The E Nebula in Aquila

The E Nebula in Aquila



Several unusual strands of darkness are prominent toward the constellation of Aquila. This particular dark nebula is known as the E Nebula, for its evocative shape, or B142 and B143, for its position(s) on a list of such nebula compiled by Barnard. The E Nebula spans roughly the angle of a full Moon and lies about 2000 light years distant. The nebula can be seen with binoculars and is particularly visible during the summer months in Earth's northern hemisphere. Other names for dark nebula include absorption nebula, as they efficiently absorb visible light emitted behind them, and molecular clouds, as they frequently attain temperatures low enough so that several different types of stable molecules can exist. The low temperatures of these interstellar clouds facilitate the formation of dense knots of gas that may then collapse into bright stars.

Mars Through a Small Telescope

Mars Through a Small Telescope



How does Mars appear through a small telescope? Viewed with the unaided eye or through a small telescope, possibly the most striking part of Mars' appearance is its red color. The color derives from rust, iron oxide, which composes perhaps 10% of the Martian soil. The oxygen that rusts the surface iron on Mars originates predominantly from carbon dioxide gas, which composes 95% of the Martian atmosphere. Mars nears its closest approach with Earth in nearly 60 millennia on August 27, the red planet continues to appear larger, brighter, and a good target for sky enthusiasts. Pictured above, Mars was captured from the Canary Islands of Spain during three days in three different orientations earlier this month. Visible through the small telescope are white polar caps of water and carbon-dioxide ice, light red areas rich in lightly colored craters, and dark red areas dominated by relatively smooth lowlands.

Bright Lights, Dark City

Bright Lights, Dark City



Last Thursday, millions of people had an unexpectedly good view of a dark night sky. Usually, the reflection of city lights off of local air impurities makes it hard for casual observers to see more than a handful of stars from a bright urban area. A large power outage in northeast North America, however, dimmed most city lights and brought unfamiliar celestial wonders to many who looked up. The unexpected starscape was perhaps a small perk in the face of hardships endured by many during the black out. Prominent in the above four-image digital montage are two of the few celestial wonders that can be seen even above the usual glare of cit light pollution: the Moon and Mars. Both appear on the far left, with Mars to the upper right of the Moon. Scrolling right will show how eerily dark New York City appeared from across the Hudson River in New Jersey at about 10 pm on 2003 August 14. Visible lights are mostly attributable to cars, local power generators, flashlights, and candles.

Natural Saturn On The Cassini Cruise

Natural Saturn On The Cassini Cruise



What could you see approaching Saturn aboard a interplanetary cruise ship?Your view would likely resembl thissubtly shaded image of the gorgeous ringed gas giant.Processed by the HubbleHeritage project, the picture intentionallyavoids overemphasizing color contrasts and presents natural looking Saturnwith cloud bands, storms, nearl edge-on rings, and the small round shadowof the moon Enceladus near the center of the planet's disk.Of course, seats were not available on the only ship currently en route, th Cassinispacecraft.Cassini flew byJupiter at the turn of the millennium and i scheduledto arrive at Saturn in the year 2004.After an extended cruise to a world 1,400 million kilometer from the Sun, Cassini will tour th Saturniansystem, conducting a remote, robotic explorationwith software and instrument designed by denizens of planet Earth.

Thackeray's Globules

Thackeray's Globules



Rich star fieldsand glowing hydrogen gas silhouettedense, opaque clouds of interstellar gas and dustin this Hubble Space Telescop close-upof IC 2944, a bright star forming regio in Centaurus, 5,900 light-years away.The largest of these dark globules,first spotted by South African astronomer A. D. Thackeray in 1950,is likely two separate but overlapping clouds, each more than on light-year wide.Combined the clouds contain materia equivalent to about15 times the mass of the Sun, but will they actuall collapse to form massive stars?Along with other data, th sharpHubble images indicate thatThackeray's globules are fractured and churning as a resultof intense ultraviolet radiation from young, hot stars alreadyenergizing and heating the bright emission nebula.These and similar dark globulesknown to be associated with otherstar forming regions may ultimately be dissipatedby their hostile environment --like cosmic lumps of butter in a hot frying pan.

