A Historic Brazilian Constellation

The night sky is filled with stories. Cultures throughout history have projected some of their most enduring legends onto the stars above. Generations of people see these stellar constellations, hear the associated stories, and pass them down. Featured here is the perhaps unfamiliar constellation of the Old Man, long recognized by the Tupi peoples native to regions of South America now known as Brazil. The Old Man, in more modern vernacular, may be composed of the Hyades star cluster as his head and the belt of Orion as part of one leg. Tupi folklore relates that the other leg was cut off by his unhappy wife, causing it to end at the orange star now known as Betelgeuse. The Pleiades star cluster, on the far left, can be interpreted as a head feather. In the featured image, the hobbled Old Man is mirrored by a person posing in the foreground. Folklore of the night sky is important for many reasons, including that it records cultural heritage and documents the universality of human intelligence and imagination. [via NASA] https://ift.tt/3nCoqyv

Moon Phases in 2021

What will the Moon phase be on your birthday this year? It is hard to predict because the Moon’s appearance changes nightly. As the Moon orbits the Earth, the half illuminated by the Sun first becomes increasingly visible, then decreasingly visible. The featured video animates images taken by NASA’s Moon-orbiting Lunar Reconnaissance Orbiter to show all 12 lunations that appear this year, 2021. A single lunation describes one full cycle of our Moon, including all of its phases. A full lunation takes about 29.5 days, just under a month (moon-th). As each lunation progresses, sunlight reflects from the Moon at different angles, and so illuminates different features differently. During all of this, of course, the Moon always keeps the same face toward the Earth. What is less apparent night-to-night is that the Moon’s apparent size changes slightly, and that a slight wobble called a libration occurs as the Moon progresses along its elliptical orbit. [via NASA] https://ift.tt/3bqMRMM

Star Cluster R136 Breaks Out

In the center of nearby star-forming region lies a huge cluster containing some of the largest, hottest, and most massive stars known. These stars, known collectively as star cluster R136, part of the Tarantula Nebula, were captured in the featured image in visible light in 2009 through the Hubble Space Telescope. Gas and dust clouds in the Tarantula Nebula, have been sculpted into elongated shapes by powerful winds and ultraviolet radiation from these hot cluster stars. The Tarantula Nebula lies within a neighboring galaxy known as the Large Magellanic Cloud and is located a mere 170,000 light-years away. [via NASA] https://ift.tt/35t5RGF

Titan: Moon over Saturn

Like Earth’s moon, Saturn’s largest moon Titan is locked in synchronous rotation. This mosaic of images recorded by the Cassini spacecraft in May of 2012 shows its anti-Saturn side, the side always facing away from the ringed gas giant. The only moon in the solar system with a dense atmosphere, Titan is the only solar system world besides Earth known to have standing bodies of liquid on its surface and an earthlike cycle of liquid rain and evaporation. Its high altitude layer of atmospheric haze is evident in the Cassini view of the 5,000 kilometer diameter moon over Saturn’s rings and cloud tops. Near center is the dark dune-filled region known as Shangri-La. The Cassini-delivered Huygens probe rests below and left of center, after the most distant landing for a spacecraft from Earth. [via NASA] https://ift.tt/3s3vZBP

NGC 1365: Majestic Island Universe

Barred spiral galaxy NGC 1365 is truly a majestic island universe some 200,000 light-years across. Located a mere 60 million light-years away toward the chemical constellation Fornax, NGC 1365 is a dominant member of the well-studied Fornax Cluster of galaxies. This impressively sharp color image shows the intense, reddish star forming regions near the ends of central bar and along the spiral arms, with details of the obscuring dust lanes cutting across the galaxy’s bright core. At the core lies a supermassive black hole. Astronomers think NGC 1365’s prominent bar plays a crucial role in the galaxy’s evolution, drawing gas and dust into a star-forming maelstrom and ultimately feeding material into the central black hole. [via NASA] https://ift.tt/38pmAN5

