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Astronomy Picture of the Day

Earthshine Moon over Sicily
Image Credit & Copyright: Dario Giannobile

Explanation: 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.

Tomorrow’s picture: colorful star cluster

Astronomy Picture of the Day

The Einstein Cross Gravitational Lens
Image Credit & License: J. Rhoads (Arizona State U.) et al., WIYN, AURA, NOIRLab, NSF

Explanation: Most galaxies have a single nucleus — does this galaxy have four? The strange answer leads astronomers to conclude that the nucleus of the surrounding galaxy is not even visible in this image. The central cloverleaf is rather light emitted from a background quasar. The gravitational field of the visible foreground galaxy breaks light from this distant quasar into four distinct images. The quasar must be properly aligned behind the center of a massive galaxy for a mirage like this to be evident. The general effect is known as gravitational lensing, and this specific case is known as the Einstein Cross. Stranger still, the images of the Einstein Cross vary in relative brightness, enhanced occasionally by the additional gravitational microlensing effect of specific stars in the foreground galaxy.

Tomorrow’s picture: earthshine fireworks

Astronomy Picture of the Day

The Moona Lisa
Image Credit & Copyright: Gianni Sarcone and Marcella Giulia Pace

Explanation: 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.

Tomorrow’s picture: looking through gravity’s lens

Astronomy Picture of the Day

NGC 289: Swirl in the Southern Sky
Image Credit & Copyright: Mike Selby

Explanation: About 70 million light-years distant, gorgeous spiral galaxy NGC 289 is larger than our own Milky Way. Seen nearly face-on, its bright core and colorful central disk give way to remarkably faint, bluish spiral arms. The extensive arms sweep well over 100 thousand light-years from the galaxy’s center. At the lower right in this sharp, telescopic galaxy portrait the main spiral arm seems to encounter a small, fuzzy elliptical companion galaxy interacting with enormous NGC 289. Of course spiky stars are in the foreground of the scene. They lie within the Milky Way toward the southern constellation Sculptor.

Tomorrow’s picture: Pixel in Space

Astronomy Picture of the Day

NGC 7293: The Helix Nebula
Image Credit & Copyright: Ignacio Diaz Bobillo

Explanation: 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.

Tomorrow’s picture: pixels in space

 


Astronomy Picture of the Day

NGC 7822: Cosmic Question Mark
Image Credit & Copyright: Yizhou Zhang

Explanation: 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.

Tomorrow’s picture: open space

Astronomy Picture of the Day

Fireball over Lake Louise
Image Credit & Copyright: Hao Qin

Explanation: 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.

Tomorrow’s picture: big question

Astronomy Picture of the Day

Juno Flyby of Ganymede and Jupiter
Video Credit: Images: NASA, JPL-Caltech, SWRI, MSSS;
Animation: Koji Kuramura, Gerald Eichstädt, Mike Stetson; Music: Vangelis

Explanation: What would it be like to fly over the largest moon in the Solar System? In June, the robotic Juno spacecraft flew past Jupiter‘s huge moon Ganymede and took images that have been digitally constructed into a detailed flyby. As the featured video begins, Juno swoops over the two-toned surface of the 2,000-km wide moon, revealing an icy alien landscape filled with grooves and craters. The grooves are likely caused by shifting surface plates, while the craters are caused by violent impacts. Continuing on in its orbit, Juno then performed its 34th close pass over Jupiter’s clouds. The digitally-constructed video shows numerous swirling clouds in the north, colorful planet-circling zones and bands across the middle — featuring several white-oval clouds from the String of Pearls, and finally more swirling clouds in the south. Next September, Juno is scheduled to make a close pass over another of Jupiter’s large moons: Europa.

Tomorrow’s picture: fireball lake

stronomy Picture of the Day

Elements in the Aftermath
Image Credit: NASA/CXC/SAO

Explanation: Massive stars spend their brief lives furiously burning nuclear fuel. Through fusion at extreme temperatures and densities surrounding the stellar core, nuclei of light elements ike Hydrogen and Helium are combined to heavier elements like Carbon, Oxygen, etc. in a progression which ends with Iron. So a supernova explosion, a massive star’s inevitable and spectacular demise, blasts back into space debris enriched in heavier elements to be incorporated into other stars and planets and people). This detailed false-color x-ray image from the orbiting Chandra Observatory shows such a hot, expanding stellar debris cloud about 36 light-years across. Cataloged as G292.0+1.8, this young supernova remnant is about 20,000 light-years distant toward the southern constellation Centaurus. Light from the inital supernova explosion reached Earth an estimated 1,600 years ago. Bluish colors highlight filaments of the mulitmillion degree gas which are exceptionally rich in Oxygen, Neon, and Magnesium. This enriching supernova also produced a pulsar in its aftermath, a rotating neutron star remnant of the collapsed stellar core. The stunning image was released as part of the 20th anniversary celebration of the Chandra X-ray Observatory.

Tomorrow’s picture: pixels in space>

Yankee Flippe

Lynds Dark Nebula 1251
Image Credit & Copyright: Francesco Sferlazza, Franco Sgueglia, Astro Brallo

Explanation: Stars are forming in Lynds Dark Nebula (LDN) 1251. About 1,000 light-years away and drifting above the plane of our Milky Way galaxy, the dusty molecular cloud is part of a complex of dark nebulae mapped toward the Cepheus flare region. Across the spectrum, astronomical explorations of the obscuring interstellar clouds reveal energetic shocks and outflows associated with newborn stars, including the telltale reddish glow from scattered Herbig-Haro objects seen in this sharp image. Distant background galaxies also lurk on the scene, visually buried behind the dusty expanse. The deep telescopic field of view imaged with broadband filters spans about two full moons on the sky, or 17 light-years at the estimated distance of LDN 1251.

Tomorrow’s picture: light-weekend