Sedimentary Mars

Sedimentary Mars



High-resolution imaging of an area in the Schiaparelli Basin of Marson June 3 by the MGS Mars Orbiter camera produce thisstunning exampleof layered formations within an old impact crater.On planet Earth, such structureswould be seen in sedimentary rock-- material deposited at the bottom of ancient lakes or oceansand then subsequently weathered away to reveal th layers.With the Sun shinin from the left,the central layer appearsto stand above the others within the 2.3 kilometerwide crater.The crater could well have been filled with water inMars' distant past, perhaps resting at thebottom of a lake filling th Schiaparelli impact basin.Still, such layers might also have been formed by material settling outof the windy martian atmosphere.As satellites continue to examine the martian surface from orbit,NASA's Spirit and Opportunityspacecraft will attempt to land onon Mars early next year to further explore th tantalizinghistory of water on the Red Planet.

Dark Matter Map

Dark Matter Map



The total mass within giant galaxy cluste CL0025+1654,about 4.5 billio light-years away,produces a cosmic gravitational lens - bendinglight as predictedby Einstein's theory of gravity and forming detectable imagesof even more distant background galaxies.Of course, the totalcluster mass is the sum of the galaxies themselves, seen asordinary luminous matter, plus the cluster'sinvisible dark matter whos natureremains unknown.But by analyzing the distribution of luminous matter and theproperties of the gravitational lensingdue to total cluster mass,researchers have solved the problem of tracingthe dark matter layout Their resulting mapshows the otherwise invisible dark matter in blue,and the positions of the clustergalaxies in yellow The work,based on extensive Hubble Space Telescope observations,reveals that the cluster' darkmatter is not evenly distributed, butfollows the clumps of luminous matter closely.

Mars Rising Behind Poodle Rock

Mars Rising Behind Poodle Rock



Have you seen Mars lately? As Earth and Mars near their closest approach in nearly 60,000 years on August 27, the red planet has begun to appear dramatically bright and show interesting details through telescopes and binoculars. Although not yet visible at sunset, Mars can be seen rising increasingly earlier in the evening. Once above the horizon, Mars is easy to spot, as it sports a distinct orange-red hue and it is the brightest object in the sky after the Sun, the nearby Moon, and Venus.After Earth overtakes Mars in their respective solar orbits, Mars will be visible right from sunset, although its historic brightness will then begin to fade. Pictured above, Mars was captured rising in the south east next to Poodle Rock in Valley of Fire State Park, Nevada, USA.

X-rays from Stephan s Quintet

X-rays from Stephan s Quintet



Stephan'sQuintet is a picturesque but clearly troubledgrouping of galaxies about 300 million light-years awaytoward the high-flying constellatio Pegasus.Spanning over 200,000 light-years at that distance thiscomposite false-color imageillustrates the powerful nature of thi multiplegalaxy collision,showing x-ray data from th ChandraObservatory in blue superposed on optical data in yellow.The x-raysfrom the central blue cloud running verticallythrough the image are produced bygas heated to millions of degrees by an energeticshock on a cosmic scale.The shock was likely the result of the interstellar gasin the large spiral galaxy, seen immediately to the rightof the cloud,colliding with the quintet's tenuous intergalactic gasas this galaxy plunged through group's central regions.In fact, over billions of years, repeated passages of thegroup galaxies through the hot intergalacticgas should progressively strip them of their own starforming material.In this view, the large spiral galaxy just seen peekingabove the bottom edge is an unrelated foreground galaxya mere 35 million light-years distant.

Elements of the Swan Nebula

Elements of the Swan Nebula



In the depths of the dark clouds of dust and molecular gas known as M17, stars continue to form. Also known as the Omega Nebula and Horseshoe Nebula, the darkness of M17's molecular clouds results from background starlight being absorbed by thick filaments of carbon-based smoke-sized dust. As bright massive stars form, they produce intense and energetic light that slowly boils away the dark shroud. Colors in the above image were picked to highlight specific elements that emit nebular light: red indicates emission from sulfur, green from hydrogen, and blue from oxygen. The Swan Nebula is visible with binoculars towards the constellation of Sagittarius, lies 5000 light-years away, and spans 20 light-years across.

