Orion's Sword in Infrared

This image from NASA's Spitzer Space Telescope shows what lies near the sword of the constellation Orion -- an active stellar nursery containing thousands of young stars and developing protostars. Many will turn out like our Sun. Some are even more massive. These massive stars light up the Orion nebula, which is seen here as the bright region near the center of the image.

To the north of the Orion nebula is a dark filamentary cloud of cold dust and gas, over 5 light-years in length, containing ruby red protostars that jewel the hilt of Orion's sword. These are the newest generation of stars in this stellar nursery, and include the protostar HOPS 68, where Spitzer spotted tiny green crystals in a surrounding cloud of gas.

Photo credit: NASA/JPL-Caltech

Juno's Solar Array

In this image technicians stow for launch solar array #2 for NASA's Juno spacecraft. The photo was taken on May 20, 2011 at the Astrotech payload processing facility in Titusville, Florida. NASA's Juno spacecraft is scheduled to launch aboard an Atlas V rocket from Cape Canaveral, Florida. August 5. The solar-powered spacecraft will orbit Jupiter's poles 33 times to find out more about the gas giant's origins, structure, atmosphere and magnetosphere and investigate the existence of a solid planetary core.

Photo credit: NASA/JPL-Caltech/KSC

Carina Nebula: Nearby Supernova Factory Ramps Up

This large Chandra image shows the Carina Nebula, a star-forming region in the Sagittarius-Carina arm of the Milky Way a mere 7,500 light years from Earth. Chandra's sharp X-ray vision has detected over 14,000 stars in this region, revealed a diffuse X-ray glow, and provided strong evidence that massive stars have already self-destructed in this nearby supernova factory.

The lower energy X-rays in this image are red, the medium energy X- rays are green, and the highest energy X-rays are blue. The Chandra survey has a large field of 1.4 square degrees, made of a mosaic of 22 individual Chandra pointings. In total, this image represents 1.2 million seconds -- or nearly two weeks -- of Chandra observing time. A great deal of multi-wavelength data has been used in combination with this new Chandra campaign, including infrared observations from the Spitzer Space Telescope and the Very Large Telescope (VLT).

Several pieces of evidence support the idea that supernova production has already begun in this star-forming region. Firstly, there is an observed deficit of bright X-ray sources in Trumpler 15, suggesting that some of the massive stars in this cluster were already destroyed in supernova explosions. Trumpler 15 is located in the northern part of the image, as shown in a labeled version [below], and is one of ten star clusters in the Carina complex. Several other well known clusters are shown in the labeled image [below].

The detection of six possible neutron stars, the dense cores often left behind after stars explode in supernovas, provides additional evidence that supernova activity is ramping up in Carina. Previous observations had only detected one neutron star in Carina. These six neutron star candidates are too faint to be easily picked out in this large-scale image of Carina.

The diffuse emission observed by Chandra also supports the idea that supernovas have already erupted in Carina. Some of the diffuse X-ray emission almost certainly comes from the winds of massive stars, but some may also come from the remains of supernova explosions.

Finally, a new population of young massive stars has been detected in Carina, potentially doubling the number of known young, massive stars that are mostly destined to be destroyed later in supernova explosions. These stars are seen as bright X-ray sources scattered across the image. Also shown in the labeled image is the most famous member of the Carina Nebula, Eta Carinae, a massive, unstable star that may be on the verge of exploding as a supernova. These latest results suggest Eta Carinae is not alone in its volatility within the Carina Nebula.

Photo credit: NASA/CXC/PSU/L.Townsley et al.

Singapore

The Republic of Singapore is a city-state off the southern tip of the Malay Peninsula. An island country made up of 63 islands, the country is largely urbanized with very little rain forest left. Part of various local empires since the 2nd century AD, Singapore declared independence in 1965. Since then it has had a massive increase in wealth: Singapore is the world's fourth leading financial center, and its port is one of the five busiest in the world. About 5 million people live in Singapore, of whom almost 3 million were born locally. The image was acquired 22 June 2001, covers an area of 42.3 x 34.8 km, and is located at 1.2 degrees north latitude, 103.9 degrees east longitude.

Photo credit: NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team

ESO's VLT Finds a Brilliant but Solitary Superstar

This view shows part of the very active star-forming region around the Tarantula Nebula in the Large Magellanic Cloud, a small neighbor of the Milky Way. At the exact center lies the brilliant but isolated star VFTS 682 and to its lower right the very rich star cluster R 136. The origins of VFTS are unclear — was it ejected from R 136 or did it form on its own? The star appears yellow-red in this view, which includes both visible-light and infrared images from the Wide Field Imager at the 2.2-meter MPG/ESO telescope at La Silla and the 4.1-meter infrared VISTA telescope at Paranal, because of the effects of dust.

Photo credit: ESO/M.-R. Cioni/VISTA Magellanic Cloud survey. Acknowledgment: Cambridge Astronomical Survey Unit

Note: For more information, click here.

Spirit, Spirit, Shining Bright

This observation catches the NASA Mars Exploration Rover Spirit gleaming in the sun beside Home Plate inside Gusev Crater. It also catches a dust devil in action.

We were surprised to see that the Spirit rover itself is the brightest spot in the image, unlike dozens of previous images of both rovers. Analysis of the illumination and viewing geometry and the tilt of the rover indicate that, by accident, we imaged it near the specular point for the flat solar panels. The specular point is where the illumination angle is the same as the viewing angle, and the vectors are aligned.

Ground-based measurements prior to launch showed that the specular reflection could be seen even when there is a thin dust cover over the panels. This result does show that the solar panels are not covered by an optically thick layer of dust (i.e., too thick for any light to pass through it). Spirit last communicated on 22 March 2010.

And a Dust Devil to Boot
Scientists have been coming to realize that dust devils on Mars are far more common that had been thought. Dust devils look like mini tornadoes and are made up of swirling vortices of air that pick up very fine pieces of dust (the smallest particles of soil, much finer than a grain of sand). They are also an important part of the Martian climate and geology.

