Creature Aurora Over Norway
It was Halloween and the sky looked like a creature. Exactly which creature, the astrophotographer was unsure (but possibly you can suggest one). Exactly what caused this eerie apparition in 2013 was sure: one of the best auroral displays that year. This spectacular aurora had an unusually high degree of detail. Pictured here, the vivid green and purple auroral colors are caused by high atmospheric oxygen and nitrogen reacting to a burst of incoming electrons. Birch trees in Tromsø, Norway formed an also eerie foreground. Frequently, new photogenic auroras accompany new geomagnetic storms.
Dinkinesh Moonrise
Last Wednesday the voyaging Lucy spacecraft encountered its first asteroid, 152830 Dinkinesh, and discovered the inner-main belt asteroid has a moon. From a distance of just over 400 kilometers, Lucy's Long-Range Reconnaissance Imager captured this close-up of the binary system during a flyby at 4.5 kilometer per second or around 10,000 miles per hour. A marvelous world, Dinkinesh itself is small, less than 800 meters (about 0.5 miles) across at its widest. Its satellite is seen from the spacecraft's perspective to emerge from behind the primary asteroid. The asteroid moon is estimated to be only about 220 meters wide.
Jupiter by Moonlight
That bright beacon you've seen rising in the east just after sunset is Jupiter. Climbing high in midnight skies, our Solar System's ruling gas giant was at its 2023 opposition, opposite the Sun in planet Earth's sky, on November 2. But only a few days earlier, on October 28, the Moon was at its own opposition. Then both Full Moon and Jupiter could share this telephoto field of view. The celestial scene is composed from two exposures, one long and one short, blended to record bright planet and even brighter Moon during that evening's partial lunar eclipse. Moonlight shining through the thin, high clouds over northern Italy creates the colorful iridescence and lunar corona. Look closely and you'll also spot some of Jupiter's Galilean moons.
Annular Solar Eclipse over Utah
Part of the Sun disappeared earlier this month, but few people were worried. The missing part, which included the center from some locations, just went behind the Moon in what is known as an annular solar eclipse. Featured here is an eclipse sequence taken as the Moon was overtaking the rising Sun in the sky. The foreground hill is Factory Butte in Utah, USA. The rays flaring out from the Sun are not real -- they result from camera aperture diffraction and are known as sunstar. The Moon is real, but it is artificially brightened to enhance its outline -- which helps the viewer better visualize the Moon's changing position during this ring-of-fire eclipse. As stunning as this eclipse sequence is, it was considered just practice by the astrophotographer. The reason? She hopes to use this experience to better photograph the total solar eclipse that will occur over North America on April 8, 2024.
Halloween and the Wizard Nebula
Halloween's origin is ancient and astronomical. Since the fifth century BC, Halloween has been celebrated as a cross-quarter day, a day halfway between an equinox (equal day / equal night) and a solstice (minimum day / maximum night in the northern hemisphere). With a modern calendar however, even though Halloween occurs today, the real cross-quarter day will occur next week. Another cross-quarter day is Groundhog Day. Halloween's modern celebration retains historic roots in dressing to scare away the spirits of the dead. Perhaps a fitting tribute to this ancient holiday is this closeup view of the Wizard Nebula (NGC 7380). Visually, the interplay of stars, gas, and dust has created a shape that appears to some like a fictional ancient sorcerer. Although the nebula may last only a few million years, some of the stars being conjured from the gas by the great gravitational powers may outlive our Sun.
Reflections of the Ghost Nebula
Do any shapes seem to jump out at you from this interstellar field of stars and dust? The jeweled expanse, filled with faint, starlight-reflecting clouds, drifts through the night in the royal constellation of Cepheus. Far from your own neighborhood on planet Earth, these ghostly apparitions lurk along the plane of the Milky Way at the edge of the Cepheus Flare molecular cloud complex some 1,200 light-years away. Over two light-years across and brighter than the other spooky chimeras, VdB 141 or Sh2-136 is also known as the Ghost Nebula, seen toward the bottom of the featured image. Within the reflection nebula are the telltale signs of dense cores collapsing in the early stages of star formation.
