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2019 February 28 Sharpest Ultima Thule Image Credit: NASA, Johns Hopkins University APL, Southwest Research Institute, National Optical Astronomy Observatory Explanation: 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…

2019 February 27 Magnetic Orion Image Credit & Copyright: NASA, SOFIA, D. Chuss et al. & ESO, M. McCaughrean et al. Explanation: Can magnetism affect how stars form? Recent analysis of Orion data from the HAWC+ instrument on the airborne SOFIA observatory indicate that, at times, it can. HAWC+ is able to measure the polarization of far-infrared light which can reveal the alignment of dust grains by expansive ambient magnetic fields. In the featured image, these magnetic fields are shown as curvy lines superposed on an infrared image of the Orion Nebula taken by a Very Large Telescope in Chile. Orion’s Kleinmann-Low Nebula is visible slightly to the upper right of the image center, while bright stars of the Trapezium cluster are visible just to…

2019 February 26 Simulation TNG50: A Galaxy Cluster Forms Video Credit: IllustrisTNG Project; Visualization: Dylan Nelson (Max Planck Institute for Astrophysics) et al. Music: Symphony No. 5 (Ludwig van Beethoven), via YouTube Audio Library Explanation: 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…

2019 February 25 Red Sprite Lightning over Kununurra Image Credit & Copyright: Ben Broady Explanation: What are those red filaments in the sky? It is a rarely seen form of lightning confirmed only about 30 years ago: red sprites. Recent research has shown that following a powerful positive cloud-to-ground lightning strike, red sprites may start as 100-meter balls of ionized air that shoot down from about 80-km high at 10 percent the speed of light and are quickly followed by a group of upward streaking ionized balls. The featured image, taken just over a week ago in Kununurra, Western Australia, captured some red sprites while shooting a time-lapse sequence of a distant lightning storm. Pictured, green trees cover the foreground, dark mountains are seen on…

2019 February 24 The Expanding Echoes of Supernova 1987A Video Credit & Copyright: David Malin, AAT Explanation: 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…

2019 February 23 The Stars of the Triangulum Galaxy Image Credit: NASA, ESA, M. Durbin, J. Dalcanton, and B. F. Williams (University of Washington) Explanation: Like grains of sand on a cosmic beach, stars of the Triangulum Galaxy are resolved in this sharp mosaic from the Hubble Space Telescope’s Advanced Camera for Surveys (ACS). The inner region of the galaxy spanning over 17,000 light-years is covered at extreme resolution, the second largest image ever released by Hubble. At its center is the bright, densely packed galactic core surrounded by a loose array of dark dust lanes mixed with the stars in the galactic plane. Also known as M33, the face-on spiral galaxy lies 3 million light-years away in the small northern constellation Triangulum. Over 50,000…

2019 February 22 NGC 4565: Galaxy on Edge Image Credit & Copyright: Christoph Kaltseis, CEDIC Explanation: Magnificent spiral galaxy NGC 4565 is viewed edge-on from planet Earth. Also known as the Needle Galaxy for its narrow profile, bright NGC 4565 is a stop on many telescopic tours of the northern sky, in the faint but well-groomed constellation Coma Berenices. This sharp, colorful image reveals the galaxy’s bulging central core cut by obscuring dust lanes that lace NGC 4565’s thin galactic plane. An assortment of other background galaxies is included in the pretty field of view, with neighboring galaxy NGC 4562 at the upper right. NGC 4565 itself lies about 40 million light-years distant and spans some 100,000 light-years. Easily spotted with small telescopes, sky enthusiasts…

2019 February 21 Reflections on vdB 9 Image Credit & Copyright: Guenter Kerschhuber Explanation: Centered in a well-composed celestial still life, pretty, blue vdB 9 is the 9th object in Sidney van den Bergh’s 1966 catalog of reflection nebulae. It shares this telescopic field of view, about twice the size of a full moon on the sky, with stars and dark, obscuring dust clouds in the northerly constellation Cassiopeia. Cosmic dust is preferentially reflecting blue starlight from embedded, hot star SU Cassiopeiae, giving vdB 9 the characteristic bluish tint associated with a classical reflection nebula. SU Cas is a Cepheid variable star, though even at its brightest it is just too faint to be seen with the unaided eye. Still Cepheids play an important role…

2019 February 20 Doomed Star Eta Carinae Image Credit: NASA, ESA, Hubble; Processing & License: Judy Schmidt Explanation: Eta Carinae may be about to explode. But no one knows when – it may be next year, it may be one million years from now. Eta Carinae’s mass – about 100 times greater than our Sun – makes it an excellent candidate for a full blown supernova. Historical records do show that about 170 years ago Eta Carinae underwent an unusual outburst that made it one of the brightest stars in the southern sky. Eta Carinae, in the Keyhole Nebula, is the only star currently thought to emit natural LASER light. This featured image brings out details in the unusual nebula that surrounds this rogue star….

2019 February 19 Comet Iwamoto Before Spiral Galaxy NGC 2903 Video Credit & Copyright: Norbert Span Explanation: It isn’t every night that a comet passes a galaxy. Last Thursday, though, binocular comet C/2018 Y1 (Iwamoto) moved nearly in front of a spiral galaxy of approximately the same brightness: NGC 2903. Comet Iwamoto was discovered late last year and orbits the Sun in a long ellipse. It last visited the inner Solar System during the Middle Ages, around the year 648. The comet reached its closest point to the Sun — between Earth and Mars — on February 6, and its closest point to Earth a few days ago, on February 13. The featured time-lapse video condenses almost three hours into about ten seconds, and was…