Lunation

Lunation



Our Moon's appearance changes nightly. This time-lapse sequence shows what our Moon looks like during a lunation, a complete lunar cycle. As the Moon orbits the Earth, the half illuminated by the Sun first becomes increasingly visible, then decreasingly visible. The Moon always keeps the same face toward the Earth. The Moon's apparent size changes slightly, though, and a slight wobble called a libration is discernable as it progresses along its elliptical orbit.During the cycle, sunlight reflects from the Moon at different angles, and so illuminates different features differently. A full lunation takes about 29.5 days, just under a month (moon-th).

A Perseid Aurora

A Perseid Aurora



Just after the Moon set but before the Sun rose in the early morning hours of 2000 August 12, meteors pelted the Earth from the direction of the constellation Perseus, while ions pelted the Earth from the Sun. The meteors were expected as sub-sand grains long left behind by Comet Swift-Tuttle annually create the Perseids Meteor Shower. The aurorae were unexpected, however, as electrons, protons, and heavier ions raced out from a large Coronal Mass Ejection that had occurred just days before on the Sun. In the foreground is Hahn's Peak, an extinct volcano in Colorado, USA.The Perseid meteor shower peaks this year over the next few days, with as much as one bright meteor per minute visible from some locations.

Blue Stragglers in NGC 6397

Blue Stragglers in NGC 6397



In our neck of th Galaxy stars are to far apartto be in danger of colliding, but in the dense cores o globular star clusters star collisionsmay be relatively common.In fact researchers have evidence that theclosely spaced blue stars near the center of the above image taken by the orbiting Hubble Space Telescopewere formed when stars directly collided.Pictured is the central region o NGC 6397, globular clusterabout 6,000 light-years distant, whos stars all formed at about the same time NGC 6397'smassive stars have long since evolved off the main sequence,exhausting their central supplies o nuclear fuel.This should leave the cluster with only old low mass stars; faint redmain sequence stars and brighter blue an red giants.However, spectroscopic data show that the indicated stars, descriptivelydubbed blue stragglers, are clearlymain sequence stars which are too blue and too massive to still be there Suggestively the stragglers appear to be two and occasionally threetimes as massive as the lower mass cluster starsotherwise present supporting evidence fortheir formation from two and even three star collisions.

Palomar at Night

Palomar at Night



What's wrong with this picture?The summer night sky is clear, andmoonlight illuminates the dome of th Hale 200-inch Telescope a Palomar Observatory,northeast of San Diego, California, USA.The familiar stars of th Teapot asterism in the constellatio Sagittariusshine above the dome and to the right.In fact, the only thing wrong with the picture is thatthe observatory dome's two massive shuttersare closed tight ... on a clear night.This extremely unusual situation is a precautionprompted by the presence of airborne ash and smoke fro wildfiresin the area on July 17which could have damaged th historic mirror's aluminum coating.Amateur astronomer Greg Redfern notes that thisyear has been a particularly bad one for observatories andwildfires, with th Mt. StromloAustralian Observatorydisaster and fires also threatening telescopes on MountLemmon near Tucson, Arizona.

Dusty Galaxy Centaurus A

Dusty Galaxy Centaurus A



Why is peculiar galaxy Centaurus A so dusty? Dramatic dust lanes that run across the galaxy's center mark Cen A. These dust lanes are so thick they almost completely obscure the galaxy's center in visible light. This is particularly unusual as Cen A's red stars and round shape are characteristic of a giant elliptical galaxy, a galaxy type usually low in dark dust. Cen A, also known as NGC 5128, is also unusual compared to an average elliptical galaxy because it contains a higher proportion of young blue stars and is a very strong source of radio emission. Evidence indicates that Cen A is likely the result of the collision of two normal galaxies. During the collision, many young stars were formed, bu details of the creation of Cen A's unusual dust belts are still being researched. Cen A lies only 13 million light years away, making it the closest active galaxy. Cen A spans 60,000 light years and can be seen with binoculars toward the constellation of Centaurus.

