Antonella Montanari

City lights on the night side of Earth. In this image taken from the ISS, we can see a significant portion of the United States, including Chicago, Illinois, and Detroit, Michigan. The dark area in the center is one of the Great Lakes—Lake Michigan—with Lake Erie visible to its right. To the east, the Sun is beginning to rise, and the glow along the visible edge of the Earth, to the left of the sunrise, is the natural luminescence of the atmosphere. Because most of the Earth in the frame is in darkness, the stars are visible—the light from the day side of the planet does not wash out the scene. One can even observe the stars beginning to fade and disappear as the sunrise approaches.

The Ghost of Cassiopeia Has Spoken Again In the constellation Cassiopeia, just 550–600 light-years from Earth, hangs a ghostly veil. This is IC 63 — a nebula astronomers call the Ghost of Cassiopeia. It both glows on its own and reflects light from elsewhere: red hydrogen ignites when ultraviolet radiation knocks electrons free from atoms, while blue clouds of dust softly mirror the brilliance of a nearby star. That star is Gamma Cassiopeiae. A furiously spinning blue-white giant, roughly 19 times more massive than the Sun, it does more than illuminate the nebula — it slowly destroys it, burning away and scattering the gas with its powerful ultraviolet wind. In 2016, Hubble revealed just how complex and fragile these clouds really are: delicate filaments, ragged clumps, and translucent folds that look as though someone is trying to hold dissolving smoke in their hands. On 21 October 2026 the story grew even more intriguing. NASA’s Astronomy Picture of the Day featured “New Ghosts Revealed in Cassiopeia.” Astronomers spent about 100 hours observing the region and used specialized oxygen filters. Around the already known nebulae IC 63 and IC 59, three new, extremely faint structures emerged — unusual blue formations of ionized oxygen. One of them may be a bow shock, a cosmic wake left by Gamma Cassiopeiae as it plows through the interstellar medium. The ghost, it turns out, is not alone. And scientists are only beginning to understand how a massive star paints these new spectral shapes into the cosmic dust.

🌌 The Witch Head and Rigel This blue nebula is nicknamed the "Witch Head" because its contours resemble a caricature-like profile. It reflects light from the nearby star Rigel, located in the constellation Orion. IC 2118 spans approximately 50 light-years across. Streams of gas and dust appear to "point" toward Rigel, as the star's radiation gradually erodes the cloud. 🔭

The Clearest View of Mars’ North Polar Ice Cap This is a real, high-resolution mosaic of Mars’ North Pole, built from dozens of orbital images taken by ESA’s Mars Express spacecraft. The bright white region is a permanent cap of water ice roughly 1,000 km across and up to about 2 km thick—equivalent in volume to nearly half the Greenland ice sheet on Earth. Dark spiral troughs cut through the ice, carved by winds and seasonal sublimation. In winter a thin layer of carbon-dioxide frost blankets the surface; in summer it disappears, revealing the cleaner water ice beneath. The ice is stacked in layers that preserve a climate record stretching back millions of years. Yes—that white material is water ice. Image credit: ESA/DLR/FU Berlin

XLSSC 122: A Mature Galaxy Cluster That Grew Up Too Fast James Webb is peering deeper into cosmic history, and one of its recent surprises is a massive, already well-developed galaxy cluster called XLSSC 122. At a redshift of z = 1.98, we see it as it was roughly 10.4 billion years ago—when the universe was only about a third of its current age. In standard hierarchical models, the largest structures are expected to assemble gradually. Gravity pulls galaxies and dark matter together over billions of years, so truly massive, concentrated clusters should be rare this early. XLSSC 122 doesn’t fit that timeline neatly. It already hosts evolved member galaxies and a hot, metal-enriched intracluster medium, and JWST has now revealed it as a strong gravitational lens—the most distant known—with giant arcs of background galaxies warped around its core. Lensing analyses show an exceptionally high concentration in the cluster’s dark-matter halo (around 6.3 in the inner regions). That high concentration, combined with the cluster’s maturity, adds to a growing body of evidence that massive structure formation in the early universe may have proceeded more rapidly than many models anticipated. It is not a total rewrite of cosmology, but it is a clear tension: a bustling, highly concentrated cluster that appears farther along in its assembly than expected. JWST’s infrared vision is exposing these early overachievers, forcing astronomers to refine how quickly gravity can gather the building blocks of the universe’s largest structures. Image notes: Comparisons of Hubble and JWST views of XLSSC 122 highlight the newly detected strong-lensing arcs.

The sky that suddenly stopped being eternal November 1572. The constellation Cassiopeia. On what seemed like an ordinary night, a star flares up in a place where no star had ever been. It shines so brightly that it remains visible even in the daytime against the pale autumn sky. For people of that era, this was not just an astronomical event. It was a blow to their entire picture of the world. The stars were believed to be unchanging and perfect — an eternal sphere untouched by earthly change. And yet here, right before everyone’s eyes, a “new star” appeared and broke all the rules. The German astronomer Wolfgang Schuler was the first to notice it, on November 6, 1572, simply by looking up. But the outburst became truly famous thanks to the Danish astronomer Tycho Brahe. He carefully observed it, measured its position and brightness, and soon published a book titled *De nova stella* (“On the New Star”). Because of him, the event entered history as Tycho’s Supernova. The brilliant guest remained visible during the day for about two weeks and could be seen with the naked eye for a full 16 months. Gradually it faded and finally disappeared. Today we know it was SN 1572 — a classic Type Ia supernova roughly 13,000 light-years away. A white dwarf that had been pulling material from a companion star reached a critical mass and detonated. And the sky still hasn’t settled down. Right now astronomers are closely watching the star T Coronae Borealis. It may erupt at any moment as a nova — a less powerful event than a supernova, after which the star survives. But even such a flare would remind us of the same lesson Tycho’s Supernova once taught: the heavens are not eternal. They change. And sometimes they do it right before the eyes of all humanity.