A Partial Lunar Eclipse
What's happened to the Moon? Within the last day, part of the Moon moved through the Earth's shadow. This happens about once or twice a year, but not every month since the Moon's orbit around the Earth is slightly tilted. Pictured here, the face of a full Hunter's Moon is shown twice from Italy during this partial lunar eclipse. On the left, most of the Moon appears overexposed except for the eclipsed bottom right, which shows some familiar lunar surface details. In contrast, on the right, most of the (same) Moon appears normally exposed, with the exception of the bottom right, which now appears dark. All lunar eclipses are visible from the half of the Earth facing the Moon at the time of the eclipse, but this eclipse was visible specifically from Europe, Africa, Asia, and Australia, clouds permitting. In April, a total solar eclipse will be visible from North America.
The Ghosts of Gamma Cas
Gamma Cassiopeiae shines high in northern autumn evening skies. It's the brightest spiky star in this telescopic field of view toward the constellation Cassiopeia. Gamma Cas shares the ethereal-looking scene with ghostly interstellar clouds of gas and dust, IC 59 (top left) and IC 63. About 600 light-years distant, the clouds aren't actually ghosts. They are slowly disappearing though, eroding under the influence of energetic radiation from hot and luminous gamma Cas. Gamma Cas is physically located only 3 to 4 light-years from the nebulae. Slightly closer to gamma Cas, IC 63 is dominated by red H-alpha light emitted as hydrogen atoms ionized by the star's ultraviolet radiation recombine with electrons. Farther from the star, IC 59 shows proportionally less H-alpha emission but more of the characteristic blue tint of dust reflected star light. The cosmic stage spans over 1 degree or 10 light-years at the estimated distance of gamma Cas and friends.
Encke and the Tadpoles
History's second known periodic comet is Comet Encke (2P/Encke). As it swings through the inner Solar System, Encke's orbit takes it from an aphelion, its greatest distance from the Sun, inside the orbit of Jupiter to a perihelion just inside the orbit of Mercury. Returning to its perihelion every 3.3 years, Encke has the shortest period of the Solar System's major comets. Comet Encke is also associated with (at least) two annual meteor showers on planet Earth, the North and South Taurids. Both showers are active in late October and early November. Their two separate radiants lie near bright star Aldebaran in the head-strong constellation Taurus. A faint comet, Encke was captured in this telescopic field of view imaged on the morning of August 24. Then, Encke's pretty greenish coma was close on the sky to the young, embedded star cluster and light-years long, tadpole-shaped star-forming clouds in emission nebula IC 410. Now near bright star Spica in Virgo Comet Encke passed its 2023 perihelion only five days ago, on October 22.
Orionids in Taurus
History's first known periodic comet, Comet Halley (1P/Halley), returns to the inner Solar System every 76 years or so. The famous comet made its last appearance to the naked-eye in 1986. But dusty debris from Comet Halley can be seen raining through planet Earth's skies twice a year during two annual meteor showers, the Eta Aquarids in May and the Orionids in October. In fact, an unhurried series of exposures captured these two bright meteors, vaporizing bits of Halley dust, during the early morning hours of October 23 against a starry background along the Taurus molecular cloud. Impacting the atmosphere at about 66 kilometers per second their greenish streaks point back to the shower's radiant just north of Orion's bright star Betelgeuse off the lower left side of the frame. The familiar Pleiades star cluster anchors the dusty celestial scene at the right.