Shuttle Ferry

Shuttle Ferry



How does a space shuttle that landed in California get back to Florida for its next launch? The answer is by ferry. NASA operates two commercial Boeing 747 airplanes modified to carry a space shuttle on their backs. Designated officially as Shuttle Carrier Aircraft or SCA, the 747s were made for commercial flights but bolstered by NASA with several struts, stabilizers, and electronic monitors. Spanning about 70 meters in length, the two aircraft's combined mass is nearly 150,000 kilograms. Pictured above, the space shuttle Atlantis is shown being ferried back to NASA Kennedy Space Center in Florida in September 1998.

In the Center of the Virgo Cluster

In the Center of the Virgo Cluster



The Virgo Cluster of Galaxies is the closest cluster of galaxies to our Milky Way Galaxy. The Virgo Cluster is so close that it spans more than 5 degrees on the sky - about 10 times the angle made by a full Moon. It contains over 100 galaxies of many types - including spiral, elliptical, and irregular galaxies. The Virgo Cluster is so massive that it is noticeably pulling our Galaxy toward it. The cluster contains not only galaxies filled with stars but also gas so hot it glows in X-rays. Motions of galaxies in and around clusters indicate that they contain more dark matter than any visible matter we can see. Pictured above, the center of the Virgo cluster might appear to some as a human face, and includes bright Messier galaxies M86 at the top, M84 on the far right, NGC 4388 at the bottom, and NGC 4387 in the middle.

Ice Fishing for Cosmic Neutrinos

Ice Fishing for Cosmic Neutrinos



Scientists are melting holes in the bottom of the world. In fact, several holes have been melted near the South Pole, and they are now being used as astronomical observatories. Astronomers with the Antarctic Muon and Neutrino Detector Array (AMANDA) lower into each vertical lake a string knotted with basketball-sized light detectors. The water in each hole soon refreezes. The detectors are sensitive to blue light emitted in the surrounding clear ice. Such light is expected from ice collisions with high-energy neutrinos emitted by objects or explosions out in the universe. The above picture was taken looking down into the dee abyss. Instruments were lowered down past 2000 meters. Analyses of data from the AMANDA II detectors have recently been used to create the first map of the high-energy neutrino sky.

Island Universe, Cosmic Sand

Island Universe, Cosmic Sand



On August 13, 2002,while countin Perseid meteors unde dark, early morning Arizona skies,Rick Scott set out to photograph their fleetingbut fiery trails.The equipment he used included a telephoto lens and fastcolor film.After 21 pictures he'd caught only two meteors, but luckilythis was one of them.Tracking the sky, his ten minute long exposure shows afield of many stars in our own Milky Way galaxy, most toofaint to be seen by the unaided eye Flashingfrom lower left to upper right, the bright meteor wouldhave been an easy eyeful though,as friction with Earth's atmospher vaporized the hurtling grain o cosmic sand, a piece of dust from Come Swift-Tuttle.Just above and left of center, well beyond the stars ofthe Milky Way, lies the island universeknown as M31 or the Andromeda galaxy.The visible meteor trail begins about 100 kilometersabove Earth's surface, one of the closest celestial objectsseen in the sky.In contrast, Andromeda, about 2 million light-yearsaway, is the most distant object easily visible to the naked-eye.

Moons and Bright Mars

Moons and Bright Mars



In this serene view,the moons of Earth along withthe bright planet Mars shine abovethe city of Turku near the southwestern tip of Finland.Of course Earth's large natural satellite theMoon, at a distance of 400,000 kilometers,is by far the brightest object in this sky.But growing brighter an closer by the hour, Mars appears asthe impressively bright "star" at the right, about 64 millionkilometers from Turku.Streaking across the twilight sky between the two celestial beacons,Earth's largest artificial moon,the InternationalSpace Station,orbits about 400 kilometers above the planet's surface.To capture the moment, amateur astronome PetteriKankaro used a digital camera and combined exposures beginningat 23:34 Universal Time on July 17th.

