Reflections on VdB 31
Riding high in the constellation of Auriga, beautiful, blue VdB 31 is the 31st object in Sidney van den Bergh's 1966 catalog of reflection nebulae. It shares this well-composed celestial still life with dark, obscuring clouds B26, B27, and B28, recorded in Edward E. Barnard's 1919 catalog of dark markings in the sky. All are these nebulae are interstellar dust clouds. Barnard's dark nebulae block the light from background stars. For VdB 31 the dust preferentially reflects bluish starlight from embedded, hot, variable star AB Aurigae. Exploring the environs of AB Aurigae with the Hubble Space Telescope has revealed the several million year young star is itself surrounded by a flattened dusty disk with evidence for the ongoing formation of a planetary system. AB Aurigae is about 470 light-years away. At that distance this cosmic canvas would span about eight light-years.
The Spider and the Fly
Will the spider ever catch the fly? Not if both are large emission nebulas toward the constellation of the Charioteer (Auriga). The spider-shaped gas cloud in the image center is actually an emission nebula labelled IC 417, while the smaller fly-shaped cloud on the left is dubbed NGC 1931 and is both an emission nebula and a reflection nebula. About 10,000 light-years distant, both nebulas harbor young star clusters. For scale, the more compact NGC 1931 (Fly) is about 10 light-years across. The featured deep image, captured over 20 hours during late January in Berkshire UK, also shows more diffuse and red-glowing interstellar gas and dust.
Auroral Hummingbird over Norway
Is this the largest hummingbird ever? Although it may look like a popular fluttering nectarivore, what is pictured is actually a beautifully detailed and colorful aurora, complete with rays reminiscent of feathers. This aurora was so bright that it was visible to the unaided eye during blue hour -- just after sunset when the sky appears a darkening blue. However, the aurora only looked like a hummingbird through a sensitive camera able to pick up faint glows. As reds typically occurring higher in the Earth's atmosphere than the greens, the real 3D shape of this aurora would likely appear unfamiliar. Auroras are created when an explosion on the Sun causes high energy particles to flow into the Earth's atmosphere and excite atoms and molecules of nitrogen and oxygen. The featured image was captured about two weeks ago above Lyngseidt, Norway.
Milky Way over the Australian Pinnacles
What strange world is this? Earth. In the foreground of the featured image are the Pinnacles, unusual rock spires in Nambung National Park in Western Australia. Made of ancient sea shells (limestone), how these human-sized picturesque spires formed remains unknown. In the background, just past the end of the central Pinnacle, is a bright crescent Moon. The eerie glow around the Moon is mostly zodiacal light, sunlight reflected by dust grains orbiting between the planets in the Solar System. Arching across the top is the central band of our Milky Way Galaxy. Many famous stars and nebulas are also visible in the background night sky. The featured 29-panel panorama was taken and composed in 2015 September after detailed planning that involved the Moon, the rock spires, and their corresponding shadows. Even so, the strong zodiacal light was a pleasant surprise.
A Conjunction of Crescents
A waxing crescent Moon and a waning crescent Venus are found at opposite corners of this twilight telephoto field of view. The close conjunction of the two brightest celestial beacons in planet Earth's western evening sky was captured on February 1 from Rosario, Argentina. On that date, the slender crescent Moon was about 3 days old. But the Moon's visible sunlit crescent will grow to a bright Full Moon by February 14. Like the Moon, Venus cycles through phases as it orbits the Sun. And while its visible sunlit crescent narrows, the inner planet's apparent size increases as it gets closer to Earth. In a Valentine from the Solar System, Venus, named for the Roman goddess of Love, will also reach its peak brightness in planet Earth's evening skies around February 14.
LEDA 1313424: The Bullseye Galaxy
The giant galaxy cataloged as LEDA 1313424 is about two and a half times the size of our own Milky Way. Its remarkable appearance in this recently released Hubble Space Telescope image strongly suggests its nickname "The Bullseye Galaxy". Known as a collisional ring galaxy it has nine rings confirmed by telescopic observations, rippling from its center like waves from a pebble dropped into a pond. Of course, the pebble dropped into the Bullseye galaxy was a galaxy itself. Telescopic observations identify the blue dwarf galaxy at center-left as the likely collider, passing through the giant galaxy's center and forming concentric rings in the wake of their gravitational interaction. The Bullseye Galaxy lies some 567 million light-years away toward the constellation Pisces. At that distance, this stunning Hubble image would span about 530,000 light-years.
IC 2574: Coddington's Nebula
Grand spiral galaxies often seem to get all the glory, flaunting their young, bright, blue star clusters in beautiful, symmetric spiral arms. But small, irregular galaxies form stars too. In fact dwarf galaxy IC 2574 shows clear evidence of intense star forming activity in its telltale reddish regions of glowing hydrogen gas. Just as in spiral galaxies, the turbulent star-forming regions in IC 2574 are churned by stellar winds and supernova explosions spewing material into the galaxy's interstellar medium and triggering further star formation. A mere 12 million light-years distant, IC 2574 is part of the M81 group of galaxies, seen toward the northern constellation Ursa Major. Also known as Coddington's Nebula, the lovely island universe is about 50,000 light-years across, discovered by American astronomer Edwin Coddington in 1898.
Anticrepuscular Rays: A Rainbow Fan over Spain
Yes, but can your rainbow do this? Late in the day, the Sun set as usual toward the west. However, on this day, the more interesting display was 180 degrees around -- toward the east. There, not only was a rainbow visible, but an impressive display of anticrepuscular rays from the rainbow's center. In the featured image from Lekeitio in northern Spain, the Sun is behind the camera. The rainbow resulted from sunlight reflecting back from falling rain. Anticrepuscular rays result from sunlight, blocked by some clouds, going all the way around the sky, overhead, and appearing to converge on the opposite horizon -- an optical illusion. Rainbows by themselves can be exciting to see, and anticrepuscular rays a rare treat, but capturing them both together is even more unusual -- and can look both serene and surreal.
