Astronomy Picture of the Day
Astronomy Picture of the Day
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2012 July 15
Orion Nebula: The Hubble View
Image Credit: NASA, ESA, M. Robberto (STScI/ESA) et al.Explanation: Few cosmic vistas excite the imagination like the Orion Nebula. Also known as M42, the nebula’s glowing gas surrounds hot young stars at the edge of an immense interstellar molecular cloud only 1,500 light-years away. The Orion Nebula offers one of the best opportunities to study how stars are born partly because it is the nearest large star-forming region, but also because the nebula’s energetic stars have blown away obscuring gas and dust clouds that would otherwise block our view – providing an intimate look at a range of ongoing stages of starbirth and evolution. This detailed image of the Orion Nebula is the sharpest ever, constructed using data from the Hubble Space Telescope‘s Advanced Camera for Surveys and the European Southern Observatory‘s La Silla 2.2 meter telescope.The mosaic contains a billion pixels at full resolution and reveals about 3,000 stars.
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2012 July 20
Moon Meets Jupiter
Image Credit & Copyright: Cristian FattinnanziExplanation: Skygazers around planet Earth enjoyed the close encounter of planets and Moon in July 15’s predawn skies. And while many saw bright Jupiter next to the slender, waning crescent, Europeans also had the opportunity to watch the ruling gas giant pass behind the lunar disk, occulted by the Moon as it slid through the night. Clouds threaten in this telescopic view from Montecassiano, Italy, but the frame still captures Jupiter after it emerged from the occultation along with all four of its large Galilean moons. The sunlit crescent is overexposed with the Moon’s night side faintly illuminated by Earthshine. Lined up left to right beyond the dark lunar limb are Callisto, Ganymede, Jupiter, Io, and Europa. In fact, Callisto, Ganymede, and Io are larger than Earth’s Moon, while Europa is only slightly smaller.
Dawn of the Dish
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2012 July 19
Dawn of the Dish
Image Credit & Copyright: Alex Cherney (Terrastro, TWAN)Explanation: Wandering planets Venus and Jupiter were joined by an old crescent Moon near the eastern horizon on July 15. This serene southern skyview of the much anticipated predawn conjunction includes the lovely Pleiades star cluster and bright stars Aldebaran and Betelgeuse in the celestial lineup. For help identifying the stars and constellations, just slide your cursor over the image. Of course, the radio telescope in the foreground is the Parkes 64 meter dish of New South Wales, Australia. Known for its exploration of the distant Universe at radio wavelengths, the large, steerable antenna is also famous for its superior lunar television reception. On July 21, 1969 the dish received broadcasts from the Moon that allowed denizens of planet Earth to watch the Apollo 11 moonwalk.
A Hole in Mars
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2012 July 18
A Hole in Mars
Image Credit: NASA, JPL, U. ArizonaExplanation: What created this unusual hole in Mars? The hole was discovered by chance on images of the dusty slopes of Mars’ Pavonis Mons volcano taken by the HiRISE instrument aboard the robotic Mars Reconnaissance Orbiter currently circling Mars. The hole appears to be an opening to an underground cavern, partly illuminated on the image right. Analysis of this and follow-up images revealed the opening to be about 35 meters across, while the interior shadow angle indicates that the underlying cavern is roughly 20 meters deep. Why there is a circular crater surrounding this hole remains a topic of speculation, as is the full extent of the underlying cavern. Holes such as this are of particular interest because their interior caves are relatively protected from the harsh surface of Mars, making them relatively good candidates to contain Martian life. These pits are therefore prime targets for possible future spacecraft, robots, and even human interplanetary explorers.
