IC 2177, The Seagull Nebula, by WISE

The Seagull nebula, seen in this infrared mosaic from NASA's Wide-field Infrared Survey Explorer, or WISE, draws its common name from it resemblance to a gull in flight. But it depends on your point of view. When the image is rotated 180 degrees it bears a passing resemblance to a galloping lizard -- or perhaps a dragon or a dinosaur. The image spans an area about seven times as wide as the full moon, and three times as high (3.55 by 1.37 degrees), straddling the border between the constellations Monoceros and Canis Major (the Big Dog). So you might say this lizard is running with the Big Dog, while the gull is flying from it.

Astronomers catalog the nebula as IC 2177. This cosmic cloud is one of many sites of star formation within the Milky Way galaxy. It is located 3,800 light-years away from Earth, inside the Orion spur -- the same partial spiral arm of the Milky Way where our solar system is located. The nebula is nearly 240 light-years across.

Astronomers list the region near the seagull's eye (or lizard's hip) as NGC 2327, which contains a cluster of stars born about 1.5 million years ago. The eye is the brightest and hottest of the newborn stars in the entire nebula, and heats up the dust so that it glows in infrared light.

All four infrared detectors aboard WISE were used to make this image. Color is representational: blue and cyan represent infrared light at wavelengths of 3.4 and 4.6 microns, which is dominated by light from stars. Green and red represent light at 12 and 22 microns, which is mostly light from warm dust.

Photo credit: NASA/JPL-Caltech/UCLA

Lunar Swirls at Mare Ingenii

LROC WAC context image of part of Mare Ingenii with the extraordinary patterns of dark and light albedo lunar swirls. The star near the center of the image shows the location of a potential future landing site within the Constellation region of interest.

Mare Ingenii is one of the few mare basalt deposits on the farside of the Moon. What makes Mare Ingenii even more unique is that it contains one of the most rare and strange geological features on the Moon: lunar swirls!

Lunar swirls are bright markings found on both mare and highland portions of the Moon. They appear as high albedo swirls and patches. They have no topography, as they are only surficial in nature. Swirls range in size from meters to tens of kilometers in length. The swirls are commonly found antipodal to huge young impact basins: Orientale, Imbrium and Crisium, but also within the large basins at Mare Ingenii, near the Airy Crater, and at Mare Moscoviense. They are accompanied by relatively high magnetic anomalies, which is surprising for a planetary body that does not, and may never have had, an active core dynamo with which to generate a magnetic field. The shapes of the swirls hint at a magnetic origin.

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Three models have been proposed to explain swirl formation: (1) deflection of the solar wind by local magnetic fields, (2) cometary impacts, or (3) impacts of meteoroid swarms. Deflection of the solar wind by local magnetic fields may protect the underlying rocks and soils from space weathering, thus leaving them with higher albedo. Recent cometary impacts might cause the high albedo of the swirls due to scouring of the topmost surface regolith and exposure of fresh, brighter material from below. The meteoroid swarm model is a variation of the cometary impact model,where cometary nuclei are fragmented into a swarm of smaller objects by solar or terrestrial tidal forces before they impact the lunar surface. During and immediately after impact, inter-particle collisions in the cloud of debris and regolith particles of the ejecta collide with each other, forming the curvilinear swirl features.

Photo credit: NASA/GSFC/Arizona State University

Saturn's Rings, Rhea and Janus

Saturn's rings occupy the foreground of this image. The small moon Janus appears to hover above, while the far larger moon Rhea is partially obscured by the rings.

Janus appears to be located directly over the rings, but the moon is actually further away, at a range of about 1.1 million kilometers (684,000 miles) from the Cassini spacecraft. Rhea is 1.6 million kilometers (994,000 miles) from the spacecraft. This view looks toward the trailing hemisphere of Janus (179 kilometers, or 111 miles across) and the Saturn-facing side of Rhea (1,528 kilometers, or 949 miles across).

This view looks toward the northern, sunlit side of the rings from just above the ringplane.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on April 8, 2010. Image scale is 7 kilometers (4 miles) per pixel on Janus and 10 kilometers (6 miles) per pixel on Rhea.

Photo credit: NASA/JPL/Space Science Institute

Fresh Impact Crater in Mare Smythii

The featured image shows the interior of a fresh impact crater (approximately 300 m in diameter) in the Mare Smythii Constellation region of interest. In the high-sun image above, it is hard to recognize topographic features because there are no shadows. The wider view below, paired with a lower-sun image of the same crater on the right, gives a sharper view of small scale features such as boulders.

A wider view of the same fresh crater under high-sun (left, image M126371530LE, incidence angle of 21°) and lower sun image with illumination from the east (right, image M113392375LE, incidence angle of 50°).