Each year myriads of dust devils crisscross the surface scouring up loose dust. By removing dust the dust devils also, in effect, clean the surface. Since a dusty surface tends to be brighter and reflect sun light, dust devils collectively darken the surface and cause more sun light to be absorbed and warm the soil surface and the air. Dust devils can also kick lots of dust into the air where the dust can absorb sun light passing through the atmosphere, thus warming the atmosphere more directly.

Many images show tell-tale dark streaks that crisscross and wiggle all over the surface. The high wind speeds of dust devils can also shift and move sand that otherwise would remain in one location. By moving surface soil grains around, dust devils can serve to mix different minerals from various locations.

Photo credit: NASA/JPL/University of Arizona

NGC 2841

Star formation is one of the most important processes in shaping the Universe; it plays a pivotal role in the evolution of galaxies and it is also in the earliest stages of star formation that planetary systems first appear.

Yet there is still much that astronomers don't understand, such as how do the properties of stellar nurseries vary according to the composition and density of gas present, and what triggers star formation in the first place? The driving force behind star formation is particularly unclear for a type of galaxy called a flocculent spiral, such as NGC 2841 shown here, which features short spiral arms rather than prominent and well-defined galactic limbs.

Photo credit: NASA, ESA and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration Acknowledgment: M. Crockett and S. Kaviraj (Oxford University, UK), R. O'Connell (University of Virginia), B. Whitmore (STScI) and the WFC3 Scientific Oversight Committee

Note: For more information, see Flocculent Spiral NGC 2841 [heic1104]

The Lockman Hole

This false-color image shows a patch of the sky known as the "Lockman Hole," as observed by the SPIRE instrument on board Herschel.

Located in northern constellation of Ursa Major, The Great Bear, the "Lockman Hole" is a field on the sky almost devoid of foreground contamination and thus ideally suited for observations of galaxies in the distant Universe.

Almost every dot in the image is an entire galaxy, each containing billions of stars and appearing as they did 10-12 billion years ago, when the Universe was only a couple of billion years old. The blue, green and red colors represent the three far-infrared wavelengths used for Herschel's observations: 250, 350 and 500 microns, respectively. The galaxies shown in white have equal intensity in all three wavebands and are the ones forming the most stars.

Detecting these galaxies individually is particularly challenging, as they are both extremely faint and numerous, so many of them overlap in Herschel's images. This creates a fog of infrared radiation known as the Cosmic Infrared Background (CIB), which reflects the clustering pattern of the galaxies responsible for this fog. Studying the CIB and its fluctuations is thus an extremely powerful tool to explore the way galaxies tend to be grouped on both small and large scales.

The size of the field is 218 arcminutes on a side.

Photo credit: ESA & SPIRE consortium & HerMES consortium

Note: For more information, see Herschel Quantifies the Dark Matter Threshold for Starburst Galaxies

J144547-5931 and J144701-5919: Hunting for the Milky Way's Heaviest Stars

Like looking for Easter eggs in a lawn of long grass, the hunt for the Milky Way's most massive stars takes persistence and sharp eyes. In their stellar search through our Galactic backyard, astronomers have used powerful telescopes sensitive to X-ray and infrared radiation to find evidence for a substantial population of X-ray emitting massive stars.

This image shows infrared data from NASA's Spitzer Space Telescope near the plane of the Milky Way galaxy. Both outlined boxes contain an artificially darkened view of the Spitzer data, to highlight a bright X-ray source (blue) detected at the center of each square with NASA's Chandra X-ray Observatory. Each X-ray source coincides with a strong infrared signal.

Analysis of the X-ray and infrared data, as well as optical and radio observations, reveals that these bright sources are, in fact, extremely massive stars. Two other massive stars have also been found near the plane of the Milky Way using similar methods. Deep observations from ESA's XMM-Newton also provided valuable information for these other two objects. All four of these stars are thought to be at least 25 times more massive than the Sun and lie between 7,500 and 18,000 light years from Earth. These stars are expected to last only a few million years and will end their lives with supernova explosions.

Finding these very massive stars is not easy. Dust and gas throughout the Milky Way obscures much of the view from optical telescopes near the plane of the galaxy. Infrared images suffer less obscuration but are extremely crowded with stars. However, these stellar behemoths shine brightly in X-ray light and easily stand out from their neighbors in Chandra images.

Why are these massive stars so bright in X-rays? Some massive stars have winds that blow material away from their surface at over 2 million miles per hour. If this high-speed material collides with the wind from a companion star, it is decelerated so suddenly that it acts like it has collided with a Solar System-sized brick wall. The shock waves resulting from this enormous collision generate temperatures up to 100 million degrees, and produce copious amounts of X-rays.

These Chandra observations followed a survey of the plane of our Galaxy by the Advanced Satellite for Cosmology and Astrophysics (ASCA), a previous X-ray mission. This survey detected about 160 X-ray sources, but only a third of them could be definitively identified due to the limited spatial resolution of ASCA. Because Chandra's ability to resolve sources is significantly greater, much more precise positions could be obtained. This has allowed scientists to identify counterparts to the X-ray sources in other wavelengths. There are many other unidentified Galactic X-ray sources with X-ray properties similar to these four sources, so a large population of massive stars may remain to be discovered with future Chandra observations.

Photo credit: X-ray: NASA/U. of Sydney/G.Anderson et al; IR: NASA/JPL-Caltech

Updrafts of Large Ammonia Crystals in Saturn Storm

This false-color infrared image, obtained by NASA's Cassini spacecraft, shows clouds of large ammonia ice particles dredged up by a powerful storm in Saturn's northern hemisphere. Large updrafts dragged ammonia gas upward more than 30 miles (50 kilometers) from below. The ammonia then condensed into large crystals in the frigid upper atmosphere. This storm is the most violent ever observed at Saturn by an orbiting spacecraft.

Cassini's visual and infrared mapping spectrometer obtained these images on Feb. 24, 2011. Scientists colorized the image by assigning red to brightness detected from the 4.08-micron wavelength, green to brightness from the 0.90-micron wavelength, and blue to brightness from the 2.73-micron wavelength. Large particles (red) reflect sunlight well at 4.08 microns. Particles at high altitude (green) reflect sunlight well at 0.9 microns. Particles comprised of ammonia -- especially large ones -- do not reflect 2.73-micron sunlight well, but instead absorb light at this wavelength.

