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Mystery: Little Red Dots in the Early Universe

What are these little red dots (LRDs)? Nobody knows. Discovered only last year, hundreds of LRDs have now been found by the James Webb Space Telescope in the early universe. Although extremely faint, LRDs are now frequently identified in deep observations made for other purposes. A wide-ranging debate is raging about what LRDs may be and what importance they may have. Possible origin hypotheses include accreting supermassive black holes inside clouds of gas and dust, bursts of star formation in young dust-reddened galaxies, and dark matter powered gas clouds. The highlighted images show six nearly featureless LRDs listed under the JWST program that found them, and z, a distance indicator called cosmological redshift. Additionally, searches are underway in our nearby universe to try to find whatever previous LRDs might have become today.

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Red Sprites and Circular Elves Lightning over Italy

What's happening in the sky? Lightning. The most commonly seen type of lightning involves flashes of bright white light between clouds. Over the past 50 years, though, other types of upper-atmospheric lightning have been confirmed, including tentacled red sprites and ringed ELVES. Although both last only a small fraction of a second, sprites are brighter and easier to photograph than their more common electrical-discharge cousins. ELVES are rapidly expanding rings that are thought to be created when an electromagnetic pulse shoots upward from charged clouds and impacts the ionosphere, causing nitrogen molecules to glow. Capturing either form of lightning takes patience and experience -- capturing them both together, since they usually occur separately, is rare. The featured image is a frame from a video recorded from Possagno, Italy late last month above a distant thunderstorm over the Adriatic Sea.

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Sunset Solstice over Stonehenge

Yesterday the Sun reached its southernmost point in planet Earth's sky. Called a solstice, many cultures mark yesterday's date as a change of seasons -- from autumn to winter in Earth's Northern Hemisphere and from spring to summer in Earth's Southern Hemisphere. The featured image was taken just before the longest night of the 2025 northern year at Stonehenge in United Kingdom. There, through stones precisely placed 4,500 years ago, a 4.5 billion year old large glowing orb is seen setting. Even given the precession of the Earth's rotational axis over the millennia, the Sun continues to set over Stonehenge in an astronomically significant way.

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Solstice on a Spinning Earth

Can you tell that today is a solstice by the tilt of the Earth? Yes. At a solstice, the Earth's terminator -- the dividing line between night and day -- is tilted the most. The featured time-lapse video demonstrates this by displaying an entire year on planet Earth in twelve seconds. From geosynchronous orbit, the Meteosat 9 satellite recorded infrared images of the Earth every day at the same local time. The video started at the September 2010 equinox with the terminator line being vertical: an equinox. As the Earth revolved around the Sun, the terminator was seen to tilt in a way that provides less daily sunlight to the northern hemisphere, causing winter in the north. At the most tilt, winter solstice occurred in the north, and summer solstice in the south. As the year progressed, the March 2011 equinox arrived halfway through the video, followed by the terminator tilting the other way, causing winter in the southern hemisphere -- and summer in the north. The captured year ends again with the September equinox, concluding another of the billions of trips the Earth has taken -- and will take -- around the Sun. APOD Review: RJN's Night Sky Network Lecture

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A Solstice Sun Tattoo

The word solstice is from the Latin for Sun and to pause or stand still. And in the days surrounding a solstice the Sun's annual north-south drift in planet Earth's sky does slow down, pause, and then reverse direction. So near the solstice the daily path of the Sun through the sky really doesn't change much. In fact, near the December solstice, the Sun's consistent, low arc through northern hemisphere skies, along with low surface temperatures, has left a noticeable imprint on this path to the mountain town of Peaio in northern Italy. The morning frost on the road has melted away only where the sunlight was able to reach the ground. But it remains in the areas persistently shadowed by the fence, tattooing in frost an image of the fence on the asphalt surface.

