http://www.acme.com/jef/apod/ The Astronomy Picture of the Day is a wonderful web site that puts up a different astronomy-related picture every day. However, the site does not have an RSS feed. This page fixes that deficiency. ]]> en-us Wed, 12 Aug 2026 13:06:00 GMT ACME Labs custom shell script jef@mail.acme.com webmaster@mail.acme.com http://www.acme.com/jef/apod/apod.GIF http://www.acme.com/jef/apod/ http://apod.nasa.gov/apod/ap260812.html Wed, 12 Aug 2026 13:06:00 GMT It looks like a view from the Little Prince's planet. The featured image is a throwback to the 2024 Perseid meteor shower, surrounded in this projection by the Bieszczady Mountains in Poland. Visible in the sky is the arch of the Milky Way, along with several nebulas in red and over a hundred meteors pointing to the radiant. The Perseids are easily visible and quite popular in the Northern Hemisphere summer. (Watching meteor showers in the winter is less convenient for a good reason). This year they are expected to offer an even more dazzling spectacle than usual, because the peak coincides with a new moon. The 2026 Perseid meteor shower will peak tonight with as many as 50-100 meteors per hour, when the Earth's path crosses through debris left behind by Comet Swift-Tuttle. Typically, the best times for seeing the meteors are between midnight and pre-dawn. You won't need binoculars to see the meteors, but a lawn chair and a dark sky location help. ]]> http://apod.nasa.gov/apod/ap260811.html Tue, 11 Aug 2026 13:06:00 GMT How many moons does Saturn have? While the total will likely continue to grow, as of June 2026 the ringed gas giant had 293 confirmed moons. That's easily more than any other planet of the Solar System, including ruling gas giant Jupiter with a mere 115 confirmed moons. Most of Saturn's known moons are small, irregular satellites. Many are only few kilometers to a fraction of a kilometer across and grouped in tilted outer orbits. Six of its largest satellites can be seen here, though, in this sharp telescopic Saturnian family portrait taken on August 5. Larger than Earth's Moon and even slightly larger than inner planet Mercury, Titan, with a diameter of 5,150 kilometers, is at lower right. You can also spot icy major moons Mimas, Tethys, Enceladus, Dione, and Rhea in the frame. Saturn's first known natural satellite, Titan was discovered in 1655 by Dutch astronomer Christiaan Huygens. During the space age Voyager and Cassini discoveries have added to the swelling ranks of Saturnian moons. ]]> http://apod.nasa.gov/apod/ap260810.html Mon, 10 Aug 2026 13:06:00 GMT Each of these pairs of galaxies is different. The two galaxies at the top are likely not interacting, at least presently. However, the top galaxy with the blue stripe, NGC 4650A, is a polar ring galaxy and may be the result of a past galaxy collision. The two galaxies in the middle of the featured image appear like they could be interacting gravitationally -- but their relative speeds make this unlikely. Of these two, the larger galaxy, NGC 4650, is a spiral galaxy with a bright bar of stars across its center. The two galaxies at the bottom are actively interacting. Possibly in a billion years or so, NGC 4622A and NGC 4622B will merge and become one single galaxy. All of these galaxies are likely members of the larger Centaurus Galaxy Cluster. ]]> http://apod.nasa.gov/apod/ap260809.html Sun, 09 Aug 2026 13:06:00 GMT Have you contemplated your home star recently? Featured here, a Sun partially eclipsed on the top left by the Moon is also seen eclipsed by earthlings contemplating the eclipse below. This spectacular menagerie of silhouettes was taken in 2012 from the Glen Canyon National Recreation Area near Page, Arizona, USA, where park rangers and astronomers expounded on the unusual event to interested gatherers. Also, faintly visible on the Sun's disk, just to the lower right of the dark Moon's disk, is a group of sunspots. A new solar eclipse will occur this week and give many people in northern North America, Europe, and northwestern Africa a new chance to contemplate a partially eclipsed Sun. A thin swath of Earth from Greenland to Portugal will further experience a total solar eclipse. An open question is whether any meteors from the peaking Perseids will be visible during totality. ]]> http://apod.nasa.gov/apod/ap260808.html Sat, 08 Aug 2026 13:06:00 GMT Which of these is not a comet? You guessed it - the one on the right is a globular star cluster. The diffuse greenish coma of