The storm here shows up as yellow, demonstrating that it has a large signal in both red and green colors. This indicates the cloud has large particles and extends upward to relatively high altitude. In addition, the lack of blue in the feature indicates that the storm cloud has a substantial component of ammonia crystals. The head of the storm is particularly rich in such particles, as created by powerful updrafts of ammonia gas from depth in the throes of Saturn's thunderstorm.

Photo credit: NASA/JPL/Univ. of Arizona

Endeavour's Rendezvous Pitch Maneuver

At 5:15 a.m. EDT today, Endeavour began the nine-minute Rendezvous Pitch Maneuver, or 'backflip,' on its last visit to the International Space Station. With Commander Mark Kelly at the controls, Endeavour rotated 360 degrees backward to enable space station astronauts Dmitry Kondratyev, Paolo Nespoli and Cady Coleman to take high resolution pictures of the shuttle’s heat shield.

Kelly then flew the shuttle through a quarter circle to a position about 400 feet directly in front of the station. Docking occurred about an hour later at 6:14 a.m.

Photo credit: NASA

Lone Planet Under a Cosmic Magnifying Glass

This artist's animation illustrates the technique used for finding free-floating, Jupiter-mass planets in space. Astronomers found evidence for 10 of these worlds, thought to have been ejected early on from their developing solar systems.

The movie begins by showing the busy, central region of our Milky Way galaxy, where the planets were found with a ground-based telescope. It then zooms in on a star that brightens. This brightening is due to the passage of an unseen, free-floating planet (and has been exaggerated here). As a planet just happens to cross in front of a more distant star, its gravity causes the starlight to warp, and this warping resulted in an overall brightening of the star as seen by the telescope. In this effect, called gravitational microlensing, the planet's gravity plays the role of a magnifying lens.

The next part of the animation shows a zoomed in view of what the microlensing of a star would look like if it could be seen at much higher resolution. The blue dot represents the planet, but has been enlarged to make it easy to see. The main star is the brightest dot in the center, shown amidst other smaller, red and yellow stars. As the planet passes by, its gravity causes light from the stars to split into multiple, mirrored and reversed images. When the planet is directly in front of the main star, that star's multiple images are stretched into arcs. The overall result is a temporary brightening of the star.

Astronomers refer to the circular shape that can be seen as the planet passes by the stars as an Einstein Ring. When a planet is directly in front of star, it will cause the starlight to bend into a full Einstein Ring. When the planet is near stars, it will cause the star images to either appear deflected away from the ring, or inverted and reversed within the ring.

The duration of the microlensing event will reveal the rough mass of the passing body. Jupiter-mass objects will cause a star to brighten more quickly, over just a day or two. A passing star would cause a more distant star to brighten over a period of weeks.

The overall density of stars, as well as the brightness of their inverted images within the Einstein ring, have been exaggerated in this animation to help show the effects of the gravitational lensing. It is very rare for one passing planet to distort the light from multiple stars at once.

The movie ends with an artist's conception of a free-floating, Jupiter-mass world.

The gravitational microlensing shown is based on simulation data from M. Freeman (University of Auckland, New Zealand).

Video credit: NASA

Note: For more information, see Free-Floating Planets May Be More Common Than Stars.

NGC 371 - The Rose-Red Glow of Star Formation

The vivid red cloud in this new image from ESO’s Very Large Telescope is a region of glowing hydrogen surrounding the star cluster NGC 371. This stellar nursery lies in our neighboring galaxy, the Small Magellanic Cloud.

The object dominating this image may resemble a pool of spilled blood, but rather than being associated with death, such regions of ionized hydrogen — known as HII regions — are sites of creation with high rates of recent star birth. NGC 371 is an example of this; it is an open cluster surrounded by a nebula. The stars in open clusters all originate from the same diffuse HII region, and over time the majority of the hydrogen is used up by star formation, leaving behind a shell of hydrogen such as the one in this image, along with a cluster of hot young stars.

The host galaxy to NGC 371, the Small Magellanic Cloud, is a dwarf galaxy a mere 200,000 light-years away, which makes it one of the closest galaxies to the Milky Way. In addition, the Small Magellanic Cloud contains stars at all stages of their evolution; from the highly luminous young stars found in NGC 371 to supernova remnants of dead stars. These energetic youngsters emit copious amounts of ultraviolet radiation causing surrounding gas, such as leftover hydrogen from their parent nebula, to light up with a colorful glow that extends for hundreds of light-years in every direction. The phenomenon is depicted beautifully in this image, taken using the FORS1 instrument on ESO’s Very Large Telescope (VLT).

Open clusters are by no means rare; there are numerous fine examples in our own Milky Way. However, NGC 371 is of particular interest due to the unexpectedly large number of variable stars it contains. These are stars that change in brightness over time. A particularly interesting type of variable star, known as slowly pulsating B stars, can also be used to study the interior of stars through asteroseismology [1], and several of these have been confirmed in this cluster. Variable stars play a pivotal role in astronomy: some types are invaluable for determining distances to far-off galaxies and the age of the Universe.

Notes

[1] Asteroseismology is the study of the internal structure of pulsating stars by looking at the different frequencies at which they oscillate. This is a similar approach to the study of the structure of the Earth by looking at earthquakes and how their oscillations travel through the interior of the planet.

Photo credit: ESO/Manu Mejias

Unique Space Image of Alabama Tornado Tracks

NASA has released a unique satellite image tracing the damage of a monster EF-4 tornado that tore through Tuscaloosa, Alabama, on April 27th. It combines visible and infrared data to reveal damage unseen in conventional photographs.

"This is the first time we've used the ASTER instrument to track the wake of a super-outbreak of tornadoes," says NASA meteorologist Gary Jedlovec of the Marshall Space Flight Center in Huntsville, Alabama.

In the picture, captured just days after the storm, pink represents vegetation and aqua is the absence of vegetation. The tornado ripped up everything in its path, scouring the Earth's surface with its terrible force. The "tearing up" of vegetation makes the tornado's track stand out as a wide swath of aqua.