The floor of this small crater looks like a basket of impact-melt covered rocks. Sampling the ejecta would help answer questions about the age of apparently recent impacts such as this one and the processes that cause their fresh rays to fade.

Mare Smythii is located on the eastern limb of the Moon and would provide an excellent place to sample relatively young (1-2 billion years old) basaltic lavas not represented in the sample collection. The western portion of the region of interest encompasses the crater Schubert C, the floor of which is fractured, possibly due to intrusions of lava beneath its surface - a great hypothesis for future explorers to assess.

Photo credit: NASA/GSFC/Arizona State University

WISE Scans for Comets and Asteroids

This movie shows asteroids observed so far by NASA's Wide-field Infrared Survey Explorer, or WISE. As WISE scans the sky from its polar orbit, more and more asteroids and comets are caught in its infrared vision. The mission has surveyed about three-fourths of the sky; however, data for only about 50 percent of the sky has been processed for asteroids and comets at this time.

The white dots show asteroids observed by WISE -- most of these are in the Main Belt between Mars and Jupiter, and some, the Trojans, orbit in front of, or behind, Jupiter. The red dots represent newfound near-Earth objects, which are asteroids and comets with orbits that come relatively close to Earth's path around the sun. The green dots are previously known near-Earth objects observed by WISE. The yellow squares show all comets seen by WISE so far. [The blue dots represent the five inner planets, from Mercury to Jupiter.]

As of May 24, 2010, WISE has seen more than 60,000 asteroids. It has observed more than 70 comets, 12 of which are new, and about 200 near-Earth objects, more than 50 of which are new.

WISE is an all-sky survey, snapping pictures of the whole sky, including everything from asteroids to stars to powerful, distant galaxies.

Photo credit: NASA/JPL-Caltech/ULCA/JHU

Notes: Please click here to watch the movie; unfortunately, I'm not able to upload the video to Blogger. For more information on this topic, please see WISE Makes Progress on Its Space Rock Catalog. With regard to the "Trojans," the asteroids that orbit in front of Jupiter (at the top of the image) are actually known as the "Greeks." The "Trojans" are the large mass of asteroids behind Jupiter (at the bottom of the image).

Birth of a Loop Current Eddy

The northern portion of the Gulf of Mexico's Loop Current, shown in red, appears about to detach a large ring of current, creating a separate eddy. An eddy is a large, warm, clockwise-spinning vortex of water -- the ocean's version of a cyclone. This image, created with measurements of sea surface height from multiple satellites, including the NASA/French Space Agency [Centre National d'Études Spatiales; CNES] Jason-1 and Ocean Surface Topography Mission/Jason-2 satellites, shows the speed and direction of surface currents in the Gulf. The star shows the former location of the Deepwater Horizon, the drilling rig that exploded and sank in April, and has been leaking oil since. A large eddy between the leak and the Loop Current might keep, at least temporarily, some of the spilling oil from reaching the Florida Straits, the ocean channel between the Florida Keys and Cuba, and being transported to the east coast of Florida and northward into the Gulf Stream.

This map was produced by the Colorado Center for Astrodynamics Research in Boulder, Colorado. The center processes satellite measurements of sea surface height in near real-time to create maps of the Gulf of Mexico, showing the location of medium-sized eddies and fronts. More information on these data products is available at http://argo.colorado.edu/~realtime/welcome/.

Photo credit: NASA/JPL/University of Colorado

Protostellar Envelopes and Jets

New evidence from NASA's Spitzer Space Telescope is showing that tight-knit twin stars might be triggered to form by asymmetrical envelopes like the ones shown in this image. All stars, even single ones like our sun, are known to form from collapsing clumps of gas and dust, called envelopes, which are seen here around six forming star systems as dark blobs, or shadows, against a dusty background. The greenish color shows jets coming away from the envelopes. The envelopes are all roughly 100 times the size of our solar system.

Two of the six envelopes are known to have already formed twin, or binary stars (Spitzer can see the envelopes but not the stars themselves). Astronomers believe that the irregular shapes of these envelopes, revealed in detail by Spitzer, might trigger binary stars to form, or might have already triggered them to form.

From top left, moving clockwise, the stars are: IRAS 03282+3035, CB230, IRAS 16253-2429, L1152, L483, HH270 VLA1. IRAS 03282+3035 and CB230 are the two known to have already formed binary stars.

Infrared light with a wavelength of 3.6 microns has been color-coded blue; 4.5-micron light is green; and 8.0-micron light is red.

Photo credit: NASA/JPL-Caltech/Univ. of Michigan

Rhea and Epimetheus Above Saturn's Rings

Saturn's moon Rhea looms "over" a smaller and more distant Epimetheus against a striking background of planet and rings.

The two moons aren't actually close to each other. The view was obtained at a distance of approximately 1.2 million kilometers (746,000 miles) from Rhea and 1.6 million kilometers (994,000 miles) from Epimetheus.

