Welcome to December’s solstice, first day of winter in the north and summer for the southern hemisphere. Astronomical markers of the seasons, solstice and equinox dates are based on the Sun’s place in its annual journey along the ecliptic, through planet Earth’s sky. At this solstice, the Sun reaches its maximum southern declination of -23.5 degrees today at 15:59 UTC, while its right ascension coordinate on the celestial sphere is 18 hours. That puts the Sun in the constellation Sagittarius in a direction near the center of our Milky Way galaxy. In fact, if you could see today’s Solstice Sun against faint background stars and nebulae (that’s really hard to do, especially in the daytime …) your view might look something like this composited panorama. To make it, images of our fair galaxy were taken under dark Namibian night skies, then stitched together in a panoramic view. From a snapshot made on 2015 December 21, the Sun was digitally overlayed as a brilliant star at today’s northern winter solstice position, close to the center of the Milky Way. via NASA https://ift.tt/3yJY6cK

This picture was supposed to feature a comet. Specifically, a series of images of the brightest comet of 2021 were being captured: Comet Leonard. But the universe had other plans. Within a fraction of a second, a meteor so bright it could be called a fireball streaked through just below the comet. And the meteor’s flash was even more green than the comet’s coma. The cause of the meteor’s green was likely magnesium evaporating from the meteor’s pebble-sized core, while the cause of the comet’s green was likely diatomic carbon recently ejected from the comet’s city-sized nucleus. The images were taken 10 days ago over the Sacramento River and Mt. Lassen in California, USA. The fireball was on the leading edge of this year’s Geminid Meteor Shower — which peaked a few days later. Comet Leonard is now fading after reaching naked-eye visibility last week — but now is moving into southern skies. via NASA https://ift.tt/3pajwg0

It is not a coincidence that planets line up. That’s because all of the planets orbit the Sun in (nearly) a single sheet called the plane of the ecliptic. When viewed from inside that plane — as Earth dwellers are likely to do — the planets all appear confined to a single band. It is a coincidence, though, when three of the brightest planets all appear in nearly the same direction. Such a coincidence was captured earlier this month. Featured above (right to left), Venus, Saturn, and Jupiter were all imaged together in a line just after sunset, from the San Fermo Hills, Bergamo, Italy. Joining the alignment are Earth’s Moon, and the position of the more distant Uranus. Bands of clouds streak across the sky toward the setting Sun. As Comet Leonard fades, this planetary alignment — absent the Moon — should persist for the rest of the month. via NASA https://ift.tt/3si6nDv

The first identified compact galaxy group, Stephan’s Quintet is featured in this eye-catching image constructed with data drawn from the extensive Hubble Legacy Archive. About 300 million light-years away, only four of these five galaxies are actually locked in a cosmic dance of repeated close encounters. The odd man out is easy to spot, though. The interacting galaxies, NGC 7319, 7318A, 7318B, and 7317 have an overall yellowish cast. They also tend to have distorted loops and tails, grown under the influence of disruptive gravitational tides. But the predominantly bluish galaxy, NGC 7320, is closer, just 40 million light-years distant, and isn’t part of the interacting group. Stephan’s Quintet lies within the boundaries of the high flying constellation Pegasus. At the estimated distance of the quartet of interacting galaxies, this field of view spans about 500,000 light-years. But moving just beyond this field, up and to the right, astronomers can identify another galaxy, NGC 7320C, that is also 300 million light-years distant. Including it would bring the interacting quartet back up to quintet status. via NASA https://ift.tt/3ISEvvE

An arid expanse of the Tengger Desert in north-central China, planet Earth fills the foreground of this starry scene. A widefield panoramic view, it was recorded shortly after moonset in the local predawn hours of December 14. Pictured in the still dark sky, stars of the northern winter hexagon surround a luminous Milky Way. Seen near the peak of the annual meteor shower, the startling flash of a bright Geminid fireball meteor was also captured on that night. Above the western horizon and just below bright star Capella, its dagger-like trail points back to the meteor shower’s radiant in Gemini. Of course, the constellation Gemini is easy to spot. Its twin bright stars, bluish Castor and yellowish Pollux are near top center in the frame. via NASA https://ift.tt/3GQduat

