The Big Bang may not have been the absolute beginning of everything. Instead, a controversial cosmological model suggests it was a boundary separating our universe from a mirror universe where time runs in the opposite direction. Developed by Neil Turok, Latham Boyle, and colleagues at the Perimeter Institute, the idea starts with a striking feature of the early cosmos. Soon after the Big Bang, the universe was remarkably simple: space was nearly flat, filled mostly with radiation, and accurately described by the standard Friedmann-Robertson-Walker model. Its tiny density fluctuations were almost perfectly scale-invariant and Gaussian, with no evidence of primordial vector or tensor disturbances. For decades, cosmologists have explained these conditions with cosmic inflation, a brief period of extremely rapid expansion before the hot Big Bang. Turok and Boyle propose a different approach. Rather than introducing an earlier inflationary phase, they extend the laws of physics smoothly through the Big Bang itself and require the universe to obey CPT symmetry, the principle that the laws of physics remain unchanged when charge, spatial coordinates, and the …

Orion is about as familiar as a patch of sky gets. Visible without a telescope, studied by nearly every major instrument ever pointed at the heavens, mapped and catalogued across centuries of astronomy. What could possibly be left to find? Quite a lot, it turns out. An international team led by Juan Diego Soler at the University of Vienna has produced the sharpest maps ever made of neutral atomic hydrogen in the Orion Nebula. The images look nothing like what the standard picture predicted. Expanding shells, previously invisible cavities, and a mysterious elongated structure of gas jutting outward from the main bubble—none of it was there in older observations. Moreover, the mass of the whole surrounding shell, which previous studies put at roughly one thousand times that of the Sun, now appears to be nearly ten times lower. That is not a small correction. It rewrites something fundamental about how efficiently young massive stars reshape the space around them. The Gas You Cannot See With Light Hydrogen is by far the most common element in …

A supernova remnant is supposed to be a rough neighborhood for a newborn star. Shock waves rip through space at thousands of kilometers per second. Cosmic rays and X-rays flood nearby gas. Rare elements get tossed into the surrounding clouds. Yet inside one of these violent leftovers, astronomers have found something unexpectedly delicate still holding together. Using the Atacama Large Millimeter/submillimeter Array, or ALMA, a team in Japan identified two warm, dense cocoons of gas around infant stars inside the supernova remnant RX J1713.7−3946. These objects, known as hot cores, are rich in molecules linked to the chemistry of star and planet formation. According to the team, this is the first time hot cores have been detected inside a supernova remnant. The finding, published in The Astrophysical Journal, suggests that even after a massive nearby star explodes, some newborn stars may stay wrapped tightly enough in their natal material to protect a surprisingly rich chemical inventory. “These observations indicate that even in the harsh environment of a supernova remnant, newborn stars can remain well protected …

Not everyone who wants to go to Mars needs to leave Earth to help get humanity there. NASA is recruiting volunteers to spend a full year sealed inside a pair of connected habitats at Johnson Space Center in Houston, living out a simulated trip to the Moon or Mars without the rocket. The agency wants four people willing to eat, sleep, work, and conduct fake spacewalks in isolation for twelve months, beginning no earlier than August 2027, all in the name of understanding what extended deep-space travel does to the human body and mind. The mission, called the Moon and Mars Exploration Analog, is the first ground-based simulation to combine two phases of an actual interplanetary mission into one continuous campaign. Previous analog programs tackled transit and surface operations separately. This one runs them back to back. Two Habitats, One Very Long Year The first phase puts crew members inside a modified version of the HERA habitat, a two-story structure that NASA has used for years to study how small groups function in confined quarters. …

Comet 3I/ATLAS arrived from beyond the Solar System carrying a chemical story unlike anything astronomers had measured before. In the gas around it, they found isotope ratios that do not match the pattern seen in known Solar System comets, raising a striking possibility: this visitor may have formed around a star far older than the Sun. That makes 3I/ATLAS more than a passing curiosity. It may be a surviving fragment from a planetary system that took shape when the universe was younger and less chemically enriched than it is today. The object is only the third known interstellar visitor ever detected, following 1I/ʻOumuamua in 2017 and 2I/Borisov in 2019. But unlike those earlier objects, 3I/ATLAS proved bright enough for astronomers to probe in much greater detail. That brightness gave researchers a rare chance to examine its isotopic makeup, the relative amounts of different forms of the same element, and use those ratios as clues to where the comet formed. “They are sort of fossils from a planetary formation process that happened very far away, but …