Arp 87: Merging Galaxies from Hubble
This dance is to the death. As these two large galaxies duel, a cosmic bridge of stars, gas, and dust currently stretches over 75,000 light-years and joins them. The bridge itself is strong evidence that these two immense star systems have passed close to each other and experienced violent tides induced by mutual gravity. As further evidence, the face-on spiral galaxy on the right, also known as NGC 3808A, exhibits many young blue star clusters produced in a burst of star formation. The twisted edge-on spiral on the left (NGC 3808B) seems to be wrapped in the material bridging the galaxies and surrounded by a curious polar ring. Together, the system is known as Arp 87. While such interactions are drawn out over billions of years, repeated close passages will ultimately create one merged galaxy. Although this scenario does look unusual, galactic mergers are thought to be common, with Arp 87 representing a stage in this inevitable process. The Arp 87 dancing pair are about 300 million light-years distant toward the constellation of the Lion (Leo). The prominent edge-on spiral galaxy at the far left appears to be a more distant background galaxy and not involved in the on-going merger.
Moon Io from Spacecraft Juno
There goes another one! Volcanoes on Jupiter's moon Io keep erupting. To investigate, NASA's robotic Juno spacecraft has begun a series of visits to this very strange moon. Io is about the size of Earth's moon, but because of gravitational flexing by Jupiter and other moons, Io's interior gets heated and its surface has become covered with volcanoes. The featured image is from last week's flyby, passing within 12,000 kilometers above the dangerously active world. The surface of Io is covered with sulfur and frozen sulfur dioxide, making it appear yellow, orange and brown. As hoped, Juno flew by just as a volcano was erupting -- with its faint plume visible near the top of the featured image. Studying Io's volcanoes and plumes helps humanity better understand how Jupiter's complex system of moons, rings, and auroras interact. Juno is scheduled to make two flybys of Io during the coming months that are almost 10 times closer: one in December and another in February 2024.
Ghost Aurora over Canada
What does this aurora look like to you? While braving the cold to watch the skies above northern Canada early one morning in 2013, a most unusual aurora appeared. The aurora definitely appeared to be shaped like something, but what? Two ghostly possibilities recorded by the astrophotographer were "witch" and "goddess of dawn", but please feel free to suggest your own Halloween-enhanced impressions. Regardless of fantastical pareidolic interpretations, the pictured aurora had a typical green color and was surely caused by the scientifically commonplace action of high-energy particles from space interacting with oxygen in Earth's upper atmosphere. In the image foreground, at the bottom, is a frozen Alexandra Falls, while evergreen trees cross the middle.
Quarter Moons
Half way between New Moon and Full Moon is the Moon's first quarter phase. That's a quarter of the way around its moonthly orbit. At the first quarter phase, half the Moon's visible side is illuminated by sunlight. For the Moon's third quarter phase, half way between Full Moon and New Moon, sunlight illuminates the other half of the visible lunar disk. At both first and third quarter phases, the terminator, or shadow line separating the lunar night and day, runs down the middle. Near the terminator, long shadows bring lunar craters and mountains in to sharp relief, making the quarter phases a good time to observe the Moon. But in case you missed some, all the quarter phases of the Moon and their calendar dates during 2022 can be found in this well-planned array of telephoto images. Of course, you can observe a first quarter Moon tonight.
Galaxies and a Comet
Galaxies abound in this sharp telescopic image recorded on October 12 in dark skies over June Lake, California. The celestial scene spans nearly 2 degrees within the boundaries of the well-trained northern constellation Canes Venatici. Prominent at the upper left 23.5 million light-years distant is big, beautiful spiral galaxy NGC 4258, known to some as Messier 106. Eye-catching edge-on spiral NGC 4217 is above and right of center about 60 million light-years away. Just passing through the pretty field of view is comet C/2023 H2 Lemmon, discovered last April in image data from the Mount Lemmon Survey. Here the comet sports more of a lime green coma though, along with a faint, narrow ion tail stretching toward the top of the frame. This visitor to the inner Solar System is presently less than 7 light-minutes away and still difficult to spot with binoculars, but it's growing brighter. Comet C/2023 H2 Lemmon will reach perihelion, its closest point to the Sun, on October 29 and perigee, its closest to our fair planet, on November 10 as it transitions from morning to evening northern skies.
