Free Republic

Explanation: Comet Lemmon is brightening and moving into morning northern skies. Besides Comet SWAN25B and Comet ATLAS, Comet C/2025 A6 (Lemmon) is now the third comet currently visible with binoculars and on long camera exposures. Comet Lemmon was discovered early this year and is still headed into the inner Solar System. The comet will round the Sun on November 8, but first it will pass its nearest to the Earth -- at about half the Earth-Sun distance -- on October 21. Although the brightnesses of comets are notoriously hard to predict, optimistic estimates have Comet Lemmon then becoming visible to...

A lunar impact could generate debris that damages key satellites, the ISS…and potentially any lunar installations that had been constructed as part of the new space race. Asteroid 2024 YR4 is a near-Earth object approximately 53–67 meters wide that was discovered in December 2024. While initial models suggested a small chance of Earth impact, refined tracking now indicates that there is no risk to Earth, but about a 4% probability that it will strike the Moon on December 22, 2032. Earlier this year, asteroid 2024 YR4 drew global attention when its estimated chance of striking Earth in 2032 reached 3%....

The autumnal equinox occurs in September each year, and in the northern hemisphere the date marks the end of summer and beginning of autumn.

We’re gonna need a bigger telescope. Scientists have discovered that the 3I/ATLAS — a Manhattan-sized interstellar object that potentially has alien tech — is much larger than previously thought, according to a new report. First discovered by NASA on July 1, the cosmic anomaly has been under watch by Harvard astrophysicist Avi Loeb and his team as it shoots across the solar system. The object, which is believed to be a comet, reportedly has interstellar origins, making it the third ever object from beyond the solar system ever detected after ‘Oumuamua, which was discovered in 2017, and 2I/Borisov in 2019....

Explanation: It may look like these comets are racing, but they are not. Comets C/2025 K1 ATLAS (left) and C/2025 R2 SWAN (right) appeared near each other by chance last week in the featured image taken from France's Reunion Island in the southern Indian Ocean. Fainter Comet ATLAS is approaching our Sun and will reach its closest approach in early October when it is also expected to be its brightest -- although still only likely visible with long exposures on a camera. The brighter comet, nicknamed SWAN25B, is now headed away from our Sun, although its closest approach to Earth...

The mysterious comet 3I/ATLAS appears to be extremely large, making it orders of magnitude more massive than two other confirmed interstellar objects observed in our solar system in years past, a new study suggests. Based on a new analysis of the most precise tracking data collected on the object since its discovery in July, the interstellar comet appears to be “anomalously massive,” a finding that raises new questions regarding our expectations about interstellar objects that occasionally traverse our solar system. The research was detailed in a new paper by Richard Cloete, Peter Vere, and Harvard astronomer Avi Loeb, which places...

Explanation: What is creating these unusual spots? Light-colored spots on Martian rocks, each surrounded by a dark border, were discovered last year by NASA's Perseverance Rover currently exploring Mars. Dubbed leopard spots because of their seemingly similarity to markings on famous Earth-bound predators, these curious patterns are being studied with the possibility they were created by ancient Martian life. The pictured spots measure only millimeters across and were discovered on a larger rock named Cheyava Falls. The exciting but unproven speculation is that long ago, microbes generated energy with chemical reactions that turned rock from red to white while leaving...

The IMAP mission will chart the boundary of the heliosphere, a bubble inflated by the solar wind that shields our solar system from galactic cosmic rays...NOAA's SWFO-L1 is designed to be a full-time operational space weather observatory...The Carruthers Geocorona Observatory is the first mission dedicated to recording changes in the outermost layer of our atmosphere, the exosphere...

Explanation: On the morning of September 24 a rocket crosses the bright solar disk in this long range telescopic snapshot captured from Orlando, Florida. That's about 50 miles north of its Kennedy Space Center launch site. This rocket carried three new space weather missions to space. Signals have now been successfully acquired from all three - NASA's Interstellar Mapping and Acceleration Probe, NASA’s Carruthers Geocorona Observatory, and the National Oceanic and Atmospheric Administration (NOAA) Space Weather Follow-On Lagrange 1 (SWFO-L1) - as they begin their journey to L1, an Earth-Sun lagrange point. L1 is about 1.5 million kilometers in the...

A New Asteroid Crater Was Just Discovered Under The Sea | 8:01 OzGeology | 149K subscribers | 106,346 views | September 24, 2025 00:00-00:36 - The Silverpit Impact Crater Is First Discovered 00:37-00:56 - The Silverpit Mystery 00:57-02:07 - The Silverpit Impact Structure 02:08-03:00 - The Geological Debate 03:01-03:57 - The Recent Data That Led To The Discovery 03:58-04:31 - What The Asteroid Collision Would've Looked Like 04:32-04:50 - The Mega Tsunami The Collision Generated 04:51-05:25 - Why The Silverpit Crater Has Survived Intact 05:26-06:11 - The Chance Discovery 06:12-06:43 - Life During The Eocene 06:44-07:16 - The Questions That...