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Long Shadows of the Montes Caucasus

When the Moon is at its first quarter phase, the Sun rises along the Montes Caucasus as seen from the lunar surface. The lunar mountain range casts the magnificent, spire-like shadows in this telescopic view from planet Earth, looking along the lunar terminator or the boundary between lunar night and day. Named for Earth's own Caucasus Mountains, the rugged lunar Montes Caucasus peaks, up to 6 kilometers high, are located between the smooth Mare Imbrium to the west and Mare Serenitatis to the east. Still mostly in shadow in this first quarter lunarscape, at the left (west) impact craters reflect the light of the rising Sun along their outer, eastern crater walls.

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Jupiter and the Meteors from Gemini

Jupiter, the Solar System's ruling gas giant, is the brightest celestial beacon at the center of this composite night skyscape. The scene was constructed by selecting the 40 exposures containing meteors from about 500 exposures made on the nights of December 13 and 14, near peak activity for this year's annual Geminid meteor shower. With each selected exposure registered in the night sky above Alentejo, Portugal, planet Earth, it does look like the meteors are streaming away from Jupiter. But the apparent radiant of the Geminid meteors is actually closer to bright star Castor, in the shower's eponymous constellation Gemini. In this frame that's just a little above and left of the Solar System's most massive planet. Still, the parent body of Geminid meteors is known to be rocky, near-Earth asteroid 3200 Phaethon. And the orbit of Phaethon itself is influenced by the gravitational attraction exerted by massive Jupiter, in concert with planets of the inner Solar System.

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W5: The Soul Nebula

Stars are forming in the Soul of the Queen of Aethopia. More specifically, a large star forming region called the Soul Nebula can be found in the direction of the constellation Cassiopeia, whom Greek mythology credits as the vain wife of a King who long ago ruled lands surrounding the upper Nile river. Also known as Westerhout 5 (W5), the Soul Nebula houses several open clusters of stars, ridges and pillars darkened by cosmic dust, and huge evacuated bubbles formed by the winds of young massive stars. Located about 6,500 light years away, the Soul Nebula spans about 100 light years and is usually imaged next to its celestial neighbor the Heart Nebula (IC 1805). The featured image, taken from near Nashville, Tennessee, USA, is a composite of 234 hours of exposures made in different colors: red as emitted by hydrogen gas, yellow as emitted by sulfur, and blue as emitted by oxygen. Explore the Universe: Random APOD Generator

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Andromeda and Sprites over Australia

What’s happening over that tree? Two very different things. On the left is the Andromeda galaxy, an object that is older than humanity and will last billions of years into the future. Andromeda (M31) is similar in size and shape to our own Milky Way Galaxy. On the right is a red sprite, a type of lightning that lasts a fraction of a second and occurs above violent thunderstorms. Red sprites were verified as real atmospheric phenomena only about 35 years ago. The tree in the center is a boab, which may live for as long as a thousand years. Boab trees grow naturally in Australia and Africa and are known for being able to store large amounts of water: up to 100,000 liters. The featured image was captured last month near Derby in Western Australia.

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Gemini Meteors over Snow Capped Mountains

Where are all of these meteors coming from? In terms of direction on the sky, the pointed answer is the constellation of Gemini. That is why the major meteor shower in December is known as the Geminids -- because shower meteors all appear to come from a radiant toward Gemini. Three dimensionally, however, sand-sized debris expelled from the unusual asteroid 3200 Phaethon follows a well-defined orbit about our Sun, and the part of the orbit that approaches Earth is superposed in front of the constellation of Gemini. Therefore, when Earth crosses this orbit, the radiant point of falling debris appears in Gemini. Featured here is a composite of many images taken over the past few days through dark skies from Slovakia and capturing the snow-covered peaks of the Belianske Tatra mountains Numerous bright meteor streaks from the Geminids meteor shower are visible. Orion is visible above the horizon, while the bright star nearest the radiant is Castor. APOD Review: RJN's Night Sky Network Lecture

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Juno Flyby of Ganymede and Jupiter

What would it be like to fly over the largest moon in the Solar System? In 2021, the robotic Juno spacecraft flew past Jupiter's huge moon Ganymede and took images that have been digitally constructed into a detailed flyby. As the featured video begins, Juno swoops over the two-toned surface of the 5,000-km wide moon, revealing an icy alien landscape filled with grooves and craters. The grooves are likely caused by shifting surface plates, while the craters are caused by violent impacts. Continuing on in its orbit, Juno then performed its 34th close pass over Jupiter's clouds. The digitally-constructed video shows numerous swirling clouds in the north, colorful planet-circling zones and bands across the middle -- featuring several white-oval clouds from the String of Pearls, and finally more swirling clouds in the south.

