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That yellow spot -- what is it? It's a young planet outside our Solar System. The featured image from the Very Large Telescope in Chile surprisingly captures a distant scene much like our own Solar System's birth, some 4.5 billion years ago. Although we can't look into the past and see Earth's formation directly, telescopes let us watch similar processes unfolding around distant stars. At the center of this frame lies a young Sun-like star, hidden behind a coronagraph that blocks its bright glare. Surrounding the star is a bright, dusty protoplanetary disk -- the raw material of planets. Gaps and concentric rings mark where a newborn world is gathering gas and dust under its gravity, clearing the way as it orbits the star. Although astronomers have imaged disk-embedded planets before, this is the first-ever observation of an exoplanet actively carving a gap within a disk -- the earliest direct glimpse of planetary sculpting in action.

Why would the sky glow like a giant repeating rainbow? Airglow. Now air glows all of the time, but it is usually hard to see. A disturbance however -- like an approaching storm -- may cause noticeable rippling in the Earth's atmosphere. These gravity waves are oscillations in air analogous to those created when a rock is thrown in calm water. Red airglow likely originates from OH molecules about 87-kilometers high, excited by ultraviolet light from the Sun, while orange and green airglow is likely caused by sodium and oxygen atoms slightly higher up. While driving near Keluke Lake in Qinghai Provence in China, the photographer originally noticed mainly the impressive central band of the Milky Way Galaxy. Stopping to photograph it, surprisingly, the resulting sensitive camera image showed airglow bands to be quite prominent and span the entire sky. The featured image has been digitally enhanced to make the colors more vibrant. Follow APOD on: Facebook, Google Plus, Instagram, or Twitter

Inside the Cocoon Nebula is a newly developing cluster of stars. Cataloged as IC 5146, the beautiful nebula is nearly 15 light-years wide. Soaring high in northern summer night skies, it's located some 4,000 light years away toward the constellation of the Swan (Cygnus). Like other star forming regions, it stands out in red, glowing, hydrogen gas excited by young, hot stars, and dust-reflected starlight at the edge of an otherwise invisible molecular cloud. In fact, the bright star found near the center of this nebula is likely only a few hundred thousand years old, powering the nebular glow as it clears out a cavity in the molecular cloud's star forming dust and gas. A 48-hour long integration resulted in this exceptionally deep color view tracing tantalizing features within and surrounding the dusty stellar nursery.

On December 1st, experienced observers patroling the night sky with binoculars noticed what seemed to be a new star in the constellation of Aquila (The Eagle). It wasn't really a new star though. A comparison with detailed skymaps revealed the amazing truth, there was a known star at that position in the sky ... its brightness had simply increased by about 70,000 times. The star, now fondly known to variable star observers as Nova V1494 Aquilae, continued to grow brighter for several days, becoming easily visible to the unaided eye before starting to slowly fade away. Its position within the constellation is indicated on this wide-angle picture taken on December 4th, near the time it was brightest. What would cause a star to undergo such a cataclysmic change? This "new star" appears to be a classical nova. Classical novae are thought to be interacting binary star systems in which one of the pair is a dense, hot white dwarf. Material from the companion falls onto the surface of the white dwarf, building up until it triggers a thermonuclear blast. A stunning increase in brightness and an expanding shell of debris result - but the binary system is likely not destroyed! Classical novae are believed to recur as the flow of material resumes and produces another outburst in perhaps hundreds of years time.

Launched in the summer of 1977, NASA's Voyager 1 and 2 spacecraft are now over 4.5 billion miles from the Sun. Still operational, the Voyagers are being tracked and commanded through the Deep Space Network. Having traveled beyond the outer planets, these remarkable spacecraft are only the third and fourth human built artifacts to escape our solar system, following in the footsteps of Pioneer 10 and 11. A 12-inch gold plated copper disk (pictured) containing recorded sounds and images representing human cultures and life on Earth, is affixed to each Voyager - a message in a bottle cast into the cosmic sea. The recorded material was selected by a committee chaired by Carl Sagan of Cornell University. The disks are intended to be played like a phonograph record at 16 and 2/3 revolutions per second. Cartridge and needle are supplied, along with some simple diagrams (visible above) which represent symbolically the spacecraft's origin and instructions for playing the disk. The exotic construction of the disks should provide them with a long lifetime as they coast through interstellar space. The two spacecraft will not make a close approach to another planetary system for at least 40,000 years.