Wolf-Rayet Star 124: Stellar Wind Machine
Some stars explode in slow motion. Rare, massive Wolf-Rayet stars are so tumultuous and hot that they are slowly disintegrating right before our telescopes. Glowing gas globs each typically over 30 times more massive than the Earth are being expelled by violent stellar winds. Wolf-Rayet star WR 124, visible near the featured image center and spanning six light years across, is thus creating the surrounding nebula known as M1-67. Details of why this star has been slowly blowing itself apart over the past 20,000 years remains a topic of research. WR 124 lies 15,000 light-years away towards the constellation of the Arrow (Sagitta). The fate of any given Wolf-Rayet star likely depends on how massive it is, but many are thought to end their lives with spectacular explosions such as supernovas or gamma-ray bursts.
Comet G3 ATLAS Disintegrates
What's happening to Comet G3 ATLAS? After passing near the Sun in mid-January, the head of the comet has become dimmer and dimmer. By late January, Comet C/2024 G3 (ATLAS) had become a headless wonder -- even though it continued to show impressive tails after sunset in the skies of Earth's Southern Hemisphere. Pictured are images of Comet G3 ATLAS on successive January nights taken from Río Hurtado, Chile. Clearly, the comet's head is brighter and more centrally condensed on the earlier days (left) than on later days (right). A key reason is likely that the comet's nucleus of ice and rock, at the head's center, has fragmented. Comet G3 ATLAS passed well inside the orbit of planet Mercury when at its solar closest, a distance that where heat destroys many comets. Some of comet G3 ATLAS' scattering remains will continue to orbit the Sun.
Nacreous Clouds over Sweden
Vivid and lustrous, wafting iridescent waves of color wash across this skyscape from northern Sweden. Known as nacreous clouds or mother-of-pearl clouds, they are rare. But their unforgettable appearance was captured in this snapshot on January 12 with the Sun just below the local horizon. A type of polar stratospheric cloud, they form when unusually cold temperatures in the usually cloudless lower stratosphere form ice crystals. Still sunlit at altitudes of around 15 to 25 kilometers, the clouds diffract the sunlight even when the Sun itself is hidden from direct view.
The Variable Nebula NGC 2261
The interstellar cloud of dust and gas captured in this sharp telescopic snapshot is seen to change its appearance noticeably over periods as short as a few weeks. Discovered over 200 years ago and cataloged as NGC 2261, bright star R Monocerotis lies at the tip of the fan-shaped nebula. About one light-year across and 2500 light-years away, NGC 2261 was studied early last century by astronomer Edwin Hubble and the mysterious cosmic cloud is now more famous as Hubble's Variable Nebula. So what makes Hubble's nebula vary? NGC 2261 is composed of a dusty reflection nebula fanning out from the star R Monocerotis. The leading variability explanation holds that dense knots of obscuring dust pass close to R Mon and cast moving shadows across the dust clouds in the rest of Hubble's Variable Nebula.
Hydrogen Clouds of M33
Gorgeous spiral galaxy Messier 33 seems to have more than its fair share of glowing hydrogen gas. A prominent member of the local group of galaxies, M33 is also known as the Triangulum Galaxy and lies a mere 3 million light-years away. The galaxy's central 60,000 light-years or so are shown in this sharp galaxy portrait. The portrait features M33's reddish ionized hydrogen clouds or HII regions. Sprawling along loose spiral arms that wind toward the core, M33's giant HII regions are some of the largest known stellar nurseries, sites of the formation of short-lived but very massive stars. Intense ultraviolet radiation from the luminous, massive stars ionizes the surrounding hydrogen gas and ultimately produces the characteristic red glow. In this image, broadband data were combined with narrowband data recorded through a filter that transmits the light of the strongest visible hydrogen and oxygen emission lines.
Dust Shells around WR 140 from Webb
What are those strange rings? Rich in dust, the rings are likely 3D shells -- but how they were created remains a topic of research. Where they were created is well known: in a binary star system that lies about 6,000 light years away toward the constellation of the Swan (Cygnus) -- a system dominated by the Wolf-Rayet star WR 140. Wolf-Rayet stars are massive, bright, and known for their tumultuous winds. They are also known for creating and dispersing heavy elements such as carbon, which is a building block of interstellar dust. The other star in the binary is also bright and massive -- but not as active. The two great stars joust in an oblong orbit as they approach each other about every eight years. When at closest approach, the X-ray emission from the system increases, as, apparently, does the dust expelled into space -- creating another shell. The featured infrared image by the Webb Space Telescope resolves greater details and more dust shells than ever before. Images taken over consecutive years show the shells moving outward.
Comet G3 ATLAS over Uruguay
Comets can be huge. When far from the Sun, a comet's size usually refers to its hard nucleus of ice and rock, which typically spans a few kilometers -- smaller than even a small moon. When nearing the Sun, however, this nucleus can eject dust and gas and leave a thin tail that can spread to an enormous length -- even greater than the distance between the Earth and the Sun. Pictured, C/2024 G3 (ATLAS) sports a tail of sunlight-reflecting dust and glowing gas that spans several times the apparent size of a full moon, appearing even larger on long duration camera images than to the unaided eye. The featured image shows impressive Comet ATLAS over trees and a grass field in Sierras de Mahoma, San Jose, Uruguay about a week ago. After being prominent in the sunset skies of Earth's southern hemisphere, Comet G3 ATLAS is now fading as it moves away from the Sun, making its impressive tails increasingly hard to see.
