How can the Moon rise through a mountain? It cannot — what was photographed here is a moonrise through the shadow of a large volcano. The volcano is Mauna Kea, Hawai’i, USA, a frequent spot for spectacular photographs since it is one of the premier observing locations on planet Earth. The Sun has just set in the opposite direction, behind the camera. Additionally, the Moon has just passed full phase — were it precisely at full phase it would rise, possibly eclipsed, at the very peak of the shadow. The Moon is actually rising in the triangular shadow cone of the volcano, a corridor of darkness that tapers off in the distance like converging train tracks. The Moon is too large and too far away to be affected by the shadow of the volcano. Refraction of moonlight through the Earth’s atmosphere makes the Moon appear slightly oval. Cinder cones from old volcanic eruptions are visible in the foreground. via NASA https://ift.tt/2EYUEkq

Normally faint and elusive, the Jellyfish Nebula is caught in this alluring telescopic field of view. The entire scene is a two panel mosaic constructed using narrowband image data, with emission from sulfur, hydrogen and oxygen atoms shown in red, green and blue hues. It’s anchored right and left by two bright stars, Mu and Eta Geminorum, at the foot of the celestial twin. The Jellyfish Nebula itself is right of center, the brighter arcing ridge of emission with dangling tentacles. In fact, the cosmic jellyfish is part of bubble-shaped supernova remnant IC 443, the expanding debris cloud from a massive star that exploded. Light from the explosion first reached planet Earth over 30,000 years ago. Like its cousin in astrophysical waters the Crab Nebula supernova remnant, the Jellyfish Nebula is known to harbor a neutron star, the remnant of the collapsed stellar core. An emission nebula cataloged as Sharpless 249 fills the field at the upper left. The Jellyfish Nebula is about 5,000 light-years away. At that distance, this image would be about 300 light-years across. via NASA https://apod.nasa.gov/apod/ap190307.html

Where have all the sunspots gone? Last month the total number of spots that crossed our Sun was … zero. Well below of the long term monthly average, the Sun’s surface has become as unusually passive this solar minimum just like it did 11 years ago during the last solar minimum. Such passivity is not just a visual spectacle, it correlates with the Sun being slightly dimmer, with holes in the Sun’s corona being more stable, and with a reduced intensity in the outflowing solar wind. The reduced wind, in turn, cools and collapses Earth’s outer atmosphere (the thermosphere), causing reduced drag on many Earth-orbiting satellites. Pictured in inverted black & white on the left, the Sun’s busy surface is shown near solar maximum in 2012, in contrast to the image on the right, which shows the Sun’s surface last August, already without spots (for a few days), as solar minimum was setting in. Effects of this unusually static solar minimum are being studied. via NASA https://ift.tt/2NOqUcQ

What created these huge galactic superbubbles? Two of these unusual bubbles, each spanning thousands of light-years, were recently discovered near the center of spiral galaxy NGC 3079. The superbubbles, shown in purple on the image right, are so hot they emit X-rays detected by NASA’s Earth-orbiting Chandra X-Ray Observatory. Since the bubbles straddle the center of NGC 3079, a leading hypothesis is that they were somehow created by the interaction of the central supermassive black hole with surrounding gas. Alternatively, the superbubbles might have been created primarily by the energetic winds from many young and hot stars near that galaxy’s center. The only similar known phenomenon is the gamma-ray emitting Fermi bubbles emanating from the center of our Milky Way Galaxy, discovered 10 years ago in images taken by NASA’s Fermi satellite. Research into the nature of the NGC 3079 superbubbles will surely continue, as well as searches for high-energy superbubbles in other galaxies. via NASA https://ift.tt/2IQwmNy

Why are bullets of gas shooting out of the Orion Nebula? Nobody is yet sure. First discovered in 1983, each bullet is actually about the size of our Solar System, and moving at about 400 km/sec from a central source dubbed IRc2. The age of the bullets, which can be found from their speed and distance from IRc2, is very young — typically less than 1,000 years. As the bullets expand out the top of the Kleinmann-Low section of the Orion Nebula, a small percentage of iron gas causes the tip of each bullet to glow blue, while each bullet leaves a tubular pillar that glows by the light of heated hydrogen gas. The detailed image was created using the 8.1 meter Gemini South telescope in Chile with an adaptive optics system (GeMS). GeMS uses five laser generated guide stars to help compensate for the blurring effects of planet Earth’s atmosphere. via NASA https://ift.tt/2VwwqDm