periodic comet 10P/Tempel 2 is at left in the frame. In fact the globular star cluster is Messier 30, also known as M30, or the 30th entry in astronomer Charles Messier's catalog of things which are not comets. The well-known 18th century astronomer kept a list of objects he observed, now his famous Messier Catalogue of Nebulae and Star Clusters, which did not move from night to night against the background stars and so were not the comets he was hunting for. So the famous comet hunter would get the correct answer too, even though his telescope would show both 10P/Tempel 2 and distant star cluster as similar looking faint and fuzzy objects in his field of view. Recorded on July 29, this modern telescopic image captures periodic comet Tempel 2 as it briefly swept close on the sky to M30. While the periodic comet's faint, narrow, orbital dust trail seems to pierce the globular star cluster, Tempel 2 was a mere 3.5 light-minutes away. Messier 30 is some 28,000 light-years distant. ]]> http://apod.nasa.gov/apod/ap260807.html Fri, 07 Aug 2026 13:06:00 GMT There are more than half a million galaxies in the central panel of this image from the NSF-DOE Vera C. Rubin Observatory in Chile. This is the COSMOS field, a patch of sky several times larger than the full moon, first observed by Hubble. It has also been observed by Webb and other telescopes because it contains comparatively few bright stars from our own galaxy, offering a relatively unimpeded view of other galaxies outside the Milky Way. The outer panels, numbered 1-10, show zoomed-in views of the corresponding small regions highlighted in the central panel. The variety of galaxy shapes and sizes is astonishing. Some of them are so far away that their light has traveled for billions of years before reaching Earth. Rubin will come back every couple of days to the COSMOS field as part of its ten-year Legacy Survey of Space and Time. It will allow a dynamic view of the COSMOS field and how the sky changes over time. ]]> http://apod.nasa.gov/apod/ap260806.html Thu, 06 Aug 2026 13:06:00 GMT What does the new sharpest image of our Sun show? Instability. To be clear, a certain kind of interactive process called the Kelvin-Helmholtz instability (KHI). This instability can create waves and swirls when two streams flow past each other -- in this case variable streams of solar magnetic plasma. Long hypothesized to occur on the Sun's surface, KHI streaks and swirls were confirmed in just-released dramatic high-resolution images taken recently by the Inouye Solar Telescope in Hawaii, USA.  The featured false-yellow image, actually taken in deep blue, is the highest resolution image yet of the Sun in visible light. It spans about the radius of the Earth, but its finest details are city sized. Visible are several smooth tops of changing solar granules, while the edges of the flower-like structures have been found to harbor multiple KHI swirls. Future research may investigate how the KHI helps move energy, magnetic fields, and may even heat the surrounding solar corona. ]]> http://apod.nasa.gov/apod/ap260805.html Wed, 05 Aug 2026 13:06:00 GMT Don’t get spooked by Saturn’s ghostly spokes! Today we feature a nearly two-hour timelapse of Saturn and its rings looping forwards and backwards. A day on Saturn is only 10 hours long, so two hours of observation covers quite a bit of its rotation. If you look closely, a ghoulish shadow appears and disappears as Saturn’s B ring rotates. Decades of observation with Voyager 2, Cassini, and Hubble show the appearance of Saturn’s spokes varies with the planet’s seasons. Like Earth, Saturn’s spin axis is tilted compared to the plane of its orbit around the Sun. During Saturn’s equinox, the rings are less tilted away from the Sun and the planet receives more evenly distributed sunlight and solar wind. Although their origin is still uncertain, Saturn’s spokes may be shadows of and reflections off of dust and ice levitating above the rings caused by electromagnetic interactions between the solar wind and the planet’s magnetic field. ]]> http://apod.nasa.gov/apod/ap260804.html Tue, 04 Aug 2026 13:06:00 GMT What causes unusual knots of gas and dust in planetary nebulas? Seen also in the Ring Nebula, the Dumbbell Nebula and NGC 2392, the knots' existence was not initially predicted, and their origins are still not well understood. Pictured here is a fascinating image of part of the Helix Nebula by the James Webb Space Telescope showing tremendous detail in infrared