2026 October 19

Treble Clef: Unusual X-ray Hot Radio Source
Image Credit: X-ray: NASA/CXC/INAF-IRA/A. Botteon et al.; Infrared: UKIDSS-GPS ; Radio: ASTRONLOFAR; Image processing: NASA/CXC/SAO/N. Wolk

What is Treble Clef? This unusual radio structure extends over 2 million light-years and resembles a common musical symbol -- but has its visible light hidden by our own Milky Way Galaxy. Examined in 2004, the nature of VLSS J0318.9+5755, dubbed Treble Clef, remained unknown. Recent observations by the Chandra X-ray Observatory and eROSITA, however, have led to the hypothesis that the Treble Clef central cloud of charged particles was originally expelled by a supermassive black hole at the center of a galaxy. After the radio emission from those particles faded, they may have been reinvigorated by a shock wave from the collision of two clusters of galaxies. The featured composite image shows radio emission in red, while recently discovered X-rays are shown in blue. Unusual objects like Treble Clef give humanity unexpected clues about how whole clusters of galaxies interact as well as the general evolution of our universe.

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2026 October 20

An Anticrepuscular Rainbow Fan
Image Credit & Copyright: Aurelia Degli Esposti

This is an unusual rainbow. For one thing, the rainbow is not complete, appearing only in a sunlit fan -- but that by itself is not very unusual. What is most unusual is the fake location of the Sun. The Sun appears to be toward the front, just below those hills -- but it is not. That is not how rainbows work. Rainbows involve a backward reflection from falling rain, so that the Sun must really be behind you. In this case, gaps between clouds near the setting Sun allowed rays to cross the entire sky and appear to converge in front, an unusual phenomenon called anticrepuscular rays. The photo was taken with a phone last week at sunset in Presenzano, Italy. The seemingly reverse rainbow was noticed when hanging up laundry.

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2026 October 21

New Ghosts Revealed in Cassiopeia
Image Credit & Copyright: Louis Leroux-Géré, Thibault Rouillée, Vincent Martin, Cédric de Decker (Starfront Observatories)

Jinkies, look at all those ghosts! It took 100 hours of observation and a special oxygen filter for today’s image to capture three faint nebulas hidden in the Cassiopeia constellation. IC 59 and IC 63, the original Ghosts of Cassiopeia, haunt the region near multi-star system γ Cassiopeia. Energetic light from γ Cassiopeia causes the hydrogen gas in IC 59 and 63 to glow red. Their dust reflects and scatters some blue-ish white starlight. Newly discovered Objects 1, 2, and 3 appear as blue phantoms, revealing the presence of ionized oxygen. But ionized by what? Like at the bow of a speeding boat, γ Cassiopeia may be piling up material as the system moves through interstellar gas and dust. It follows that Object 3 may be the compressed and heated oxygen of that bow shock. Object 1 could be a planetary nebula if a central white dwarf is identified. The origins of these astronomical apparitions remain a mystery to be solved.

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2026 October 22

The First Green Star, WD J1330+6435
Image Credit & Copyright: Mark A. Garlick/University of Warwick

Star light, star bright: is there a green star out tonight? Other than the Sun, all stars are so far from Earth that they appear as points in the sky. They are mostly white, but sometimes noticeably red or blue. This color typically relates to the temperature: blue stars are hotter than red stars. What about other colors? The featured image is an illustration showing WD J1330+6435, a white dwarf star, surrounded by an accretion disk with gas and rocks orbiting the star. White dwarfs are small, faint stars that are left over when a star like the Sun exhausts its nuclear fuel. Astronomers recently found that some white dwarf stars, despite their name, would appear yellow, green, cyan, pink, or purple. In these cases, trace elements that were accreted to these stars interact with the stellar atmosphere and shift its normally white color. But, alas! I wish I may, I wish I might, but they are too faint to see tonight...

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2026 October 23

Andromeda in Southern Spring
Image Credit & Copyright: Lucy Yunxi Hu

Looking toward the north from Mullion, New South Wales, Australia, the Andromeda Galaxy never gets more than a few degrees above the horizon. During the southern hemisphere spring, Andromeda is highest in the sky around midnight though. And in this telephoto scene from October 10/11, multiple exposures were used to reveal the spiral galaxy in tantalizing detail as it climbed above rolling Australian hills. Also known as M31, the Andromeda Galaxy is one of the brightest objects in the Messier catalog, but is only visible to the unaided eye as a small, faint, fuzzy patch. Digitally tracked and stacked frames were combined with a foreground shot in the deep astro-image composite to reveal the galaxy's greater extent in planet Earth's night. In the springtime night skyscape,the closest large spiral galaxy spans nearly 6 full moons.

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2026 October 24

Rosetta's Selfie
Image Credit & Copyright: ESA/Rosetta/Philae/CIVA

This Rosetta spacecraft selfie was snapped on October 7th, 2014. At the time the comet-chasing spacecraft was about 472 million kilometers from planet Earth, but only 16 kilometers from the surface of comet 67P/Churyumov-Gerasimenko. Looming beyond the spacecraft near the top of the frame, dust and gas stream away from the comet's curious double-lobed nucleus. Bright sunlight glints off one of Rosetta's 14 meter long solar arrays. In fact, two exposures, one short and one long, were combined to record the dramatic high contrast scene using the CIVA camera system on Rosetta's still-attached Philae lander. Its chosen primary landing site was on the visible hemisphere of the smaller lobe of the nucleus. This was the last image from Philae's camera before the lander separated from Rosetta on November 12. Shortly after separation Philae took another image looking back toward the orbiter, and began its descent to the nucleus of the comet.

