Why can we see the entire face of this Moon? When the Moon is in a crescent phase, only part of it appears directly illuminated by the Sun. The answer is earthshine, also known as earthlight and the da Vinci glow. The reason is that the rest of the Earth-facing Moon is slightly illuminated by sunlight first reflected from the Earth. Since the Earth appears near full phase from the Moon -- when the Moon appears as a slight crescent from the Earth -- earthshine is then near its brightest. Featured here in combined, consecutively-taken, HDR images taken earlier this month, a rising earthshine Moon was captured passing slowly near the planet Venus, the brightest spot near the image center. Just above Venus is the star Dschubba (catalogued as Delta Scorpii), while the red star on the far left is Antares. The celestial show is visible through scenic cloud decks. In the foreground are the lights from Palazzolo Acreide, a city with ancient historical roots in Sicily, Italy.

Only natural colors of the Moon in planet Earth's sky appear in this creative visual presentation. Arranged as pixels in a framed image, the lunar disks were photographed at different times. Their varying hues are ultimately due to reflected sunlight affected by changing atmospheric conditions and the alignment geometry of Moon, Earth, and Sun. Here, the darkest lunar disks are the colors of earthshine. A description of earthshine, in terms of sunlight reflected by Earth's oceans illuminating the Moon's dark surface, was written over 500 years ago by Leonardo da Vinci. But stand farther back from your monitor or just shift your gaze to the smaller versions of the image. You might also see one of da Vinci's most famous works of art.

Tonight: International Observe the Moon Night

A mere seven hundred light years from Earth, toward the constellation Aquarius, a sun-like star is dying. Its last few thousand years have produced the Helix Nebula (NGC 7293), a well studied and nearby example of a Planetary Nebula, typical of this final phase of stellar evolution. A total of 90 hours of exposure time have gone in to creating this expansive view of the nebula. Combining narrow band image data from emission lines of hydrogen atoms in red and oxygen atoms in blue-green hues, it shows remarkable details of the Helix's brighter inner region about 3 light-years across. The white dot at the Helix's center is this Planetary Nebula's hot, central star. A simple looking nebula at first glance, the Helix is now understood to have a surprisingly complex geometry.

It may look like a huge cosmic question mark, but the big question really is how does the bright gas and dark dust tell this nebula's history of star formation. At the edge of a giant molecular cloud toward the northern constellation Cepheus, the glowing star forming region NGC 7822 lies about 3,000 light-years away. Within the nebula, bright edges and dark shapes stand out in this colorful and detailed skyscape. The 9-panel mosaic, taken over 28 nights with a small telescope in Texas, includes data from narrowband filters, mapping emission from atomic oxygen, hydrogen, and sulfur into blue, green, and red hues. The emission line and color combination has become well-known as the Hubble palette. The atomic emission is powered by energetic radiation from the central hot stars. Their powerful winds and radiation sculpt and erode the denser pillar shapes and clear out a characteristic cavity light-years across the center of the natal cloud. Stars could still be forming inside the pillars by gravitational collapse but as the pillars are eroded away, any forming stars will ultimately be cut off from their reservoir of star stuff. This field of view spans over 40 light-years across at the estimated distance of NGC 7822.

Supernova Remnant

A violent and chaotic-looking mass of gas and dust is seen in this Hubble Space Telescope image of a nearby supernova remnant. Denoted N 63A, the object is the remains of a massive star that exploded, spewing its gaseous layers out into an already turbulent region.

The supernova remnant is part of a star-forming region in the Large Magellanic Cloud (LMC), an irregular galaxy 160,000 light-years from our own Milky Way.

Supernova remnants have long been thought to set off episodes of star formation when their expanding shock encounters nearby gas. N 63A is still young, and its ruthless shocks are destroying the ambient gas clouds, rather than coercing them to collapse and form stars.

Image Credit: NASA/ESA/HEIC and The Hubble Heritage Team (STScI/AURA)
Source: www.nasa.gov

What makes a meteor a fireball? First of all, everyone agrees that a fireball is an exceptionally bright meteor. Past that, the International Astronomical Union defines a fireball as a meteor brighter than apparent magnitude -4, which corresponds (roughly) to being brighter than any planet -- as well as bright enough to cast a human-noticeable shadow. Pictured, an astrophotographer taking a long-duration sky image captured by accident the brightest meteor he had ever seen. Clearly a fireball, the disintegrating space-rock created a trail so bright it turned night into day for about two seconds earlier this month. The fireball has been artificially dimmed in the featured image to bring up foreground Lake Louise in Alberta, Canada. Although fireballs are rare, many people have been lucky enough to see them. If you see a fireball, you can report it. If more than one person recorded an image, the fireball might be traceable back to the Solar System body from which it was ejected.