NASA has just pulled off a deep space first that could forever change the way we communicate beyond Earth. A silent beam of light traveled an unimaginable distance—and then something remarkable happened. In a major step toward high-speed space internet, NASA has successfully exchanged laser-encoded messages with a spacecraft over 350 million kilometers from Earth. The story, reported by IFLScience, marks the success of one of the most ambitious space communication tests ever attempted—and may open the door to a future where humans on Mars send back livestreams in real time.... To carry out this experiment, NASA’s Jet Propulsion Laboratory...

Explanation: A new visitor to the inner Solar System, comet C/2025 R2 (SWAN) sports a long ion tail extending diagonally across this almost 7 degree wide telescopic field of view recorded on September 21. A fainter fellow comet also making its inner Solar System debut, C/2025 K1 (ATLAS), can be spotted above and left of SWAN's greenish coma, just visible against the background sea of stars in the constellation Virgo. Both new comets were only discovered in 2025 and are joined in this celestial frame by ruddy planet Mars (bottom), a more familiar wanderer in planet Earth's night skies. The...

Explanation: This year Saturn was at opposition on September 21, opposite the Sun in planet Earth's sky. At its closest to Earth, Saturn was also at its brightest of the year, rising as the Sun set and shining above the horizon all night long among the fainter stars of the constellation Pisces. In this snapshot from the Qinghai Lenghu Observatory, Tibetan Plateau, southwestern China, the outer planet is immersed in a faint, diffuse oval of light known as the gegenschein or counter glow. The diffuse gegenschein is produced by sunlight backscattered by interplanetary dust along the Solar System's ecliptic plane,...

Explanation: It was the strongest gravitational wave signal yet measured -- what did it show? GW250114 was detected by both arms of the Laser Interferometer Gravitational-wave Observatory (LIGO) in Washington and Louisiana USA earlier this year. Analysis showed that the event was created when two black holes, each of mass around 33 times the mass of the Sun, coalesced into one larger black hole with a mass of around 63 solar masses. Even though the event happened about a billion light years away, the signal was so strong that the spin of all black holes, as well as initial ringing...

Explanation: How massive can a normal star be? Estimates made from distance, brightness and standard solar models had given one star in the open cluster Pismis 24 over 200 times the mass of our Sun, making it one of the most massive stars known. This star is the brightest object located in the central cavity near the bottom center of the featured image taken with the Webb Space Telescope in infrared light. For comparison, a rollover image from the Hubble Space Telescope is also featured in visible light. Close inspection of the images, however, has shown that Pismis 24-1 derives...

A new study explains that time travel itself eventually leads to a reality without it. Is time travel truly possible? The prospect presents its fair share of paradoxes. Of course, there are famous logical examples, such as the Grandfather paradox, which explores what would happen if a time traveler killed their grandparent before their parent was conceived (an idea not so far removed from the plot of the sci-fi great Back to the Future). Other paradoxes are more concerned with mathematical or physical impossibilities within our current understanding of space-time—even though time travel is theoretically possible through phenomena like closed...

Explanation: On Saturn, the rings tell you the season. On Earth, today marks an equinox, the time when the Earth's equator tilts directly toward the Sun. Since Saturn's grand rings orbit along the planet's equator, these rings appear most prominent -- from the direction of the Sun -- when the spin axis of Saturn points toward the Sun. Conversely, when Saturn's spin axis points to the side, an equinox occurs, and the edge-on rings are hard to see from not only the Sun -- but Earth. In the featured montage, images of Saturn between the years of 2020 and 2025...

Earlier this year, astronomers watched a burst of high-energy light that kept roaring back for nearly a full day. Gamma-ray bursts (GRBs) are usually sorted into short and long events, and they generally last from milliseconds to a few minutes. In a new study, researchers describe a signal named GRB 250702B that fired three distinct times over a few hours, with soft X-rays flaring even earlier. The team also reported evidence that the source lies beyond our galaxy. Lead researchers Antonio Martin-Carrillo of University College Dublin (UCD) and Andrew J. Levan of Radboud University (RU) directed the effort. Their teams...

Explanation: Does the Sun set in the same direction every day? No, the direction of sunset depends on the time of the year. Although the Sun always sets approximately toward the west, on an equinox like tomorrow the Sun sets directly toward the west. After tomorrow's September equinox, the Sun will set increasingly toward the southwest, reaching its maximum displacement at the December solstice. Before tomorrow's September equinox, the Sun had set toward the northwest, reaching its maximum displacement at the June solstice. The featured time-lapse image shows seven bands of the Sun setting one day each month from 2019...

Astronomers have been fascinated after spotting an object earlier this year that came from interstellar space as is now hurtling through our inner solar system. Since then, they've been using powerful telescopes to study the mysterious object, trying to understand its unusual composition and exact origins. Most agree that it's probably a comet, albeit an unusual one, though at least one has posited that it could be a remnant of an advanced extraterrestrial civilization — a colorful claim, but one that NASA has disputed as a flight of fancy. Regardless, it's an interesting visitor. In a paper presented at the...