NASA Astronomy Picture of the Day:

The failed unit was beyond the reach of the robotic Canadarm2. Therefore, this repair of the International Space Station would require humans. The humans on duty were NASA's Jessica Meir and Christina Koch. This was the fourth spacewalk for Koch, the first for Meir, and the first all-female spacewalk in human history. The first woman to walk in space was Svetlana Savitskaya in 1984. Koch (red stripe) and Meir are pictured hard at work on the P6 Truss, with solar panels and the darkness of space in the background. Working over seven hours, the newly installed Battery Charge / Discharge Unit (BCDU) was successfully replaced and, when powered up, operated normally.

NASA Astronomy Picture of the Day:

After the 2017 detecton of 1I/'Oumuamua, comet 2I/Borisov has become the second recognized interstellar interloper. Like 'Oumuamua, Borisov's measured hyperbolic trajectory and speed as it falls toward the Sun confirm that its origin is from beyond our Solar System. But while detailed observations indicate 'Oumuamua is a rocky body with differences from known Solar System objects, Borisov is definitely a far wandering comet. Taken on October 12, 2019 this Hubble Space Telescope image of Borisov reveals a familiar looking comet-like activity and concentration of dust around around its nucleus. Not resolved in the image, some estimates suggest the nucleus could be between 2 and 16 kilometers in diameter. At the time of the Hubble image, comet 2I/Borisov was about 418 million kilometers away. Borisov is still inbound though and will make its closest approach to the Sun on December 7 at a distance of about 300 million kilometers (2 Astronomical units).

NASA Astronomy Picture of the Day:

On July 29, 2011 the Cassini spacecraft's narrow-angle camera took this snapshot and captured 5 of Saturn's moons, from just above the ringplane. Left to right are small moons Janus and Pandora respectively 179 and 81 kilometers across, shiny 504 kilometer diameter Enceladus, and Mimas, 396 kilometers across, seen just next to Rhea. Cut off by the right edge of the frame, Rhea is Saturn's second largest moon at 1,528 kilometers across. So how many moons does Saturn have? Twenty new found outer satellites bring its total to 82 known moons, and since Jupiter's moon total stands at 79, Saturn is the Solar System's new moon king. The newly announced Saturnian satellites are all very small, 5 kilometers or so in diameter, and most are in retrograde orbits inclined to Saturn's ringplane. You can help name Saturn's new moons, but you should understand the rules. Hint: A knowledge of Norse, Inuit, and Gallic mythology will help.

NASA Astronomy Picture of the Day:

How do binary stars form? To help find out, ESO's Atacama Large Millimeter Array (ALMA) recently captured one of the highest resolution images yet taken of a binary star system in formation. Most stars are not alone -- they typically form as part of a multiple star systems where star each orbits a common center of gravity. The two bright spots in the featured image are small disks that surround the forming proto-stars in [BHB2007] 11, while the surrounding pretzel-shaped filaments are gas and dust that have been gravitationally pulled from a larger disk. The circumstellar filaments span roughly the radius of the orbit of Neptune. The BHB2007 system is a small part of the Pipe Nebula (also known as Barnard 59), a photogenic network of dust and gas that protrudes from Milky Way's spiral disk in the constellation of Ophiuchus. The binary star formation process should be complete within a few million years.

NASA Astronomy Picture of the Day:

Have you contemplated your home galaxy lately? If your sky looked like this, perhaps you'd contemplate it more often! The featured picture is actually a composite of two images taken last month from the same location in south Brazil and with the same camera -- but a few hours apart. The person in the image -- also the astrophotographer -- has much to see in the Milky Way Galaxy above. The central band of our home Galaxy stretches diagonally up from the lower left. This band is dotted with spectacular sights including dark nebular filaments, bright blue stars, and red nebulas. Millions of fainter and redder stars fill in the deep Galactic background. To the lower right of the Milky Way are the colorful gas and dust clouds of Rho Ophiuchi, featuring the bright orange star Antares. On this night, just above and to the right of Antares was the bright planet Jupiter. The sky is so old and so familiar that humanity has formulated many stories about it, some of which inspired this very picture.