2012 July 14
AR1520: Islands in the Photosphere
Image Credit & Copyright: Alan Friedman (Averted Imagination)Explanation: Awash in a sea of plasma and anchored in magnetic fields, sunspots are planet-sized, dark islands in the solar photosphere, the bright surface of the Sun. Dark because they are slightly cooler than the surrounding surface, this group of sunspots is captured in a close-up telescopic snapshot from July 11. The field of view spans nearly 100,000 miles. They lie in the center of active region AR1520, now crossing the Sun’s visible face. In fact, an X-class solar flare and coronal mass ejection erupted from AR1520 on July 12, releasing some of the energy stored in the region’s twisted magnetic fields. Headed this way, the coronal mass ejection is expected to arrive today and may trigger geomagnetic storms. As a result, some weekend auroral displays could grace planet Earth’s skies along withSunday’s predawn conjunction of bright planets and crescent Moon.
2012 July 12
Teimareh Petroglyphs and Star Trails
Image Credit & Copyright: Babak Tafreshi (TWAN)Explanation: Engraved in rock, these ancient petroglyphs are abundant in the Teimareh valley, located in the Zagros Mountains of central Iran. They likely tell a taleof hunters and animals found in the middle eastern valley 6,000 years ago or more, etched by artists in a prehistoric age. In the night sky above are star trails etched by the rotation of planet Earth during the long composite exposure made with a modern digital camera. On the left, the center of the star trail arcs is the North Celestial Pole (NCP), the extension of Earth’s axis into space. Polaris, the North Star, leaves the bright, short, stubby trail closest to the NCP. But when these petroglyphs were carved, Polaris would have made a long arc through the night. Since the Earth’s rotation axis precesses like a wobbling top, 6,000 years ago the NCP was near the border of the constellations Draco and Ursa Major, some 30 degrees from its current location in planet Earth’s sky.
2012 July 11
A Morning Line of Stars and Planets
Image Credit & Copyright: Yuri Beletsky (Las Campanas Observatory, Carnegie Institution for Science)Explanation: Early morning dog walkers got a visual treat last week as bright stars and planets appeared to line up. Pictured above, easily visible from left to right, were the Pleiades open star cluster, Jupiter, Venus, and the “Follower” star Aldebaran, all seen before a starry background. The image was taken from the Atacama desert in western South America. The glow of the rising Sun can be seen over the eastern horizon. Jupiter and Venus will continue to dazzle pre-dawn strollers all over planet Earth for the rest of the month, although even now the morning planets are seen projected away from the line connecting their distant stellar sky mates.
2012 July 9
Greeley Panorama on Mars
Image Credit: NASA/JPL-Caltech/Cornell/Arizona State U.Explanation: What did you do over your winter vacation? If you were the Opportunity rover on Mars, you spent four months of it stationary and perched on the northern slope of Greeley Haven — and tilted so that your solar panels could absorb as much sunlight as possible. During its winter stopover, the usually rolling robotundertook several science activities including snapping over 800 images of its surroundings, many of which have been combined into this 360-degree digitally-compressed panorama and shown in exaggerated colors to highlight different surface features. Past tracks of Opportunity can be seen toward the left, while Opportunity’s dust covered solar panels cross the image bottom. Just below the horizon and right of center, an interior wall of 20-kilometer Endeavour Crater can be seen. Now that the northern Martian winter is over, Opportunity is rolling again, this time straight ahead (north). The rover is set to investigate unusual light-colored soil patches as it begins again to further explore the inside of Endeavour, a crater that may hold some of the oldest features yet visited.
2012 July 8
Volcano and Aurora in Iceland
Image Credit & Copyright: Sigurdur H. StefnissonExplanation: Sometimes both heaven and Earth erupt. In Iceland in 1991, the volcano Hekla erupted at the same time that auroras were visible overhead. Hekla, one of the most famous volcanoes in the world, has erupted at least 20 times over the past millennium, sometimes causing great destruction. The last eruptionoccurred only twelve years ago but caused only minor damage. The green auroral band occurred fortuitously about 100 kilometers above the erupting lava. Is Earththe Solar System’s only planet with both auroras and volcanos?
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