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Explanation: Comet R3 PanSTARRS might be best remembered as an Orion comet. A key reason is because Comet C/2025 R3 (PanSTARRS) was near its most spectacular -- in terms of tail visibility -- when passing in front of the iconic constellation. Although rare, other bright comets, too, have ventured across Orion, including Lovejoy in 2015, Hale-Bopp in 1997, and the Great Comet of 1264. Best visible in long duration exposures, the featured image was captured last week from the Craigieburn Mountain Range in New Zealand. Visible in the deep background image are the Orion Nebula, Barnard's Loop, and through R3's...

Explanation: What are some of the most interesting astronomical objects you can see in the night sky? Armed with a good pair of binoculars or a small telescope, if you live in the Northern Hemisphere, you can look for the very popular objects in the Messier Catalog. Most of them, but not all, are also visible from the southern half of the Earth. The featured image shows all 110 objects in the catalog at uniform scale -- the same magnification. Charles Messier created the catalog in the 18th century. He was interested in comets, and his catalog was a list...

Explanation: The New General Catalog of star clusters and nebulae really isn't so new. In fact, it was published in 1888 - an effort by J. L. E. Dreyer to consolidate the work of astronomers William, Caroline, and John Herschel along with others into a useful single, complete catalog of astronomical discoveries and measurements. Dreyer's work was largely successful and is still important today, as this famous catalog continues to lend its "NGC" to bright clusters, galaxies, and nebulae. Take for example the star cluster known as NGC 188 (item number 188 in the NGC compilation). It lies about 6,000...

Explanation: Today’s composite image features something old, something new, something borrowed, and something blue! Comet R3 PanSTARRS, streaking across the right of the image, likely originated from the Oort Cloud, meaning it is an old Solar System relic from billions of years ago. It’s bright extended ion tail glows blue as the gas escaping the comet’s core is ionized by sunlight. Astronomers are fascinated by comets for all sorts of reasons: comet compositions are untouched time capsules containing the building blocks of Solar System planets; comets may have delivered water to the young Earth; the behavior of cometary tails shed...

Explanation: These people are not in danger. What is coming down from the left is just the Moon, far in the distance. Luna appears so large here because she is being photographed through a telescopic lens. What is moving is mostly the Earth, whose spin causes the Moon to slowly disappear behind Mount Teide, a volcano in the Canary Islands of Spain off the northwest coast of Africa. The people pictured are 16 kilometers away and many are facing the camera because they are watching the Sun rise behind the photographer. It is not a coincidence that a full moon...

Explanation: Orion never had a sword like this. As Comet C/2025 R3 (PanSTARRS) heads out of the inner Solar System, it is putting on quite a show for long exposure cameras. Currently seen toward the constellation of Orion the Hunter, the distant Orion Nebula is visible on the upper right. Comet R3 PanSTARRS is now showing two distinct tails: a short dust tail pointing toward the top of the image and a long and wavy ion tail trailing off toward the upper left. The ion tail points away from the Sun and glows blue from excited carbon monoxide. Large particles...

Explanation: Many bright nebulae and star clusters in planet Earth's sky are associated with the name of astronomer Charles Messier from his famous 18th century catalog. His name is also given to these two large and remarkable craters on the Moon. Standouts in the dark, smooth lunar Sea of Fertility or Mare Fecunditatis, Messier (left) and Messier A have dimensions of 15 by 8 and 16 by 11 kilometers respectively. Their elongated shapes are explained by the extremely shallow-angle trajectory followed by an impactor, moving left to right, that gouged out the craters. The shallow impact also resulted in two...

Explanation: Which way is Comet R3 PanSTARRS going? Not towards the star at the top of the image, because that is Rigel, which, being far in the background, is unrelated to the comet. Not through the nebula in the image middle, because that is the Witch Head Nebula and it, too, is far in the distance -- but not far from Rigel. Not into northern skies because over the past week Comet C/2025 R3 (PanSTARRS) has moved into southern skies and is now best visible in Earth's Southern Hemisphere toward the west after sunset. Angularly, Comet R3 PanSTARRS is slowly...

Explanation: A long time ago, in a distant galaxy, a massive star was destroyed in a supernova explosion. The light of this event travelled for tens of millions of years and reached Earth last week as Supernova 2026kid. The featured video shows a time-lapse over three nights of the host galaxy NGC 5907, an edge-on spiral also known as the Splinter or Knife Edge Galaxy, as the supernova appears and becomes brighter. (The occasional streaks are satellites in Earth orbit.) At its brightest, a supernova can outshine the sum of all other stars in its galaxy. Supernova 2026kid appears relatively...

Explanation: What does it mean for Saturn and Neptune to be in retrograde? Featured is a composite of images taken over 34 nights from May 2025 to February 2026 tracing Saturn (brighter, foreground) and Neptune (dimmer, background). Over that time, the two planets exhibited retrograde motion, meaning they appeared to move backward in the sky. This apparent backwards motion occurs when Earth overtakes the slower outer planets as they orbit the Sun. Imagine the Solar System is a running track. Earth "runs" faster along the inside of the track compared to the outer planets. As Earth approaches, aligns, and then...