Lit terrain seen here is in the area between the trailing hemisphere and anti-Saturn side of Rhea (1,528 kilometers, or 949 miles across). Lit terrain seen on Epimetheus (113 kilometers, or 70 miles across) is mostly on the Saturn-facing side. This view looks toward the sunlit side of the rings from just above the ringplane.

The image was taken in visible green light with the Cassini spacecraft narrow-angle camera on March 24, 2010. Image scale is 7 kilometers (4 miles) per pixel on Rhea and 10 kilometers (6 miles) per pixel on Epimetheus.

Photo credit: NASA/JPL/Space Science Institute

Jupiter Loses a Stripe

In a development that has transformed the appearance of the solar system's largest planet, one of Jupiter's two main cloud belts has completely disappeared.

"This is a big event," says planetary scientist Glenn Orton of NASA's Jet Propulsion Lab. "We're monitoring the situation closely and do not yet fully understand what's going on."

Known as the South Equatorial Belt (SEB), the brown cloudy band is twice as wide as Earth and more than twenty times as long. The loss of such an enormous "stripe" can be seen with ease halfway across the solar system.

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Orton thinks the belt is not actually gone, but may be just hiding underneath some higher clouds.

"It's possible," he hypothesizes, "that some 'ammonia cirrus' has formed on top of the SEB, hiding the SEB from view." On Earth, white wispy cirrus clouds are made of ice crystals. On Jupiter, the same sort of clouds can form, but the crystals are made of ammonia (NH3) instead of water (H20).

What would trigger such a broad outbreak of "ammonia cirrus"? Orton suspects that changes in global wind patterns have brought ammonia-rich material into the clear, cold zone above the SEB, setting the stage for formation of the high-altitude, icy clouds.

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This isn't the first time the SEB has faded out.

"The SEB fades at irregular intervals, most recently in 1973-75, 1989-90, 1993, 2007, 2010," says John Rogers, director of the British Astronomical Association's Jupiter Section. "The 2007 fading was terminated rather early, but in the other years the SEB was almost absent, as at present."

The return of the SEB can be dramatic.

"We can look forward to a spectacular outburst of storms and vortices when the 'SEB Revival' begins," says Rogers. "It always begins at a single point, and a disturbance spreads out rapidly around the planet from there, often becoming spectacular even for amateurs eyeballing the planet through medium-sized telescopes. However we can't predict when or where it will start. On historical precedent it could be any time in the next 2 years. We hope it will be in the next few months so that everyone can get a good view.

Photo credit: Anthony Wesley

Runaway Star 30 Dor #16 in the Tarantula Nebula

This image of the 30 Doradus Nebula, a rambunctious stellar nursery, and the enlarged inset photo show a heavyweight star that may have been kicked out of its home by a pair of heftier siblings.

In the inset image at right, an arrow points to the stellar runaway and a dashed arrow to its presumed direction of motion. The image was taken by the Wide Field and Planetary Camera 2 (WFPC2) aboard the NASA/ESA Hubble Space Telescope. The heavyweight star, called 30 Dor #016, is 90 times more massive than the Sun and is traveling at more than 400 000 kilometers an hour from its home.

In the wider view of 30 Doradus, the homeless star, located on the outskirts of the nebula, is centered within a white box. The box shows Hubble's field of view. The image was taken by the European Southern Observatory's (ESO) Wide Field Imager at the MPG/ESO 2.2-meter telescope on La Silla, Chile.

The young star, only one million to two million years old, may have traveled about 375 light-years from its suspected home in R136, the bright star cluster marked by a circle. Nestled in the core of 30 Doradus, R136 is one of the most massive young star clusters in nearby galaxies, containing several stars topping 100 solar masses each. 30 Doradus, also called the Tarantula Nebula, resides roughly 170 000 light-years from Earth, in the Large Magellanic Cloud.

Instruments at three observatories, including Hubble's WFPC2 and recently installed Cosmic Origins Spectrograph, have provided tantalizing clues that the star was ejected from R136.

In the ESO and WFPC2 images, hot stars are represented by the color blue. Hydrogen is in red and oxygen in green. Radiation from the runaway star is making the nebula glow.

The Hubble image was taken on 30 June 1995; the ESO image was released in December 2006.

Photo credits:
Credit: NASA, ESA, J. Walsh (ST-ECF).
Acknowledgment: Z. Levay (STScI).

Credit for ESO image: ESO.
Acknowledgments: J. Alves (Calar Alto, Spain), B. Vandame, and Y. Beletski (ESO). Processing by B. Fosbury (ST-ECF).

The Hole in NGC 1999

The dark hole seen in the green cloud at the top of this image was likely carved out by multiple jets and blasts of radiation. The hole was originally thought to be a really dark cloud, but this new infrared picture from the Herschel space observatory and the National Optical Astronomy Observatory on Kitt Peak near Tucson, reveals that the dark spot is actually a gap in a "nest" of gas and dust containing fledgling stars.