Galaxy Group HCG 87

Galaxy Group HCG 87



Posing fo this cosmic family photo are the galaxies of HCG Hickson Compact Group)87, about four hundred millionlight-years distant toward the amphibious constellatio Capricornus.The large edge-onspiral near picture center, the fuzzyelliptical galaxy immediately to its right, and thespiral near the top of the image are identified members of thegroup, while the small spira galaxy in the middle is likely amore distant background galaxy.In any event, a careful examination of the deep image reveals othergalaxies which certainly lie far beyon HCG 87.While not exactly locked i agroup hug, the HCG 87 galaxiesare interactinggravitationally, influencing theirfellow group members' structure and evolution This new imageis from an instrument undergoing commissioningon th Gemini Observatory'sSouth Telescope at Cerro Pachon, Chile.It compares favorably with views of this photogenic galaxy grouprecorded by th HubbleSpace Telescope.

Frosty Mountains on Mars

Frosty Mountains on Mars



What causes the unusual white color on some Martian mountains? The answer can be guessed by noticing that the bright areas disappear as springtime takes hold in the south of Mars: dry ice. Dry carbon dioxide ice sublimates directly to gas from its frozen state. The frosty mountains, named Charitum Montes, have been covered with carbon dioxide ice over the Martian winter. The serene scene pictured above is not a photograph, but rather a computationally constructed digital illusion resulting from the fusion of two color images from the Mars Orbital Camera and topographic data from the Mars Orbiter Laser Altimeter. Both instruments operate from the Mars Global Surveyor robot spacecraft currently orbiting Mars. The red planet continues to grow larger in terrestrial skies as Earth and Mars move closer to their recent-record closest approach on August 27.

Orange Sun Simmering

Orange Sun Simmering



Even a quiet Sun is a busy place. The above image, taken in a single color of light called Hydrogen Alpha, records a great amount of detail of the simmering surface of our parent star. The gradual darkening towards the Sun's edge, called limb darkening, is caused by increased absorption of relatively cool solar gas. Further over the edge, a giant prominence is visible, while a different prominence can be seen in silhouette as the dark streak near the image center. Two active areas of the Sun are marked by bright plages. The above amateur photograph of the Sun was taken just last month through a small telescope and a standard digital camera. In contrast, there are times when our Sun appears much more active.

Launch of the Spirit Rover Toward Mars

Launch of the Spirit Rover Toward Mars



Next stop: Mars. Last month the first of two missions to Mars was launched from Cape Canaveral, Florida, USA above a Boeing Delta II rocket.Pictured above, solid fuel boosters are seen falling away as light from residual exhaust is reflected by the soaring rocket.The Mars Exploration Rover dubbed Spirit is expected to arrive at the red planet this coming January. Upon arriving, parachutes will deploy to slow the spacecraft and surrounding airbags will inflate. The balloon-like package will then bounce around the surface a dozen times or more before coming to a stop. The airbags will then deflate, the spacecraft will right itself, and the Spirit rover will prepare to roll onto Mars. The robotic Spirit is expected to cover as much as 40 meters per day, much more than Sojourner, its 1997 predecessor. Spirit will search for evidence of ancient Martian water, from which implications might be drawn about the possibility of ancient Martian life.A second rover named Opportunity was successfully launched on July 7 and will arrive at Mars a few weeks later.

The Aquarius Dwarf

The Aquarius Dwarf



Our Milky Way Galaxy is not alone. It is part of a gathering of about 50 galaxies known as the Local Group. Members include the Great Andromeda Galaxy (M31), M32, M33, the Large Magellanic Cloud, the Small Magellanic Cloud, Dwingeloo 1, several small irregular galaxies, and many dwarf elliptical an dwarf spheroidal galaxies. Pictured above is the Aquarius Dwarf, a faint dwarf irregular galaxy over 3 million light years away. An earlier APOD erroneously identified the above image as the Sagittarius Dwarf.

