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Astronomy Picture of the Day (APoD)
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Propeller Shadows on Saturn's Rings
Image Credit: +NASA, +NASA Jet Propulsion LaboratoryCaltech, Space Science Institute

What created these unusually long shadows on Saturn's rings? The dark shadows visible near the middle of the image - extend opposite the Sun and, given their length, stem from objects having heights up to a few kilometers. The long shadows were unexpected given that the usual thickness of Saturn's A and B rings is only about 10 meters. After considering the choppy but elongated shapes apparent near the B-ring edge, however, a leading theory has emerged that some kilometer-sized moonlets exist there that have enough gravity to create even larger vertical deflections of nearby small ring particles. The resulting ring waves are called propellers, named for how they appear individually. It is these coherent groups of smaller ring particles that are hypothesized to be casting the long shadows. The featured image was taken by the robotic Cassini spacecraft currently orbiting Saturn. The image was captured in 2009, near Saturn's equinox, when sunlight streamed directly over the ring plane and caused the longest shadows to be cast.
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Eagle Aurora over Norway
Image Credit & Copyright: Bjørn Jørgensen

What's that in the sky? An aurora. A large coronal mass ejection occurred on our Sun five days before this 2012 image was taken, throwing a cloud of fast moving electrons, protons, and ions toward the Earth. Although most of this cloud passed above the Earth, some of it impacted our Earth's magnetosphere and resulted in spectacular auroras being seen at high northern latitudes. Featured here is a particularly photogenic auroral corona captured above Grotfjord, Norway. To some, this shimmering green glow of recombining atmospheric oxygen might appear as a large eagle, but feel free to share what it looks like to you. Although now past Solar Maximum, our Sun continues to show occasional activity creating impressive auroras on Earth visible only last week.
David Rodriguez's profile photoRodford Smith's profile photoRita Snowden's profile photoKristine L Lubumad's profile photo
Really omg are you sure it's and eagle not vulture lol
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Full Moon in Mountain Shadow
Image Credit & Copyright: Greg Chavdarian

On October 15, standing near the summit of Hawaii's Mauna Kea and looking away from a gorgeous sunset produced this magnificent snapshot of a Full Moon rising within the volcanic mountain's shadow. An alignment across the Solar System is captured in the stunning scene and seeming contradiction of bright Moon in dark shadow. The triangular appearance of a shadow cast by a mountain's irregular profile is normal. It's created by the perspective of the distant mountaintop view through the dense atmosphere. Rising as the Sun sets, the antisolar point or the point opposite the Sun is close to the perspective's vanishing point near the mountain shadow's peak. But extending in the antisolar direction, Earth's conical shadow is only a few lunar diameter's wide at the distance of the Moon. So October's Full Hunters Moon is still reflecting sunlight, seen through the mountain's atmospheric shadow but found too far from the antisolar point and the Earth's extended shadow to be eclipsed.
Shelley Young's profile photo
Pretty colours 
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M45: The Pleiades Star Cluster
Image Credit & Copyright: Hermann von Eiff

Have you ever seen the Pleiades star cluster? Even if you have, you probably have never seen it as dusty as this. Perhaps the most famous star cluster on the sky, the bright stars of the Pleiades can be seen without binoculars even from the heart of a light-polluted city. With a long exposure from a dark location, though, the dust cloud surrounding the Pleiades star cluster becomes very evident. The featured image was a long duration exposure taken last month from Namibia and covers a sky area many times the size of the full moon. Also known as the Seven Sisters and M45, the Pleiades lies about 400 light years away toward the constellation of the Bull (Taurus). A common legend with a modern twist is that one of the brighter stars faded since the cluster was named, leaving only six stars visible to the unaided eye. The actual number of visible Pleiades stars, however, may be more or less than seven, depending on the darkness of the surrounding sky and the clarity of the observer's eyesight.
Mr. Em Aaejae's profile photoBarbie Dudley's profile photoKarin  Ettinger's profile photoReynaldo Gonzalez's profile photo
This constellation of stars, is only made of light.
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An Atlas V Rocket Launches OSIRIS-REx
Video Credit & Copyright: United Launch Alliance, +NASA

