Sunset Afterimage

On May 7, the Sun setting behind a church bell tower was captured in this filtered and manipulated digital skyscape from Ragusa, Sicily, planet Earth. In this version of the image the colors look bizarre. Still, an intriguing optical illusion known as an afterimage can help you experience the same scene with a more natural looking appearance. To try it, find the sunspots of active region AR4079 grouped near the bottom of the blue solar disk. Relax and stare at the dark sunspot group for about 30 seconds, then close your eyes or shift your gaze to a plain white surface. In a moment an afterimage of the sunset should faintly appear. But the afterimage sunset will have this image's complementary colors and a more normal yellow Sun against a familiar blue sky.

https://apod.nasa.gov/apod/ap250531.html ( May 31, 2025)

Mars in the Loop

This composite of images spaced a weather-permitting 5 to 9 days apart, from 2024 September 19 (top right) through 2025 May 18 (bottom left), faithfully traces ruddy-colored Mars as it makes a clockwise loop through the constellations Gemini and Cancer in planet Earth's night sky. You can connect the dots and dates with your cursor over the image, but be sure to check out this animation of the Red Planet's 2024/25 retrograde motion. Of course Mars didn't actually reverse the direction of its orbit. Instead, the apparent backwards motion with respect to the background stars is a reflection of the orbital motion of Earth itself. Retrograde motion can be seen each time Earth overtakes and laps planets orbiting farther from the Sun, the Earth moving more rapidly through its own relatively close-in orbit. In this case Mars' apparent eastward motion began to reverse around December 8, when it seemed to linger near open star cluster M44 in Cancer. After wandering back to the west, under Gemini's bright stars Castor and Pollux, Mars returned to pose near M44 by early May. At its brightest near opposition on 2025 January 16, Mars was a mere 96 million kilometers away.

https://apod.nasa.gov/apod/ap250530.html ( May 30, 2025)

Irregular Dwarf Galaxy Sextans A

Grand spiral galaxies often seem to get all the attention, flaunting young, bright, blue star clusters and pinkish star forming regions along graceful, symmetric spiral arms. But small galaxies form stars too, like irregular dwarf galaxy Sextans A. Its young star clusters and star forming regions are gathered into a gumdrop-shaped region a mere 5,000 light-years across. Seen toward the navigational constellation Sextans, the small galaxy lies some 4.5 million light-years distant. That puts it near the outskirts of the local group of galaxies, that includes the large, massive spirals Andromeda and our own Milky Way. Brighter Milky Way foreground stars appear spiky and yellowish in this colorful telescopic view of Sextans A.

https://apod.nasa.gov/apod/ap250529.html ( May 29, 2025)

Herbig Haro 24

This might look like a double-bladed lightsaber, but these two cosmic jets actually beam outward from a newborn star in a galaxy near you. Constructed from Hubble Space Telescope image data, the stunning scene spans about half a light-year across Herbig-Haro 24 (HH 24), some 1,300 light-years or 400 parsecs away in the stellar nurseries of the Orion B molecular cloud complex. Hidden from direct view, HH 24's central protostar is surrounded by cold dust and gas flattened into a rotating accretion disk. As material from the disk falls toward the young stellar object, it heats up. Opposing jets are blasted out along the system's rotation axis. Cutting through the region's interstellar matter, the narrow, energetic jets produce a series of glowing shock fronts along their path.

https://apod.nasa.gov/apod/ap250528.html ( May 28, 2025)

Behold one of the most photogenic regions of the night sky, captured impressively. Featured, the band of our Milky Way Galaxy runs diagonally along the bottom-left corner, while the colorful Rho Ophiuchi cloud complex is visible just right of center and the large red circular Zeta Ophiuchi Nebula appears near the top. In general, red emanates from nebulas glowing in the light of excited hydrogen gas, while blue marks interstellar dust preferentially reflecting the light of bright young stars. Thick dust usually appears dark brown. Many iconic objects of the night sky appear, including (can you find them?) the bright star Antares, the globular star cluster M4, and the Blue Horsehead nebula. This wide field composite, taken over 17 hours, was captured from South Africa last June.