An older picture of the hole captured in visible light by NASA's Hubble Space Telescope is shown as an inset. At the time the picture was taken, astronomers thought the hole was a dark cloud. When Herschel looked in its direction to study nearby young stars, astronomers were surprised to see the cloud continued to look black, which shouldn't have been the case. Herschel's infrared eyes are designed to see into such clouds.

The glowing, green cloud around the hole is called NGC 1999. It contains a fairly bright star, called V38O Ori, which is heating up the dust and creating the bright greenish glow. V380 Ori is a triple star system -- one of these three stars appears to have launched a jet that helped clear the hole, as well as other jets and stellar radiation.

The red, filamentary glow extending through the middle of the image is a cloud of cold, dense gas and dust -- the raw material from which new stars are forming. Three new, embryonic stars can be seen as the triangle of orangish, yellow-white spots. Bipolar jets are visible streaming out of one of these stars in blue. The dark region below and to the right of the top orange-white star of the triangle is thought to be another hole carved by jets from the star. This possible hole is not yet lit up by a star, as is the case with the hole seen above it.

Shorter-wavelength infrared light captured by the "NEWFIRM" camera at the National Optical Astronomy Observatory is colored blue, while longer-wavelength infrared light seen by the photodetector array camera and spectrometer instrument on Herschel is green and red.

Photo credits:
Top: ESA/NASA/JPL-Caltech/AURA/NSF/Univ. of Toledo
Bottom: ESA/NASA/JPL-Caltech/AURA/NSF/STScI/Univ. of Toledo

Daphnis Hidden Among Waves

Saturn's moon Daphnis, appearing as a tiny speck in the Keeler Gap of the A ring on the far right of this Cassini spacecraft image, is almost lost among the moon's attendant edge waves.

Daphnis (8 kilometers, or 5 miles across) has an inclined orbit relative to the ringplane. Its gravitational pull perturbs the orbits of the particles of the A ring forming the Keeler Gap's edge and sculpts the edge into waves having both horizontal (radial) and out-of-plane components. Material on the inner edge of the gap orbits faster than the moon so that the waves there lead the moon in its orbit. Material on the outer edge moves slower than the moon, so waves there trail the moon. See PIA11656 to learn more about this process.

The Encke Gap of the A ring, wider than the Keeler Gap, can be seen passing through the middle of the image. Several background stars are also visible. This view looks toward the southern, unilluminated side of the rings from about 16 degrees below the ringplane.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Jan. 7, 2010. The view was acquired at a distance of approximately 1.7 million kilometers (1.1 million miles) from Saturn. Image scale is 10 kilometers (6 miles) per pixel.

Photo credit: NASA/JPL/Space Science Institute

Voyager 2 and the "Aliens"

The Minister is occasionally perplexed by the silliness some people say. In late April (last month), NASA engineers announced that the spacecraft Voyager 2 was having some software errors in its transmissions back home to Earth:

Engineers have shifted NASA's Voyager 2 spacecraft into a mode that transmits only spacecraft health and status data while they diagnose an unexpected change in the pattern of returning data. Preliminary engineering data received on May 1 show the spacecraft is basically healthy, and that the source of the issue is the flight data system, which is responsible for formatting the data to send back to Earth. The change in the data return pattern has prevented mission managers from decoding science data.

The first changes in the return of data packets from Voyager 2, which is near the edge of our solar system, appeared on April 22. Mission team members have been working to troubleshoot and resume the regular flow of science data. Because of a planned roll maneuver and moratorium on sending commands, engineers got their first chance to send commands to the spacecraft on April 30. It takes nearly 13 hours for signals to reach the spacecraft and nearly 13 hours for signals to come down to NASA's Deep Space Network on Earth. (Source)

Considering that the two Voyager spacecraft have been in flight for 33 years (Voyager 2 was launched on August 20, 1977), the occasional software glitch is a very minor hiccup for such an old but functional spacecraft.

But some people, instead of viewing the problem rationally, choose to let their imaginations run rampant:

German researcher Hartwig Hausdorf has chalked up the problem to aliens. To be specific, he posits that the Voyager 2 was hijacked by aliens. According to Bild.com, Hausdorf said

"It seems almost as if someone had reprogrammed or hijacked the probe – thus perhaps we do not yet know the whole truth…”

Bild writer Attila Albert speculated that the Golden Record might have attracted the aliens.

Really now! Aliens have hijacked Voyager 2! Tell me, Herr Hausdorf, don't you think you should take off that aluminum foil cap you're wearing?

Image credits:
Top: NASA/JPL-Caltech
Bottom: Touchstone Pictures/Blinding Edge Pictures/The Kennedy/Marshall Company

HT: Digital Journal

In an Instant!

