Huygens Lands on Titan


Delivered by Saturn-bound Cassini, ESA’s Huygens probe touched down on the ringed planet’s largest moon Titan, ten years ago on January 14, 2005. These panels show fisheye images made during its slow descent by parachute through Titan’s dense atmosphere. Taken by the probe’s descent imager/spectral radiometer instrument they range in altitude from 6 kilometers (upper left) to 0.2 kilometers (lower right) above the moon’s surprisingly Earth-like surface of dark channels, floodplains, and bright ridges. But at temperatures near -290 degrees F (-180 degrees C), the liquids flowing across Titan’s surface are methane and ethane, hydrocarbons rather than water. After making the most distant landing for a spacecraft from Earth, Huygens transmitted data for more than an hour. The Huygens data and a decade of exploration by Cassini have shown Titan to be a tantalizing world hosting a complex chemistry of organic compounds, dynamic landforms, lakes, seas, and a possible subsurface ocean of liquid water.

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Venus and Mercury at Sunset


Inner planets Venus and Mercury can never wander far from the Sun in Earth’s sky. This week you’ve probably seen them both gathered near the western horizon just after sunset, a close conjunction of bright celestial beacons in the fading twilight. The pair are framed in this early evening skyview captured on January 13 from the ruins of Szarvasko Castle in northwestern Hungary. Above the silhouette of the landscape’s prominent volcanic hill Venus is much the brighter, separated from Mercury by little more than the width of two Full Moons. On Friday, planet Earth’s early morning risers will also be treated to a close conjunction, when Saturn meets an old crescent Moon near the southeastern horizon at dawn.

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The Hunter, the Bull, and Lovejoy


Heading north, Comet Lovejoy (C/2014 Q2) is putting on its best show for comet watchers now, with moonlight absent from mid-January’s early evening skies. An easy binocular target and just visible to the unaided eye from dark sites, the comet sweeps across the constellation Taurus the Bull in this deep night skyscape. The starry scene was captured just two days ago on January 12, from Jackson Hole, Wyoming, planet Earth. In fact, the head of Taurus formed by the V-shaped Hyades star cluster points toward Lovejoy at the right. The comet’s greenish coma and tail streaming in the anti-sunward direction also seem to have been shot from Orion’s bow. You can spot the familiar stars of the nebula rich constellation of the Hunter on the left, and follow this link to highlight Comet Lovejoy in the wide field of view.

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The Soap Bubble Nebula


Adrift in the rich star fields of the constellation Cygnus, this lovely, symmetric nebula was only recognized a few years ago and does not yet appear in some astronomical catalogs. In fact, amateur astronomer Dave Jurasevich identified it as a nebula on 2008 July 6 in his images of the complex Cygnus region that included the Crescent Nebula (NGC 6888). He subsequently notified the International Astronomical Union. Only eleven days later the same object was independently identified by Mel Helm at Sierra Remote Observatories, imaged by Keith Quattrocchi and Helm, and also submitted to the IAU as a potentially unknown nebula. The nebula, appearing on the left of the featured image, is now known as the Soap Bubble Nebula. What is the newly recognized nebula? Most probably it is a planetary nebula, a final phase in the life of a sun-like star.

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Cataclysmic Dawn


Will this dawn bring another nova? Such dilemmas might be pondered one day by future humans living on a planet orbiting a cataclysmic variable binary star system. Cataclysmic variables involve gas falling from a large star onto an accretion disk surrounding a massive but compact white dwarf star. Explosive cataclysmic events such as a dwarf nova can occur when a clump of gas in the interior of the accretion disk heats up past a certain temperature. At that point, the clump will fall more quickly onto the white dwarf and land with a bright flash. Such dwarf novas will not destroy either star, and may occur irregularly on time scales from a few days to tens of years. Although a nova is much less energetic than a supernova, if recurrent novas are not violent enough to expel more gas than is falling in, mass will accumulate onto the white dwarf star until it passes its Chandrasekhar limit. At that point, a foreground cave may provide little protection, as the entire white dwarf star will explode in a tremendous supernova.

