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Astronomy Picture of the Day

Starlink Satellite Trails over Brazil
Image Credit & Copyright: Egon Filter

Explanation: What are those streaks over the horizon? New Starlink satellites reflecting sunlight. SpaceX launched 60 Starlink communication satellites in May and 60 more in November. These satellites and thousands more are planned by communications companies in the next few years that may make streaks like these relatively common. Concern has been voiced by many in the astronomical community about how reflections from these satellites may affect future observations into space. In the pictured composite of 33 exposures, parallel streaks from Starlink satellites are visible over southern Brazil. Sunflowers dot the foreground, while a bright meteor was caught by chance on the upper right. Satellite reflections are not new — the constellation of 66 first-generation Iridium satellites launched starting 20 years ago produced some flares so bright that they could be seen during the day. Most of these old Iridium satellites, however, have been de-orbited over the past few years.

Tomorrow’s picture: supernova firefox

Astronomy Picture of the Day

Looking Sideways from the Parker Solar Probe
Video Credit: NASA, JHUAPL, Naval Research Lab, Parker Solar Probe

Explanation: Everybody sees the Sun. Nobody’s been there. Starting in 2018 though, NASA launched the robotic Parker Solar Probe (PSP) to investigate regions near to the Sun for the first time. The PSP‘s looping orbit brings it yet closer to the Sun each time around — every few months. The featured time-lapse video shows the view looking sideways from behind PSP‘s Sun shield during its first approach to the Sun a year ago — to about half the orbit of Mercury. The PSP‘s Wide Field Imager for Solar Probe (WISPR) cameras took the images over nine days, but they are digitally compressed here into about 14 seconds. The waving solar corona is visible on the far left, with stars, planets, and even the central band of our Milky Way Galaxy streaming by in the background as the PSP orbits the Sun. PSP has found the solar neighborhood to be surprisingly complex and to include switchbacks — times when the Sun’s magnetic field briefly reverses itself. The Sun is not only Earth’s dominant energy source, its variable solar wind compresses Earth’s atmosphere, triggers auroras, affects power grids, and can even damage orbiting communication satellites.

Tomorrow’s picture: satellite swarm

Astronomy Picture of the Day

Geminid Meteors over Chile
Image Credit & Copyright: Yuri Beletsky (Carnegie Las Campanas Observatory, TWAN)

Explanation: Are meteors streaming out from a point in the sky? Yes, in a way. When the Earth crosses a stream of Sun-orbiting meteors, these meteors appear to come from the direction of the stream — with the directional point called the radiant.  An example occurs every mid-December for the Geminids meteor shower, as apparent in the featured image.  Recorded near the shower’s peak in 2013, the featured skyscape captures Gemini’s shooting stars in a four-hour composite from the dark skies of the Las Campanas Observatory in Chile. In the foreground the 2.5-meter du Pont Telescope is visible as well as the 1-meter SWOPE telescope. The skies beyond the meteors are highlighted by Jupiter, seen as the bright spot near the image center, the central band of our Milky Way Galaxy, seen vertically on the image left, and the pinkish Orion Nebula on the far left. Dust swept up from the orbit of active asteroid 3200 Phaethon, Gemini’s meteors enter the atmosphere traveling at about 22 kilometers per second. The 2019 Geminid meteor shower peaks again this coming weekend.

Tomorrow’s picture: the sun sideways

Astronomy Picture of the Day

Pleiades to Hyades
Image Credit & Copyright: Amir H. Abolfath (TWAN)

Explanation: This cosmic vista stretches almost 20 degrees from top to bottom, across the dusty constellation Taurus. It begins at the Pleiades and ends at the Hyades, two star clusters recognized since antiquity in Earth’s night sky. At top, the compact Pleiades star cluster is about 400 light-years away. The lovely grouping of young cluster stars shine through dusty clouds that scatter blue starlight. At bottom, the V-shaped Hyades cluster looks more spread out in comparison and lies much closer, 150 light-years away. The Hyades cluster stars seem anchored by bright Aldebaran, a red giant star with a yellowish appearance. But Aldebaran actually lies only 65 light-years distant and just by chance along the line of sight to the Hyades cluster. Faint and darkly obscuring dust clouds found near the edge of the Taurus Molecular Cloud are also evident throughout the celestial scene. The wide field of view includes the dark nebula Barnard 22 at left with youthful star T Tauri and Hind’s variable nebula just above Aldebaran in the frame.

Tomorrow’s picture: pixels in space

Astronomy Picture of the Day

Spiral Galaxy NGC 6744
Image Credit & Copyright: Zhuokai Liu, Jiang Yuhang

Explanation: Beautiful spiral galaxy NGC 6744 is nearly 175,000 light-years across, larger than our own Milky Way. It lies some 30 million light-years distant in the southern constellation Pavo and appears as only a faint, extended object in small telescopes. We see the disk of the nearby island universe tilted towards our line of sight in this remarkably detailed galaxy portrait, a telescopic view that spans an area about the angular size of a full moon. In it, the giant galaxy’s elongated yellowish core is dominated by the light from old, cool stars. Beyond the core, grand spiral arms are filled with young blue star clusters and speckled with pinkish star forming regions. An extended arm sweeps past a smaller satellite galaxy (NGC 6744A) at the lower right. NGC 6744’s galactic companion is reminiscent of the Milky Way’s satellite galaxy the Large Magellanic Cloud.

Tomorrow’s picture: pixels in space

Astronomy Picture of the Day

Electric Night
Image Credit & Copyright: Ivan Pedretti

Explanation: It may appear, at first, like the Galaxy is producing the lightning, but really it’s the Earth. The featured nighttime landscape was taken from a southern tip of the Italian Island of Sardinia in early June. The foreground rocks and shrubs are near the famous Capo Spartivento Lighthouse, and the camera is pointed south toward Algeria in Africa. In the distance, across the Mediterranean Sea, a thunderstorm is threatening, with several electric lightning strokes caught together during this 25-second wide-angle exposure. Much farther in the distance, strewn about the sky, are hundreds of stars in the neighborhood of our Sun in the Milky Way Galaxy. Furthest away, and slanting down from the upper left, are billions of stars that together compose the central band of our Milky Way.

Tomorrow’s picture: open space

Astronomy Picture of the Day

M27: The Dumbbell Nebula
Image Credit & Copyright: Steve Mazlin

Explanation: Is this what will become of our Sun? Quite possibly. The first hint of our Sun‘s future was discovered inadvertently in 1764. At that time, Charles Messier was compiling a list of diffuse objects not to be confused with comets. The 27th object on Messier’s list, now known as M27 or the Dumbbell Nebula, is a planetary nebula, the type of nebula our Sun will produce when nuclear fusion stops in its core. M27 is one of the brightest planetary nebulae on the sky, and can be seen toward the constellation of the Fox (Vulpecula) with binoculars. It takes light about 1000 years to reach us from M27, featured here in colors emitted by hydrogen and oxygen. Understanding the physics and significance of M27 was well beyond 18th century science. Even today, many things remain mysterious about bipolar planetary nebula like M27, including the physical mechanism that expels a low-mass star’s gaseous outer-envelope, leaving an X-ray hot white dwarf.

Tomorrow’s picture: electric night