Orbiting 400 kilometers above Quebec, Canada, planet Earth, the International Space Station Expedition 59 crew captured this snapshot of the broad St. Lawrence River and curiously circular Lake Manicouagan on April 11. Right of center, the ring-shaped lake is a modern reservoir within the eroded remnant of an ancient 100 kilometer diameter impact crater. The ancient crater is very conspicuous from orbit, a visible reminder that Earth is vulnerable to rocks from space. Over 200 million years old, the Manicouagan crater was likely caused by the impact of a rocky body about 5 kilometers in diameter. Currently, there is no known asteroid with a significant probability of impacting Earth in the next century. But a fictional scenario to help practice for an asteroid impact is on going at the 2019 IAA Planetary Defense Conference.
To some it looks like a cat’s eye. To others, perhaps like a giant cosmic conch shell. It is actually one of brightest and most highly detailed planetary nebula known, composed of gas expelled in the brief yet glorious phase near the end of life of a Sun-like star. This nebula’s dying central star may have produced the outer circular concentric shells by shrugging off outer layers in a series of regular convulsions. The formation of the beautiful, complex-yet-symmetric inner structures, however, is not well understood. The featured image is a composite of a digitally sharpened Hubble Space Telescope image with X-ray light captured by the orbiting Chandra Observatory. The exquisite floating space statue spans over half a light-year across. Of course, gazing into this Cat’s Eye, humanity may well be seeing the fate of our sun, destined to enter its own planetary nebula phase of evolution … in about 5 billion years.
The galaxy was never in danger. For one thing, the Triangulum galaxy (M33), pictured, is much bigger than the tiny grain of rock at the head of the meteor. For another, the galaxy is much farther away — in this instance 3 million light years as opposed to only about 0.0003 light seconds. Even so, the meteor’s path took it angularly below the galaxy. Also the wind high in Earth’s atmosphere blew the meteor’s glowing evaporative molecule train away from the galaxy, in angular projection. Still, the astrophotographer was quite lucky to capture both a meteor and a galaxy in a single exposure — which was subsequently added to two other images of M33 to bring up the spiral galaxy’s colors. At the end, the meteor was gone in a second, but the galaxy will last billions of years. Follow APOD on: Instagram, Facebook, Reddit, or Twitter
Massive stars, abrasive winds, mountains of dust, and energetic light sculpt one of the largest and most picturesque regions of star formation in the Local Group of Galaxies. Known as N11, the region is visible on the upper right of many images of its home galaxy, the Milky Way neighbor known as the Large Magellanic Clouds (LMC). The featured image was taken for scientific purposes by the Hubble Space Telescope and reprocessed for artistry by an amateur to win a Hubble’s Hidden Treasures competition. Although the section imaged above is known as NGC 1763, the entire N11 emission nebula is second in LMC size only to the Tarantula Nebula. Compact globules of dark dust housing emerging young stars are also visible around the image. A new study of variable stars in the LMC with Hubble has helped to recalibrate the distance scale of the observable universe, but resulted in a slightly different scale than found using the pervasive cosmic microwave background. Astrophysicists: Browse 1,900+ codes in the Astrophysics Source Code Library
Only six years ago, the entire surface of planet Mercury was finally mapped. Detailed observations of the innermost planet’s surprising crust began when the robotic have been ongoing since the robotic MESSENGER spacecraft first passed Mercury in 2008 and continued until its controlled crash landing in 2015. Previously, much of the Mercury’s surface was unknown as it is too far for Earth-bound telescopes to see clearly, while the Mariner 10 flybys in the 1970s observed only about half. The featured video is a compilation of thousands of images of Mercury rendered in exaggerated colors to better contrast different surface features. Visible on the rotating world are rays emanating from a northern impact that stretch across much of the planet, while about half-way through the video the light colored Caloris Basin rotates into view, a northern ancient impact feature that filled with lava. Recent analysis of MESSENGER data indicates that Mercury has a solid inner core. Surf the Universe: Click here to see a randomly selected APOD!
Tracking along the southern Milky Way this beautiful celestial mosaic was recorded under dark Brazilian skies. Spanning some 20 degrees it actually starts with the dark expanse of the Coalsack nebula at the lower left, tucked under an arm of the Southern Cross. That compact constellation is topped by bright yellowish Gamma Crucis, a cool giant star a mere 88 light-years distant. A line from Gamma Crucis through the blue star at the bottom of the cross, Alpha Crucis, points toward the South Celestial Pole. Follow the Milky Way to the right and your gaze will sweep across IC 2948, popularly known as the Running Chicken nebula, before it reaches Eta Carinae and the Carina Nebula near the right edge of the frame. About 200 light-years across, the Carina Nebula is a star forming region much larger than the more northerly stellar nursery the Orion Nebula. The Carina Nebula lies around 7,500 light-years from Earth along the plane of the Milky Way.
Ridges of glowing interstellar gas and dark dust clouds inhabit the turbulent, cosmic depths of the Lagoon Nebula. Also known as M8, the bright star forming region is about 5,000 light-years distant. But it still makes for a popular stop on telescopic tours of the constellation Sagittarius, toward the center of our Milky Way Galaxy. Dominated by the telltale red emission of ionized hydrogen atoms recombining with stripped electrons, this stunning view of the Lagoon is over 100 light-years across. At its center, the bright, compact, hourglass shape is gas ionized and sculpted by energetic radiation and extreme stellar winds from a massive young star. In fact, the many bright stars of open cluster NGC 6530 drift within the nebula, just formed in the Lagoon several million years ago. Broadband image data from Pan-STARRS (Panoramic Survey Telescope & Rapid Response System) was combined with narrowband data from amateur telescopes to create this wide and deep portrait of the Lagoon Nebula.
The symmetric, multi-legged appearance of the Southern Crab Nebula is certainly distinctive. About 7,000 light-years distant toward the southern sky constellation Centaurus, its glowing nested hourglass shapes are produced by the remarkable symbiotic binary star system at its center. The nebula’s dramatic stellar duo consists of a hot white dwarf star and cool, pulsating red giant star shedding outer layers that fall onto the smaller, much hotter companion. Embedded in a disk of material, outbursts from the white dwarf cause an outflow of gas driven away both above and below the disk resulting in the bipolar hourglass shapes. The bright central shape is about half a light-year across. This new Hubble Space Telescope image celebrates the 29th anniversary of Hubble’s launch on April 24, 1990 on board the Space Shuttle Discovery.
Meteor showers are caused by streams of solid particles, dust size and larger, moving as a group through space. In most cases, the orbits of these meteor streams can be identified with dust expelled from a comet. When the Earth passes through a stream, the particles leave brilliant trails through the night sky as they disintegrate in Earth’s atmosphere. The meteor paths are all parallel to each other, but, like train tracks, the effect of perspective causes them to appear to originate from a radiant point in the distance. The featured image composite was taken during January’s Quadrantid meteor shower from La Palma, one of Spain’s Canary Islands, off the northwest coast of Africa. The Quadrantids radiant is visible just below the handle of the Big Dipper. A careful eye will also discern the faint green coma of Comet Wirtanen. Tonight is the peak of the modest Lyrid meteor shower, with several meteors per hour visible from dark locations with clear skies.