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Orion and the Ocean of Storms

On December 5, 2022, a camera on board the uncrewed Orion spacecraft captured this view as Orion approached its return powered flyby of the Moon. Beyond one of Orion's extended solar arrays lies dark, smooth, terrain along the western edge of the Oceanus Procellarum. Prominent on the lunar nearside Oceanus Procellarum, the Ocean of Storms, is the largest of the Moon's lava-flooded maria. The lunar terminator, the shadow line between lunar night and day, runs along the left of this frame. The 41 kilometer diameter crater Marius is top center, with ray crater Kepler peeking in at the edge, just right of the solar array wing. Kepler's bright rays extend to the north and west, reaching the dark-floored Marius. By December 11, 2022 the Orion spacecraft had returned to its home world. The historic Artemis 1 mission ended with Orion's successful splashdown in planet Earth's water-flooded Pacific Ocean. Watch: The Geminid Meteor Shower

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Northern Fox Fires

In a Finnish myth, when an arctic fox runs so fast that its bushy tail brushes the mountains, flaming sparks are cast into the heavens creating the northern lights. In fact the Finnish word "revontulet", a name for the aurora borealis or northern lights, can be translated as fire fox. So that evocative myth took on a special significance for the photographer of this northern night skyscape from Finnish Lapland near Kilpisjarvi Lake. The snowy scene is illuminated by moonlight. Saana, an iconic fell or mountain of Lapland, rises at the right in the background. But as the beautiful nothern lights danced overhead, the wild fire fox in the foreground enthusiastically ran around the photographer and his equipment, making it difficult to capture in this lucky single shot. Watch: The Geminid Meteor Shower

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Galaxies in the River

Large galaxies grow by eating small ones. Even our own galaxy engages in a sort of galactic cannibalism, absorbing small galaxies that are too close and are captured by the Milky Way's gravity. In fact, the practice is common in the universe and illustrated by this striking pair of interacting galaxies from the banks of the southern constellation Eridanus, The River. Located over 50 million light years away, the large, distorted spiral NGC 1532 is seen locked in a gravitational struggle with dwarf galaxy NGC 1531, a struggle the smaller galaxy will eventually lose. Seen nearly edge-on in this sharp image, spiral NGC 1532 spans about 100,000 light-years. The NGC 1532/1531 pair is thought to be similar to the well-studied system of face-on spiral and small companion known as M51.

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The Horsehead Nebula

Sculpted by stellar winds and radiation, this dusty interstellar molecular cloud has by chance assumed an immediately recognizable shape. Fittingly known as The Horsehead Nebula, it lies some 1,500 light-years distant, embedded in the vast Orion cloud complex. About five light-years "tall," the dark cloud is cataloged as Barnard 33, first identified on a photographic plate taken in the early 20th century. B33 is visible primarily because its obscuring dust is silhouetted against the glow of emission nebula IC 434. Hubble Space Telescope images from the early 21st century find young stars forming within B33. Of course, the magnificent interstellar cloud will slowly shift its apparent shape over the next few million years. But for now the Horsehead Nebula is a rewarding though difficult object to view with small telescopes from planet Earth.

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The Heart of the Soul Nebula

This cosmic close-up looks deep inside the Soul Nebula. The dark and brooding dust clouds outlined by bright ridges of glowing gas are cataloged as IC 1871. About 25 light-years across, the telescopic field of view spans only a small part of the much larger Heart and Soul nebulae. At an estimated distance of 6,500 light-years, the star-forming complex lies within the Perseus spiral arm of the Milky Way, seen in planet Earth's skies toward the constellation of the Queen of Aethiopia (Cassiopeia). An example of triggered star formation, the dense star-forming clouds of IC 1871 are themselves sculpted by the intense winds and radiation of the region's massive young stars. This color image adopts a palette made popular in Hubble images of star-forming regions.