Bright and dark patterns show the distribution of ejecta of a 5 km diameter crater (8.0°N, 182.2°E), portion of LROC images M125733619L, R subsampled to 5 m/pixel [NASA/GSFC/Arizona State University].

Outside of the protective veil of the Earth's atmosphere, the Solar System is a dynamic, constantly changing environment. Nowhere is this more true than on the lunar surface. Asteroids and comets slam into the Moon at speeds greater than 16 km per second (10 miles per second) creating impact craters in a matter of seconds. So much energy is released in these impacts that the impactor is mostly vaporized and some of the target rock is melted. Rocks and soil are thrown out and form spectacular ejecta aprons. Rocks excavated from the deepest part of the crater typically land very near the rim, and material from the original surface is thrown out towards the edge of the ejecta blanket. Astronauts can easily sample the full range of depth of the crater without having to go down the steep slopes - they can simply collect samples as they approach the rim. Nature has provided a convenient look into the subsurface!

The full resolution sub-image focuses on the northeast wall (upper right) of the spectacular crater seen above. The low reflectance material is most likely impact melt that was thrown out during the impact. The streamers of impact melt (black materials) help scientists trace the path of ejecta taken during the cratering process. The floor of the crater is flat and dark: it is the remnant of impact melt that pooled in the bottom of the crater. The fact that these features are so well preserved is evidence that the crater formed recently in geologic terms. But how recent is recent? Over time smaller impacts will degrade these exquisite details and slowly this crater will fade into the background. Without samples, the only way we have of estimating ages of young craters is by counting the number of even smaller craters that have formed on their surfaces. The best way to date impact craters is to sample their impact melt - as the molten rock cooled and formed new minerals their radiometric clock was reset. Scientists can measure the ratio of parent atoms to their daughter products and very accurately determine the age of crystallization. Planetary scientists would very much like to obtain accurate age dates for many of these young craters to determine the rate of recent impacts on the Moon. Current impact rates determined for the Moon are applicable to the Earth!

Photo credit: NASA/GSFC/Arizona State University

Asteroid 1719 Jens and the Tadpole Nebula

A new infrared image from NASA's Wide-field Infrared Survey Explorer, or WISE, showcases the Tadpole nebula [IC 410], a star-forming hub in the Auriga constellation about 12,000 light-years from Earth. As WISE scanned the sky, capturing this mosaic of stitched-together frames, it happened to catch an asteroid in our solar system passing by. The asteroid, called 1719 Jens, left tracks across the image, seen as a line of yellow-green dots in the boxes near center (Figure 1). A second asteroid was also observed cruising by, as highlighted in the boxes near the upper left (the larger boxes are blown-up versions of the smaller ones).

But that's not all that WISE caught in this busy image -- two satellites orbiting above WISE (highlighted in the ovals) streak through the image, appearing as faint green trails. The apparent motion of asteroids is slower than satellites because asteroids are much more distant, and thus appear as dots that move from one WISE frame to the next, rather than streaks in a single frame.

This Tadpole region is chock full of stars as young as only a million years old -- infants in stellar terms -- and masses over 10 times that of our sun. It is called the Tadpole nebula because the masses of hot, young stars are blasting out ultraviolet radiation that has etched the gas into two tadpole-shaped pillars, called Sim 129 and Sim 130. These "tadpoles" appear as the yellow squiggles near the center of the frame. The knotted regions at their heads are likely to contain new young stars. WISE's infrared vision is helping to ferret out hidden stars such as these.

The 1719 Jens asteroid, discovered in 1950, orbits in the main asteroid belt between Mars and Jupiter. The space rock, which has a diameter of 19 kilometers (12 miles), rotates every 5.9 hours and orbits the sun every 4.3 years.

Twenty-five frames of the region, taken at all four of the wavelengths detected by WISE, were combined into this one image. The space telescope caught 1719 Jens in 11 successive frames. Infrared light of 3.4 microns is color-coded blue: 4.6-micron light is cyan; 12-micron-light is green; and 22-micron light is red.

Photo credit: NASA/JPL-Caltech/UCLA

Hokusai Crater

Pictured above is an impact crater first imaged during Mercury flyby 2 and drawing scientific attention because of its extensive system of rays, which extend over a thousand kilometers across the planet. The International Astronomical Union (IAU) recently approved the name Hokusai for this spectacular rayed crater. Hokusai is a prominent feature seen in Earth-based radar images of Mercury, and the name Hokusai was suggested by radar astronomer John K. Harmon. The crater's name honors the Japanese painter, draftsman, and printmaker, Katsushika Hokusai (1760-1849). Hokusai is perhaps best known for the painting "Mount Fuji Seen Below a Wave at Kanagawa."

