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After nearly 30 years, NASA realized this near-Earth asteroid is actually a comet. The discovery may help us defend the planet some day

A near-Earth object that astronomers believed was an asteroid for nearly three decades has been unmasked as a faint, active comet, revealing a case of cosmic mistaken identity that could help improve planetary defense. The object, known since its discovery in 1998 as 1998 SH2, appeared to be an ordinary asteroid . It follows a 4.5-year orbit around the sun and showed no obvious signs of cometary activity, such as the glowing coma or tail produced when sunlight vaporizes surface ice. However, during a close pass about 2 million miles (3 million kilometers) from Earth in August 2025, researchers using NASA's Deep Space Network planetary radar system noticed something unexpected: The object wasn't where orbital predictions said it should be, according to a statement from the space agency. That discrepancy prompted scientists to take a closer look, and what they found surprised them. Using ...

NASA's Roman Space Telescope could reveal black holes ripping up stars. It's set to launch Aug. 30

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The launch of NASA's next super telescope, the Nancy Grace Roman Space Telescope (Roman), may mean there is nowhere left for violent black holes to hide. In fact, these cosmic cannibals may not even be able to hide from Roman at "cosmic noon," a period of the universe's history that occurred around 11 billion to 12 billion years ago. The study of these gory stellar events so early in the history of the universe could help reveal how supermassive black holes grew so big, so rapidly. Occurrences of black holes ripping apart stars are called tidal disruption events (TDEs), and they happen when an unfortunate star's orbit brings it too close to the immense gravitational influence of a supermassive black hole. This simultaneously squashes and squeezes the star in a process called "spaghettification," with plasma pasta wrapping around the black hole and being fed gra...

Alien life likely can't survive on exoplanets smaller than Mars, scientists say

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A rocky planet orbiting in the habitable zone of a sun-like star may look like a perfect place for life to thrive — but not if it's too small to hold onto its atmosphere. So, we may wonder: How much smaller Earth could be and still have its delightfully breathable atmosphere ? How small could an exoplanet be to sustain life as we know it? With these questions in mind, University of California Riverside planetary scientist Michelle Hill and her colleagues recently simulated what happens to the atmospheres of different sizes of rocky worlds. The worlds tested were similar to Earth and orbited in the habitable zones around sun-like stars . It turns out for a world to maintain an atmosphere long enough for life to gain a foothold (a few billion years at minimum), it needs to be at least as big as Mars . Narrowing down the search for life The habitable zone — the area around a star where tempera...

Space Force orders 36 more Golden Dome missile-tracking satellites, for $1.75 billion

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The U.S. Space Force is adding three dozen spacecraft to its growing constellation designed to detect and track incoming missiles from orbit. The Space Development Agency (SDA) announced the agreements, worth a combined $1.75 billion, on July 14, naming L3Harris Technologies and Sierra Space as the recipients. Each company will provide 18 Accelerated Missile Defense Tranche 3 (AMDT3) spacecraft, for a total of 36 satellites that will grow the SDA Proliferated Warfighter Space Architecture's Tranche 3 Tracking Layer constellation, part of the Trump Administration's Golden Dome initiative. All 36 are expected to be ready for launch by the end of 2028, according to an SDA statement . SDA's contracts with each company differ slightly. One calls for "18 missile warning and missile tracking variant space vehicles" from Sierra Space, while the other requests "18 missile defe...

SpaceX Falcon 9 rocket sends Starlink satellites to orbit a day after rare launch abort

Twenty-four Starlink satellites reached low Earth orbit on Tuesday (July 21), a day later than originally scheduled due to a last-second rocket engine abort. SpaceX at first tried to launch the broadband internet relay units on a Falcon 9 rocket on Monday morning (July 20), but an unexpected engine cutoff at the point of ignition scrubbed the day's attempt . The company did not provide a reason for the abort. By Tuesday, whatever the problem was had been addressed and the Falcon 9 was ready to fly. It liftoff off at 10:49 a.m. EDT (1449 GMT; 7:49 a.m. PDT local time) from Space Launch Complex 4 East at Vandenberg Space Force Base in California. About an hour later, after a normal ascent, the new Starlink batch ( Group 17-39 ) were deployed into their intended orbit. "Deployment of 24 Starlink satellites confirmed," SpaceX posted on social media . Previous Booster B1082 missions: ...

Billions of miles and thousands of years in the making: This is the life of a Perseid shooting star

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Picture it: A slash of vivid green light splits the starry sky. There for a moment and then gone, leaving nothing but a short-lived glowing trail and a moment of pure joy. You've finally caught it, your first Perseid shooting star of the season. What you saw was the final moment of a story billions of miles and thousands of years in the making. A story that began with that same shooting star locked inside the icy body of the wandering comet 109P/Swift-Tuttle. The 16-mile-wide (26 kilometer) giant of a comet spends its life journeying back and forth between the outer and inner solar system, where its frigid body is heated by the sun , triggering dramatic outbursts of activity. While in close proximity to our star, ice near to the surface of the comet is transformed into gas, skipping the water stage entirely as it escapes out into the vastness of interplanetary space. Embedded within that i...

Scientists discover mystery molecule on Pluto and Saturn's moon Titan: 'We cannot say what it is'

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Separated by billions of miles and shaped by very different environments, Saturn's smoggy moon Titan and the dwarf planet Pluto have, on paper, little in common. Titan is a geologically active world cloaked in an atmosphere denser than Earth's, its landscape shaped by seas of liquid methane and vast dunes built from organic particles that rain out of its skies. Pluto, by contrast, is a frigid outpost with a tenuous atmosphere hovering above an icy, frozen surface. Yet, observations from the James Webb Space Telescope (JWST) have revealed these two disparate worlds share an identical, unexplained infrared signature on their surfaces — a sign that similar chemistry may be unfolding on both worlds despite their stark differences, scientists say. Detailed in a new study , the feature appears at precisely the same infrared wavelength on both Titan and Pluto, indicating that it absorbs light...