Fireflies flash along a moonlit countryside in this scene taken on the night of December 13/14 from southern Uruguay, planet Earth. On that night meteors fell in the partly cloudy skies above during the annual Geminid meteor shower. Frames recorded over a period of 1.5 hours are aligned in the composite image made with the camera facing south. That direction was opposite the shower’s radiant toward the north and so the Geminid meteor streaks appear to converge at an antiradiant below the southern horizon. The shower’s apparent radiant (and antiradiant) is just due to perspective though. As Earth sweeps through the dust trail of mysterious asteroid 3200 Phaethon, the dust grains that create the Geminid shower meteors are really moving along parallel tracks. They enter Earth’s atmosphere traveling at about 22 kilometers per second. via NASA https://ift.tt/3ywEF7b

What does Comet Leonard look like from space? Today’s featured image from Origin.Space’s Yangwang-1 space telescope shows not only the currently bright comet — but several other space delights as well. Taken in optical and ultraviolet light, C/2021 A1 (Leonard) is visible with an extended tail near the image center as it appeared five days ago. The Earth is visible on the lower right, while layers of the Earth’s atmosphere glow diagonally from the lower left to the upper right. The trails of two satellites can be seen in front of a myriad of distant stars that dot the background on the upper left. The faint bands of light running diagonally from the lower right to the upper left are auroras. Finally, the image also caught a meteor streaking just below the airglow. To see Comet Leonard yourself from the Earth’s surface during the next few days, look toward the western horizon just after sunset or just before sunrise. via NASA https://ift.tt/3s76npT

To some, it may look like a beehive. In reality, the featured image from the Hubble Space Telescope captures a cosmic pillar of dust, over two-light years long, inside of which is Herbig-Haro 666 — a young star emitting powerful jets. The structure lies within one of our galaxy’s largest star forming regions, the Carina Nebula, shining in southern skies at a distance of about 7,500 light-years. The pillar’s layered outline are shaped by the winds and radiation of Carina’s young, hot, massive stars, some of which are still forming inside the nebula. A dust-penetrating view in infrared light better shows the two, narrow, energetic jets blasting outward from a still hidden infant star. via NASA https://ift.tt/3dMtTA3

Comet Leonard is now visible to the unaided eye — but just barely. Passing nearest to the Earth today, the comet is best seen this week soon after sunset, toward the west, low on the horizon. Currently best visible in the north, by late December the comet will best be seen from south of Earth’s equator. The featured image of Comet C/2021 A1 (Leonard) was taken a week ago from California, USA. The deep exposure shows in great detail the comet’s green gas coma and developing dust tail. The comet — across our inner Solar System and only light-minutes away — was captured passing nearly in front of globular star cluster M3. In contrast, M3 is about 35,000 light-years away. In a week, Comet Leonard will pass unusually close to Venus, but will continue on and be at its closest to the Sun in early January. via NASA https://ift.tt/3DZFjvj

From this vantage point about three quarters of a mile from planet Earth’s geographic South Pole, the December 4 eclipse of the Sun was seen as a partial eclipse. At maximum eclipse the New Moon blocked 90 percent of the solar disk. Of course, crews at the South Pole Telescope (left) and BICEP telescope (right) climbed to the roof of Amundsen-Scott station’s Dark Sector Laboratory to watch. Centered near the local eclipse maximum, the composite timelapse view features an image of the Sun in cold antarctic skies taken every four minutes. Left to right along the roof line it also features the raised arms of Brandon Amat, Aman Chokshi, Cheng Zhang, James Bevington and Allen Forster. via NASA https://ift.tt/3EN2ASi