Astronomy Picture of the Day

[Steve Gardner]

Source: NASA

Flying Over the Columbia Hills of Mars
Animated Illustration Credit: Doug Ellison, Randolph Kirk (USGS), MSSS, MER, NASA

Explanation: What it would be like to fly over Mars? Combining terrain data from the orbiting Mars Reconnaissance Orbiter spacecraft with information about the robotic Spirit rover currently rolling across Mars has resulted in a digital movie that shows what a flight over the Columbia Hills might look like. Dark rippled sand dunes are highlighted against the Columbia Hills in the above opening image. Clicking on the above image, though, will launch you across Mars, approaching the Columbia Hills. On the far side of the hills, the dark sand dunes come into view. Soon you pass an unusual white-rimmed structure, slightly raised, known as Home Plate, the origin of which is currently unknown and being researched. Turning, you re-approach the hills from a different angle, this time zooming in on Spirit, a curious alien rover sent from planet Earth. A final zoom pans out over the region. This coming Sunday, NASA's Phoenix Lander will attempt to set down near the icy North Pole of Mars and search for signs of ancient life.

[Steve Gardner]

Source: NASA

The Perseus Cluster of Galaxies
Credit & Copyright: Jean-Charles Cuillandre (CFHT) & Giovanni Anselmi (Coelum Astronomia), Hawaiian Starlight

Explanation: Here is one of the largest objects that anyone will ever see on the sky. Each of these fuzzy blobs is a galaxy, together making up the Perseus Cluster, one of the closest clusters of galaxies. The cluster is seen through a foreground of faint stars in our own Milky Way Galaxy. Near the cluster center, roughly 250 million light-years away, is the cluster's dominant galaxy NGC 1275, seen above as the large galaxy on the image left. A prodigious source of x-rays and radio emission, NGC 1275 accretes matter as gas and galaxies fall into it. The Perseus Cluster of Galaxies is part of the Pisces-Perseus supercluster spanning over 15 degrees and containing over 1,000 galaxies. At the distance of NGC 1275, this view covers about 7.5 million light-years.

[Jack]

Source: NASA

Jupiter's Three Red Spots
Credit NASA, ESA, M. Wong, I. de Pater (UC Berkeley), et al.

Explanation: For about 300 years Jupiter's banded atmosphere has shown a remarkable feature to telescopic viewers, a large swirling storm system known as The Great Red Spot. In 2006, another red storm system appeared, actually seen to form as smaller whitish oval-shaped storms merged and then developed the curious reddish hue. Now, Jupiter has a third red spot, again produced from a smaller whitish storm. All three are seen in this image made from data recorded on May 9 and 10 with the Hubble Space Telescope's Wide Field and Planetary Camera 2. The spots extend above the surrounding clouds and their red color may be due to deeper material dredged up by the storms and exposed to ultraviolet light, but the exact chemical process is still unknown. For scale, the Great Red Spot has almost twice the diameter of planet Earth, making both new spots less than one Earth-diameter across. The newest red spot is on the far left (west), along the same band of clouds as the Great Red Spot and is drifting toward it. If the motion continues, the new spot will encounter the much larger storm system in August. Jupiter's recent outbreak of red spots is likely related to large scale climate change as the gas giant planet is getting warmer near the equator.

[Steve Gardner]

Source: NASA

Space Station in the Sun
Credit & Copyright: Dirk Ewers

Explanation: Still bathed in sunlight, the International Space Station tracked through night skies above Hombressen, Germany on May 12. From a range of at least 360 kilometers, astronomer Dirk Ewers was able to record an impressively sharp video sequence of the passage with a small telescope, using some of the individual frames to construct this composite image. Sporting solar arrays, the station's integrated truss structure is nearly 90 meters long. The ATV Jules Verne is docked with the station, while the space station itself is orbiting at aproximately 27,800 kilometers per hour (17,200 mph). A complete video sequence is available as a 1 megabyte mpeg file or avi file.

[Steve Gardner]

Source: NASA

Phoenix Lander Arrives at Mars
Animated Illustration Credit & Copyright: MAAS Digital, SVV Project, NASA

Explanation: Will Phoenix survive its landing today on Mars? Phoenix's landing sequence will ramp up starting at about 7:30 pm EDT (23:30 UTC) today and last just over an hour. If all goes well, one of Phoenix's first images from Mars will appear on APOD tomorrow. The Phoenix Lander is programmed to set down near the North Pole of Mars, and, over the next three months, sample alien soil and ice and look for conditions conducive for ancient microbial life. Shown above is an artistic animation of what it might look like to see Phoenix land on Mars. In the animated sequence, the Phoenix spacecraft arrives at Mars, deploys its breaking parachute, jettisons its heat shield, fires it thrusters, lands, unfurls its solar panels, deploys its instruments, scoops up some of Mars, and begins its analysis.