Photo credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Galactic Metropolis

A surprisingly large collection of galaxies (red dots in center) stand out at a remarkably large distance in this composite image combining infrared and visible-light observations. NASA's Spitzer Space Telescope contributed to the infrared component of the observations, while shorter-wavelength infrared and visible data are provided by Japan's Subaru telescope atop Mauna Kea, Hawaii.

Looking out to this distance, the cluster appears as it was 9.6 billion years ago, only about three billion years after the Big Bang. Astronomers were surprised to find such a "modern" cluster at an era when its peers tended to be much smaller, presumably taking billions of more years to collect enough galaxies to reach such a size.

Infrared light from Spitzer at wavelengths of 3.6 and 4.5 microns is displayed in red. Subaru observations of near infrared and visible light with wavelengths of 0.9 and 0.44 microns are rendered in green and blue, respectively. The purple overlay is a calculated measure of overall galaxy density and highlights the high concentration of galaxies in the distant cluster.

Photo credit: NASA/JPL-Caltech/Subaru

Herschel Crater on Mimas

Subtle color differences on Saturn's moon Mimas are apparent in this false-color view of Herschel Crater captured by NASA's Cassini spacecraft during its closest-ever flyby of that moon.

The image shows terrain-dependent color variations, particularly the contrast between the bluish materials in and around Herschel Crater (130 kilometers, or 80 miles, wide) and the greenish cast on older, more heavily cratered terrain elsewhere. The origin of the color differences is not yet understood, but may be caused by subtle differences in the surface composition between the two terrains. False color images from Cassini's previous closest encounter, in 2005, also showed such variations (see PIA06257).

Herschel Crater covers most of the bottom of this image. To create this false-color view, ultraviolet, green and infrared images were combined into a single picture that exaggerates the color differences of terrain on the moon. These data were combined with a high-resolution image taken in visible light to provide the high-resolution information from the clear-filter image and the color information from the ultraviolet, green and infrared filter images.

The natural color of Mimas visible to the human eye may be a uniform gray or yellow color, but this mosaic has been contrast-enhanced and shows differences at other wavelengths of light.

During its closest-ever flyby on Feb. 13, 2010, Cassini came within about 9,500 kilometers (5,900 miles) of Mimas. This view looks toward the northern part of the hemisphere of Mimas that leads in the moon's orbit around Saturn. Mimas is 396 kilometers (246 miles) across. North on Mimas is up and rotated 12 degrees to the left.

The images were obtained with Cassini's narrow-angle camera on that day at a distance of approximately 16,000 kilometers (10,000 miles) from Mimas. The images were re-projected into an orthographic map projection. A black and white image, taken in visible light with the wide-angle camera, is used to fill in parts of the mosaic. Image scale is 90 meters (195 feet) per pixel.

Photo credit: NASA/JPL/Space Science Institute

Note: The Minister dislikes using the same photo that Astronomy Picture of the Day uses, especially on the same day! However, the Minister finds this picture of Herschel Crater so wonderful, that he can't help but to highlight this photo as soon as possible!

Bursting with Stars

This image is taken looking towards a region of our Milky Way galaxy in the Eagle constellation, closer to the galactic center than our sun. Here, we see the outstanding end products of the stellar assembly line. At the center and the left of the image, the two massive star-forming regions G29.9 and W43 are clearly visible. These mini-starbursts are forming, as we speak, hundreds and hundreds of stars of all sizes: from those similar to our sun, to monsters several tens of times heavier than our sun.

These newborn large stars are catastrophically disrupting their original gas embryos by kicking away their surroundings and excavating giant cavities in the galaxy. This is clearly visible in the "fluffy chimney" below W43.

Photo credit: ESA/Hi-GAL Consortium

Mare Frigoris

The floor of a l.2-km diameter crater in the Mare Frigoris Constellation region of interest. Samples of this material could help us understand the complex geologic history of this region of the Moon. NAC image M126752534RE; scene width is 510 m.

Samples from small, relatively fresh craters like the one above may someday help us learn more about Mare Frigoris [the Cold Sea] and its place in lunar geologic history. Mare Frigoris is located on the lunar nearside, to the north of the Imbrium and Serenitatis basins. Instead of being low in reflectance like typical mare basalts, its reflectance is intermediate between the mare to the south and highlands terrain to the north. This is likely due to a lower iron and titanium content than any of the sampled mare basalts, making it an intriguing end-member in the spectrum of lunar mare volcanism.

Portions of Mare Frigoris, like the area near the Constellation region of interest outlined below, are so high in reflectance they're considered "light plains." Light plains can form in several different ways: through volcanism, with a composition even lower in iron and titanium; as the result of impact basin ejecta, which acts as a fluid, filling in topographic lows; or as ancient volcanic plains that were subsequently covered with a thin layer of highlands material ejected from nearby craters or basins which masks the true basaltic surface (a hidden, or "cryptomare"). Small craters like the one above excavate material from below the surface, and can help discern whether or not the material there is distinct in composition (as would be expected for cryptomare). Sampling this material would provide a definitive resolution to the geologic history of this fascinating region.