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Flying Over the Earth at Night

Many wonders are visible when flying over the Earth at night. Such visual spectacles occur every day for astronauts in low Earth orbit, but the featured video captured several from the International Space Station (ISS) in 2011 and set them to rousing music. Passing below are white clouds, orange city lights, lightning flashes in thunderstorms, and dark blue seas. On the horizon is the golden haze of Earth's thin atmosphere, frequently decorated by dancing auroras as the video progresses. The green parts of auroras typically remain below the space station, but the station flies right through the red and purple auroral peaks. Solar panels of the ISS are seen around the frame edges. The ominous wave of approaching brightness at the end of each sequence is just the dawn of the sunlit half of Earth, a dawn that occurs every 90 minutes. Free APOD Lecture in Phoenix: This Wednesday (December 10) at 7 pm

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The Sun and Its Missing Colors

It is still not known why the Sun's light is missing some colors. Here are all the visible colors of the Sun, produced by passing the Sun's light through a prism-like device. The spectrum was created at the McMath-Pierce Solar Observatory and shows, first off, that although our white-appearing Sun emits light of nearly every color, it appears brightest in yellow-green light. The dark patches in the featured spectrum arise from gas at or above the Sun's surface absorbing sunlight emitted below. Since different types of gas absorb different colors of light, it is possible to determine what gasses compose the Sun. Helium, for example, was first discovered in 1868 on a solar spectrum and only later found here on Earth. Today, the majority of spectral absorption lines have been identified - but not all. Free APOD Lecture in Phoenix: Wednesday, December 10 at 7 pm

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Apollo 17 at Shorty Crater

Fifty three years ago, in December of 1972, Apollo 17 astronauts Eugene Cernan and Harrison Schmitt spent about 75 hours on the Moon exploring the Taurus-Littrow valley, while colleague Ronald Evans orbited overhead. This snapshot from another world was taken by Cernan as he and Schmitt roamed the lunar valley's floor. The image shows Schmitt next to the lunar rover parked along the south rim of Shorty Crater. That location is near the spot where geologist Schmitt discovered orange lunar soil. The Apollo 17 crew returned with 110 kilograms of rock and soil samples, more than was returned from any of the other lunar landing sites. And for now, Cernan and Schmitt are the last to walk on the Moon.

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The Bipolar Jets of KX Andromedae

Blasting outward from variable star KX Andromedae, these stunning bipolar jets are 19 light-years long. Recently discovered, they are revealed in unprecedented detail in this deep telescopic image centered on KX And and composed from over 692 hours of combined image data. In fact, KX And is spectroscopically found to be an interacting binary star system consisting of a bright, hot B-type star with a swollen cool giant star as its co-orbiting, close companion. The stellar material from the cool giant star is likely being transferred to the hot B-type star through an accretion disk, with spectacular symmetric jets driven outward perpendicular to the disk itself. The known distance to KX And of 2,500 light-years, angular size of the jets, and estimated inclination of the accretion disk lead to the size estimate for each jet of an astonishing 19 light-years. Free APOD Lecture in Phoenix: Wednesday, December 10 at 7 pm

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Galaxies in the Furnace

An example of violence on a cosmic scale, enormous elliptical galaxy NGC 1316 lies about 75 million light-years away toward Fornax, the southern constellation of the Furnace. Investigating the startling sight, astronomers suspect the giant galaxy of colliding with smaller neighbor NGC 1317 seen just right of the large galaxy's center, producing far flung star streams in loops and shells. Light from their close encounter would have reached Earth some 100 million years ago. In the sharp telescopic image, the central regions of NGC 1316 and NGC 1317 appear separated by over 100,000 light-years. Complex dust lanes visible within also indicate that NGC 1316 is itself the result of a merger of galaxies in the distant past. Found on the outskirts of the Fornax galaxy cluster, NGC 1316 is known as Fornax A. One of the visually brightest of the Fornax cluster galaxies it is one of the strongest and largest celestial radio sources with radio emission extending well beyond this one degree wide field-of-view.

