How great was the Great American Eclipse? The featured HDR image shows it to be perhaps greater than we knew. On August 21 of last year, the Moon blocked the Sun for a few minutes along a narrow path across the USA. Although one of the most photographed events in human history, this image — only recently completed after an extraordinary amount of digital processing — shows one of the most detailed depictions of a solar corona ever taken. Composed of extremely hot gas, the solar corona is only visible to the unaided eye during a total solar eclipse. The featured image combined over 70 images of different time exposures. The series of complementary HDR images recovered enough detail to see motion of the solar corona. The images were taken in Unity, Oregon in the morning to get steady atmospheric seeing conditions. The next total solar eclipse visible on Earth will be in 2019 July, while the next one visible across North America and the USA will occur in 2024 April.
Flanked by satellite galaxies of the Milky Way a volcanic peak rises from this rugged horizon. The southern night skyscape looks toward the south over Laguna Lejia and the altiplano of the Antofagasta Region of northern Chile. Extending the view across extragalactic space, the Large (right) and Small Magellanic Clouds are so named for the 16th century Portuguese explorer Ferdinand Magellan, leader of planet Earth’s first circumnavigation. The larger cloud lies some 180,000 light-years, and the smaller 210,000 light-years beyond the mountaintop. Left of the Small Cloud of Magellan and also reflected in the foreground watery shallows on that starry night, 47 Tucanae shines like a bright star. A globular star cluster that roams the halo of the Milky Way, 47 Tucanae is about 13,000 light-years away.
This grand allsky view of our Milky Way and nearby galaxies is not a photograph. It’s a map based on individual measurements for nearly 1.7 billion stars. The astronomically rich data set used to create it, the sky-scanning Gaia satellite’s second data release, includes remarkably precise determinations of position, brightness, colour, and parallax distance for 1.3 billion stars. Of course, that’s about 1 percent of the total number of stars in the Milky Way. Still, the flat plane of our galaxy dominates the view. Home to most Milky Way stars it stretches across the center of Gaia’s stellar data map. Voids and rifts along the galactic plane correspond to starlight-obscuring interstellar dust clouds. At lower right are stars of the Large and Small Magellanic Clouds, neighboring galaxies that lie just beyond the Milky Way.
What will become of Jupiter’s Great Red Spot? Gas giant Jupiter is the solar system’s largest world with about 320 times the mass of planet Earth. Jupiter is home to one of the largest and longest lasting storm systems known, the Great Red Spot (GRS), visible to the left. The GRS is so large it could swallow Earth, although it has been shrinking. Comparison with historical notes indicate that the storm spans only about one third of the surface area it had 150 years ago. NASA’s Outer Planets Atmospheres Legacy (OPAL) program has been monitoring the storm more recently using the Hubble Space Telescope. The featured Hubble OPAL image shows Jupiter as it appeared in 2016, processed in a way that makes red hues appear quite vibrant. Modern GRS data indicate that the storm continues to constrict its surface area, but is also becoming slightly taller, vertically. No one knows the future of the GRS, including the possibility that if the shrinking trend continues, the GRS might one day even do what smaller spots on Jupiter have done — disappear completely.
The Blue Horsehead Nebula looks quite different in infrared light. In visible light, the reflecting dust of the nebula appears blue and shaped like a horse’s head. In infrared light, however, a complex labyrinth of filaments, caverns, and cocoons of glowing dust and gas emerges, making it hard to even identify the equine icon. The featured image of the nebula was created in three infrared colors (R=22, G=12, B=4.6 microns) from data taken by NASA’s orbiting Wide Field Infrared Survey Explorer (WISE) spacecraft. The nebula is cataloged as IC 4592 and spans about 40 light years, lying about 400 light years away toward the constellation Scorpius along the plane of our Milky Way Galaxy. IC 4592 is fainter but covers an angularly greater region than the better known Horsehead Nebula of Orion. The star that predominantly illuminates and heats the dust is Nu Scorpii, visible as the yellow star left of center.
Did you see it? One of the more common questions during a meteor shower occurs because the time it takes for a meteor to flash is typically less than the time it takes for a head to turn. Possibly, though, the glory of seeing bright meteors shoot across and knowing that they were once small granules on another world might make it all worthwhile, even if your observing partner(s) could not share in every particular experience. Peaking late tonight, a dark sky should enable the Lyrids meteor shower to exhibit as many as 20 visible meteors per hour from some locations. In the featured composite of nine exposures taken during the 2012 shower, a bright Lyrid meteor streaks above picturesque Crater Lake in Oregon, USA. Snow covers the foreground, while the majestic central band of our home galaxy arches well behind the serene lake. Other meteor showers this year — and every year — include the Perseids in mid-August and the Leonids in mid-November.
Have you seen the Moon lately? On April 18, its waxing sunlit crescent moved through planet Earth’s night across a background of stars in the Hyades. Anchored by bright star Aldebaran, the nearby, V-shaped star cluster and complete lunar orb appear in this telephoto image. The engaging skyview is actually digitally composed from a series of varying exposures. Recorded in 1/60th of a second, the shortest in the series captures the Moon’s bright crescent in sharp detail. Longer exposures, ranging up to 15 seconds, capture fainter background stars as well as earthshine, visible to the eye as the earthlit lunar night side.
Blown by the wind from a massive star, this interstellar apparition has a surprisingly familiar shape. Cataloged as NGC 7635, it is also known simply as The Bubble Nebula. Although it looks delicate, the 7 light-year diameter bubble offers evidence of violent processes at work. Above and left of the Bubble’s center is a hot, O-type star, several hundred thousand times more luminous and some 45 times more massive than the Sun. A fierce stellar wind and intense radiation from that star has blasted out the structure of glowing gas against denser material in a surrounding molecular cloud. The intriguing Bubble Nebula and associated cloud complex lie a mere 7,100 light-years away toward the boastful constellation Cassiopeia. This sharp, tantalizing view of the cosmic bubble is a composite of Hubble Space Telescope image data from 2016, reprocessed to present the nebula’s intense narrowband emission in an approximate true color scheme.
Except for the rings of Saturn, the Ring Nebula (M57) is probably the most famous celestial band. Its classic appearance is understood to be due to our own perspective, though. The recent mapping of the expanding nebula’s 3-D structure, based in part on this clear Hubble image,indicates that the nebula is a relatively dense, donut-like ring wrapped around the middle of a (American) football-shaped cloud of glowing gas. The view from planet Earth looks down the long axis of the football, face-on to the ring. Of course, in this well-studied example of a planetary nebula, the glowing material does not come from planets. Instead, the gaseous shroud represents outer layers expelled from the dying, once sun-like star, now a tiny pinprick of light seen at the nebula’s center. Intense ultraviolet light from the hot central star ionizes atoms in the gas. The Ring Nebula is about one light-year across and 2,000 light-years away.
What would it look like to fly over the North Pole of Jupiter? A fictional animation made from real images and data captured by NASA’s Juno spacecraft shows an answer. Since the pole is presently in shadow, the video uses infrared light emitted by Jupiter — specifically an infrared color where the hottest features glows the brightest. As the animation starts, Juno zooms in on the enormous world. Soon, one of the eight cyclones orbiting the North Pole is featured. One by one, all eight cyclones circling the pole are inspected, each the size of an entire continent on Earth, and each containing bumpy and fragmented spiral walls. The virtual trip ends with a zoom out. Studying Jovian cyclones helps humanity to better understand dangerous storm systems that occur here on Earth. Juno has recently concluded another close pass by Jupiter — Perijove 12 — and seems healthy enough to complete several more of the two-month orbits.