https://apod.nasa.gov/apod/ap250527.html ( May 27, 2025)

What’s happening in the center of spiral galaxy NGC 2566? First, the eight rays that appear to be coming out of the center in the featuredinfraredimage are not real — they are diffractionspikes caused by the mechanical structure of the Webb space telescope itself. The center of NGC 2566 is bright but not considered unusual, which means that it likely contains a supermassive black hole, although currently not very active. At only 76 million light years away, the light we see from NGC 2566 today left when dinosaurs roamed the Earth. The picturesque galaxy is close enough so that Earthly telescopes, including Webb and Hubble, can resolve the turbulent clouds of gas and dust where stars can form and so allows study of stellar evolution. NGC 2566, similar in size to our Milky Way Galaxy, is notable for its bright central bar and its prominent outer spiral arms.

https://apod.nasa.gov/apod/ap250526.html ( May 26, 2025)

Jupiter is stranger than we knew. NASA's Juno spacecraft has now completed over 70 swoops past Jupiter as it moves around its highly elliptical orbit. Pictured from 2017, Jupiter is seen from below where, surprisingly, the horizontal bands that cover most of the planet disappear into swirls and complex patterns. A line of white oval clouds is visible nearer to the equator. Impressive results from Juno show that Jupiter's weather phenomena can extend deep below its cloud tops, that Jupiter's center has a core that is unexpectedly large and soft, and that Jupiter's magnetic field varies greatly with location. Although Juno is scheduled to keep orbiting Jupiter further into 2025, at some time the robotic spacecraft will be maneuvered to plunge into the giant planet.

https://apod.nasa.gov/apod/ap250525.html ( May 25, 2025)

Deimos Before Sunrise

Deimos takes 30 hours and 18 minutes to complete one orbit around the Red Planet. That's a little more than one Martian day or sol which is about 24 hours and 40 minutes long, so Deimos drifts westward across the Martian sky. About 15 kilometers across at its widest, the smallest of Mars' two moons is bright though. In fact Deimos is the brightest celestial object in this Martian skyscape captured before sunrise by Perseverance on March 1, the 1,433rd sol of the Mars rover's mission. The image is a composed of 16 exposures recorded by one of the rover's navigation cameras. The individual exposures were combined into a single image for an enhanced low light view. Regulus and Algeiba, bright stars in the constellation Leo, are also visible in the dark Martian predawn sky.

https://apod.nasa.gov/apod/ap250524.html ( May 24, 2025)

NGC6366 vs 47 Ophiuchi

Most globular star clusters roam the halo of our Milky Way galaxy, but globular cluster NGC 6366 lies close to the galactic plane. About 12,000 light-years away toward the constellation Ophiuchus, the cluster's starlight is dimmed and reddened by the Milky Way's interstellar dust when viewed from planet Earth. As a result, the stars of NGC 6366 look almost golden in this telescopic scene, especially when seen next to relatively bright, bluish, and nearby star 47 Ophiuchi. Compared to the hundred thousand stars or so gravitationally bound in distant NGC 6366, 47 Oph itself is a binary star system a mere 100 light-years away. Still, the co-orbiting stars of 47 Oph are too close together to be individually distinguished in the image.

https://apod.nasa.gov/apod/ap250523.html ( May 23, 2025)

Curly Spiral Galaxy M63

A bright spiral galaxy of the northern sky, Messier 63 is nearby, about 30 million light-years distant toward the loyal constellation Canes Venatici. Also cataloged as NGC 5055, the majestic island universe is nearly 100,000 light-years across, about the size of our own Milky Way. Its bright core and majestic spiral arms lend the galaxy its popular name, The Sunflower Galaxy. This exceptionally deep exposure also follows faint loops and curling star streams far into the galaxy's halo. Extending nearly 180,000 light-years from the galactic center, the star streams are likely remnants of tidally disrupted satellites of M63. Other satellite galaxies of M63 can be spotted in the remarkable wide-field image, including dwarf galaxies, which could contribute to M63's star streams in the next few billion years.