Have you ever seen a rocket launched into the Solar System? Last month a large Atlas V rocket blasted off from Launch Complex 41 in Florida carrying the ORISIX-REx spacecraft. This robotic spacecraft will attempt to land on Asteroid Bennu and return some of its soil to Earth. Asteroid 101955 Bennu orbits the Sun near the Earth, spans about 500-meters, is dark because its surface is covered with carbon, and has about a 1 in 2500 chance of striking the Earth in the next few thousand years. The exciting 2.5-minute video shows the Atlas V rocket being rolled out, prepared, and launched -- complete with a clip of side-boosters separating. If things go according to plan, ORISIS-REx will reach Bennu in 2018 and return samples to Earth in 2023. One science goal of OSIRIS-REx is to better determine whether ancient collisions between Earth and carbonaceous asteroids like Bennu provided Earth with a significant amount of the water and organic molecules necessary for the development of life.
2016 October 17
Pendi Saptariyanto's profile photoEli S's profile photo
Eli S
Just Amazing! Lov it
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Gemini Observatory North
Image Credit & Copyright: Joy Pollard (Gemini Observatory)

It does look like a flying saucer, but this technologically advanced structure is not here to deliver the wise extraterrestrial from the scifi classic movie The Day the Earth Stood Still. It is here to advance our knowledge of the Universe though. Shown sitting near the top of a mountain in Hawaii, the dome of the Gemini Observatory North houses one of two identical 8.1-meter diameter telescopes. Used with its southern hemisphere twin observatory in Chile, the two can access the entire sky from planet Earth. Constructed from 85 exposures lasting 30 seconds each with camera fixed to a tripod, the image also clearly demonstrates that the Earth did not stand still. Adjusted to be slighter brighter at the ends of their arcs, the concentric star trails centered on the North Celestial Pole are a reflection of Earth's rotation around its axis. Close to the horizon at Hawaiian latitudes, Polaris, the North Star, makes the shortest star trail. The fainter denser forest of star trails toward the right are in the rising Milky Way.
Tom Cooper (Austin)'s profile photoChandra's profile photo
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Clouds Near Jupiter's South Pole from Juno
Image Credit: +NASA, +NASA Jet Propulsion Laboratory-Caltech, SwRI, MSSS; Processing & CC-BY: Alex Mai

What's happening near the south pole of Jupiter? Recent images sent back by NASA's robotic Juno spacecraft are showing an interesting conglomeration of swirling clouds and what appear to be white ovals. Juno arrived at Jupiter in July and is being placed into a wide, looping orbit that will bring it near the gas giant -- and over its poles -- about twice a month. The featured image is a composite taken by JunoCam and post-processed by a digitally savvy citizen scientist. White ovals have been observed elsewhere on Jupiter and are thought to be giant storm systems. They have been observed to last for years, while typically showing Category 5 wind speeds of around 350 kilometers per hour. Unlike Earthly cyclones and hurricanes where high winds circle regions of low pressure, white ovals on Jupiter show rotational directions indicating that they are anticylones -- vortices centered on high pressure regions. Juno will continue to orbit Jupiter over thirty more times while recording optical, spectral, and gravitational data meant to help determine Jupiter's structure and evolution.
BL B's profile photoMike Demitre's profile photoMatthew Brown's profile photoOne Minute History's profile photo
This is so unreal. Let's send more out there!
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HI4PI: The Hydrogen Sky
Image Credit: Benjamin Winkel & the HI4PI Collaboration

Where are the Milky Way's gas clouds and where are they going? To help answer this question, a new highest-resolution map of the sky in the universe's most abundant gas -- hydrogen -- has been completed and recently released, along with its underlying data. Featured above, the all-sky map of hydrogen's 21-cm emission shows abundance with brightness and speed with color. Low radial speeds toward us artificially colored blue and low radial speeds away colored green. The band across the middle is the plane of our Milky Way Galaxy, while the bright spots on the lower right are the neighboring Magellanic Clouds. The HI4PI map collects data from over one million observations with the northern Eiffelsberg 100-Meter Radio Telescope in Germany and the southern Parkes 64-Meter Radio Telescope in Australia, also known as "The Dish". The details of the map not only better inform humanity about star formation and interstellar gas in our Milky Way galaxy, but also how much light this local gas is likely to absorb when observing the outside universe. Many details on the map are not yet well understood.
david mezo's profile photonagendra s's profile photokiran sontakke's profile photoMarleny Colocho's profile photo
+david mezo the earth is our planet therefore is the atmosphere our body lives from earth went water we are humanity use u critical thinking.
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Cerro Tololo Trails
Image Credit & Copyright: Babak Tafreshi (TWAN), AURA