light. The cometary knots have masses similar to the Earth but have sizes typically several times the orbit of Pluto. One hypothesis for the fragmentation and evolution of the knots includes existing gas being driven out by a less dense but highly energetic stellar wind of the central evolving star. The Helix Nebula is one of the closest examples of a planetary nebula created at the end of the life of a Sun-like star. Given a technical designation of NGC 7293, the Helix Nebula lies about 650 light-years away towards the constellation of Water Carrier (Aquarius). ]]> http://apod.nasa.gov/apod/ap260803.html Mon, 03 Aug 2026 13:06:00 GMT What's happening to this meteor? This bright meteor streak appeared and disappeared quickly during a long exposure of the Great Lacerta Nebula, seen faintly in red toward the center of the image. The meteoroid, likely a small pebble, creates its glow partly by heating and exciting surrounding air in Earth's atmosphere, but itself vaporizes and leaves wind-blown gas and dust with colors that give clues to its composition. The featured image was captured last month from Death Valley Observatories in Nevada, USA. This month, though, is particularly good for seeing meteors. Presently there are three meteor showers ongoing, although they are currently competing for visibility with the glow of a bright gibbous Moon. The most active of these showers, the Perseids, will be busiest in about 10 days -- after the Moon has dimmed considerably. This year, the Perseids peak nearly coincides with not only a new Moon, but, from some locations, one that totally eclipses the Sun. ]]> http://apod.nasa.gov/apod/ap260802.html Sun, 02 Aug 2026 13:06:00 GMT What's happening to this cloud? Ice crystals in a distant cirrus cloud are acting like little floating prisms. Known informally as a fire rainbow for its flame-like appearance, a circumhorizon arc appears parallel to the horizon. For a circumhorizontal arc to be visible, the Sun must be at least 58 degrees high in a sky where cirrus clouds present below -- in this case cirrus fibratus. The numerous, flat, hexagonal ice-crystals that compose the cirrus cloud must be aligned horizontally to properly refract sunlight in a collectively similar manner. Therefore, circumhorizontal arcs are somewhat unusual to see. The featured fire rainbow was photographed in 2021 near North Fork Mountain in West Virginia, USA. ]]> http://apod.nasa.gov/apod/ap260801.html Sat, 01 Aug 2026 13:06:00 GMT The Buck Moon is a traditional name for the full moon of July. In this colorful Adriatic sea and skyscape captured on July 28 from Krk Island along the coast of Croatia, a full Buck Moon is just rising over distant mountains. Since a full moon rises as the Sun sets, Earth's shadow also rises in the twilight scene, a diffuse gray band extending above the mountainous southeastern horizon. Above Earth's shadow band is the pinkish antitwilight arch. That subtly tinted band of backscattered sunlight is more widely known as the Belt of Venus. But as it shares the eastern horizon with the atmospheric shadow of Earth and Belt of Venus, this full Buck Moon seems to set the stage for the New Moon to come. The New Moon of August 12 will cast its shadow on planet Earth in a much anticipated total solar eclipse. ]]> http://apod.nasa.gov/apod/ap260731.html Fri, 31 Jul 2026 13:06:00 GMT The Dark Doodad Nebula drifts through southern skies, a tantalizing target for binoculars toward the small constellation Musca, The Fly. A dusty interstellar cloud, it's seen against rich starfields just south of the Coalsack Nebula and the Southern Cross. Stretching for about 3 degrees across this telescopic field of view, the Dark Doodad is punctuated near its southern tip (upper right) by yellowish globular star cluster NGC 4372. Of course NGC 4372 roams the halo of our Milky Way galaxy, a background object some 20,000 light-years away and only by chance along our line-of-sight to the Dark Doodad. About 700 light-years distant and over 30 light-years long, the Dark Doodad's well defined silhouette belongs to the potentially star-forming Musca molecular cloud. The dusty Dark Doodad's delightfully alliterative moniker was first coined by astro-imager and writer Dennis di Cicco in 1986 while observing Comet Halley from the Australian outback. ]]> http://apod.nasa.gov/apod/ap260730.html Thu, 30 Jul 2026 13:06:00 GMT This could be the view from an exoplanet orbiting around a red dwarf star, but it is our own Sun. This image