"This image and others like it are helping us study the torn landscape to determine just how huge and powerful these twisters were and to assess the damage they inflicted," says Jedlovec.

ASTER, short for Advanced Spaceborne Thermal Emission and Reflection Radiometer, orbits Earth onboard NASA's Terra spacecraft. Its data products include digital elevation maps from stereo images; surface temperatures; vegetation maps; cloud and sea ice data; and more. Last spring the instrument helped track the movement of the oil spill in the Gulf of Mexico.

To detect the scars left by the twisters, ASTER senses the visible and infrared energy reflected from the planet's surface. Destruction like crushed houses, torn and snapped trees, and uprooted crops are evident in the multi-wavelength images.

"A demolished house, debris and soil scattered on vegetated surfaces, and damaged trees and crops all change the pattern of reflected radiation measured by the satellite," explains Jedlovec. "We can analyze these patterns to help storm survey teams evaluate the damage."

Ground teams conducting field surveys of tornado damage must try to pinpoint where the twisters touched down, how long they stayed on the ground, and the force of their winds. But doing this from ground level can be tricky. Some places are nearly impossible to reach by foot or car. Also, in remote areas, damage often goes unreported, so survey teams don't know to look there.

This is where satellites can help.

"To get an accurate picture survey teams need to look everywhere that sustained damage – even unreported areas. Satellite sensors detect damage in rural areas, wilderness areas, and other unpopulated areas. Only with that knowledge can surveyors determine the true track of a tornado."

Otherwise, says Jedlovec, a twister could have flattened a single dwelling in a remote location, killing everyone inside, and no one would know.

Less critical but still important are home owners' insurance issues. To evaluate claims submitted by storm victims, insurance companies rely on National Weather Service storm reports based on the field surveys.

"Let's say you live in a remote area," says Jedlovec. "If there's no record of a storm passing over your area, you could be out of luck."

Jedlovec and colleagues are working now to produce satellite images of other areas ravaged by the historic outbreak of tornadoes.

"We want to help the storm victims any way we can."

Text credit: Science@NASA; photo credit: NASA/GSFC/METI/ERSDAC/JAROS, and U.S./Japan ASTER Science Team

NGC 3582 - Celestial Fireworks from Dying Stars

This image of the nebula NGC 3582, which was captured by the Wide Field Imager on the MPG/ESO 2.2-meter telescope at ESO’s La Silla Observatory in Chile, shows giant loops of gas bearing a striking resemblance to solar prominences. These loops are thought to have been ejected by dying stars, but new stars are also being born within this stellar nursery. These energetic youngsters emit intense ultraviolet radiation that makes the gas in the nebula glow, producing the fiery display shown here.

NGC 3582 is part of a large star-forming region in the Milky Way, called RCW 57. It lies close to the central plane of the Milky Way in the southern constellation of Carina (The Keel of Jason’s ship, the Argo). John Herschel first saw this complex region of glowing gas and dark dust clouds in 1834, during his stay in South Africa.

Some of the stars forming in regions like NGC 3582 are much heavier than the Sun. These monster stars emit energy at prodigious rates and have very short lives that end in explosions as supernovae. The material ejected from these dramatic events creates bubbles in the surrounding gas and dust. This is the probable cause of the loops visible in this picture.

This image was taken through multiple filters. From the Wide Field Imager, data taken through a red filter are shown in green and red, and data taken through a filter that isolates the red glow characteristic of hydrogen are also shown in red. Additional infrared data from the Digitized Sky Survey are shown in blue.

The image was processed by ESO using the observational data identified by Joe DePasquale, from the United States, who participated in ESO’s Hidden Treasures 2010 astrophotography competition. The competition was organized by ESO in October–November 2010, for everyone who enjoys making beautiful images of the night sky using astronomical data obtained using professional telescopes.

Photo credit: ESO, Digitized Sky Survey 2 and Joe DePasquale

NGC 3166 and 3169

This image from the Wide Field Imager on the MPG/ESO 2.2-meter telescope at the La Silla Observatory in Chile captures the pair of galaxies NGC 3169 (left) and NGC 3166 (right). These adjacent galaxies display some curious features, demonstrating that each member of the duo is close enough to feel the distorting gravitational influence of the other. The gravitational tug of war has warped the spiral shape of one galaxy, NGC 3169, and fragmented the dust lanes in its companion NGC 3166.

Photo credit: ESO/Igor Chekalin

Note: For more information, see A Disturbed Galactic Duo.

Wide-Field and Close-Up Views of the Tarantula Nebula

This image shows, on the left, a wide-field view of the Tarantula Nebula, a vast stellar nursery in the Large Magellanic Cloud. This was taken with the Wide Field Imager (WFI) on the MPG/ESO 2.2-meter telescope at the European Southern Observatory's site at La Silla, Chile. On the right is a narrower, more detailed view of part of the nebula, observed by Hubble's Advanced Camera for Surveys. The location of the Hubble image is marked by a square near the center of the WFI image.

Photo credits: NASA, ESA, ESO

Note: For more information, see Arachnophobes Beware: Hubble Snaps Close-Up of the Tarantula [heic1105].

Cygnus X-1

This illustration depicts the X-ray binary Cygnus X-1, composed of a 35 Msun blue O9 supergiant star and a black hole with a mass of about 10 Msun.

With its intense gravitational field, the black hole draws matter from its companion, and the stripped material spirals around the black hole, forming an accretion disc. Friction in the disc heats the material up to millions of degrees, making it shine in X-rays. Furthermore, the rotation of the disc funnels part of the accreted material into highly collimated, bipolar jets of particles that are released at relativistic speeds.

Based on the existing link between accretion and ejection of matter in X-ray binaries, astronomers also refer to these objects as 'microquasars' because they appear as miniature versions of quasars - the nuclei of active galaxies.

Illustration credit: ESA

Note: "Msun" means "solar mass," the mass of our sun. It is a common measurement to compare the sizes of stars. For more information, see INTEGRAL Discovers Gamma Rays Originating From Black Hole Jets.