https://apod.nasa.gov/apod/ap250522.html ( May 22, 2025)

Typically, the International Space Station is visible only at night. Slowly drifting across the night sky as it orbits the Earth, the International Space Station (ISS) can be seen as a bright spot about once a month from many locations. The ISS is then visible only just after sunset or just before sunrise because it shines by reflected sunlight -- once the ISS enters the Earth's shadow, it will drop out of sight. The only occasion when the ISS is visible during the day is when it passes right in front of the Sun. Then, it passes so quickly that only cameras taking short exposures can visually freeze the ISS's silhouette onto the background Sun. The featured picture did exactly that -- it is actually a series of images taken a month ago from Sant Feliu de Buixalleu, Spain with perfect timing. This image series was later combined with a separate image highlighting the texture of the active Sun which included several Sun's prominences around the edge.

https://apod.nasa.gov/apod/ap250521.html ( May 21, 2025)

Have you ever seen the band of our Milky Way Galaxy? In a clear sky from a dark location at the right time, a faint band of light becomes visible across the sky. Soon after your eyes become dark adapted, you might spot the band for the first time. It may then become obvious. Then spectacular. One reason for your growing astonishment might be the realization that this fuzzy swath, the Milky Way, contains billions of stars. Visible in the featured image, high above in the night sky, the band of the Milky Way Galaxy arcs. Also visible are the colorful clouds of Rho Ophiuchi on the right, and the red and circular Zeta Ophiuchi nebula near the top center. Taken in late February from Maunakea, Hawaii, USA, the foreground telescope is the University of Hawaii's 2.2-Meter Telescope. Fortunately, you don’t need to be near the top of a Hawaiian volcano to see the Milky Way.

https://apod.nasa.gov/apod/ap250520.html ( May 20, 2025)

Ares 3 Landing Site: The Martian Revisited

This close-up from the Mars Reconnaissance Orbiter's HiRISE camera shows weathered craters and windblown deposits in southern Acidalia Planitia. A striking shade of blue in standard HiRISE image colors, to the human eye the area would probably look grey or a little reddish. But human eyes have not gazed across this terrain, unless you count the eyes of NASA astronauts in the sci-fi novel, "The Martian," by Andy Weir. The novel chronicles the adventures of Mark Watney, an astronaut stranded at the fictional Mars mission Ares 3 landing site, corresponding to the coordinates of this cropped HiRISE frame. For scale, Watney's 6-meter-diameter habitat at the site would be about 1/10th the diameter of the large crater. Of course, the Ares 3 landing coordinates are only about 800 kilometers north of the (real life) Carl Sagan Memorial Station, the 1997 Pathfinder landing site.

https://apod.nasa.gov/apod/ap250517.html ( May 17, 2025)

Messier 101

Big, beautiful spiral galaxy M101 is one of the last entries in Charles Messier's famous catalog, but definitely not one of the least. About 170,000 light-years across, this galaxy is enormous, almost twice the size of our own Milky Way. M101 was also one of the original spiral nebulae observed by Lord Rosse's large 19th century telescope, the Leviathan of Parsontown. Assembled from 51 exposures recorded by the Hubble Space Telescope in the 20th and 21st centuries, with additional data from ground based telescopes, this mosaic spans about 40,000 light-years across the central region of M101 in one of the highest definition spiral galaxy portraits ever released from Hubble. The sharp image shows stunning features of the galaxy's face-on disk of stars and dust along with background galaxies, some visible right through M101 itself. Also known as the Pinwheel Galaxy, M101 lies within the boundaries of the northern constellation Ursa Major, about 25 million light-years away.

https://apod.nasa.gov/apod/ap250516.html ( May 16, 2025)