Explanation: Orion is rarely seen like this. To achieve this majestic vista, you need a camera capable of taking such long duration exposures that faint features in the night sky become revealed. Iconic nebulas that appear include the Orion Nebula, the Flame Nebula, and Barnard's Loop. For contrast, it also helps to have a volcano on the foreground, in this case the Teide volcano on Tenerife on the Canary Islands of Spain. But if you want your Teide volcano snow-covered, you also need good timing -- because that only happens, typically, for a few days each year. Good timing also...

Explanation: Why are there huge, unusual masses inside the Earth? No one is sure. By noting how earthquakes rumble through our planet's interior, humanity has discovered two deep structures that appear to have unusual temperatures and/or chemical compositions. One hypothesis holds that the superplumes are sunken debris left over from the Earth-shattering collision that created Earth's Moon about 4.5 billion years ago. A competing hypothesis is that they are graveyards for old tectonic plates that slowly slid under each other over the past few billion years. No matter their origin, the superplumes are thought to affect Earth’s surface volcanism, possibly...

Explanation: Dust pillars are like interstellar mountains. They survive because they are more dense than their surroundings, but they are slowly being eroded away by a hostile environment. Visible in the featured picture by the Hubble Space Telescope is the end of a huge gas and dust pillar in the Trifid Nebula (M20), punctuated by a smaller pillar pointing up and an unusual jet pointing to the upper left. Many of the bright dots are newly formed stars. A star near the small pillar's end is slowly being stripped of its accreting gas by radiation from a tremendously brighter star...

Explanation: Shrouded in a thick atmosphere, the surface of Saturn's largest moon, Titan, is really hard to see. Small particles suspended in Titan's upper atmosphere cause an almost impenetrable haze, strongly scattering light at visible wavelengths and hiding surface features from prying eyes. Still, Titan's surface is better imaged at infrared wavelengths, where scattering is weaker and atmospheric absorption is reduced. Arrayed around this visible light image (center) of Titan are some of the clearest global infrared views of the tantalizing moon so far. In false color, the six panels present a consistent processing of 13 years of infrared image...

Explanation: Near the heart of the Virgo Galaxy Cluster, a string of galaxies known as Markarian's Chain stretches across this telescopic field of view. Anchored in the frame at bottom right by prominent lenticular galaxies, M84 (bottom) and M86, you can follow the chain's gentle arc up and toward the left. Near center you'll spot the pair of interacting galaxies NGC 4438 and NGC 4435, known to some as Markarian's Eyes. An estimated 50 million light-years distant, the Virgo Cluster itself is the nearest galaxy cluster. With up to about 2,000 member galaxies, it has a noticeable gravitational influence on...

Explanation: Have you ever thought about surfing on an alien world? We can now expand the search for the perfect wave from Earth to the rest of the Solar System, and beyond. Scientists have developed a new model for simulating waves on other planets. Titan is one of the 274 confirmed moons of Saturn to date, and the only object in the solar system (besides Earth) known to have liquid lakes and seas on its surface. The featured video shows a simulation of waves on Earth (right) and on Titan (left), under the same conditions (the scale marker is in...

Explanation: No, Earth did not recently acquire six more moons! Today’s APOD is a combination of images following the Moon, Venus, and the Pleiades across a southern Sicilian sky as twilight turned to evening on April 19. From 2023 to 2029, the Pleiades' and the Moon “visit" each other once per month due to the Pleiades' location in the ecliptic plane. April 2026 saw the celestial alignment of their visit with Venus. About six stars in the Pleiades cluster (Messier 45) are typically visible with the unaided eye. Due to the cluster’s visibility across the world, there are many myths...

Explanation: They're like mountain peaks, but they are forming stars. Bright-rimmed, flowing shapes gather near the center of this rich starfield toward the borders of the nautical southern constellations Puppis and Vela. Composed of interstellar gas and dust, the grouping of light-year sized cometary globules is about 1300 light-years distant. Energetic ultraviolet light from nearby hot stars has molded the globules and ionized their bright rims. The globules also stream away from the Vela supernova remnant which may have influenced their swept-back shapes. Within them, cores of cold gas and dust are likely collapsing to form low mass stars whose...

Explanation: Can you find the comet? Somewhere through this web of satellite trails is Comet C/2025 R3 (PanSTARRS), a bright visitor passing through the inner Solar System. Now, the orbiting satellites themselves only appear as streaks because of the long camera exposure, over 10 minutes in this case. On the contrary, to the eye, satellites appear as points that drift slowly across the night sky and shine by reflecting sunlight -- primarily just after sunset and before sunrise. The featured image was taken just before sunrise two weeks ago from Bavaria, Germany. Presently, Comet R3 PanSTARRS is hard to see...

Explanation: Inside the head of this interstellar monster is a star that is slowly destroying it. The huge monster, actually an inanimate series of pillars of gas and dust, measures light years in length. The in-head star is not itself visible through the opaque interstellar dust but is bursting out partly by ejecting opposing beams of energetic particles called Herbig-Haro jets. Located about 7,500 light years away in the Carina Nebula and known informally as Mystic Mountain, the appearance of these pillars is dominated by dark dust even though they are composed mostly of clear hydrogen gas. The featured image...