[Steve Gardner]

Source: NASA

A New Horizon for Phoenix
Credit: Phoenix Mission Team, NASA, JPL-Caltech, Univ. Arizona

Explanation: This flat horizon stretches across the red planet as seen by the Phoenix spacecraft after yesterday's landing on Mars. Touching down shortly after 7:30pm Eastern Time, Phoenix made the first successful soft landing on Mars, using rockets to control its final speed, since the Viking landers in 1976. Launched in August of 2007, Phoenix has now made the northernmost landing and is intended to explore the Martian arctic's potentially ice-rich soil. The lander has returned images and data initially indicating that it is in excellent shape after a nearly flawless descent. News updates will be available throughout the day.

[Steve Gardner]

Source: NASA

Phoenix at Mars
Credit: Phoenix, HiRISE, NASA, JPL-Caltech, Univ. Arizona

Explanation: The Phoenix lander's footpads are about the size of a dinner plate. One of three is shown at the right, covered with Martian soil after a successful soft landing on the Red Planet on May 25. Amazingly, the left panel image is of the spacecraft during its descent phase, captured by the HiRISE camera onboard Mars Reconnaissance Orbiter -- the first image ever of a spacecraft descending to the surface of another planet. Taken from a range of 750 kilometers, the picture shows Phoenix suspended beneath its unfurling, 10 meter-wide parachute, against the much darker Martian surface. The lander is still attached to its protective backshell. Phoenix released its parachute at an altitude of 12.6 kilometers. Using rockets to further reduce its speed for landing, Phoenix now rests in the northern polar region of Mars at about 68 degrees latitude.

[Steve Gardner]

Source: NASA

Dark Clouds of the Carina Nebula
Credit: NASA, ESA, N. Smith (U. California, Berkeley) et al., and The Hubble Heritage Team (STScI/AURA)

Explanation: What dark forms lurk in the mists of the Carina Nebula? These ominous figures are actually molecular clouds, knots of molecular gas and dust so thick they have become opaque. In comparison, however, these clouds are typically much less dense than Earth's atmosphere. Pictured above is part of the most detailed image of the Carina Nebula ever taken, a part where dark molecular clouds are particularly prominent. The entire Carina Nebula spans over 300 light years and lies about 7,500 light-years away in the constellation of Carina. NGC 3372, known as the Great Nebula in Carina, is home to massive stars and changing nebula. Eta Carinae, the most energetic star in the nebula, was one of the brightest stars in the sky in the 1830s, but then faded dramatically. Wide-field annotated and zoomable versions of the larger image composite are also available.

[Steve Gardner]

Source: NASA

A Fog Bow Over Ocean Beach
Credit & Copyright: Keith C. Langill (missionblvd.com)

Explanation: What is that white arch over the water? What is being seen is a fogbow, a reflection of sunlight by water drops similar to a rainbow but without the colors. The fog itself is not confined to an arch -- the fog is mostly transparent but relatively uniform. The fogbow shape is created by those drops with the best angle to divert sunlight to the observer. The fogbow's relative lack of colors are caused by the relatively smaller water drops. The drops active above are so small that the quantum mechanical wavelength of light becomes important and smears out colors that would be created by larger rainbow water drops acting like small prisms reflecting sunlight. The above striking image of a fogbow was taken last week with the Sun behind the photographer. The rocks in the foreground are part of Ocean Beach in California, USA.

[Steve Gardner]

Source: NASA

Descent of the Phoenix
Credit: MRO-HiRISE, NASA, JPL, Univ. Arizona

Explanation: In this sweeping view, the 10 kilometer-wide crater Heimdall lies on the north polar plains of Mars. But the bright spot highlighted in the inset is the Phoenix lander parachuting toward the surface. The amazing picture was captured on May 25th by the HiRISE camera onboard the Mars Reconnaissance Orbiter. Though the lander looks like it might be dropping straight into Heimdall, it is really descending about 20 kilometers in front of the crater, in the foreground of the scene. The orbiter was 760 kilometers away from Phoenix when picture was taken, at an altitude of 310 kilometers. Subsequently the orbiter's camera was also able to image the lander on the surface. The parachute attached to the backshell and the heat shield were identified in the image, scattered nearby. Of course, the Phoenix lander itself is now returning much closer views of its landing site as it prepares to dig into the Martian surface.