A Plutonian Landscape

This shadowy landscape of majestic mountains and icy plains stretches toward the horizon on a small, distant world. It was captured from a range of about 18,000 kilometers when New Horizons looked back toward Pluto, 15 minutes after the spacecraft's closest approach on July 14, 2015. The dramatic, low-angle, near-twilight scene follows rugged mountains formally known as Norgay Montes from foreground left, and Hillary Montes along the horizon, giving way to smooth Sputnik Planum at right. Layers of Pluto's tenuous atmosphere are also revealed in the backlit view. With a strangely familiar appearance, the frigid terrain likely includes ices of nitrogen and carbon monoxide with water-ice mountains rising up to 3,500 meters (11,000 feet). That's comparable in height to the majestic mountains of planet Earth. The Plutonian landscape is 380 kilometers (230 miles) across.

https://apod.nasa.gov/apod/ap250515.html ( May 15, 2025)

This pretty nebula lies some 1,500 light-years away, its shape and color in this telescopic view reminiscent of a robin's egg. The cosmic cloud spans about 3 light-years, nestled securely within the boundaries of the southern constellation of the Furnace (Fornax). Recognized as a planetary nebula, egg-shaped NGC 1360 doesn't represent a beginning, though. Instead, it corresponds to a brief and final phase in the evolution of an aging star. In fact, visible at the center of the nebula, the central star of NGC 1360 is known to be a binary star system likely consisting of two evolved white dwarf stars, less massive but much hotter than the Sun. Their intense and otherwise invisible ultraviolet radiation has stripped away electrons from the atoms in their mutually surrounding gaseous shroud. The blue-green hue inside of NGC 1360 seen here is the strong emission produced as electrons recombine with doubly ionized oxygen atoms.

https://apod.nasa.gov/apod/ap250514.html ( May 14, 2025)

What does our Milky Way Galaxy look like from the top? Because we are on the inside, humanity can’t get an actual picture. Recently, however, just such a map has been made using location data for over a billion stars from ESA’s Gaia mission. The resulting featured illustration shows that just like manyotherspiralgalaxies, our Milky Way has distinct spiral arms. Our Sun and most of the bright stars we see at night are in just one arm: Orion. Gaia data bolsters previous indications that our Milky Way has more than two spiral arms. Our Galaxy's center sports a prominent bar. The colors of our Galaxy's thin disk derive mostly from dark dust, bright blue stars, and red emission nebula. Although data analysis is ongoing, Gaia was deactivated in March after a succession mission.

https://apod.nasa.gov/apod/ap250513.html ( May 13, 2025)

What does our Milky Way Galaxy look like from the side? Because we are on the inside, humanity can’t get an actual picture. Recently, however, just such a map has been made using location data for over a billion stars from ESA’s Gaia mission. The resulting featured illustration shows that just like manyotherspiralgalaxies, our Milky Way has a very thin central disk. Our Sun and all the stars we see at night are in this disk. Although hypothesized before, perhaps more surprising is that the disk appears curved at the outer edges. The colors of our Galaxy's warped central band derive mostly from dark dust, bright blue stars, and red emission nebulas. Although data analysis is ongoing, Gaia was deactivated in March after a successful mission.

https://apod.nasa.gov/apod/ap250512.html ( May 12, 2025)

If you could stand on Venus -- what would you see? Pictured is the view from Venera 14, a robotic Soviet lander which parachuted and air-braked down through the thick Venusian atmosphere in March of 1982. The desolate landscape it saw included flat rocks, vast empty terrain, and a featureless sky above Phoebe Regio near Venus' equator. On the lower left is the spacecraft's penetrometer used to make scientific measurements, while the light piece on the right is part of an ejected lens-cap. Enduring temperatures near 450 degrees Celsius and pressures 75 times that on Earth, the hardened Venera spacecraft lasted only about an hour. Although data from Venera 14 was beamed across the inner Solar System over 40 years ago, digital processing and merging of Venera's unusual images continues even today. Recent analyses of infrared measurements taken by ESA's orbiting Venus Express spacecraft indicate that active volcanoes may currently exist on Venus.

