The Red Square Nebula


How did a round star create this square nebula? No one is quite sure. The round star, known as MWC 922 and possibly part of a multiple star system, appears at the center of the Red Square Nebula. The featured image combines infrared exposures from the Hale Telescope on Mt. Palomar in California, and the Keck-2 Telescope on Mauna Kea in Hawaii. A leading progenitor hypothesis for the square nebula is that the central star or stars somehow expelled cones of gas during a late developmental stage. For MWC 922, these cones happen to incorporate nearly right angles and be visible from the sides. Supporting evidence for the cone hypothesis includes radial spokes in the image that might run along the cone walls. Researchers speculate that the cones viewed from another angle would appear similar to the gigantic rings of supernova 1987A, possibly indicating that a star in MWC 922 might one day itself explode in a similar supernova.

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The Bubble and the Star Cluster


To the eye, this cosmic composition nicely balances the Bubble Nebula at the right with open star cluster M52. The pair would be lopsided on other scales, though. Embedded in a complex of interstellar dust and gas and blown by the winds from a single, massive O-type star, the Bubble Nebula, also known as NGC 7635, is a mere 10 light-years wide. On the other hand, M52 is a rich open cluster of around a thousand stars. The cluster is about 25 light-years across. Seen toward the northern boundary of Cassiopeia, distance estimates for the Bubble Nebula and associated cloud complex are around 11,000 light-years, while star cluster M52 lies nearly 5,000 light-years away. The wide telescopic field of view spans about 1.5 degrees on the sky or three times the apparent size of a full Moon.

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Perseid Outburst at Westmeath Lookout


This year an outburst of Perseid meteors surprised skywatchers. The reliable meteor shower’s peak was predicted for the night of August 12/13. But persistent visual observers in North America were deluged with a startling Perseid shower outburst a day later, with reports of multiple meteors per minute and sometimes per second in the early hours of August 14. The shower radiant is high in a dark night sky in this composite image. It painstakingly registers the trails of 282 Perseids captured during the stunning outburst activity between 0650 UT (02:50am EDT) and 0900 UT (05:00am EDT) on August 14 from Westmeath Lookout, Ontario. Of course the annual Perseid meteor shower is associated with planet Earth’s passage through dusty debris from periodic comet 109P/Swift-Tuttle. The 2021 outburst could have been caused by an unanticipated encounter with the Perseid Filament, a denser ribbon of dust inside the broader debris zone.

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Harvest Moon Trail


Famed in festival, story, and song the best known full moon is the Harvest Moon. For northern hemisphere dwellers that’s a traditional name of the full moon nearest the September equinox. Seen from Saunderstown, Rhode Island, planet Earth, this Harvest Moon left a broad streak of warm hues as it rose through a twilight sky over the Newport Bridge. On September 20 its trail was captured in a single 22 minute exposure using a dense filter and a digital camera. Only two days later the September equinox marked a change of season and the beginning of autumn in the north. In fact, recognizing a season as the time between solstice and equinox, this Harvest Moon was the fourth full moon of the season, coming just before the astronomical end of northern summer.

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Equinox on a Spinning Earth


When does the line between night and day become vertical? Today. Today is an equinox on planet Earth, a time of year when day and night are most nearly equal. At an equinox, the Earth’s terminator — the dividing line between day and night — becomes vertical and connects the north and south poles. The featured time-lapse video demonstrates this by displaying an entire year on planet Earth in twelve seconds. From geosynchronous orbit, the Meteosat 9 satellite recorded these infrared images of the Earth every day at the same local time. The video started at the September 2010 equinox with the terminator line being vertical. As the Earth revolved around the Sun, the terminator was seen to tilt in a way that provides less daily sunlight to the northern hemisphere, causing winter in the north. As the year progressed, the March 2011 equinox arrived halfway through the video, followed by the terminator tilting the other way, causing winter in the southern hemisphere — and summer in the north. The captured year ends again with the September equinox, concluding another of billions of trips the Earth has taken — and will take — around the Sun.