It's only 50 light-years to 51 Pegasi. That star's position is indicated in this snapshot from August, taken on a hazy night with mostly brighter stars visible above the dome at Observatoire de Haute-Provence in France. Twenty-six years ago, in October of 1995, astronomers Michel Mayor and Didier Queloz announced a profound discovery made at the observatory. Using a precise spectrograph they had detected a planet orbiting 51 Peg, the first known exoplanet orbiting a sun-like star. Mayor and Queloz had used the spectrograph to measure changes in the star's radial velocity, a regular wobble caused by the gravitational tug of the orbiting planet. Designated 51 Pegasi b, the planet was determined to have a mass at least half of Jupiter's mass and an orbital period of 4.2 days, making it much closer to its parent star than Mercury is to the Sun. Their discovery was quickly confirmed and Mayor and Queloz were ultimately awarded the Nobel Prize in physics in 2019. Now recognized as the prototype for the class of exoplanets fondly known as hot Jupiters, 51 Pegasi b was formally named Dimidium, latin for half, in 2015. Since its discovery, over 4,000 exoplanets have been found.

This NASA/ESA Hubble Space Telescope image features two interacting galaxies that are so intertwined, they have a collective name – Arp 91. Their delicate galactic dance takes place more than 100 million light-years from Earth.

This NASA/ESA Hubble Space Telescope image features two interacting galaxies that are so intertwined, they have a collective name – Arp 91. Their delicate galactic dance takes place more than 100 million light-years from Earth. The two galaxies comprising Arp 91 have their own names: the lower galaxy, which looks like a bright spot, is NGC 5953, and the oval-shaped galaxy to the upper right is NGC 5954. In reality, both of them are spiral galaxies, but their shapes appear very different because of their orientation with respect to Earth.

Arp 91 provides a particularly vivid example of galactic interaction. NGC 5953 is clearly tugging at NGC 5954, which looks like it is extending one spiral arm downward. The immense gravitational attraction of the two galaxies is causing them to interact. Such gravitational interactions are common and an important part of galactic evolution. Most astronomers think that collisions between spiral galaxies lead to the formation of another type of galaxy, known as elliptical galaxies. These extremely energetic and massive collisions, however, happen on timescales that dwarf a human lifetime. They take place over hundreds of millions of years, so we should not expect Arp 91 to look any different over the course of our lifetimes!

Text credit: European Space Agency (ESA)
Image credit: ESA/Hubble & NASA, J. Dalcanton; Acknowledgment: J. Schmidt

Media Contact:
Rob Gutro
NASA's Goddard Space Flight Center

Source: www.nasa.gov

This pretty starfield spans about three full moons (1.5 degrees) across the heroic northern constellation of Perseus. It holds the famous pair of open star clusters, h and Chi Persei. Also cataloged as NGC 869 (top) and NGC 884, both clusters are about 7,000 light-years away and contain stars much younger and hotter than the Sun. Separated by only a few hundred light-years, the clusters are both 13 million years young based on the ages of their individual stars, evidence that they were likely a product of the same star-forming region. Always a rewarding sight in binoculars, the Double Cluster is even visible to the unaided eye from dark locations. But a shroud of guitar strings was used to produced diffraction spikes on the colorful stars imaged in this vibrant telescopic view.

Global Moon Party: Including APOD's Best Moon Images: Saturday, October 9

The seven-member Expedition 65 crew gathers for a portrait

On Oct. 4, 2021, the seven-member Expedition 65 crew gathered for a portrait inside the vestibule in between the International Space Station's Unity module and Tranquility module. In the front row from left are; Commander Thomas Pesquet of the European Space Agency; and NASA astronauts Megan McArthur and Shane Kimbrough. In the back are: Roscosmos cosmonaut Oleg Novitskiy; astronaut Akihiko Hoshide of the Japan Aerospace Exploration Agency; NASA astronaut Mark Vande Hei; and Roscosmos cosmonaut Pyotr Dubrov.

Image Credit: NASA

Source: www.nasa.gov

Slide your telescope just east of the Lagoon Nebula to find this alluring field of view in the rich starfields of the constellation Sagittarius toward the central Milky Way. Of course the Lagoon nebula is also known as M8, the eighth object listed in Charles Messier's famous catalog of bright nebulae and star clusters. Close on the sky but slightly fainter than M8, this complex of nebulae was left out of Messier's list though. It contains obscuring dust, striking red emission and blue reflection nebulae of star-forming region NGC 6559 at right. Like M8, NGC 6559 is located about 5,000 light-years away along the edge of a large molecular cloud. At that distance, this telescopic frame nearly 3 full moons wide would span about 130 light-years.

