Astro Facts

An Unusual Globule in IC 1396

Image Credit & Copyright: Joachim Korb

Explanation: Is there a monster in IC 1396? Known to some as the Elephant’s Trunk Nebula, parts of gas and dust clouds of this star formation region may appear to take on foreboding forms, some nearly human. The only real monster here, however, is a bright young star too far from Earth to hurt us. Energetic light from this star is eating away the dust of the dark cometary globule near the top of the featured image. Jets and winds of particles emitted from this star are also pushing away ambient gas and dust. Nearly 3,000 light-years distant, the relatively faint IC 1396 complex covers a much larger region on the sky than shown here, with an apparent width of more than 10 full moons.

IC 1805: The Heart Nebula

Image Credit & Copyright: Toni Fabiani toni_fabiani

Explanation: What electrifies the Heart Nebula? First, the large emission nebula on the left, catalogued as IC 1805, looks somewhat like a human heart. The nebula glows brightly in red light emitted by its most prominent element, hydrogen, but this long-exposure image was also blended with light emitted by silicon (yellow) and oxygen (blue). In the center of the Heart Nebula are young stars from the open star cluster Melotte 15 that are eroding away several picturesque dust pillars with their atom-exciting energetic light and winds. The Heart Nebula is located about 7,500 light years away toward the constellation of Cassiopeia. At the top right of the Heart Nebula is the companion Fishhead Nebula. This wide and deep image clearly shows, though, that glowing gas surrounds the Heart Nebula in all directions.

Comet Lemmon over the High Tatras

Image Credit & Copyright: Tomáš Slovinský slovinsky.art & Constantine Themelis constantinethemelis

Explanation: Comet Lemmon putting on a show for cameras around the globe. Passing nearest to the Earth this week, the photogenic comet C/2025 A6 (Lemmon) is now extending two long tails : a blue ion tail and a white dust tail. The ion tail is pushed away from the Sun by the ever-present by ever-changing solar wind, and shows structure also created by how much gas is ejected at any one moment. It glows because it is ionized by high energy sunlight. The dust tail is pushed away from the comet by sunlight and shines by reflecting sunlight. The featured image is an enhanced composite of 50 exposures all taken two days ago from Mlynica, Slovakia. The mountains in the foreground are the High Tatras that partly separate Slovakia from Poland. Although Comet Lemmon is best visible in long camera exposures, the shedding ice ball has become faintly visible in northern skies even to unaided eyes through dark skies toward the west after sunset.

SWAN, Swan, Eagle

Image Credit & Copyright: Adam Block adamblock64

Explanation: Comet C/2025 R2 (SWAN) sports a greenish coma and fainter tail, seen against congeries of stars and dusty interstellar clouds in this 7 degree wide telescopic field of view from October 17. On that date, the new visitor to the inner Solar System obligingly posed with two other celestial birds seen toward the center of our Milky Way. Messier 16, near the bottom of the frame, and Messier 17 are also known to deep skywatchers as the Eagle and the Swan nebulae. While the comet coma’s greenish glow recorded in the image is due to diatomic carbon gas fluorescing in sunlight, reddish hues seen in the nebulae, star forming regions some 5,000 light-years distant, are characteristic of ionized hydrogen gas. Comet SWAN is outbound now but still a good comet for binoculars and small telescopes that can look close to the southern horizon in the northern hemisphere’s early evening skies. C/2025 R2 (SWAN) was closest to our fair planet on October 20, a mere 2.2 light-minutes away.

Saturn at Night

Image Credit: NASA, JPL-Caltech, Space Science Institute, Mindaugas Macijauskas

Explanation: Saturn is bright in Earth’s night skies. Telescopic views of the outer gas giant planet and its beautiful rings often make it a star at star parties. But this stunning view of Saturn’s rings and night side just isn’t possible from telescopes in the vicinity of planet Earth. Peering out from the inner Solar System they can only bring Saturn’s day side into view. In fact, this image of Saturn’s slender sunlit crescent with night’s shadow cast across its broad and complex ring system was captured by the Cassini spacecraft. A robot spacecraft from planet Earth, Cassini called Saturn orbit home for 13 years before it was directed to dive into the atmosphere of the gas giant on September 15, 2017. This magnificent mosaic is composed of frames recorded by Cassini’s wide-angle camera only two days before its grand final plunge. Saturn’s night will not be seen again until another spaceship from Earth calls.