was taken on July 22, 2026, in the Okanagan region in the Canadian province of British Columbia. Wildfire smoke from the Pacific Northwest acted as a solar filter, allowing the photographer to take this photo of the Sun directly. Several sunspots are also visible in this eerie image; just below and right of the center is AR 4493, a fast evolving, giant active solar region and sunspot group. The smoke is made of tiny particles that help block and scatter light with bluer colors, so the light we see coming from the Sun is dimmer and redder than usual (but it is never safe to stare directly at the Sun). Sunsets and sunrises are also more colorful because of the smoke. Some 6 billion years from now, the Sun will actually start to turn redder as it approaches its red giant phase. ]]> http://apod.nasa.gov/apod/ap260729.html Wed, 29 Jul 2026 13:06:00 GMT Solar System bodies make deep space exploration more fuel efficient! Today’s video shows the Psyche spacecraft gaining speed and changing its trajectory with minimal fuel spent due to a gravity assist from Mars in May 2026. Mars has an average orbital speed of almost 87,000 km/h (54,000 mph) around the Sun. Its orbital motion and its gravity allowed Mars to pull Psyche along with it, increasing the spacecraft’s speed. Gravity assists have been used since 1959’s Luna 3 mission to allow for spacecraft (the Voyagers, Cassini) to reach farther than they could with fuel alone. This assist helped the Psyche spacecraft on its journey to the Psyche asteroid, which it will reach in 2029. While passing Mars, the spacecraft tested instruments that will analyze the asteroid’s composition and magnetic field. This is the first mission to an asteroid thought to be largely made of metal, an essential building block for planets, rather than rock or ice. ]]> http://apod.nasa.gov/apod/ap260728.html Tue, 28 Jul 2026 13:06:00 GMT What's connecting these two volcanoes? In ancient folklore, the two volcanoes, Parinacota (left) and Pomerape (right), are connected by representing a mythical prince and princess who engaged in a forbidden romance. Beneath the ground, the two peaks are not known to be connected by a common pool of hot magma, and neither volcano has erupted in the past 1000 years. Above the ground, there is usually nothing in the sky that connects them -- except if you use careful timing and look from a specific location. The featured well-planned image was captured from Bolivia in mid-April with a series of camera exposures taken on the same day and from the same location. Then, Barnard's Loop appeared to connect the volcanic peaks. Also visible in the image is the Orion Nebula in the center, the star Betelgeuse on the right, and the Rosette Nebula on the upper right. ]]> http://apod.nasa.gov/apod/ap260727.html Mon, 27 Jul 2026 13:06:00 GMT What created this huge space bubble? Blown by the wind from a star, this tantalizing, head-like apparition is cataloged as NGC 7635, but known simply as the Bubble Nebula. Taken from Krakow, Poland, the featured view utilizes a long exposure to reveal the intricate details of this cosmic bubble and its environment. Although it looks delicate, the 10 light-year diameter bubble offers evidence of violent processes at work. Seen here right of the Bubble's center, a bright hot star is embedded in the nebula's reflecting dust. A fierce stellar wind and intense radiation from the star, which likely has a mass 10 to 20 times that of the Sun, has blasted out the structure of glowing gas against denser material in a surrounding molecular cloud. The intriguing Bubble Nebula lies a mere 11,000 light-years away toward the boastful constellation Cassiopeia. ]]> http://apod.nasa.gov/apod/ap260726.html Sun, 26 Jul 2026 13:06:00 GMT How do clusters of galaxies form? Since our universe moves too slowly to watch, faster-moving computer simulations are created to help find out. One famous effort is TNG50 from IllustrisTNG, an upgrade of the famous Illustris Simulation. The first part of the featured video tracks cosmic gas (mostly hydrogen) as it evolves into galaxies and galaxy clusters from the early universe to today, with brighter colors marking faster moving gas. As the universe matures, gas falls into gravitational wells, galaxies forms, galaxies spin, galaxies collide and merge, all while black holes form in galaxy centers and expel surrounding gas at high speeds. The second half of the video switches to tracking stars, showing a galaxy cluster coming together, complete