Global Moon Party: NASA's Night Sky Network: Saturday, October 9

Rogue planet

This artist's conception illustrates a Jupiter-like planet alone in the dark of space, floating freely without a parent star.  

Exoplanet hunters have found thousands of planets, most orbiting close to their host stars, but relatively few alien worlds have been detected that float freely through the galaxy as so-called rogue planets, not bound to any star. Many astronomers believe that these planets are more common than we know, but that our planet-finding techniques haven’t been up to the task of locating them.

A planet survey, called the Microlensing Observations in Astrophysics (MOA), scanned the central bulge of our Milky Way galaxy from 2006 to 2007. It used a 5.9-foot (1.8-meter) telescope at Mount John University Observatory in New Zealand, and a technique called gravitational microlensing. In this method, a planet-sized body is identified indirectly as it just happens to pass in front of a more distant star, causing the star to brighten. The effect is like a cosmic funhouse mirror, or magnifying lens – light from the background star is warped and amplified, becoming brighter.

Using the latest technology, NASA’s Nancy Grace Roman Space Telescope will conduct a survey to discover many more exoplanets using powerful techniques available to a wide-field telescope. 

Image Credit: NASA/JPL-Caltech

Source: www.nasa.gov

Where do the dark streams of dust in the Orion Nebula originate? This part of the Orion Molecular Cloud Complex, M43, is the often imaged but rarely mentioned neighbor of the more famous M42. M42, seen in part to the upper right, includes many bright stars from the Trapezium star cluster. M43 is itself a star forming region that displays intricately-laced streams of dark dust -- although it is really composed mostly of glowing hydrogen gas. The entire Orion field is located about 1600 light years away. Opaque to visible light, the picturesque dark dust is created in the outer atmosphere of massive cool stars and expelled by strong outer winds of protons and electrons.

Sunrise at the South Pole is different. Usually a welcome sight, it follows months of darkness -- and begins months of sunshine. At Earth's poles, it can take weeks for the Sun to rise, in contrast with just minutes at any mid-latitude location. Sunrise at a pole is caused by the tilt of the Earth as it orbits the Sun, not by the rotation of the Earth. Although at a pole, an airless Earth would first see first Sun at an equinox, the lensing effect of the Earth's atmosphere and the size of the solar disk causes the top of the Sun to appear about two-weeks early. Pictured two weeks ago, the Sun peaks above the horizon of a vast frozen landscape at Earth's South Pole. The true South Pole is just a few meters to the left of the communications tower. This polar sunrise capture was particularly photogenic as the Sun appeared capped by a green flash.

At left, xenon plasma emits a blue glow from an electric Hall thruster

When it comes time for NASA’s Psyche spacecraft to power itself through deep space, it’ll be more brain than brawn that does the work. Once the stuff of science fiction, the efficient and quiet power of electric propulsion will provide the force that propels the Psyche spacecraft all the way to the main asteroid belt between Mars and Jupiter. The orbiter’s target is a metal-rich asteroid also called Psyche.

The photo on the left captures an operating electric Hall thruster identical to those that will propel NASA's Psyche spacecraft, which is set to launch in August 2022 and travel to the main asteroid belt between Mars and Jupiter. The xenon plasma emits a blue glow as the thruster operates. The photo on the right shows a similar non-operating Hall thruster. The photo on the left was taken at NASA's Jet Propulsion Laboratory; the photo on the right was taken at NASA's Glenn Research Center.

Psyche's Hall thrusters will be the first to be used beyond lunar orbit, demonstrating that they could play a role in supporting future missions to deep space. The spacecraft is set to launch in August 2022 and its super-efficient mode of propulsion uses solar arrays to capture sunlight that is converted into electricity to power the spacecraft's thrusters. The thrusters work by turning xenon gas, a neutral gas used in car headlights and plasma TVs, into xenon ions. As the xenon ions are accelerated out of the thruster, they create the thrust that will propel the spacecraft.

Solar Electric Propulsion Makes NASA’s Psyche Spacecraft Go

Image Credit: NASA/JPL-Caltech

Source: www.nasa.gov

These two mighty galaxies are pulling each other apart. Known as the "Mice" because they have such long tails, each spiral galaxy has likely already passed through the other. The long tails are created by the relative difference between gravitational pulls on the near and far parts of each galaxy. Because the distances are so large, the cosmic interaction takes place in slow motion -- over hundreds of millions of years. NGC 4676 lies about 300 million light-years away toward the constellation of Bernice's Hair (Coma Berenices) and are likely members of the Coma Cluster of Galaxies. The featured picture was taken with the Hubble Space Telescope's Advanced Camera for Surveys in 2002. These galactic mice will probably collide again and again over the next billion years so that, instead of continuing to pull each other apart, they coalesce to form a single galaxy.