Total Solar Eclipse 2020

Along a narrow path crossing southern South America through Chile and Argentina, the final New Moon of 2020 moved in front of the Sun on December 14 in the year’s only total solar eclipse. Within about 2 days of perigee, the closest point in its elliptical orbit, the New Moon’s surface is faintly lit by earthshine in this dramatic composite view. The image is a processed composite of 55 calibrated exposures ranging from 1/640 to 3 seconds. Covering a large range in brightness during totality, it reveals the dim lunar surface and faint background stars, along with planet-sized prominences at the Sun’s edge, an enormous coronal mass ejection, and sweeping coronal structures normally hidden in the Sun’s glare. Look closely for an ill-fated sungrazing Kreutz family comet (C/2020 X3 SOHO) approaching from the lower left, at about the 7 o’clock position. In 2021 eclipse chasers will see an annular solar eclipse coming up on June 10. They’ll have to wait until December 4 for the only total solar eclipse in 2021 though. That eclipse will be total along a narrow path crossing the southernmost continent of Antarctica. [via NASA] https://ift.tt/3q0DPKj

Striped Sand Dunes on Mars

Why are these sand dunes on Mars striped? No one is sure. The featured image shows striped dunes in Kunowsky Crater on Mars, photographed recently with the Mars Reconnaissance Orbiter’s HiRISE Camera. Many Martian dunes are known to be covered unevenly with carbon dioxide (dry ice) frost, creating patterns of light and dark areas. Carbon dioxide doesn’t melt, but sublimates, turning directly into a gas. Carbon dioxide is also a greenhouse material even as a solid, so it can trap heat under the ice and sublimate from the bottom up, causing geyser-like eruptions. During Martian spring, these eruptions can cause a pattern of dark defrosting spots, where the darker sand is exposed. The featured image, though, was taken during Martian autumn, when the weather is getting colder – making these stripes particularly puzzling. One hypothesis is that they are caused by cracks in the ice that form from weaker eruptions or thermal stress as part of the day-night cycle, but research continues. Watching these dunes and others through more Martian seasons may give us more clues to solve this mystery. [via NASA] https://ift.tt/35fdBvU

The Small Cloud of Magellan

What is the Small Magellanic Cloud? It has turned out to be a galaxy. People who have wondered about this little fuzzy patch in the southern sky included Portuguese navigator Ferdinand Magellan and his crew, who had plenty of time to study the unfamiliar night sky of the south during the first circumnavigation of planet Earth in the early 1500s. As a result, two celestial wonders easily visible for southern hemisphere skygazers are now known in Western culture as the Clouds of Magellan. Within the past 100 years, research has shown that these cosmic clouds are dwarf irregular galaxies, satellites of our larger spiral Milky Way Galaxy. The Small Magellanic Cloud actually spans 15,000 light-years or so and contains several hundred million stars. About 210,000 light-years away in the constellation of the Tucan (Tucana), it is more distant than other known Milky Way satellite galaxies, including the Sagittarius Dwarf galaxy and the Large Magellanic Cloud. This sharp image also includes the foreground globular star cluster 47 Tucanae on the right. [via NASA] https://ift.tt/3ojVdtd

Sprite Lightning at 100000 Frames Per Second

What causes sprite lightning? Mysterious bursts of light in the sky that momentarily resemble gigantic jellyfish have been recorded for over 30 years, but apart from a general association with positive cloud-to-ground lightning, their root cause remains unknown. Some thunderstorms have them — most don’t. Recently, however, high speed videos are better detailing how sprites actually develop. The featured video, captured in mid-2019, is fast enough — at about 100,000 frames per second — to time-resolve several sprite “bombs” dropping and developing into the multi-pronged streamers that appear on still images. Unfortunately, the visual clues provided by videos like these do not fully resolve the sprite origins mystery. High speed vidoes do indicate to some researchers, though, that sprites are more likely to occur when plasma irregularities exist in the upper atmosphere. [via NASA] https://ift.tt/35nQoI7

A Phoenix Aurora over Iceland

All of the other aurora watchers had gone home. By 3:30 am in Iceland, on a quiet September night, much of that night’s auroras had died down. Suddenly, unexpectedly, a new burst of particles streamed down from space, lighting up the Earth’s atmosphere once again. This time, surprisingly, pareidoliacally, the night lit up with an amazing shape reminiscent of a giant phoenix. With camera equipment at the ready, two quick sky images were taken, followed immediately by a third of the land. The mountain in the background is Helgafell, while the small foreground river is called Kaldá, both located about 30 kilometers north of Iceland’s capital Reykjavík. Seasoned skywatchers will note that just above the mountain, toward the left, is the constellation of Orion, while the Pleiades star cluster is also visible just above the frame center. The 2016 aurora, which lasted only a minute and was soon gone forever — would possibly be dismissed as an fanciful fable — were it not captured in the featured, digitally-composed, image mosaic. [via NASA] https://ift.tt/3hAKBn8