Webb’s Rho Ophiuchi

Image Credit: NASA, ESA, CSA, STScI, Klaus Pontoppidan (STScI)

Explanation: A mere 390 light-years away, Sun-like stars and future planetary systems are forming in the Rho Ophiuchi molecular cloud complex, the closest star-forming region to our fair planet. The James Webb Space Telescope’s NIRCam peered into the nearby natal chaos to capture this infrared image at an inspiring scale. The frame spans less than a light-year across the Rho Ophiuchi region and contains about 50 young stars. Brighter stars clearly show Webb’s characteristic pattern of diffraction spikes. Huge jets of shocked molecular hydrogen blasting from newborn stars are red in the image, with the large, yellowish dusty cavity carved out by the energetic young star near its center. Near some stars in the stunning image are shadows cast by their protoplanetary disks. The spectacular cosmic snapshot was released in 2023 to celebrate the successful first year of Webb’s exploration of the Universe.

Tails of Comet Wierzchoś

Image Credit & Copyright: José J. Chambó;
Text: Cecilia Chirenti (NASA GSFC, UMCP, CRESST II)

Explanation: Some comets are regular guests of our solar neighborhood; others come by only once, never to return. We won’t have another chance to see Comet C/2024 E1 (Wierzchoś), which is currently making its way through the inner Solar System. The hyperbolic orbit of this comet indicates that it will likely become an interstellar traveler. Comet Wierzchoś is today near its closest approach to the Earth, passing roughly the same distance from the Earth as is the Sun. The featured 30-minute exposure was taken last week in Chile and shows a 5-degree long ion tail as well as three shorter dust tails. The green hue of the coma comes from the breakdown of dicarbon molecules by sunlight, but that process does not last long enough to also tinge the tails. On the far right lies a spiral galaxy far in the distance: NGC 300.

Orion’s Cradle

Image Credit & Copyright: Piotr Czerski piotr.czerski.photo

Explanation: Cradled in red-glowing hydrogen gas, stars are being born in Orion. These stellar nurseries lie at the edge of the giant Orion molecular cloud complex, some 1,500 light-years away. This detailed view spans about 12 degrees across the center of the well-known constellation, with the Great Orion Nebula, the closest large star-forming region, visible toward the lower right. The deep mosaic also includes, near the top center, the Flame Nebula and the Horsehead Nebula. Image data acquired with a hydrogen-alpha filter adds other remarkable features to this wide-angle cosmic vista: pervasive tendrils of energized atomic hydrogen gas and portions of the surrounding Barnard’s Loop. While the Orion Nebula and many stars in Orion are easy to see with the unaided eye, emission from the extensive interstellar gas is faint and much harder to record, even in telescopic views of the nebula-rich complex.

Webb and Hubble: IC 5332

Image Credit: ESA/Webb, NASA, CSA, J. Lee and the PHANGS-JWST and PHANGS-HST Teams
Text: Cecilia Chirenti (NASA GSFC, UMCP, CRESST II)

Explanation: What does the universe look like through infrared goggles? Our eyes can only see visible light, but astronomers want to see more. Today’s APOD shows spiral galaxy IC 5332 as seen by two NASA telescopes: Webb in mid-infrared and Hubble in ultraviolet and visible light. To toggle between the two space-based views just slide your cursor over the image (or follow this link). The Hubble image highlights the spiral arms of the galaxy separated by dark regions, whereas the Webb image reveals a finer, more tangled structure. Interstellar dust scatters and absorbs light from the stars in the galaxy, causing the dark dust lanes in the Hubble image, and then emits heat in infrared light, so dust glows in this Webb image. The Mid-InfraRed Instrument on Webb needs to operate at a chilling temperature of -266ºC (or - 447ºF), otherwise it would detect infrared radiation from the telescope itself. Combining these observations, astronomers connect the “small scale” of gas and stars to the truly large scale of galactic structure and evolution

Sharpless 249 and the Jellyfish Nebula

Image Credit & Copyright: Katelyn Beecroft kates.universe

Explanation: Normally faint and elusive, the Jellyfish Nebula is caught in this alluring telescopic field of view. Floating in the interstellar sea, the nebula is anchored right and left by two bright stars, Mu and Eta Geminorum, at the foot of the celestial twins. The Jellyfish Nebula itself is right of center, seen as a brighter arcing ridge of emission with dangling tentacles. In fact, this cosmic jellyfish is part of bubble-shaped supernova remnant IC 443, the expanding debris cloud from a massive star that exploded. Light from the explosion first reached planet Earth over 30,000 years ago. Like its cousin in astrophysical waters the Crab Nebula supernova remnant, the Jellyfish Nebula is known to harbor a neutron star, the ultradense remnant of the collapsed stellar core. An emission nebula cataloged as Sharpless 249 fills the field at the upper left. The Jellyfish Nebula is about 5,000 light-years away. At that distance, this image would be about 300 light-years across.