[Steve Gardner]

source: NASA

A Twisted Solar Eruptive Prominence
Credit: SOHO Consortium, EIT, ESA, NASA

Explanation: Ten Earths could easily fit in the "claw" of this seemingly solar monster. The monster, though, visible on the lower left, is a huge eruptive prominence seen moving out from our Sun. The above dramatic image taken early in the year 2000 by the Sun-orbiting SOHO satellite. This large prominence, though, is significant not only for its size, but its shape. The twisted figure eight shape indicates that a complex magnetic field threads through the emerging solar particles. Differential rotation inside the Sun might help account for the surface explosion. Although large prominences and energetic Coronal Mass Ejections (CMEs) are relatively rare, they are occurred more frequently near Solar Maximum, the time of peak sunspot and solar activity in the eleven-year solar cycle.

[Jack]

Source: NASA

Two-Armed Spiral Milky Way
Illustration Credit: R. Hurt (SSC), JPL-Caltech, NASA
Survey Credit: GLIMPSE

Explanation: Gazing out from within the Milky Way, our own galaxy's true structure is difficult to discern. But an ambitious survey effort with the Spitzer Space Telescope now offers convincing evidence that we live in a large galaxy distinguished by two main spiral arms (the Scutum-Centaurus and Perseus arms) emerging from the ends of a large central bar. In fact, from a vantage point that viewed our galaxy face-on, astronomers in distant galaxies would likely see the Milky Way as a two-armed barred spiral similar to this artist's illustration. Previous investigations have identified a smaller central barred structure and four spiral arms. Astronomers still place the Sun about a third of the way in from the Milky Way's outer edge, in a minor arm called the Orion Spur. To locate the Sun and identify the Milky Way's newly mapped features, just place your cursor over the image.

[Jack]

Source: NASA

June's Young Crescent Moon
Credit & Copyright: Miguel Claro

Explanation: Serene skyviews were enjoyed across planet Earth earlier this week with a young crescent Moon low in the western sky just after sunset. Recorded on June 4, this colorful example includes a quiet beach in the foreground with the city lights of Lisbon, Portugal, and the Sintra Mountains along the horizon. Posing between cloud banks, the Moon's slender, sunlit arc represents only about 1 percent of the full lunar disc. The rest of the Moon's nearside is faintly visible though, illuminated by Earthshine. A waxing crescent Moon should also create some lovely western skies at dusk this weekend. The bright star in the sky near tonight's (Saturday's) Moon will actually be the planet Mars. On Sunday the Moon will move closer to a pair of celestial beacons, bright star Regulus and Saturn.

[Steve Gardner]

Source: NASA

Mars Soil Sample Ready to Analyze
Credit: Phoenix Mission Team, NASA, JPL-Caltech, U. Arizona

Explanation: What surprises are hidden in the soils of Mars? To help find out, the Phoenix Lander Phoenix Lander which arrived on Mars two weeks ago has attempted to place a scoop of soil in Phoenix's Thermal and Evolved-Gas Analyzer (TEGA). Pictured above, the dirt-filled scoop approaches one of TEGA's eight ovens. Once in the oven, a soil material will be baked and the emitted gasses categorized by a mass spectrometer. Quite possibly, some of the light colored material visible in the scoop has the same composition as the light material imaged near the foot of the Lander, which may be ice. Phoenix is scheduled to spend the next three months digging, baking and chemically analyzing its immediate surroundings to better understand Mars and whether the boundary between ice and soil was ever capable of supporting life.

[Steve Gardner]

Source: NASA

Saturn's Rings from the Other Side
Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA

Explanation: What do Saturn's rings look like from the other side? From Earth, we usually see Saturn's rings from the same side of the ring plane that the Sun illuminates them. Geometrically, in the above picture taken in April by the robot Cassini spacecraft now orbiting Saturn, the Sun is behind the camera but on the other side of the ring plane. This vantage point, specifically 17 degrees above the ring plane, gives a breathtaking views of the most splendid ring system in the Solar System. Strangely, the rings have similarities to a photographic negative of a front view. The ring brightness as recorded from different angles indicates ring thickness and particle density of ring particles. Elsewhere, ring shadows can be seen on the sunlit face of Saturn, shown sporting numerous cloud structures in nearly true color.