NGC 4214

Galaxy NGC 4214, pictured here in an image from the NASA/ESA Hubble Space Telescope's newest camera, is an ideal location to study star formation and evolution. Dominating much of the galaxy is a huge glowing cloud of hydrogen gas in which new stars are being born. A heart-shaped hollow - possibly galaxy NGC 4214's most eye-catching feature - can be seen at the center of this. Inside this cavity lies a large cluster of massive, young stars ranging in temperature from 10&nbps;000 to 50&nbps;000 degrees Celsius. Their strong stellar winds are responsible for the creation of this bubble. These features have the effect of stemming any further star formation due to the subsequent lack of gas.

Photo credit: NASA, ESA and the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration. Acknowledgment: R. O'Connell (University of Virginia) and the WFC3 Scientific Oversight Committee

Note: For more information, see Galaxy NGC 4214: A Star Formation Laboratory [heic1109].

Venusian South Polar Winds

This image shows thermal infrared radiation (at a wavelength of 5 microns) emitted by the cloud-tops at the southern polar region of Venus on 20 January 2008, as viewed by the VIRTIS imaging spectrometer on Venus Express. The white arrows show the atmospheric winds, measured by tracking the movement of cloud features.

Photo credit: ESA/VIRTIS-VenusX/INAF-IASF/LESIA-Obs. Paris/Univ. Lisbon/Univ. Evora (D. Luz, Univ. Lisbon & D. Berry, Univ. Evora)

IC 5146 - Cocoon Nebula

This color-composite image of IC 5146 shows the extended filamentary structure of this star-forming cloud. A detailed study of this complex has shown a total of 27 filaments that all appear to have very similar widths, with a value of about 0.3 light years.

Over 350 compact starless cores have been detected embedded in the filaments in this region: about 45 of these are gravitationally bound, pre-stellar core candidates, the seeds of future stars. All pre-stellar cores are located in the densest, unstable filaments of the cloud - mostly along the main filamentary streamer visible in the central part of the image.

The glowing cavity on the left side of the image, also known as the Cocoon Nebula, is an HII region, where a young and bright B0 star illuminates the ionized hydrogen gas, causing it to shine. Some young stellar objects are visible as bright spots along the main filaments; many other young stellar objects are located in the Cocoon Nebula but are not visible in this image.

Located at a distance of about 1500 light years, the IC 5146 complex belongs to the Gould Belt, a giant ring of stars and star-forming clouds in the vicinity of the Sun.

This image is based on observations performed by SPIRE at 500 and 250 μm and by PACS at 70 μm. These observations of IC 5146 are part of an extensive survey of the Gould Belt currently undertaken with Herschel.

Photo credit: ESA/Herschel/SPIRE/PACS/D. Arzoumanian (CEA Saclay) for the 'Gould Belt survey' Key Programme Consortium

ARP 273 - A Rose Made of Galaxies

In celebration of the 21st anniversary of the Hubble Space Telescope's deployment into space, astronomers pointed Hubble at an especially photogenic group of interacting galaxies called Arp 273.

This image, taken by the NASA/ESA Hubble Space Telescope, shows a group of interacting galaxies called Arp 273. The larger of the spiral galaxies, known as UGC 1810, has a disc that is tidally distorted into a rose-like shape by the gravitational pull of the companion galaxy below it, known as UGC 1813. The swathe of blue jewels across the top is the combined light from clusters of intensely bright and hot young blue stars. These massive stars glow fiercely in ultraviolet light.

The smaller, nearly edge-on companion shows distinct signs of intense star formation at its nucleus, perhaps triggered by the encounter with the companion galaxy.

A series of uncommon spiral patterns in the large galaxy are a telltale sign of interaction. The large, outer arm appears partially as a ring, a feature that is seen when interacting galaxies actually pass through one another. This suggests that the smaller companion actually dived deeply, but off-center, through UGC 1810. The inner set of spiral arms is highly warped out of the plane, with one of the arms going behind the bulge and coming back out the other side. How these two spiral patterns connect is still not precisely known.

A possible mini-spiral may be visible in the spiral arms of UGC 1810 to the upper right. It is noticeable how the outermost spiral arm changes character as it passes this third galaxy, from smooth with lots of old stars (reddish in color) on one side, to clumpy and extremely blue on the other. The fairly regular spacing of the blue star-forming knots fits with what is seen in the spiral arms of other galaxies and can be predicted from the known instabilities in the gas contained within the arm.

The larger galaxy in the UGC 1810-UGC 1813 pair has a mass that is about five times that of the smaller galaxy. In unequal pairs such as this, the relatively rapid passage of a companion galaxy produces the lopsided or asymmetric structure in the main spiral. Also in such encounters, the starburst activity typically begins earlier in the minor galaxy than in the major galaxy. These effects could be due to the fact that the smaller galaxies have consumed less of the gas present in their nucleus, from which new stars are born.

Arp 273 lies in the constellation Andromeda and is roughly 300 million light-years away from Earth. The image shows a tenuous tidal bridge of material between the two galaxies that are separated by tens of thousands of light-years from each other.

The interaction was imaged on 17 December 2010, with Hubble's Wide Field Camera 3 (WFC3).

This Hubble image is a composite of data taken with three separate filters on WFC3 that allow a broad range of wavelengths covering the ultraviolet, blue, and red portions of the spectrum.

Photo credit: NASA, ESA and the Hubble Heritage Team (STScI/AURA)

Galactic Outflows

This illustration shows an Ultra-Luminous InfraRed Galaxy (ULIRG) that exhibits massive outflows of molecular gas.

In one of the most widely accepted theories of galaxy evolution, ULIRGs are an intermediate stage in the merger-driven process that gives rise to elliptical galaxies. Within this framework, the merger of gas-rich spiral galaxies hosting supermassive black holes in their centers initially produces a galaxy with an active nucleus that is enshrouded by a mixture of gas and dust. In this phase, the object is completely obscured and can only be detected in infrared light as an ULIRG. As the system evolves, gas and dust are gradually dispersed, eventually giving rise to an exposed Active Galactic Nucleus — a quasar.

Initially, it is the merger process that triggers starbursts and the growth of the central supermassive black hole in the galaxy. Later, the starburst and accretion by the black hole generate powerful gas outflows that sweep away the galaxy's reservoir of gas. Due to these negative feedback mechanisms — that at times suppress both star formation and black hole growth — the galaxy that forms from the merger is gas-poor, populated by old stellar populations and harbors a supermassive black hole with a mass that strongly correlates with the galaxy's stellar mass, as is observed in elliptical galaxies.

