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. via NASA https://ift.tt/3CBp332

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. via NASA https://ift.tt/3EF3m3Q

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. via NASA https://ift.tt/3nSAgbp

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 via NASA https://ift.tt/3nGZ85Y

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. via NASA https://ift.tt/2XsmDV6

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. via NASA https://ift.tt/3Ekughz

North America and the Pelican

Fans of our fair planet might recognize the outlines of these cosmic clouds. On the left, bright emission outlined by dark, obscuring dust lanes seems to trace a continental shape, lending the popular name North America Nebula to the emission region cataloged as NGC 7000. To the right, just off the North America Nebula’s east coast, is IC 5070, whose avian profile suggests the Pelican Nebula. The two bright nebulae are about 1,500 light-years away, part of the same large and complex star forming region, almost as nearby as the better-known Orion Nebula. At that distance, the 3 degree wide field of view would span 80 light-years. This careful cosmic portrait uses narrow band images combined to highlight the bright ionization fronts and the characteristic glow from atomic hydrogen, sulfur, and oxygen gas. These nebulae can be seen with binoculars from a dark location. Look northeast of bright star Deneb in the constellation Cygnus the Swan. via NASA https://ift.tt/3AhvdEX

Cyclone Paths on Planet Earth

Where on Earth do cyclones go? Known as hurricanes when in the Atlantic Ocean and typhoons when in the Pacific, the featured map shows the path of all major storms from 1985 through 2005. The map shows graphically that cyclones usually occur over water, which makes sense since evaporating warm water gives them energy. The map also shows that cyclones never cross — and rarely approach — the Earth’s equator, since the Coriolis effect goes to zero there, and cyclones need the Coriolis force to circulate. The Coriolis force also causes cyclone paths to arc away from the equator. Although long-term trends remain a topic of research, evidence indicates that hurricanes have become, on the average, more powerful in the North Atlantic over the past 30 years, and their power is projected to keep increasing. via NASA https://ift.tt/3AeJYYT

Mars Panorama 360 from Curiosity

Which way up Mount Sharp? In early September, the robotic rover Curiosity continued its ascent up the central peak of Gale Crater, searching for more clues about ancient water and further evidence that Mars could once have been capable of supporting life. On this recent Martian morning, before exploratory drilling, the rolling rover took this 360-degree panorama, in part to help Curiosity’s human team back on Earth access the landscape and chart possible future routes. In the horizontally-compressed featured image, an amazing vista across Mars was captured, complete with layered hills, red rocky ground, gray drifting sand, and a dusty atmosphere. The hill just left of center has been dubbed Maria Gordon Notch in honor of a famous Scottish geologist. The current plan is to direct Curiosity to approach, study, and pass just to the right of Gordon Notch on its exploratory trek. via NASA https://ift.tt/3htPpvZ

Night Sky Reflected

What’s that in the mirror? In the featured image of the dark southern sky, the three brightest galaxies of the night are all relatively easy to identify. Starting from the left, these are the Small Magellanic Cloud (SMC), the Large Magellanic Cloud (LMC), and part of the central band of our Milky Way Galaxy. All three are also seen reflected in a shallow pool of water. But what is seen in the mirror being positioned by the playful astrophotographer? Dust clouds near the center of our Milky Way — and the planet Jupiter. The composite was carefully planned and composed from images captured from the same camera in the same location and during the same night in mid-2019 in Mostardas, south Brazil. The picture won first place in the Connecting to the Dark division of the International Dark-Sky Association’s Capture the Dark contest for 2021. via NASA https://ift.tt/3A7gTPc