Photo credit: NASA/GSFC/Arizona State University

Menkhib and NGC 1499, the California Nebula, by WISE

This infrared image from NASA's WISE (Wide-field Infrared Survey Explorer) features one of the bright stars in the constellation Perseus, named Menkhib (the bright star in the upper left near the red dust cloud) along with a large star forming cloud cataloged as NGC 1499, or more commonly called the California Nebula (running diagonally through the image).

Menkhib [Xi Persei] is one of the hottest stars visible in the night sky; its surface temperature is about 37,000 Kelvin (about 66,000 degrees Fahrenheit -- over 6 times hotter than the Sun). Because of its high temperature it appears blue-white to the human eye (almost all stars appear bluish to WISE). It has about 40 times the mass of the Sun and gives off 330,000 times the amount of light. Menkhib is a runaway star, and the fast stellar wind it blows is piling up in front of it to create a shock wave in the gas and dust surrounding it in the space between the stars. This shock wave is heating up the dust within and WISE sees it as the red cloud in the upper left of the image.

Menkhib is part of an association of very hot stars that were born from the California Nebula only a few million years ago. These stars are lighting up the nebula; heating and ionizing it. In visible light, the ionized gas glows red, while in infrared light we see the heated dust (which appears in green and red in this image from WISE). The California Nebula gets its name due to a resemblance to the shape of the U.S. State of California (which you can just make out as outlined by the green dust if you rotate the image by a little more than 90 degrees clockwise). The entire California Nebula stretches across about 100 light-years, and we see about 80% of it in this view.

Menkhib and the California Nebula are about 1,800 light-years away from Earth. This is within the same spur of the Orion spiral arm of the Milky Way in which we are located.

All four infrared detectors aboard WISE were used to make this image. Color is representational: blue and cyan represent infrared light at wavelengths of 3.4 and 4.6 microns, which is dominated by light from stars. Green and red represent light at 12 and 22 microns, which is mostly light from warm dust.

Photo credit: NASA/JPL-Caltech/UCLA

Odysseus Crater on Tethys, by Cassini

A huge impact created Odysseus Crater, which covers a large part of Saturn's moon Tethys in this Cassini spacecraft image.

Odysseus Crater is 450 kilometers (280 miles) across. This view looks toward the leading hemisphere of Tethys (1,062 kilometers, or 660 miles across). North on Tethys is up and rotated 3 degrees to the left.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Jan. 27, 2010. The view was obtained at a distance of approximately 703,000 kilometers (437,000 miles) from Tethys and at a Sun-Tethys-spacecraft, or phase, angle of 79 degrees. Image scale is 4 kilometers (2 miles) per pixel.

Photo credit: NASA/JPL/Space Science Institute

HII Region RCW 120 by Herschel

A Herschel image of the HII region RCW 120, highlighting the newly detected young stars at the borders of the ionizing bubble. The massive protostar, with mass 8-10 times that of the Sun is visible on the lower edge of the bubble, to the right. This color-composite image combines observations at wavelengths of 100 µm (red; PACS), 160 µm (green; PACS) and 250 µm (blue; SPIRE).

Photo credit: ESA, PACS & SPIRE Consortia, A. Zavagno (Laboratoire d'Astrophysique de Marseille) for the Herschel HOBYS and Evolution of Interstellar Dust Key Programmes

Central Peak of Copernicus Crater

Today's LROC NAC image (M102293451) is a close up of the 93-km (58 miles) diameter Copernicus crater showing light-toned fractured bedrock exposed on the higher slopes on the central structural uplift. The bedrock observed in this NAC frame appears to be somewhat intact, and not a breccia (i.e., a rock consisting of a jumble of randomly oriented rock fragments). It is only slightly brecciated (or fragmented), which is consistent with the manner in which crater central peak rocks are uplifted and exposed. This location gives us a glimpse of bedrock that was protected beneath the surface until exposed by the Copernicus impact event and later landslides. Dark materials appear to fill fractures in this outcrop that may be highly shocked materials (e.g., impact melt or breccias) that were injected into the rock during the formation of Copernicus.

Photo credit: NASA/GSFC/Arizona State University

Note: For more information and photos (including an anaglyph), please see LROC: Central Peak of Copernicus Crater.

Hubble Pinpoints Distant Galaxies in Deepest View of Universe

This is the deepest image of the Universe ever taken in near-infrared light by the NASA/ESA Hubble Space Telescope. The faintest and reddest objects (left inset) in the image are galaxies that correspond to lookback times of approximately 12.9 billion years to 13.1 billion years. No galaxies have been seen before at such early epochs. These galaxies are much smaller than the Milky Way galaxy and have populations of stars that are intrinsically very blue. This may indicate the galaxies are so primordial that they are deficient in the heavier elements, and as a result, are quite free of the dust that reddens light through scattering.