The detection of outflows powerful enough to strip galaxies of their molecular gas reservoir represents solid evidence in support of the merger-driven scenario for the formation of elliptical galaxies.

Illustration credit: ESA/AOES Medialab

For more information, see Caught in the Act by Herschel: Galactic Storms Sweep Away the Gas

NGC 2442 - The Meathook Galaxy

The Meathook Galaxy, or NGC 2442, has a dramatically lopsided shape. One spiral arm is tightly folded in on itself and host to a recent supernova, while the other, dotted with recent star formation, extends far out from the nucleus. The MPG/ESO 2.2-meter telescope and the NASA/ESA Hubble Space Telescope have captured two contrasting views of this asymmetric spiral galaxy.

The Meathook Galaxy, or NGC 2442, in the southern constellation of Volans (The Flying Fish), is easily recognized for its asymmetric spiral arms. The galaxy’s lopsided appearance is thought to be due to gravitational interactions with another galaxy at some point in its history — though astronomers have not so far been able to positively identify the culprit.

This broad view, taken by the Wide Field Imager on the MPG/ESO 2.2-meter telescope at La Silla, Chile, very clearly shows the double hook shape that gives the galaxy its nickname. This image also captures several other galaxies close to NGC 2442 as well as many more remote galaxies that form a rich backdrop. Although the Wide Field Imager, on the ground, cannot approach the sharpness of images from Hubble in space, it can cover a much bigger section of sky in a single exposure. The two tools often provide complementary information to astronomers.

A close-up image from the NASA/ESA Hubble Space Telescope (eso1115b) focuses on the galaxy’s nucleus and the more compact of its two spiral arms. In 1999, a massive star at the end of its life exploded in this arm in a supernova. By comparing older ground-based observations, previous Hubble images made in 2001, and these shots taken in late 2006, astronomers have been able to study in detail what happened to the star in its dying moments. By the time of this image the supernova itself had faded and is not visible.

ESO’s observations also highlight the other end of the life cycle of stars from Hubble. Dotted across much of the galaxy, and particularly in the longer of the two spiral arms, are patches of pink and red. This color comes from hydrogen gas in star-forming regions: as the powerful radiation of new-born stars excites the gas in the clouds they formed from, it glows a bright shade of red.

The interaction with another galaxy that gave the Meathook Galaxy its unusual asymmetric shape is also likely to have been the trigger of this recent episode of star formation. The same tidal forces that deformed the galaxy disrupted clouds of gas and triggered their gravitational collapse.

Photo credit: European Southern Observatory

For more information, see Two Views of a Lopsided Galaxy [heic1108].

The Aquila Rift

This color-composite image of the Aquila Rift shows the extended filamentary structure of this star-forming cloud. A detailed study of this complex has shown 32 filaments that all appear to have very similar widths, with a value of about 0.3 light years.

Over 500 compact cores have been detected embedded in the filaments in this region: about 60 per cent of these are gravitationally bound, pre-stellar core candidates, the seeds of future stars. All pre-stellar cores are located in the densest, unstable filaments of the cloud - mostly along the two main filamentary streamers crossing the image diagonally from the top right to the lower left and from the top left downwards, respectively. About two hundred proto-stars have also been detected; some of them are visible as bright 'spots' along the main filaments.

The two glowing cavities on opposite sides of the image are HII regions, where young and bright stars illuminate the ionized hydrogen gas, causing it to shine.

Located at a distance of about 850 light years, the Aquila Rift belongs to the Gould Belt, a giant ring of stars and star-forming clouds in the vicinity of the Sun.

This image is based on observations performed by SPIRE at 500 μm and by PACS at 160 and 70 μm. These observations of the Aquila Rift are part of an extensive survey of the Gould Belt currently undertaken with Herschel.

Photo credit: ESA/Herschel/SPIRE/PACS/Ph. André (CEA Saclay) for the 'Gould Belt survey' Key Programme Consortium

Crab Nebula: The Crab in Action & The Case of The Dog That Did Not Bark

A new movie from NASA's Chandra X-ray Observatory shows a sequence of Chandra images of the Crab Nebula, taken over an interval of seven months. Dramatic variations are seen, including the expansion of a ring of X-ray emission around the pulsar (white dot near center) and changes in the knots within this ring.

However, arguably the most striking result of these observations is the variations that were not observed, or in analogy with a famous Sherlock Holmes story [see below], this could be a case where the fact that the dog that did not bark helps to solve a mystery.

The pulsar at the center of the Crab Nebula is a neutron star that spins around about 30 times a second. It was created from a supernova explosion in our galaxy that was observed by astronomers in China and other countries in the year 1054.

As the young pulsar slows down, large amounts of energy are injected into its surroundings. In particular, a high-speed wind of matter and anti-matter particles plows into the surrounding nebula, creating a shock wave that forms the expanding ring seen in the movie. Jets from the poles of the pulsar spew X-ray emitting matter and antimatter particles in a direction perpendicular to the ring.

The goal of these latest Chandra observations was to pinpoint the location of remarkable gamma-ray flares observed by NASA's Fermi Gamma Ray Observatory and Italy's AGILE Satellite. A strong gamma-ray flare was observed from the Crab in September 2010, followed by an even stronger series of "superflares" in April 2011. The gamma-ray observatories were not able to locate the source of the flares within the nebula, but it was hoped that Chandra, with its high-resolution images, would.

Chandra began observing the Crab on monthly intervals beginning six days after the discovery of the gamma-ray flare in September 2010. This established a baseline of seven images of the nebula before the superflare was seen just last month.

When Fermi scientists saw that more flaring activity was beginning in April 2011, a pre-planned set of five Chandra observations was initiated. Two of these observations were made when strong gamma-ray flares occurred, but no clear evidence was seen for correlated flares in the Chandra images. The movie shows the April observations in "slow motion" to focus on the time when the gamma-ray superflares occurred. The movie shows three loops through the sequence of images, along with a timeline near the bottom.