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Sure, you can see the 2D rectangle of colors, but can you see deeper? Counting color patches in the featured image, you might estimate that the most information that this 2D digital image can hold is about 60 (horizontal) x 50(vertical) x 256 (possible colors) = 768,000 bits. However, the yet-unproven Holographic Principle states that, counter-intuitively, the information in a 2D panel can include all of the information in a 3D room that can be enclosed by the panel. The principle derives from the idea that the Planck length, the length scale where quantum mechanics begins to dominate classical gravity, is one side of an area that can hold only about one bit of information. The limit was first postulated by physicist Gerard 't Hooft in 1993. It can arise from generalizations from seemingly distant speculation that the information held by a black hole is determined not by its enclosed volume but by the surface area of its event horizon. The term "holographic" arises from a hologram analogy where three-dimension images are created by projecting light through a flat screen. Beware, some people staring at the featured image may not think it encodes just 768,000 bits -- nor even 2563,000 bit permutations -- rather they might claim it encodes a three-dimensional teapot.

Posing as a brilliant evening star, Venus lies near the western horizon in this southern hemisphere, early spring, night skyscape. To create the composite view exposures tracking the sky and fixed for the foreground were taken on September 25 from Cascavel in southern Brazil. In view after sunset, Venus appears immersed in a cone of zodiacal light, sunlight scattered from dust along the Solar System's ecliptic plane. In fact from either hemisphere of planet Earth, zodiacal light is most visible after sunset near a spring equinox, (or before sunrise near an autumn equinox) when its luminous arc lies at steep angles to the horizon. Extending above the sunset on this night, the zodiacal light reaches toward rich starfields and immense interstellar dust clouds in the bulge of the central Milky Way. Follow along the Milky Way from the central bulge back toward the horizon and you'll spot the closest star system to the Sun, Alpha Centauri, a mere 4.37 light-years away.

Gallaudet test subjects in a zero-g flight.

Harold Domich. Robert Greenmun. Barron Gulak. Raymond Harper. Jerald Jordan. Harry Larson. David Myers. Donald Peterson. Raymond Piper. Alvin Steele. John Zakutney.

Before NASA could send humans to space, the agency needed to better understand the effects of prolonged weightlessness on the human body. So, in the late 1950s, NASA and the U.S. Naval School of Aviation Medicine established a joint research program to study these effects and recruited 11 deaf men aged 25-48 from Gallaudet College (now Gallaudet University). Today, these men are known to history as the “Gallaudet Eleven."

In this image, the study participants chat in the zero-g aircraft that flew out of Naval Air Station in Pensacola, Fla.

In 2017, Gallaudet University and NASA celebrated the achievements of these little-known pioneers. All but one of the men had become deaf early in their lives due to spinal meningitis, which damaged the vestibular systems of their inner ear in a way that made them "immune" to motion sickness. Throughout a decade of various experiments, researchers measured the volunteers' non-reaction to motion sickness on both a physiological and psychological level, relying on the 11 men to report in detail their sensations and changes in perception. These experiments help to improve understanding of how the body’s sensory systems work when the usual gravitational cues from the inner ear aren't available, as is the case in spaceflight.


Image Credit: U.S. Navy/Gallaudet University Collection

Source: www.nasa.gov

Dark markings and colorful clouds inhabit this stellar landscape. The deep and expansive view spans more than 30 full moons across crowded star fields toward the center of our Milky Way Galaxy. Cataloged in the early 20th century by astronomer E. E. Barnard, the obscuring interstellar dust clouds seen toward the right include B59, B72, B77 and B78, part of the Ophiuchus molecular cloud complex a mere 450 light-years away. To the eye their combined shape suggests a pipe stem and bowl, and so the dark nebula's popular name is the Pipe Nebula. Three bright nebulae gathered on the left are stellar nurseries some 5,000 light-years distant toward the constellation Sagittarius. In the 18th century astronomer Charles Messier included two of them in his catalog of bright clusters and nebulae; M8, the largest of the triplet, and colorful M20 just above. The third prominent emission region includes NGC 6559 at the far left. Itself divided by obscuring dust lanes, M20 is also known as the Trifid. M8's popular moniker is the Lagoon Nebula.

Duna en Sossusvlei, Namibia, 2018-08-06, DD 002.jpg

Huge dune in Km 39, Sossusvlei, Namibia.