Photo by Rodrigo Guerra

NASA Astronomy Picture of the Day:

What does the Andromeda galaxy really look like? The featured image shows how our Milky Way Galaxy's closest major galactic neighbor really appears in a long exposure through Earth's busy skies and with a digital camera that introduces normal imperfections. The picture is a stack of 223 images, each a 300 second exposure, taken from a garden observatory in Portugal over the past year. Obvious image deficiencies include bright parallel airplane trails, long and continuous satellite trails, short cosmic ray streaks, and bad pixels. These imperfections were actually not removed with Photoshop specifically, but rather greatly reduced with a series of computer software packages that included Astro Pixel Processor, DeepSkyStacker, and PixInsight. All of this work was done not to deceive you with a digital fantasy that has little to do with the real likeness of the Andromeda galaxy (M31), but to minimize Earthly artifacts that have nothing to do with the distant galaxy and so better recreate what M31 really does look like.

NASA Astronomy Picture of the Day:

Jewels don't shine this bright -- only stars do. Like gems in a jewel box, though, the stars of open cluster NGC 290 glitter in a beautiful display of brightness and color. The photogenic cluster, pictured here, was captured in 2006 by the orbiting Hubble Space Telescope. Open clusters of stars are younger, contain few stars, and contain a much higher fraction of blue stars than do globular clusters of stars. NGC 290 lies about 200,000 light-years distant in a neighboring galaxy called the Small Cloud of Magellan (SMC). The open cluster contains hundreds of stars and spans about 65 light years across. NGC 290 and other open clusters are good laboratories for studying how stars of different masses evolve, since all the open cluster's stars were born at about the same time.

NASA Astronomy Picture of the Day:

In an interplanetary first, on July 19, 2013 Earth was photographed on the same day from two other worlds of the Solar System, innermost planet Mercury and ringed gas giant Saturn. Pictured on the left, Earth is the pale blue dot just below the rings of Saturn, as captured by the robotic Cassini spacecraft then orbiting the outermost gas giant. On that same day people across planet Earth snapped many of their own of their own pictures of Saturn. On the right, the Earth-Moon system is seen against the dark background of space as captured by the robotic MESSENGER spacecraft, then in Mercury orbit. MESSENGER took its image as part of a search for small natural satellites of Mercury, moons that would be expected to be quite dim. In the MESSENGER image, the Earth (left) and Moon (right) are overexposed and shine brightly with reflected sunlight. Destined not to return to their home world, both Cassini and Messenger have since retired from their missions of Solar System exploration.

NASA Astronomy Picture of the Day:

Nature photographers and other fans of planet Earth always look forward to the blue hour. That's the transition in twilight, just before sunrise or after sunset, when the Sun is below the horizon but land and sky are still suffused with beautiful bluish hues of light. On August 8 this early morning blue hour panorama scanned along the clear western sky, away from the impending sunrise. A breathtaking scene, it looks down the slopes of Mt. Whitney, from along the John Muir Trail toward rugged peaks of planet Earth's Sierra Nevada mountain range. Above the horizon a faint pinkish band of back scattered sunlight, the anti-twilight arch or Belt of Venus, borders the falling grey shadow of Earth itself. Subtle bands of light across the clear sky are anti-crepuscular rays, defined by shadows of clouds near the sunward horizon. Actually following parallel lines they seem to converge along the horizon at the point opposite the rising Sun due to perspective.

Photo by Matthias Ciprian

NASA Astronomy Picture of the Day:

On September 24, a late evening commercial flight from Singapore to Australia offered stratospheric views of the southern hemisphere's night sky, if you chose a window seat. In fact, a well-planned seating choice with a window facing toward the Milky Way allowed the set up of a sensitive digital camera on a tripod mount to record the galaxy's central bulge in a series of 10 second long exposures. By chance, one of the exposures caught this bright fireball meteor in the starry frame. Reflected along the wing of the A380 aircraft, the brilliant greenish streak is also internally reflected in the double layer window, producing a fainter parallel to the original meteor track. In the southern sky Jupiter is the bright source beneath the galactic bulge and seen next to a green beacon, just off the wing tip.

Photo by Eric Wagner