Despite the lack of a "barking dog" in the X-ray data, these observations, as in the Sherlock Holmes story, will help scientists to home in on an explanation of the gamma-ray flares. The Chandra data provide strong constraints on the behavior, at relatively low energies, of the particles that have been accelerated to produce the gamma-ray flares. Another possible explanation follows if the gamma-ray flaring occurred in regions very close to the pulsar. Then they would have been missed by Chandra, because the Crab pulsar is so bright that the detectors are in essence "overexposed" so variations from that region cannot be observed. Note that in the movie an artificial source of constant brightness is included to show the position of the pulsar.

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"Is there any point to which you would wish to draw my attention?"
"To the curious incident of the dog in the night-time."
"The dog did nothing in the night-time."
"That was the curious incident," remarked Sherlock Holmes.

The story by Sir Arthur Conan Doyle is "Silver Blaze,"

Photo credit: NASA/CXC/MSFC/M.Weisskopf et al

Note: The movie can be watched by either clicking on the title link above, or by clicking here.

First Image of Vesta by Dawn

This image, processed to show the true size of the giant asteroid Vesta, shows Vesta in front of a spectacular background of stars. It was obtained by the framing camera aboard NASA's Dawn spacecraft on May 3, 2011, from a distance of about 1.2 million kilometers (750,000 miles). Since Vesta is so bright that it outshines its starry background, Dawn team members commanded a long exposure time to make the stars visible. They corrected the resulting exaggerated size of Vesta by superimposing a short exposure image of the target asteroid, showing its true size. Vesta is the small, bright pearl in the middle of the image.

Vesta is 330 miles (530 kilometers) in diameter and the second most massive object in the asteroid belt. But, as the inset shows, Vesta is approximately five pixels across in size in Dawn's early approach images.

This and other images will help Dawn fine tune navigation during its approach to Vesta, with arrival expected on July 16, 2011.

Photo credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Note: For more information, see NASA's Dawn Captures First Image of Nearing Asteroid.

Abell 383

The giant cluster of elliptical galaxies in the center of this image contains so much dark matter mass that its gravity bends light. This means that for very distant galaxies in the background, the cluster's gravitational field acts as a sort of magnifying glass, bending and concentrating the distant object's light towards Hubble. These gravitational lenses are one tool astronomers can use to extend Hubble's vision beyond what it would normally be capable of observing.

Using Abell 383, a team of astronomers have identified and studied a galaxy so far away we see it as it was less than a thousand million years after the Big Bang. Viewing this galaxy through the gravitational lens meant that the scientists were able to discern many intriguing features that would otherwise have remained hidden, including that its stars were unexpectedly old for a galaxy this close in time to the beginning of the Universe. This has profound implications for our understanding of how and when the first galaxies formed, and how the diffuse fog of neutral hydrogen that filled the early Universe was cleared.

Photo credit: NASA, ESA, J. Richard (CRAL) and J.-P. Kneib (LAM). Acknowledgement: Marc Postman (STScI)

Note: For more information, see First Galaxies Were Born Much Earlier Than Expected [heic1106]; for an annotated version of the above photo, see here.

A Very Cool Pair of Brown Dwarfs

Observations with the European Southern Observatory’s Very Large Telescope, along with two other telescopes, have shown that there is a new candidate for the coldest known star: a brown dwarf in a double system with about the same temperature as a freshly made cup of tea — hot in human terms, but extraordinarily cold for the surface of a star. This object is cool enough to begin crossing the blurred line dividing small cold stars from big hot planets.

Brown dwarfs are essentially failed stars: they lack enough mass for gravity to trigger the nuclear reactions that make stars shine. The newly discovered brown dwarf, identified as CFBDSIR 1458+10B, is the dimmer member of a binary brown dwarf system located just 75 light-years from Earth [1].

The powerful X-shooter spectrograph on ESO’s Very Large Telescope (VLT) was used to show that the composite object was very cool by brown dwarf standards. "We were very excited to see that this object had such a low temperature, but we couldn’t have guessed that it would turn out to be a double system and have an even more interesting, even colder component," said Philippe Delorme of the Institut de planétologie et d’astrophysique de Grenoble (CNRS/Université Joseph Fourier), a co-author of the paper. CFBDSIR 1458+10 is the coolest brown dwarf binary found to date.

The dimmer of the two dwarfs has now been found to have a temperature of about 100 degrees Celsius — the boiling point of water, and not much different from the temperature inside a sauna [2]. “At such temperatures we expect the brown dwarf to have properties that are different from previously known brown dwarfs and much closer to those of giant exoplanets — it could even have water clouds in its atmosphere," said Michael Liu of the University of Hawaii’s Institute for Astronomy, who is lead author of the paper describing this new work. "In fact, once we start taking images of gas-giant planets around Sun-like stars in the near future, I expect that many of them will look like CFBDSIR 1458+10B."

Unraveling the secrets of this unique object involved exploiting the power of three different telescopes. CFBDSIR 1458+10 was first found to be a binary using the Laser Guide Star (LGS) Adaptive Optics system on the Keck II Telescope in Hawaii [3]. Liu and his colleagues then employed the Canada–France–Hawaii Telescope, also in Hawaii, to determine the distance to the brown dwarf duo using an infrared camera [4]. Finally the ESO VLT was used to study the object’s infrared spectrum and measure its temperature.

The hunt for cool objects is a very active astronomical hot topic. The Spitzer Space Telescope has recently identified two other very faint objects as other possible contenders for the coolest known brown dwarfs, although their temperatures have not been measured so precisely. Future observations will better determine how these objects compare to CFBDSIR 1458+10B. Liu and his colleagues are planning to observe CFBDSIR 1458+10B again to better determine its properties and to begin mapping the binary's orbit, which, after about a decade of monitoring, should allow astronomers to determine the binary’s mass.

Notes

[1] CFBDSIR 1458+10 is the name of the binary system. The two components are known as CFBDSIR 1458+10A and CFBDSIR 1458+10B, with the latter the fainter and cooler of the two. They seem to be orbiting each other at a separation of about three times the distance between the Earth and the Sun in a period of about thirty years.

[2] By comparison the temperature of the surface of the Sun is about 5500 degrees Celsius.