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Sun Spot Hill


Is this giant orange ball about to roll down that tree-lined hill? No, because the giant orange ball is actually the Sun. Our Solar System’s central star was captured rising beyond a hill on Earth twelve days ago complete with a delightfully detailed foreground. The Sun’s disk showed five sunspots, quite a lot considering that during the solar minimum in solar activity of the past few years, most days showed no spots. A close look at the hill — Sierra del Cid in Perter, Spain — reveals not only silhouetted pine trees, but silhouetted people — by coincidence three brothers of the photographer. The trees and brothers were about 3.5-kilometers away during the morning of the well-planned, single-exposure image. A dark filter muted the usually brilliant Sun and brought up great detail on the lower sunspots. Within a few minutes, the Sun rose far above the hill, while within a week, the sunspots rotated around the Sun, out of view. The captured scene, however, is now frozen in time for all to enjoy.

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Lynds Dark Nebula


Stars are forming in Lynds Dark Nebula (LDN) 1251. About 1,000 light-years away and drifting above the plane of our Milky Way galaxy, the dusty molecular cloud is part of a complex of dark nebulae mapped toward the Cepheus flare region. Across the spectrum, astronomical explorations of the obscuring interstellar clouds reveal energetic shocks and outflows associated with newborn stars, including the telltale reddish glow from scattered Herbig-Haro objects hiding in the image. Distant background galaxies also lurk on the scene, almost buried behind the dusty expanse. This alluring view spans over two full moons on the sky, or 17 light-years at the estimated distance of LDN 1251.

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Rings and Seasons of Saturn


On Saturn, the rings tell you the season. On Earth, Wednesday marks an equinox, the time when the Earth’s equator tilts directly toward the Sun. Since Saturn’s grand rings orbit along the planet’s equator, these rings appear most prominent — from the direction of the Sun — when the spin axis of Saturn points toward the Sun. Conversely, when Saturn‘s spin axis points to the side, an equinox occurs and the edge-on rings are hard to see from not only the Sun — but Earth. In the featured montage, images of Saturn between the years of 2004 and 2015 have been superposed to show the giant planet passing from southern summer toward northern summer. Saturn was as close as it can get to planet Earth last month, and this month the ringed giant is still bright and visible throughout much of the night

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Rubin’s Galaxy


In this Hubble Space Telescope image the bright, spiky stars lie in the foreground toward the heroic northern constellation Perseus and well within our own Milky Way galaxy. In sharp focus beyond is UGC 2885, a giant spiral galaxy about 232 million light-years distant. Some 800,000 light-years across compared to the Milky Way’s diameter of 100,000 light-years or so, it has around 1 trillion stars. That’s about 10 times as many stars as the Milky Way. Part of an investigation to understand how galaxies can grow to such enormous sizes, UGC 2885 was also part of An Interesting Voyage and astronomer Vera Rubin’s pioneering study of the rotation of spiral galaxies. Her work was the first to convincingly demonstrate the dominating presence of dark matter in our universe.

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Video: Flash on Jupiter


There has been a flash on Jupiter. A few days ago, several groups monitoring our Solar System’s largest planet noticed a two-second long burst of light. Such flashes have been seen before, with the most famous being a series of impactor strikes in 1994. Then, fragments of Comet Shoemaker-Levy 9 struck Jupiter leaving dark patches that lasted for months. Since then, at least seven impacts have been recorded on Jupiter — usually discovered by amateur astronomers. In the featured video, variations in the Earth’s atmosphere cause Jupiter’s image to shimmer when, suddenly, a bright flash appears just left of center. Io and its shadow are visible on the right. What hit Jupiter will likely never be known, but considering what we do know of the nearby Solar System, it was likely a piece of rocky and ice — perhaps the size of a bus — that broke off long-ago from a passing comet or asteroid.

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