Spiral Galaxy NGC 7742

Spiral Galaxy NGC 7742



Thismight resemble a fried egg you've ha for breakfast, but it'sactually much larger.In fact, ringed by blue-tinte star forming regions andfaintly visible spiral arms,the yolk-yellow center of this face-on spiral galaxy, NGC 7742, is about 3,000 light-years across.About 72 million light-years away in the constellation Pegasus,NGC 7742 is known to b a Seyfert galaxy - a type o active spiral galaxy with a center ornucleus which is very brigh atvisible wavelengths.Across the spectrum,the tremendous brightness of Seyferts can change over periods ofjust days to months and galaxies like NGC 7742 aresuspected of harborin massiveblack holes at their cores.This beautiful color picture is courtesy of the Hubble Space Telescope Heritage Project.

Dumbbell Nebula Halo

Dumbbell Nebula Halo



In 1764, French astronome CharlesMessier sighted this gorgeouscosmic cloud whic hedescribed as an oval nebula without stars Cataloged as M27,it is now popularly known as th DumbbellNebula, not for its substandard academic performance butfor the elongated shape, like a bar with weights on each end, whic firstcaught Messier's eye. This deep image of the bright planetarynebula does reveal the Dumbell's central star though, andan array of foreground and background starstoward the sly constellatio Vulpecula.The picture i a compositethat includes 8 hours ofexposure through a filter designed to record only the lightof hydrogen atoms, tracing the intricate details ofthe nebula's faint outer halowhich spans light-years.Thought to be an example of th fate awaiting our ownSun 5 billion years hence, the Dumbbell Nebula isabout 1,200 light-years away.

Mars at the Moon's Edge

Mars at the Moon's Edge



What was that bright "star" near the Moon last week Mars of course, asthe Red Planet wandered near thewaning gibbous Moon early last Thursday morning, passingbehind the lunar orb when viewedfrom some locationsin South and Central America, the Caribbean, and Florida.The Clay Center Observatory expedition to Bonita Springs, Floridaproduced this evocative picture o Mars grazing the Moon's dark edge bydigitally stacking and processing a series of telescopicimages of the event. With the cratered Moon in the foreground,the bright planet Mars seems alarminglyclose, its global scale featuresand white south polar cap easily visible.Already impressive, the apparent size of the martian diskwill continue to grow in the coming weeks,until, on August 27, Mars reaches itsclosest approach to planet Earth in over 50,000 years.

GRACE Maps the Gravity of Earth

GRACE Maps the Gravity of Earth



Why do some places on Earth have higher gravity than others? Sometimes the reason is unknown. To help better understand the Earth's surface, slight distance changes between a pair of identically orbiting satellites named GRACE have been used to create the best ever map of Earth' gravitational field. High points on thismap, also colored red, indicate areas where gravity is slightly stronger than usual, while in blue areas gravity isslightly weaker.Many bumps and valleys on the map can be attributed to surface features, such as the NorthMid-Atlantic Ridge and the Himalayan Mountains, but others cannot, and so might relate to unusually high or low sub-surface densities. Mapslike this also help calibrate changes in the Earth's surface including variable ocean currents and the melting of glaciers.

A Tornado on Planet Earth

A Tornado on Planet Earth



Large storms on Earth can spawn unusual, small, violent clouds known as tornadoes. Tornado clouds swirl as fast as hundreds of kilometers per hour and, when they touch down, can destroy nearly everything in their long, narrow path. Many tornadoes last only a few minutes, but the largest and most dangerous can endure for hours. The above image, although somewhat unfocussed, appears to show a dropping funnel cloud interacting with a light pole. If so, and this interpretation is controversial, this photograph would be one of the few indicating a clear distance to the funnel cloud. The pictured tornado occurred in 1981 in Dallas, Texas, USA. Tornadoes occur all over Earth but are most commonly found over parts of central North America during spring. Much about tornadoes remains under study, including predicting when they will occur.