[3] Adaptive optics cancels out much of Earth’s atmospheric interference, improving the image sharpness by a factor of ten and enabling the very small separation binary to be resolved.

[4] The astronomers measured the apparent motion of the brown dwarfs against the background of more distant stars caused by Earth's changing position in its orbit around the Sun. The effect, known as parallax, allowed them to determine the distance to the brown dwarfs.

Illustration credit: ESO/L. Calçada

NGC 6729 - The Drama of Starbirth

A new image from ESO’s Very Large Telescope gives a close-up view of the dramatic effects new-born stars have on the gas and dust from which they formed. Although the stars themselves are not visible, material they have ejected is colliding with the surrounding gas and dust clouds and creating a surreal landscape of glowing arcs, blobs and streaks.

The star-forming region NGC 6729 is part of one of the closest stellar nurseries to the Earth and hence one of the best studied. This new image from ESO’s Very Large Telescope gives a close-up view of a section of this strange and fascinating region (a wide-field view is available here: eso1027).

Stars form deep within molecular clouds and the earliest stages of their development cannot be seen in visible-light telescopes because of obscuration by dust. In this image there are very young stars at the upper left of the picture. Although they cannot be seen directly, the havoc that they have wreaked on their surroundings dominates the picture. High-speed jets of material that travel away from the baby stars at velocities as high as one million kilometers per hour are slamming into the surrounding gas and creating shock waves. These shocks cause the gas to shine and create the strangely colored glowing arcs and blobs known as Herbig–Haro objects [1].

In this view the Herbig–Haro objects form two lines marking out the probable directions of ejected material. One stretches from the upper left to the lower center, ending in the bright, circular group of glowing blobs and arcs at the lower center. The other starts near the left upper edge of the picture and extends towards the center right. The peculiar scimitar-shaped bright feature at the upper left is probably mostly due to starlight being reflected from dust and is not a Herbig–Haro object.

This enhanced-color picture [2] was created from images taken using the FORS1 instrument on ESO’s Very Large Telescope. Images were taken through two different filters that isolate the light coming from glowing hydrogen (shown as orange) and glowing ionized sulfur (shown as blue). The different colors in different parts of this violent star formation region reflect different conditions — for example where ionized sulfur is glowing brightly (blue features) the velocities of the colliding material are relatively low — and help astronomers to unravel what is going on in this dramatic scene.

Notes

[1] The astronomers George Herbig and Guillermo Haro were not the first to see one of the objects that now bear their names, but they were the first to study the spectra of these strange objects in detail. They realized that they were not just clumps of gas and dust that reflected light, or glowed under the influence of the ultraviolet light from young stars, but were a new class of objects associated with ejected material in star formation regions.

[2] Both the ionized sulfur and hydrogen atoms in this nebula emit red light. To differentiate between them in this image the sulfur emission has been colored blue.

Photo credit: ESO/Sergey Stepanenko

The Most Distant Mature Galaxy Cluster

Astronomers have used an armada of telescopes on the ground and in space, including the Very Large Telescope at ESO’s Paranal Observatory in Chile to discover and measure the distance to the most remote mature cluster of galaxies yet found. Although this cluster is seen when the Universe was less than one quarter of its current age it looks surprisingly similar to galaxy clusters in the current Universe.

“We have measured the distance to the most distant mature cluster of galaxies ever found,” says the lead author of the study in which the observations from ESO’s VLT have been used, Raphael Gobat (CEA, Paris). “The surprising thing is that when we look closely at this galaxy cluster it doesn’t look young — many of the galaxies have settled down and don’t resemble the usual star-forming galaxies seen in the early Universe.”

Clusters of galaxies are the largest structures in the Universe that are held together by gravity. Astronomers expect these clusters to grow through time and hence that massive clusters would be rare in the early Universe. Although even more distant clusters have been seen, they appear to be young clusters in the process of formation and are not settled mature systems.

The international team of astronomers used the powerful VIMOS and FORS2 instruments on ESO’s Very Large Telescope (VLT) to measure the distances to some of the blobs in a curious patch of very faint red objects first observed with the Spitzer Space Telescope. This grouping, named CL J1449+0856 [1], had all the hallmarks of being a very remote cluster of galaxies [2]. The results showed that we are indeed seeing a galaxy cluster as it was when the Universe was about three billion years old — less than one quarter of its current age [3].

Once the team knew the distance to this very rare object they looked carefully at the component galaxies using both the NASA/ESA Hubble Space Telescope and ground-based telescopes, including the VLT. They found evidence suggesting that most of the galaxies in the cluster were not forming stars, but were composed of stars that were already about one billion years old. This makes the cluster a mature object, similar in mass to the Virgo Cluster, the nearest rich galaxy cluster to the Milky Way.

Further evidence that this is a mature cluster comes from observations of X-rays coming from CL J1449+0856 made with ESA’s XMM-Newton Space Observatory. The cluster is giving off X-rays that must be coming from a very hot cloud of tenuous gas filling the space between the galaxies and concentrated towards the center of the cluster. This is another sign of a mature galaxy cluster, held firmly together by its own gravity, as very young clusters have not had time to trap hot gas in this way.

As Gobat concludes: “These new results support the idea that mature clusters existed when the Universe was less than one quarter of its current age. Such clusters are expected to be very rare according to current theory, and we have been very lucky to spot one. But if further observations find many more then this may mean that our understanding of the early Universe needs to be revised.”

Notes

[1] The strange name refers to the object’s position in the sky.

[2] The galaxies appear red in the picture partly because they are thought to be mainly composed of cool, red stars. In addition the expansion of the Universe since the light left these remote systems has increased the wavelength of the light further so that it is mostly seen as infrared radiation when it gets to Earth.

[3] The astronomers measured the distance to the cluster by splitting the light up into its component colors in a spectrograph. They then compared this spectrum with one of a similar object in the nearby Universe. This allowed them to measure the redshift of the remote galaxies — how much the Universe has expanded since the light left the galaxies. The redshift was found to be 2.07, which means that the cluster is seen about three billion years after the Big Bang.

Photo credit: ESO/NOAJ/Subaru/R. Gobat