https://apod.nasa.gov/apod/ap250511.html ( May 11, 2025)

Yogi and Friends in 3D

This picture from July 1997 shows a ramp from the Pathfinder lander, the Sojourner robot rover, deflated landing airbags, a couch, Barnacle Bill and Yogi Rock appear together in this 3D stereo view of the surface of Mars. Barnacle Bill is the rock just left of the house cat-sized, solar-paneled Sojourner. Yogi is the big friendly-looking boulder at top right. The "couch" is the angular rock shape visible near center on the horizon. Look at the image with red/blue glasses (or just hold a piece of clear red plastic over your left eye and blue or green over your right) to get the dramatic 3D perspective. The stereo view was recorded by the remarkable Imager for Mars Pathfinder (IMP) camera. The IMP had two optical paths for stereo imaging and ranging and was equipped with an array of color filters for spectral analysis. Operating as the first astronomical observatory on Mars, the IMP also recorded images of the Sun and Deimos, the smallest of Mars' two tiny moons.

https://apod.nasa.gov/apod/ap250510.html ( May 10, 2025)

How do black holes create X-rays? Answering this long-standing question was significantly advanced recently with data taken by NASA’s IXPE satellite. X-rays cannot exit a black hole, but they can be created in the energetic environment nearby, in particular by a jet of particles moving outward. By observing X-ray light arriving from near the supermassive black hole at the center of galaxy BL Lac, called a blazar, it was discovered that these X-rays lacked significant polarization, which is expected when created more by energetic electrons than protons. In the featured artistic illustration, a powerful jet is depicted emanating from an orange-colored accretion disk circling the black hole. Understanding highly energetic processes across the universe helps humanity to understand similarprocesses that occur on or near our Earth.

https://apod.nasa.gov/apod/ap250509.html ( May 09, 2025)

M1: The Incredible Expanding Crab

Cataloged as M1, the Crab Nebula is the first on Charles Messier's famous list of things which are not comets. In fact, the Crab Nebula is now known to be a supernova remnant, an expanding cloud of debris from the death explosion of a massive star. The violent birth of the Crab was witnessed by astronomers in the year 1054. Roughly 10 light-years across, the nebula is still expanding at a rate of about 1,500 kilometers per second. You can see the expansion by comparing these sharp images from the Hubble Space Telescope and James Webb Space Telescope. The Crab's dynamic, fragmented filaments were captured in visible light by Hubble in 2005 and Webb in infrared light in 2023. This cosmic crustacean lies about 6,500 light-years away in the constellation Taurus.

https://apod.nasa.gov/apod/ap250508.html ( May 08, 2025)

In the upper left corner, surrounded by blue arms and dotted with red nebulas, is spiral galaxy M81. In the lower right corner, marked by a light central line and surrounded by red glowing gas, is irregular galaxy M82. This stunning vista shows these two mammoth galaxies locked in gravitational combat, as they have been for the past billion years. The gravity from each galaxy dramatically affects the other during each hundred-million-year pass. Last go-round, M82's gravity likely raised density waves rippling around M81, resulting in the richness of M81's spiral arms. But M81 left M82 with violent star forming regions and colliding gas clouds so energetic the galaxy glows in X-rays. This big battle is seen from Earth through the faint glow of an Integrated Flux Nebula, a little studied complex of diffuse gas and dust clouds in our Milky Way Galaxy. In a few billion years, only one galaxy will remain.

https://apod.nasa.gov/apod/ap250507.html ( May 07, 2025)

If one black hole looks strange, what about two? Light rays from accretion disks around a pair of orbiting supermassive black holes make their way through the warped space-time produced by extreme gravity in this detailed computer visualization. The simulated accretion disks have been given different false color schemes, red for the disk surrounding a 200-million-solar-mass black hole, and blue for the disk surrounding a 100-million-solar-mass black hole. For these masses, though, both accretion disks would actually emit most of their light in the ultraviolet. The video allows us to see both sides of each black hole at the same time. Red and blue light originating from both black holes can be seen in the innermost ring of light, called the photon sphere, near their event horizons. In the past decade, gravitational waves from black hole collisions have actually been detected, although the coalescence of supermassive black holes remains undiscovered.