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Visualization: Near a Black Hole and Disk

What would it look like to plunge into a monster black hole? This image from a supercomputer visualization shows the entire sky as seen from a simulated camera plunging toward a 4-million-solar-mass black hole, similar to the one at the center of our galaxy. The camera lies about 16 million kilometers from the black hole’s event horizon and is moving inward at 62% the speed of light. Thanks to gravity’s funhouse effects, the starry band of the Milky Way appears both as a compact loop at the top of this view and as a secondary image stretching across the bottom. Move the cursor over the image for additional explanations. Visualizations like this allow astronomers to explore black holes in ways not otherwise possible.

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M77: Spiral Galaxy with an Active Center

What's happening in the center of nearby spiral galaxy M77? The face-on galaxy lies a mere 47 million light-years away toward the constellation of the Sea Monster (Cetus). At that estimated distance, this gorgeous island universe is about 100 thousand light-years across. Also known as NGC 1068, its compact and very bright core is well studied by astronomers exploring the mysteries of supermassive black holes in active Seyfert galaxies. M77's active core glows bright at x-ray, ultraviolet, visible, infrared, and radio wavelengths. The featured sharp image of M77 was taken by the Hubble Space Telescope. The image shows details of the spiral's winding spiral arms as traced by obscuring red dust clouds and blue star clusters, all circling the galaxy's bright white luminous center. Free APOD Lecture in Phoenix: Wednesday, December 10 at 7 pm

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3I ATLAS: Tails of an Interstellar Comet

How typical is our Solar System? Studying 3I/ATLAS, a comet just passing through, is providing clues. Confirmed previous interstellar visitors include an asteroid, a comet, a meteor, and a gas wind dominated by hydrogen and helium. Comet 3I/ATLAS appears relatively normal when compared to Solar System comets, therefore providing more evidence that our Solar System is a somewhat typical star system. For example, Comet 3I/ATLAS has a broadly similar chemical composition and ejected dust. The featured image was captured last week from Texas and shows a green coma, a wandering blue-tinted ion tail likely deflected by our Sun's wind, and a slight anti-tail, all typical cometary attributes. The comet, visible with a telescope, passed its closest to the Sun in late October and will pass its closest to the Earth in mid-December, after which it will return to interstellar space and never return. Explore the Universe: Random APOD Generator

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The Surface of Titan from Huygens

If you could stand on Titan -- what would you see? The featured color view from Titan gazes across an unfamiliar and distant landscape on Saturn's largest moon. The scene was recorded by ESA's Huygens probe in 2005 after a 2.5-hour descent through a thick atmosphere of nitrogen laced with methane. Bathed in an eerie orange light at ground level, rocks strewn about the scene could well be composed of water and hydrocarbons frozen solid at an inhospitable temperature of negative 179 degrees C. The large light-toned rock below and left of center is only about 15 centimeters across and lies 85 centimeters away. The saucer-shaped spacecraft is believed to have penetrated about 15 centimeters into a place on Titan's surface that had the consistency of wet sand or clay. Huygen's batteries enabled the probe to take and transmit data for more than 90 minutes after landing. Titan's bizarre chemical environment may bear similarities to planet Earth's before life evolved.

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Moon Games

This is not a screen from a video game. Nestled below the treeline, the small mountain church does look like it might be hiding from Moon though. In the well-composed telephoto snapshot, taken on November 23, the church walls are partly reflecting light from terrestrial flood lights. Of course, the Moon is reflecting light from the Sun. At any given time the Sun illuminates fully half of the Moon's surface, also known as the lunar dayside, but on that night only a sliver of its sunlit surface was visible. About three days after New Moon, the Moon was in a waxing crescent phase. The single exposure was captured shortly after sunset in skies near Danta di Cadore, northern Italy, planet Earth.