The image was taken with Hubble's newly installed Wide Field Camera 3 (WFC3), which collects light from near-infrared wavelengths and therefore looks even deeper into the Universe. The light from very distant galaxies is stretched out of the ultraviolet and visible regions of the spectrum into near-infrared wavelengths by the expansion of the Universe.

Hubble's WFC3 took this image in late August 2009 during a total of four days of pointing for 173,000 seconds [i.e., 48 hours] of exposure time. Infrared light is invisible and therefore does not have colors that can be perceived by the human eye. The colors in the image are assigned comparatively to short, medium and long near-infrared wavelengths (blue, 1.05 microns; green, 1.25 microns; and red, 1.6 microns). The representation is "natural" in that shorter wavelengths appear blue while longer wavelengths are redder. The faintest objects are about one-billionth as bright as can be seen with the naked eye. The galaxy distances are estimated from the infrared colors of their light.

Photo credit: NASA, ESA, G. Illingworth (UCO/Lick Observatory and University of California, Santa Cruz) and the HUDF09 Team

Dione Passing by Tethys

Saturn's moon Dione passes by the moon Tethys in this Cassini spacecraft depiction of a "mutual event." Mutual events occur when, from the vantage point of Cassini, one moon appears to pass close to or in front of another moon.

Mutual event observations help scientists refine their understanding of the orbits of Saturn's moons. See PIA11692 to watch a movie of a mutual event. Lit terrain seen here is on Saturn-facing, trailing hemisphere side of both Tethys (1,062 kilometers, or 660 miles across) and Dione (1,123 kilometers, or 698 miles across).

The image was taken in visible green light with the Cassini spacecraft narrow-angle camera on March 26, 2010. The view was obtained at a distance of approximately 2 million kilometers (1.2 million miles) from Dione and 2.4 million kilometers (1.5 million miles) from Tethys. Image scale in the original image was 12 kilometers (7 miles) per pixel on Dione and 14 kilometers (9 miles) per pixel on Tethys. The image was contrast enhanced and magnified by a factor of two to enhance the visibility of surface features.

Photo credit: NASA/JPL/Space Science Institute

NGC 2359, Thor's Helmet, by WISE

This heroic image from WISE is of a special cloud of dust and gas in the constellation Canis Major cataloged as NGC 2359. The nebula is more commonly known as Thor's Helmet due to its remarkable resemblance to depictions of the headwear donned by the famed Norse god of thunder and lightning.

Powering Thor's Helmet is HD 56925, a highly luminous "Wolf-Rayet" star (seen at the center of the helmet). These kinds of stars are massive; from 10 to 80 times the mass of our Sun. Such stars are often associated with bright nebulae, many of which appear to be spherical bubbles with the Wolf-Rayet star at the center. It is thought that the progenitors of these stars are either red supergiants or luminous blue variable stars, both of which slowly shed matter as they age. Once the star enters its Wolf-Rayet phase its strong, fast stellar wind sweeps up the surrounding debris left by the original star and even gathers up interstellar matter from its environment. It literally blows a bubble in space. These hot stars become 200,000 times more luminous than the Sun. They flood the nebula with ultraviolet light that ionizes much of the gaseous material leading to the bright emission in visible light. Interactions with a nearby large molecular cloud are thought to have contributed to the more complex shape and curved bow-shock structure of Thor's Helmet.

NGC 2359 was the first Wolf-Rayet nebula to be discovered. Between 1917 and 1919, Francis Pease studied the nebula at the Mt. Wilson observatory in southern California. He described the bright regions of the nebula as matching the descriptions of early observers such as Sir John Herschel (son of the discoverer of infrared light, William Herschel), who saw a bust rather than a helmet. The object was later found to show nitrogen emission by Edwin Hubble and listed in his 1922 paper, "A General Study of Diffuse Galactic Nebulae." The object has also been of interest to members of the WISE science team during their careers having been studied by Martin Cohen and the WISE Principal Investigator Ned Wright, who co-authored an article in the March 1980 issue of Sky & Telescope, "A Bubble in Space - The Shell of NGC 2359."

Thor's Helmet is about 30 light-years across and its distance from Earth is estimated to be about 15,000 light-years. This image covers an area of sky about 2.5 times the size of the full Moon. All four infrared detectors aboard WISE were used to make this image. Color is representational: blue and cyan represent infrared light at wavelengths of 3.4 and 4.6 microns, which is dominated by light from stars. Green and red represent light at 12 and 22 microns, which is mostly light from warm dust.

Photo credit: NASA/JPL-Caltech/UCLA