The ozone layer’s most famous wound opened over Antarctica, but the damage may have started much earlier, and somewhere else entirely. A new modeling study suggests the first detectable sign of human-caused ozone loss appeared in 1957, nearly three decades before the Antarctic ozone hole was reported. The earliest signal did not show up near the poles. It emerged in the tropical upper stratosphere, in a part of the atmosphere where natural variability is relatively quiet and small changes are easier to spot. That result surprised even Susan Solomon, the MIT atmospheric chemist whose work helped explain why chlorine from industrial chemicals was destroying ozone over Antarctica. “The fact that ozone depletion would have happened as early as the late 1950s, which is much earlier than I would have thought, just absolutely blew my mind,” Solomon said. The study, published in the Proceedings of the National Academy of Sciences, asked a counterfactual question: If scientists had possessed today’s monitoring tools and modeling techniques in the middle of the 20th century, when would the first human …

The Milky Way’s farthest spiral arms have long been sketched more from motion than measurement. Now three violent explosions far beyond our galaxy have helped redraw that map, showing that parts of the outer Milky Way sit farther away than astronomers thought. The work used the fading X-ray afterglow of three gamma-ray bursts, brief but extraordinarily bright blasts that erupted in distant galaxies. As that X-ray light crossed the Milky Way, some of it scattered off dust in the galaxy’s spiral arms, creating expanding rings that space telescopes could track. Those rings, the team found, offer a rare direct way to measure remote stretches of the galactic disk. That matters because getting your bearings inside the Milky Way is hard. Earth sits buried in the galaxy’s disk, not above it, and thick dust clouds block many lines of sight. Astronomers have built galactic maps using tracers such as hydrogen gas, carbon monoxide, giant molecular clouds, H II regions, and methanol masers, but distances in the outer galaxy often depend on models of how the Milky …

GJ 3378b has moved closer to the kind of world astronomers most want to find: small, rocky, temperate, and near enough for future telescopes to inspect in far greater detail. The planet circles a red dwarf star about 25 light-years from Earth, in the northern constellation Camelopardalis. It sits in the star’s habitable zone, the range where temperatures could allow liquid water. And after a fresh look with the Hobby-Eberly Telescope at McDonald Observatory, researchers say the planet appears significantly lighter than earlier estimates suggested. That matters because mass helps determine what kind of world a planet is. A heavier planet is more likely to hold a thick envelope of gas. A lighter one, especially in this range, has better odds of being rocky. “Our mantra is ‘follow the water,’” said Paul Robertson, an astronomer at the University of California, Irvine, and lead author of the study published in The Astrophysical Journal. “It’s the one thing every known living thing on Earth needs, so that’s the first thing we look for when trying to find …

Space looks empty until you try to cross it. Far beyond Pluto, where sunlight is faint and the planets are long behind, NASA’s New Horizons spacecraft is moving through a region where the Sun’s outflow begins to lose its grip. There, a stream of charged particles called the solar wind is gradually slowing down. The new measurements help show why. The answer lies in a quiet, persistent encounter with material drifting in from interstellar space. A team led by Southwest Research Institute scientist Dr. Heather Elliott found that the solar wind measured by New Horizons at 58 astronomical units from the Sun was 13% to 15% slower than the solar wind measured near Earth, at 1 astronomical unit. That extends an earlier pattern. Previous measurements between 30 and 43 astronomical units had suggested a slowdown of about 5% to 10%. The change is not dramatic in the way a shock wave would be. But over those enormous distances, it matters. “As the solar wind travels away from the Sun at supersonic speeds, roughly 1 million …

A large asteroid does not need to hit Earth to expose a hard truth: the most dangerous space rocks may be the ones spotted too late. That is the problem behind a new analysis of how to stop the biggest threats. It is also why older interception ideas may not be enough when time is short. The study examines near-Earth asteroids more than 100 meters wide, objects large enough to cause destruction on an intercontinental or even global scale. Some recent flybys have underscored the risk. The asteroid 2019 OK, estimated at 57 to 130 meters across, passed Earth in 2019 at 24.5 kilometers per second. It came within 72,000 kilometers. On June 29, 2024, asteroid 2024 MK, about 150 meters wide, passed at a distance of 295,000 kilometers. The paper notes that 2024 MK was identified only 13 days in advance. That short warning time changes everything. Slower methods, such as using small forces over long periods or relying on a conventional kinetic impact, may not deliver enough energy to shift the path of …