IC 4603 Reflection Nebula in Ophiuchius

IC 4603 Reflection Nebula in Ophiuchius



Why does this starfield photograph resemble an impressionistic painting? The effect is created not by digital trickery but by large amounts of interstellar dust. Dust, minute globs rich in carbon and similar in size to cigarette smoke, frequently starts in the outer atmospheres of large, cool, young stars.The dust is dispersed as the star dies and grows as things stick to it in the interstellar medium. Dense dust clouds are opaque to visible light and can completely hide background stars. For less dense clouds, the capacity of dust to preferentially reflect blue starlight becomes important, effectively blooming the stars blue light out and marking the surrounding dust. Nebular gas emissions, typically brightest in red light, can combine to form areas seemingly created on an artist's canvas. Photographed above is roughly one square degree of the nebula IC 4603 near the bright star Antares toward the constellation of Ophiuchus.

An Ion Drive for Deep Space 1

An Ion Drive for Deep Space 1



Space travel entered the age of the ion drive in 1998 with the launch of Deep Space 1, a NASA mission designed primarily to test new technologies. Although the ion drive on Deep Space 1 provided acceleration much smaller than we feel toward Earth, it gradually gave the spacecraft the speed it needed to travel across our Solar System. The propulsion drive worked by ionizing xenon atoms with power provided by large panels that collect sunlight. As these ions were expelled by a strong electric field out the back, the spacecraft slowly gained speed. Pictured above, hot blue ions emerge from a prototype drive that was successfully tested at JPL in 1997. Deep Space 1 successfully zoomed past asteroid 9969 Braille in July 1999 and then Comet Borrelly in September 2001, then obtaining the most detailed photograph ever taken of a comet nucleus.The spacecraft was retired in December 2001

NGC 3621 Far Beyond the Local Group

NGC 3621 Far Beyond the Local Group



Far beyondthe localgroup of galaxies lie NGC 3621,some 22 million light-years away.Found in the serpentine southern constellatio Hydra,the loose spiral arms of this gorgeou island universe are loaded withluminous young star clusters and dark dust lanes.Still, for earthbound astronomers NGC 3621 is not jus anotherpretty face-on spiral galaxy.Some of it brighterstars have been used a standardcandles to establish important estimates ofextragalactic distances and th scaleof the Universe.This color picture was constructed from astronomical imagedata recorded with the Very Large Telescop Antu, at ParanalObservatory in Chile. At the original resolution, individual hot supergiant stars canbe identified and studied across NGC 3621.

The Planet, the White Dwarf, and the Neutron Star

The Planet, the White Dwarf, and the Neutron Star



A planet,a white dwarf, anda neutron starorbit each other inthe giant globular sta cluster M4,some 5,600 light-years away.The most visible member of thetrio is the white dwarf star, indicated above in a imagefrom the Hubble Space Telescope,while the neutron star is detected at radio frequencies a a pulsar.A third body was known to be present in the pulsar/whitedwarf system and a detailed analysis of th Hubbledata has indicated it i indeed a planetwith about 2.5 times the mass of Jupiter.In such a system, the planet is likely to beabout 13 billion years old. Compared to our solar system's tender 4.5 billion yearsand othe identifiedplanets of nearby stars,this truly ancient world is by far the oldest planet known,almost as old as the Universe itself.Its discovery as part of an evolved cosmic trio suggests thatplanet formation spans the age of the Universe and thatthis newly discovered planet is likely only one of many formedin the crowded environsof globular star clusters.

The Cat's Paw Nebula

The Cat's Paw Nebula



As soon as we find out whose cat did this . . . Nebulae are as famous for being identified with familiar shapes as perhaps cats are for getting into trouble. No cat, though, could have created the vast Cat's Paw Nebula visible in Scorpius. At 5500 light years distant, Cat's Paw is an emission nebula with a red color that originates from an abundance of ionized hydrogen atoms. Alternatively known as the Bear Claw Nebula or NGC 6334, stars nearly ten times the mass of our Sun have been born there in only the past few million years Pictured above, the Cat's Paw nebula was photographed during an astrophotography expedition to Namibia.