Early one moonlit evening car lights left a wandering trail along the road to the Chilean Cerro Tololo Inter-American Observatory. Setting stars left the wandering trails in the sky. The serene view toward the mountainous horizon was captured in a telephoto timelapse image and video taken from nearby Cerro Pachon, home to Gemini South. Afforded by the mountaintop vantage point, the clear, long sight-line passes through layers of atmosphere. The changing atmospheric refraction shifts and distorts the otherwise steady apparent paths of the stars as they set. That effect also causes the distorted appearance of Sun and Moon as they rise or set near a distant horizon.
Karin  Ettinger's profile photoAmir Azad's profile photo
Astronomer's Paradise!
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The Tulip in the Swan
Image Credit & Copyright: Martin Pugh

Framing a bright emission region this telescopic view looks out along the plane of our Milky Way Galaxy toward the nebula rich constellation Cygnus the Swan. Popularly called the Tulip Nebula, the glowing cloud of interstellar gas and dust is also found in the 1959 catalog by astronomer Stewart Sharpless as Sh2-101. About 8,000 light-years distant and 70 light-years across the complex and beautiful nebula blossoms at the center of the composite image. Red, green, and blue hues map emission from ionized sulfur, hydrogen, and oxygen atoms. Ultraviolet radiation from young, energetic stars at the edge of the Cygnus OB3 association, including O star HDE 227018, ionizes the atoms and powers the visible light emission from the Tulip Nebula. HDE 227018 is the bright star very near the blue arc at the center of the cosmic tulip.
Boonkoon Chindasri's profile photoRebecca Jumg's profile photoKarin  Ettinger's profile photo
WonDeRousphaSis etCheTed among in aMidSt...
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The Antlia Cluster of Galaxies
Image Credit & Copyright: Rolf Olsen

Galaxies dot the sky in this impressively wide and deep image of the Antlia Cluster. The third closest cluster of galaxies to Earth after Virgo and Fornax, the Antlia cluster is known for its compactness and its high fraction of elliptical galaxies over (spirals. Antlia, cataloged as Abell S0636, spans about 2 million light years and lies about 130 million light years away toward the constellation of the Air Pump (Antlia). The cluster has two prominent galaxy groups - bottom center and upper left -- among its over 200 galactic members, but no single central dominant galaxy. The vertical red ribbon of gas on the left is thought related to the foreground Antlia supernova remnant and not associated with the cluster. The featured image composite, taken from New Zealand, resulted from 150+ hours of exposures taken over six months.
sabanber saban's profile photoKarin  Ettinger's profile photoJose Sanchez's profile photo
What makes
It more beautiful is that we are a small part of it
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Cylindrical Mountains on Venus
Image Credit: Magellan Spacecraft Team, USGS, +NASA

What could cause a huge cylindrical mountain to rise from the surface of Venus? Such features that occur on Venus are known as coronas. Pictured here in the foreground is 500-kilometer wide Atete Corona found in a region of Venus known as the Galindo. The featured image was created by combining multiple radar maps of the region to form a computer-generated three-dimensional perspective. The series of dark rectangles that cross the image from top to bottom were created by the imaging procedure and are not real. The origin of massive coronas remains a topic of research although speculation holds they result from volcanism. Studying Venusian coronas help scientists better understand the inner structure of both Venus and Earth.
Kyaw Thura Maung's profile photoTom Cooper (Austin)'s profile photoSuryanarayana Garikina's profile photoLucas Solomon's profile photo
+Tom Cooper I don't know, we might need it to happen.
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Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.