Nacreous Clouds over Lapland


Vivid and lustrous, wafting iridescent waves of color wash across this skyscape from Kilpisjärvi, Finland. Known as nacreous clouds or mother-of-pearl clouds, they are rare. But their unforgettable appearance was captured looking south at 69 degrees north latitude at sunset on January 24. A type of polar stratospheric cloud, they form when unusually cold temperatures in the usually cloudless lower stratosphere form ice crystals. Still sunlit at altitudes of around 15 to 25 kilometers, the clouds can diffract sunlight even after sunset and just before the dawn.

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Imagine traveling to a star about 100 times as massive as our Sun, a million times more luminous, and with 30 times the surface temperature. Such stars exist, and some are known as Wolf Rayet (WR) stars, named after French astronomers Charles Wolf and Georges Rayet. The central star in this image is WR 40 which is located toward the constellation of Carina. Stars like WR 40 live fast and die young in comparison with the Sun. They quickly exhaust their core hydrogen supply, move on to fusing heavier core elements, and expand while ejecting their outer layers via high stellar winds. In this case, the central star WR 40 ejects the atmosphere at a speed of nearly 100 kilometers per second, and these outer layers have become the expanding oval-shaped nebula RCW 58.

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Can you still see the comet? Yes. Even as C/2022 E3 (ZTF) fades, there is still time to see it if you know where and when to look. Geometrically, Comet ZTF has passed its closest to both the Sun and the Earth and is now headed back to the outer Solar System. Its orbit around the Sun has it gliding across the northern sky all month, after passing near Polaris and both the Big and Little Dippers last month. Pictured, Comet ZTF was photographed between the two dippers in late January while sporting an ion tail that extended over 10 degrees. Now below naked-eye visibility, Comet ZTF can be found with binoculars or a small telescope and a good sky map. A good time to see the comet over the next week is after the Sun sets — but before the Moon rises. The comet will move nearly in front of Mars in a few days

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In the heart of the Rosette Nebula lies a bright cluster of stars that lights up the nebula. The stars of NGC 2244 formed from the surrounding gas only a few million years ago. The featured image taken in mid-January using multiple exposures and very specific colors of Sulfur (shaded red), Hydrogen (green), and Oxygen (blue), captures the central region in tremendous detail. A hot wind of particles streams away from the cluster stars and contributes to an already complex menagerie of gas and dust filaments while slowly evacuating the cluster center. The Rosette Nebula‘s center measures about 50 light-years across, lies about 5,200 light-years away, and is visible with binoculars towards the constellation of the Unicorn (Monoceros).

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This moon is shining by the light of its planet. Specifically, a large portion of Enceladus pictured here is illuminated primarily by sunlight first reflected from the planet Saturn. The result is that the normally snow-white moon appears in the gold color of Saturn’s cloud tops. As most of the illumination comes from the image left, a labyrinth of ridges throws notable shadows just to the right of the image center, while the kilometer-deep canyon Labtayt Sulci is visible just below. The bright thin crescent on the far right is the only part of Enceladus directly lit by the Sun. The featured image was taken in 2011 by the robotic Cassini spacecraft during a close pass by by the enigmatic moon. Inspection of the lower left part of this digitally sharpened image reveals plumes of ice crystals thought to originate in a below-surface sea.

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NGC 2626 along the Vela Molecular Ridge


Centered in this colorful cosmic canvas, NGC 2626 is a beautiful, bright, blue reflection nebula in the southern Milky Way. Next to an obscuring dust cloud and surrounded by reddish hydrogen emission from large H II region RCW 27 it lies within a complex of dusty molecular clouds known as the Vela Molecular Ridge. NGC 2626 is itself a cloud of interstellar dust reflecting blue light from the young hot embedded star visible within the nebula. But astronomical explorations reveal many other young stars and associated nebulae in the star-forming region. NGC 2626 is about 3,200 light-years away. At that distance this telescopic field of view would span about 30 light-years along the Vela Molecular Ridge.

