and I’m trying to discover a new kind of planet from a few meters outside,” says Venzor, a hobby astronomer. “It’s effortless.” More

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      The universe’s first supernovas probably produced water

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      The first generation of stars in the universe could have produced significant amounts of water upon their deaths, just 100 million to 200 million years after the Big Bang.

      Signatures of water have previously been observed some 780 million years after the Big Bang. But now, computer simulations suggest that this essential condition for life existed far earlier than astronomers thought, researchers report March 3 in Nature Astronomy.

      “The surprise was that the ingredients for life were all in place in dense cloud cores [leftover after stellar deaths] so early after the Big Bang,” says astrophysicist Daniel Whalen of the University of Portsmouth in England. More