https://apod.nasa.gov/apod/ap250506.html ( May 06, 2025)

What’s causing those lines? Objects in the sky sometimes appear reflected as lines across water — but why? If the water’s surface is smooth, then reflected objects would appear similarly -- as spots. But if the water is choppy, then there are many places where light from the object can reflect off the water and still come to you -- and so together form, typically, a line. The same effect is frequently seen for the Sun just before sunset and just after sunrise. Pictured about 10 days ago in Ibiza, Spain, images of the setting Moon, Venus (top), and Saturn (right, faint) were captured both directly and in line-reflected forms from the Mediterranean Sea. The other bright object on the right with a water-reflected line is a beacon on a rock to warn passing boats.

https://apod.nasa.gov/apod/ap250505.html ( May 05, 2025)

How fast can a black hole spin? If any object made of regular matter spins too fast -- it breaks apart. But a black hole might not be able to break apart -- and its maximum spin rate is really unknown. Theorists usually model rapidly rotating black holes with the Kerr solution to Einstein's General Theory of Relativity, which predicts several amazing and unusual things. Perhaps its most easily testable prediction, though, is that matter entering a maximally rotating black hole should be last seen orbiting at near the speed of light, as seen from far away. This prediction was tested by NASA's NuSTAR and ESA's XMM satellites by observing the supermassive black hole at the center of spiral galaxy NGC 1365. The near light-speed limit was confirmed by measuring the heating and spectral line broadening of nuclear emissions at the inner edge of the surrounding accretion disk. Pictured here is an artist's illustration depicting an accretion disk of normal matter swirling around a black hole, with a jet emanating from the top. Since matter randomly falling into the black hole should not spin up a black hole this much, the NuSTAR and XMM measurements also validate the existence of the surrounding accretion disk.

https://apod.nasa.gov/apod/ap250504.html ( May 04, 2025)

Titan: Moon over Saturn

Like Earth's moon, Saturn's largest moon Titan is locked in synchronous rotation with its planet. This mosaic of images recorded by the Cassini spacecraft in May of 2012 shows its anti-Saturn side, the side always facing away from the ringed gas giant. The only moon in the solar system with a dense atmosphere, Titan is the only solar system world besides Earth known to have standing bodies of liquid on its surface and an earthlike cycle of liquid rain and evaporation. Its high altitude layer of atmospheric haze is evident in the Cassini view of the 5,000 kilometer diameter moon over Saturn's rings and cloud tops. Near center is the dark dune-filled region known as Shangri-La. The Cassini-delivered Huygens probe rests below and left of center, after the most distant landing for a spacecraft from Earth.

https://apod.nasa.gov/apod/ap250503.html ( May 03, 2025)

Young Star Cluster NGC 346

The most massive young star cluster in the Small Magellanic Cloud is NGC 346, embedded in our small satellite galaxy's largest star forming region some 210,000 light-years distant. Of course the massive stars of NGC 346 are short lived, but very energetic. Their winds and radiation sculpt the edges of the region's dusty molecular cloud triggering star-formation within. The star forming region also appears to contain a large population of infant stars. A mere 3 to 5 million years old and not yet burning hydrogen in their cores, the infant stars are strewn about the embedded star cluster. This spectacular infrared view of NGC 346 is from the James Webb Space Telescope's NIRcam. Emission from atomic hydrogen ionized by the massive stars' energetic radiation as well as molecular hydrogen and dust in the star-forming molecular cloud is detailed in pink and orange hues. Webb's sharp image of the young star-forming region spans 240 light-years at the distance of the Small Magellanic Cloud.

https://apod.nasa.gov/apod/ap250502.html ( May 02, 2025)