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The Sky from Mauna Kea


What if you could stand at the top of a volcano and peer out across the universe? If the timing is right, you might see an amazing panorama like the one featured here. In this case, the volcano is the Hawaii’s Mauna Kea, and the time was a clear night last summer In the foreground of this south-facing panorama lies a rugged landscape dotted with rocks and hardy plants. Slightly above and further out, a white blanket of clouds spreads horizontally to the horizon, seemingly dividing heaven and Earth. City lights illuminate the clouds and sky on the far left, while orange lava in the volcanic caldera of Kilauea lights up the clouds just left of center. The summit of an even more distant Hawaiian volcano, Mauna Loa, is visible in dark silhouette near the central horizon. Green airglow is visible above the clouds, caused by air molecules excited by the Sun during the day. The Moon is the bright orb on the right. A diffuse band of light-colored zodiacal light extends up from the far right. Most distant, the dramatic central band of our Milky Way Galaxy appears to rise vertically from Mauna Loa. The person who witnessed and captured this breathtaking panorama stands before you in the image center.

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The Windmill s Moon


Seen from the Canary Island of Fuerteventura, this bright Full Moon rose at sunset. Reaching its full phase on the night of January 4/5, it was the first Full Moon of the new year and the first to follow December’s solstice. Of course, in North America the first Full Moon of January has been known as the Wolf’s Moon. But this Full Moon, posed in the twilight above an island of strong winds and traditional windmills, suggests another name. The telephoto image, taken at a distance from the foreground windmill, creates the dramatic comparison in apparent size for windmill and Full Moon.

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In the Arms of NGC 1097


Spiral galaxy NGC 1097 shines in southern skies, about 45 million light-years away in the chemical constellation Fornax. Its blue spiral arms are mottled with pinkish star forming regions in this colorful galaxy portrait. They seem to have wrapped around a small companion galaxy below and left of center, about 40,000 light-years from the spiral’s luminous core. That’s not NGC 1097’s only peculiar feature, though. The very deep exposure hints of faint, mysterious jets, most easily seen to extend well beyond the bluish arms toward the left. In fact, four faint jets are ultimately recognized in optical images of NGC 1097. The jets trace an X centered on the galaxy’s nucleus, but probably don’t originate there. Instead, they could be fossil star streams, trails left over from the capture and disruption of a much smaller galaxy in the large spiral’s ancient past. A Seyfert galaxy, NGC 1097’s nucleus also harbors a supermassive black hole.

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Stars and Dust in Corona Australis


Cosmic dust clouds and young, energetic stars inhabit this telescopic vista, less than 500 light-years away toward the northern boundary of Corona Australis, the Southern Crown. The dust clouds effectively block light from more distant background stars in the Milky Way. But the striking complex of reflection nebulae cataloged as NGC 6726, 6727, and IC 4812 produce a characteristic blue color as light from the region’s young hot stars is reflected by the cosmic dust. The dust also obscures from view stars still in the process of formation. At the left, smaller yellowish nebula NGC 6729 bends around young variable star R Coronae Australis. Just below it, glowing arcs and loops shocked by outflows from embedded newborn stars are identified as Herbig-Haro objects. On the sky this field of view spans about 1 degree. That corresponds to almost 9 light-years at the estimated distance of the nearby star forming region.

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100 Million Stars in the Andromeda Galaxy


What stars compose the Andromeda galaxy? To better understand, a group of researchers studied the nearby spiral by composing the largest image ever taken with the Hubble Space Telescope. The result, called the Panchromatic Hubble Andromeda Treasury (PHAT), involved thousands of observations, hundreds of fields, spanned about a third of the galaxy, and resolved over 100 million stars. In the featured composite image, the central part of the galaxy is seen on the far left, while a blue spiral arm is prominent on the right. The brightest stars, scattered over the frame, are actually Milky Way foreground stars. The PHAT data is being analyzed to better understand where and how stars have formed in M31 in contrast to our Milky Way Galaxy, and to identify and characterize Andromeda’s stellar clusters and obscuring dust.

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