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2026 October 25

Dark Matter in a Simulated Universe
Illustration Credit & Copyright: Tom Abel & Ralf Kaehler (KIPAC, SLAC), AMNH

Is our universe haunted? It might look that way on this dark matter map. The gravity of unseen dark matter is the leading explanation for why galaxies rotate so fast, why galaxies orbit clusters so fast, why gravitational lenses so strongly deflect light, and how visible matter is distributed. The featured image from the American Museum of Natural History's Hayden Planetarium Space Show, Dark Universe, highlights one example of how pervasive dark matter might haunt our universe. In this frame from a detailed computer simulation, complex filaments of dark matter, shown in black, are strewn about the universe like spider webs, while the relatively rare clumps of familiar baryonic matter are colored orange. These simulations are good statistical matches to astronomical observations. In what is perhaps a scarier turn of events, dark matter -- although quite strange and in an unknown form -- is no longer thought to be the strangest source of gravity in the universe. That honor now falls to dark energy, a more uniform source of repulsive gravity that seems to now dominate the expansion of the entire universe.

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2026 October 26

M42: The Great Nebula in Orion
Credit & Copyright: Roberto Palaia

The Great Nebula in Orion, an immense, nearby starbirth region, is one the most famous of all astronomical nebulas. Here, glowing gas surrounds hot young stars at the edge of an immense interstellar molecular cloud only 1500 light-years away. In the featured deep image in assigned colors highlighted by emission in hydrogen, wisps and sheets of dust and gas are particularly evident. The Great Nebula in Orion can be found with the unaided eye near the easily identifiable belt of three stars in the popular constellation Orion. In addition to housing a bright open cluster of stars known as the Trapezium, the Orion Nebula contains many stellar nurseries. These nurseries contain much hydrogen gas, hot young stars, proplyds, and stellar jets spewing material at high speeds. Also known as M42, the Orion Nebula spans about 40 light years and is located in the same spiral arm of our Galaxy as the Sun.

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2026 October 27

Noctilucent Clouds over Sweden
Credit & Copyright: V. Höfer, D. Večerník & B. Večerníková

Sometimes it's night on the ground but day in the air. As the Earth rotates to eclipse the Sun, sunset rises up from the ground. Therefore, at sunset on the ground, sunlight still shines on clouds above. Under usual circumstances, a pretty sunset might be visible, but unusual noctilucent clouds float so high up they can be seen well after dark. Normally too dim to be seen, they may become visible just after sunset during the summer when illuminated by sunlight from below the horizon. Noctilucent clouds are the highest clouds and are known more technically as polar mesospheric clouds. Featured here as they appeared in early August, a network of blue noctilucent clouds was captured in the distant sky above a field of green grass near Linköping, Sweden, with trees in stark silhouette across the horizon. Much about noctilucent clouds has been discovered only in the past two decades, while how they form and evolve remains a topic of active research.

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2026 October 28

The Mutual Occultation of Ganymede and Io
Image Credit & Copyright: Michael Wong

Jupiter is one of the least lonely planets in the Solar System, at least when it comes to natural satellites. 115 moons have been discovered orbiting Jupiter so far! (Saturn has the most with 293, but who’s counting.) Ganymede and Io, two of Jupiter’s Galilean moons, met in the sky on October 20th, 2026. Today’s video captures the meeting, with Ganymede briefly blocking Io from view. This event, when an astronomical object passes in front of another and either completely or partially blocks it, is called a mutual occultation. The mutual occultations of Galilean moons are rare to witness because they require Earth’s edge-on view of their orbits. This occurs once every 6 years when Jupiter reaches its equinox and appears less “tilted”. Ganymede is also casting its shadow on Jupiter’s right side. Any fictional Jovian species within the shadow would experience a solar eclipse!

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2026 October 29

The Horns of Venus
Image Credit & Copyright: Thierry Legault

That's no moon. But you could be forgiven for thinking it was a crescent Moon in the sky. It is a lesser known fact that Venus also has phases. (What about other planets?) The featured image shows Venus seen almost directly between the Sun and the Earth. This happens once every year and a half, and it is like the alignment that happens every month during a new Moon. But the new Moon is dark, while Venus' backlit atmosphere refracts and scatters the sunlight, creating a glowing crescent arc that extends beyond 180 degrees: the tips of this arc are called the "horns". The crescent can be seen with a small telescope or binoculars during twilight, but those with exceptionally acute eyesight may be able to see it with the unaided eye. Ancient Babylonian astronomers may have been the first to study Venus' brightness changes, which are related to its phases. Many other cultures have similar astronomical records, including the oldest surviving Maya book.

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2026 October 30

Haunting the Cepheus Flare
Image Credit & Copyright: Mirko Tondinelli

Spooky shapes seem to haunt this dusty expanse, drifting through the night in the royal constellation Cepheus. Of course, the shapes are cosmic dust clouds visible in dimly reflected starlight. Far from your own neighborhood, they lurk above the plane of the Milky Way at the edge of the Cepheus Flare molecular cloud complex some 1,200 light-years away. Over 2 light-years across and brighter than most of the other ghostly apparitions, vdB 141 or Sh2-136 is also known as the Ghost Nebula. It lies at lower right in the starry field of view. Inside the Ghost Nebula are reddish telltale signs of dense cores collapsing in the early stages of star formation. With the eerie hue of interstellar dust reflecting bluish light from hot young stars of NGC 7023, the Iris Nebula stands out against the dark just left of center. In the broad telescopic frame, these fertile interstellar dust fields stretch almost six full moons across the sky.

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