The bright clusters and nebulae of planet Earth’s night sky are often named for flowers or insects. Though its wingspan covers over 3 light-years, NGC 6302 is no exception. With an estimated surface temperature of about 250,000 degrees C, the dying central star of this particular planetary nebula has become exceptionally hot, shining brightly in ultraviolet light but hidden from direct view by a dense torus of dust. This sharp close-up was recorded by the Hubble Space Telescope in 2009. The Hubble image data is reprocessed here, showing off the remarkable details of the complex planetary nebula. Cutting across a bright cavity of ionized gas, the dust torus surrounding the central star is near the center of this view, almost edge-on to the line-of-sight. Molecular hydrogen has been detected in the hot star’s dusty cosmic shroud. NGC 6302 lies about 4,000 light-years away in the arachnologically correct constellation of the Scorpion (Scorpius). via NASA https://ift.tt/2NK2cdH

Still racing across planet Earth’s night skies, Comet Iwamoto (C/2018 Y1) shares this pretty telescopic field of view with stars and nebulae of northern constellation Auriga, the Charioteer. Captured on February 27, Iwamoto’s greenish coma and faint tail appear between a complex of reddish emission nebulae and open star cluster M36 (bottom right). The reddish emission is light from hydrogen gas ionized by ultraviolet radiation from hot stars near the region’s giant molecular cloud some 6,000 light-years distant. The greenish glow from the comet, less than 5 light-minutes away, is predominantly emission from diatomic carbon molecules fluorescing in sunlight. M36, one of Auriga’s more familiar star clusters, is also a background object far beyond the Solar System, about 4,000 light-years away. Comet Iwamoto passed closest to Earth on February 12 and is outward bound in a highly elliptical orbit that will carry it beyond the Kuiper belt. With an estimated orbital period of 1,317 years it should return to the inner Solar System in 3390 AD. via NASA https://ift.tt/2IJyruy

On January 1, New Horizons swooped to within 3,500 kilometers of the Kuiper Belt world known as Ultima Thule. That’s about 3 times closer than its July 2015 closest approach to Pluto. The spacecraft’s unprecedented feat of navigational precision, supported by data from ground and space-based observing campaigns, was accomplished 6.6 billion kilometers (over 6 light-hours) from planet Earth. Six and a half minutes before closest approach to Ultima Thule it captured the nine frames used in this composite image. The most detailed picture possible of the farthest object ever explored, the image has a resolution of about 33 meters per pixel, revealing intriguing bright surface features and dark shadows near the terminator. A primitive Solar System object, Ultima Thule’s two lobes combine to span just 30 kilometers. The larger lobe, referred to as Ultima, is recently understood to be flattened like a fluffy pancake, while the smaller, Thule, has a shape that resembles a dented walnut. via NASA https://ift.tt/2UjlMQ4

How do clusters of galaxies form? Since our universe moves too slowly to watch, faster-moving computer simulations are created to help find out. A recent effort is TNG50 from IllustrisTNG, an upgrade of the famous Illustris Simulation. The first part of the featured video tracks cosmic gas (mostly hydrogen) as it evolves into galaxies and galaxy clusters from the early universe to today, with brighter colors marking faster moving gas. As the universe matures, gas falls into gravitational wells, galaxies forms, galaxies spin, galaxies collide and merge, all while black holes form in galaxy centers and expel surrounding gas at high speeds. The second half of the video switches to tracking stars, showing a galaxy cluster coming together complete with tidal tails and stellar streams. The outflow from black holes in TNG50 is surprisingly complex and details are being compared with our real universe. Studying how gas coalesced in the early universe helps humanity better understand how our Earth, Sun, and Solar System originally formed. via NASA https://ift.tt/2XxA5CW

Can you find supernova 1987A? It isn’t hard — it occurred at the center of the expanding bullseye pattern. Although this stellar detonation was first seen in 1987, light from SN 1987A continued to bounce off clumps of interstellar dust and be reflected to us even many years later. Light echoes recorded between 1988 and 1992 by the Anglo Australian Telescope (AAT) in Australia are shown moving out from the position of the supernova in the featured time-lapse sequence. These images were composed by subtracting an LMC image taken before the supernova light arrived from later LMC images that included the supernova echo. Other prominent light echo sequences include those taken by the EROS2 and SuperMACHO sky monitoring projects. Studies of expanding light echo rings around other supernovas have enabled more accurate determinations of the location, date, and symmetry of these tremendous stellar explosions. Yesterday marked the 32nd anniversary of SN 1987A: the last recoded supernova in or around our Milky Way Galaxy, and the last to be visible to the unaided eye. via NASA https://ift.tt/2VhAEPi