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NGC 6888: The Crescent Nebula

NGC 6888, also known as the Crescent Nebula, is a about 25 light-years across, a cosmic bubble blown by winds from its central, massive star. This deep telescopic image includes narrowband image data, to isolate light from hydrogen and oxygen atoms. The oxygen atoms produce the blue-green hue that seems to enshroud the nebula's detailed folds and filaments. Visible within the nebula, NGC 6888's central star is classified as a Wolf-Rayet star (WR 136). The star is shedding its outer envelope in a strong stellar wind, ejecting the equivalent of the Sun's mass every 10,000 years. In fact, the Crescent Nebula's complex structures are likely the result of this strong wind interacting with material ejected in an earlier phase. Burning fuel at a prodigious rate and near the end of its stellar life, this star should ultimately go out with a bang in a spectacular supernova explosion. Found in the nebula rich constellation Cygnus, NGC 6888 is about 5,000 light-years away.

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Portrait of NGC 1055

Big, beautiful spiral galaxy NGC 1055 is a dominant member of a small galaxy group a mere 60 million light-years away toward the aquatically intimidating constellation Cetus. Seen edge-on, the island universe spans over 100,000 light-years, a little larger than our own Milky Way galaxy. The colorful, spiky stars decorating this cosmic portrait of NGC 1055 are in the foreground, well within the Milky Way. But telltale pinkish star forming regions and young blue star clusters are scattered through winding dust lanes along the distant galaxy's thin disk. With a smattering of even more distant background galaxies, the deep image also reveals a boxy halo that extends far above and below the central bulge and disk of NGC 1055. The halo itself is laced with faint, narrow structures, and could represent the mixed and spread out debris from a satellite galaxy disrupted by the larger spiral some 10 billion years ago.

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Globular Cluster M15 Deep Field

Stars, like bees, swarm around the center of bright globular cluster M15. The central ball of over 100,000 stars is a relic from the early years of our Galaxy, and continues to orbit the Milky Way's center. M15, one of about 150 globular clusters remaining, is noted for being easily visible with only binoculars, having at its center one of the densest concentrations of stars known, and containing a high abundance of variable stars and pulsars. The featured image of M15 was taken by combining very long exposures -- 122 hours in all -- and so brings up faint wisps of gas and dust in front of the giant ball of stars. M15 lies about 35,000 light years away toward the constellation of the Winged Horse (Pegasus). Almost Hyperspace: Random APOD Generator

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Comet Lemmon and the Milky Way

What did Comet Lemmon look like when it was at its best? One example is pictured here, featuring three celestial spectacles all at different distances. The closest spectacle is the snowcapped Meili Mountains, part of the Himalayas in China. The middle marvel is Comet Lemmon near its picturesque best early this month, showing not only a white dust tail trailing off to the right but its blue solar wind-distorted ion tail trailing off to the left. Far in the distance on the left is the magnificent central plane of our Milky Way Galaxy, featuring dark dust, red nebula, and including billions of Sun-like stars. Comet C/2025 A6 (Lemmon) is already fading as it heads back into the outer Solar System, while the Himalayan mountains will gradually erode over the next billion years. The Milky Way Galaxy, though, will live on -- forming new mountains and comets -- for many billions of years into the future.

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Apep: Unusual Dust Shells from Webb

What created this unusual space sculpture? Stars. This unusual system of swirls and shells, known as Apep, was observed in unprecedented detail by NASA’s James Webb Space Telescope in infrared light in 2024. Observations indicate that the unusual shape originates from two massive Wolf-Rayet stars orbiting each other every 190 years with each close passes causing a new shell of dust and gas to be expelled. Holes in these shells are thought to be caused by a third orbiting star. This stellar dust dance will likely continue for hundreds of thousands of years, possibly ending only when one of the massive stars runs out of internal nuclear fuel and explodes in a supernova punctuated by a burst of gamma-rays. Build your own star system: Astronomy Puzzle of the Day

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