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Polaris and the Trail of Comet ZTF


Stars trace concentric arcs around the North Celestial Pole in this three hour long night sky composite, recorded with a digital camera fixed to a tripod on January 31, near Àger, Lleida, Spain. On that date Comet C/2022 E3 (ZTF) was near its northernmost declination in planet Earth’s sky. That put the comet about 10 degrees from Earth’s North Celestial Pole making the comet’s position circumpolar, always above the horizon, from all locations on planet Earth at more than 10 degrees northern latitude. In the startrail image, the extension of Earth’s axis of rotation into space is at the left. North star Polaris traces the short, bright, concentric arc less than a degree from the North Celestial Pole. The trail of Comet ZTF is indicated at the right, its apparent motion mostly reflecting Earth’s rotation like the stars. But heading for its closest approach to planet Earth on February 1, the comet is also moving significantly with respect to the background stars. The diffuse greenish trail of Comet ZTF is an almost concentric arc mingled with startrails as it sweeps through the long-necked constellation Camelopardalis.

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Reflections on the 1970s


The 1970s are sometimes ignored by astronomers, like this beautiful grouping of reflection nebulae in Orion – NGC 1977, NGC 1975, and NGC 1973 – usually overlooked in favor of the substantial glow from the nearby stellar nursery better known as the Orion Nebula. Found along Orion’s sword just north of the bright Orion Nebula complex, these reflection nebulae are also associated with Orion’s giant molecular cloud about 1,500 light-years away, but are dominated by the characteristic blue color of interstellar dust reflecting light from hot young stars. In this sharp color image a portion of the Orion Nebula appears along the bottom border with the cluster of reflection nebulae at picture center. NGC 1977 stretches across the field just below center, separated from NGC 1973 (above right) and NGC 1975 (above left) by dark regions laced with faint red emission from hydrogen atoms. Taken together, the dark regions suggest the region’s popular moniker, the Running Man Nebula. At the estimated distance of Orion’s dusty molecular cloud this running man would be about 15 light-years across.

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Seven worlds orbit the ultracool dwarf star TRAPPIST-1. A mere 40 light-years away, many of the exoplanets were discovered in 2016 using the Transiting Planets and Planetesimals Small Telescope (TRAPPIST) located in the Atlas Mountains of Morocco, and later confirmed with telescope including NASA’s Spitzer Space Telescope. The TRAPPIST-1 planets are likely all rocky and similar in size to Earth, and so compose one of the largest treasure troves of terrestrial planets ever detected around a single star. Because they orbit very close to their faint, tiny star they could also have regions where surface temperatures allow for the presence of ice or even liquid water, a key ingredient for life. Their tantalizing proximity to Earth makes them prime candidates for future telescopic explorations of the atmospheres of potentially habitable planets. All seven exoplanets appear in the featured illustration, which imagines a view from the most distant known world of this system, TRAPPIST-1h, as having a rocky landscape covered in ice. Meanwhile, in the imagined background, one of the system’s inner planets crosses in front of the dim, orange, nearly Jupiter-sized parent star.

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Comet ZTF has a distinctive shape. The now bright comet visiting the inner Solar System has been showing not only a common dust tail, ion tail, and green gas coma, but also an uncommonly distinctive antitail. The antitail does not actually lead the comet — it is just that the head of the comet is seen superposed on part of the fanned-out and trailing dust tail. The giant dirty snowball that is Comet C/2022 E3 (ZTF) has now passed its closest to the Sun and tomorrow will pass its closest to the Earth. The main panel of the featured triple image shows how Comet ZTF looked last week to the unaided eye under a dark and clear sky over Cáceres, Spain. The top inset image shows how the comet looked through binoculars, while the lower inset shows how the comet looked through a small telescope. The comet is now visible all night long from northern latitudes but will surely fade from easy observation during the next few weeks.

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