with stellar streams. The outflow from black holes in TNG50 is surprisingly complex and details are being compared with our real universe. Studying how gas coalesced in the early universe helps humanity better understand how our Earth, Sun, and Solar System originally formed. ]]> http://apod.nasa.gov/apod/ap260725.html Sat, 25 Jul 2026 13:06:00 GMT The Seas of Tranquility and Serenity are calm today. They're calm most every day though, since they are actually lunar maria, ancient lava flows filling in large impact basins on the Moon. Also known by Latin names Mare Tranquillitatis (right) and Mare Serenitatis, the smooth dark lunar "seas" are in stark contrast to the bright cratered lunar highlands surrounding them in this telescopic view. Of course their names are based on the historical, pre-telescopic designations of lunar maria. Easily visible to the unaided eye, the broad features on the Moon's near side were imagined to be like the expansive oceans of planet Earth. On July 20, 1969, the Apollo 11 lunar module Eagle touched down on the Mare Tranquillitatis (at lower right), establishing Tranquility base and the first human presence on the Moon. ]]> http://apod.nasa.gov/apod/ap260724.html Fri, 24 Jul 2026 13:06:00 GMT In 185 AD, Chinese astronomers recorded the appearance of a new star in the Nanmen asterism. That part of the sky is identified with part of the southern constellation Centaurus on modern star charts. In fact, the new star was reported to be visible to the naked-eye for months before it faded from view, and is now thought to be the earliest recorded supernova. In this 21st century telescopic image, the wispy outlines of a faint emission nebula recognized as the remnant of that historical stellar explosion can be traced against a starry background. The ragged but roughly circular extent of the nebula, cataloged as RCW 86, represents interstellar gas ionized by the supernova's still expanding shock wave. Space-based images indicate an abundance of the element iron in RCW 86 and the absence of a neutron star or pulsar within the remnant, suggesting that the original supernova was Type Ia. Unlike the core collapse supernova explosion of a massive star, a Type Ia supernova is a thermonuclear detonation on a white dwarf star that has accreted material from its companion in a binary star system. Near the plane of our Milky Way galaxy and larger than the full moon on the sky this supernova remnant is too faint to be seen by eye though. RCW 86 is some 8,000 light-years distant and around 100 light-years across. ]]> http://apod.nasa.gov/apod/ap260723.html Thu, 23 Jul 2026 13:06:00 GMT Have you ever seen another galaxy with your own eyes? The featured image shows the Large Magellanic Cloud (LMC), one of the closest neighbors of our Milky Way. If you are anywhere south of latitude 20° N (but the further south, the better), you can see it with the unaided eye if you go to a dark sky location, away from big cities and light polution. It is a dwarf irregular galaxy about 163,000 light-years away, and a member of our Local Group of galaxies. Despite being small, with a total mass approximately equivalent to 10% - 20% of the mass of the Milky Way, the LMC is very actively forming stars. This is likely due in part to the gravitational push and pull of tides caused by the Milky Way on the LMC. Some astronomers have predicted that it will collide with the Milky Way in in about 2 billion years. ]]> http://apod.nasa.gov/apod/ap260722.html Wed, 22 Jul 2026 13:06:00 GMT The Southern Crown (Corona Australis) dazzles with young and ancient celestial jewels. The Corona Australis Cloud is a collage of reflection and emission nebulae on the left of today’s image. At 430 light years away, this cloud is one of the closest star-forming regions to Earth. It contains gas cool enough (-260 Celsius or -440 Fahrenheit) to collapse into protostars. Recently formed stars paint blue hues across the cloud as their light reflects off surrounding material. The waltz of the R Coronae Australis binary system stirs up the nebula NGC 6729. The younger of the pair ionizes nearby gas with its ultraviolet light, causing it to glow. The Chandelier Cluster (NGC 6723) dangles from the top right, but is actually tens of thousands of light years farther away than its apparent star-forming neighbor. While NGC 6723 experienced multiple periods of star formation creating slightly younger stars, the chandelier twinkles with stars almost as old as the universe. ]]>