This dream-like image of Mir was recorded by astronauts as the Space Shuttle Atlantis approached the Russian space station prior to docking during the STS-76 mission. Sporting spindly appendages and solar panels, Mir resembles a whimsical flying insect hovering about 350 kilometers above New Zealand's South Island and the city of Nelson near Cook Strait. In late March 1996, Atlantis shuttled astronaut Shannon W. Lucid to Mir for a five month visit, increasing Mir's occupancy from 2 to 3. It returned to pick Lucid up and drop off astronaut John Blaha during the STS-79 mission in August of that year. Since becoming operational in 1986, Mir has been visited by over 100 spacefarers from the nations of planet Earth including, Russia, the United States, Great Britain, Germany, France, Japan, Austria, Kazakhstan and Slovakia. After joint Shuttle-Mir training missions in support of the International Space Station, continuous occupation of Mir ended in August 1999. The Mir was deorbited in March 2001.

$Perhaps the most famous star cluster on the sky, the Pleiades can be seen without binoculars from even the depths of a light-polluted city. Also known as the Seven Sisters and M45, the Pleiades is one of the brightest and closest open clusters. The Pleiades contains over 3000 stars, is about 400 light years away, and only 13 light years across. Quite evident in the above photograph are the blue reflection nebulae that surround the brighter cluster stars. Low mass, faint, brown dwarfs have also been found in the Pleiades. (Editors' note: The prominent diffraction spikes were added to the image for aesthetic reasons, produced by kite string donated by Rob Gendler's kids and placed over the telescope dew shield.)$

On September 18, the setting Sun illuminated both sides of the steep brick and steel canyon otherwise known as Jasper Avenue in downtown Edmonton, Alberta, Canada, planet Earth. The Stonehenge-like alignment is captured from the middle of the road in this daring snapshot. In Edmonton streets are laid out on a grid almost oriented along the cardinal directions, so aligned Edmonton sunsets (and sunrises) occur along the nearly east-west streets twice a year, close to the Equinox. In fact, at today's Equinox, the Sun crosses the celestial equator at 1421 UT and on this day the Sun will rise due east and set due west, bringing approximately equal hours of day and night to denizens of planet Earth. The September Equinox marks the astronomical beginning of Fall in the north and Spring in the southern hemisphere.

NASA's Europa Clipper is now headed toward an ocean world beyond Earth. The large spacecraft is tucked into the payload fairing atop the Falcon Heavy rocket in this photo, taken at Kennedy Space Center the day before the mission's successful October 14 launch. Europa Clipper's interplanetary voyage will first take it to Mars, then back to Earth, and then on to Jupiter on gravity assist trajectories that will allow it to enter orbit around Jupiter in April 2030. Once orbiting Jupiter, the spacecraft will fly past Europa 49 times, exploring a Jovian moon with a global subsurface ocean that may have conditions to support life. Posing in the background next to the floodlit rocket is Comet Tsuchinsan-ATLAS, about a day after the comet's closest approach to Earth. A current darling of evening skies, the naked-eye comet is a visitor from the distant Oort cloud Growing Gallery: Comet Tsuchinshan-ATLAS in 2024

Which way to the interstate? What appears to be a caricature of a complex highway system on Earth is actually a system of ridges and cracks on the icy surface of Jupiter's moon Europa. The distance between parallel ridges in the above photograph is typically about 1 kilometer. The complexity of the cracks and ridges tell a story of Europa's past that is mostly undecipherable -- planetary geologists try to understand just the general origin of the overall features. One noteworthy feature is the overall white sheen, possibly indicating the presence of frost. Another is the dark centers between parallel ridges, which might indicate that dirty water from an underground ocean recently welled up in the cracks and froze. Recent research indicates that enough carbon exists to support an underwater biosphere, but that Europa's ice crust may be over three kilometers thick in some places.

$Part of the Sun disappeared earlier this month, but few people were worried. The missing part, which included the center from some locations, just went behind the Moon in what is known as an annular solar eclipse. Featured here is an eclipse sequence taken as the Moon was overtaking the rising Sun in the sky. The foreground hill is Factory Butte in Utah, USA. The rays flaring out from the Sun are not real -- they result from camera aperture diffraction and are known as sunstar. The Moon is real, but appears only in silhouette in this ring-of-fire eclipse. As stunning as this eclipse sequence is, it was considered just practice by the astrophotographer. The reason? She hopes to use this experience to better photograph the total solar eclipse that will occur over North America on April 8, 2024. Apply today (USA): Become a NASA Partner Eclipse Ambassador Eclipse Album: Selected images sent in to APOD$