Mars' Simulated View

Mars' Simulated View



When earthdwelle Patrick Vantuynewondered what his home planet'ssingle large moon would look like i viewed from Mars on July 17, heavailed himself of the JP Solar System Simulator.Of course, when viewed from Earth on that date (tomorrow), the gibbousMoon will pass tantalizingly clos to Mars for observers in North,Central, and South America and will actuall pass in front of (occult)the Red Planet for some locations, including much of Florida.Vantuyne's effortswere rewarded with this remarkable simulated view ofthe crescent Moon against the background of a darkened Earth.From the martian vantagepoint, the lunar orb is seen just below thetip of the Florida peninsula at 8:05 GMT.Observers on planet Earth who want to watch the correspondin Moon/Mars showin tomorrow's predawn sky should note the viewing times fo selected cities.

Mars Rising Through Arch Rock

Mars Rising Through Arch Rock



Mars is heading for its closest encounter with Earth in over 50,000 years.Although Mars and Earth continue in their normal orbits around the Sun, about every two years Earth and Mars are on the same part of their orbit as seen from the Sun. When this happens again in late August, Mars will be almost as near to the Sun as it ever gets, while simultaneously Earth will be almost as far from the Sun as it ever gets. This means that now is a great time to launch your space probe to Mars. Alternatively, these next few months are a great time to see a bright red Mars from your backyard. Mars is so close that global features should be visible even through a small telescope. Look for Mars to rise about 11 pm and to remain the brightest red object in the sky until sunrise. Mars will rise increasingly earlier until its closest approach in late August. Mars was captured above rising through the Arch Rock inValley of Fire State Park, Nevada, USA.

The Satellites that Surround Earth

The Satellites that Surround Earth



Thousands of satellites orbit the Earth. Costing billions of dollars, this swarm of high altitude robots is now vital to communication, orientation, and imaging both Earth and space. One common type of orbit is geostationary where a satellite will appear to hover above one point on Earth's equator. Geostationary orbits are very high up -- over five times the radius of the Earth -- and possible only because the satellite orbital period is exactly one day. It is usually cheaper to place a satellite in low Earth orbit, around 500 kilometers, just high enough to avoid the effect of Earth's atmosphere. The above animated sequence starts by showing the halo of Earth's satellites, including the ring at geostationary, and finishes by zooming in on the only one currently hosting humans: the International Space Station.

The Horsehead Nebula

The Horsehead Nebula



One of the most identifiable nebulae in the sky, the Horsehead Nebula in Orion, is part of a large, dark, molecular cloud. Also known as Barnard 33, the unusual shape was first discovered on a photographic plate in the late 1800s. The red glow originates from hydrogen gas predominantly behind the nebula, ionized by the nearby bright star Sigma Orionis. The darkness of the Horsehead is caused mostly by thick dust, although the lower part of the Horsehead's neck casts a shadow to the left. Streams of gas leaving the nebula are funneled by a strong magnetic field. Bright spots in the Horsehead Nebula's base are young stars just in the process of forming. Light takes about 1500 years to reach us from the Horsehead Nebula. The above image was taken with the 0.9-meter telescope at Kitt Peak National Observatory.

X-Ray Milky Way

X-Ray Milky Way



If you had x-ray vision,the center regionsof our Galaxy would not be hidden fromview by the immense cosmic dust cloudsopaque to visible light Instead,the Milky Waytoward Sagittarius might look somethinglike this stunning mosaicof images from the orbitin Chandra Observatory.Pleasing to look at, the gorgeous false-colorrepresentation o the x-ray data showshigh energy x-rays in blue, medium energies in green,and low energies in red.Hundreds of white dwarf stars,neutron stars, and black holes immersed in afog of multimillion-degree gas are included in thex-ray vista.Within the white patch at the image center liesthe Galaxy's central supermassive black hole.Chandra's shar x-ray vision will likely lead to a newappreciation of our Milky Way's most active neighborhoodand has already indicated that the hot gas itself mayhave a temperature of a mere 10 million degrees Celsiusinstead of 100 million degrees as previously thought.The full mosaic is composed of 30 separate images and coversa 900 by 400 light-year swat atthe galactic center.

NGC 1068 and the X-Ray Flashlight

NGC 1068 and the X-Ray Flashlight



At night,tilting a flashlight up under your chin hides theglowing bulb from the direct view of your friends.Light from the bulb still reflects from your face though, and cangive you a startling appearance SpiralGalaxy NGC 1068may be playing a similar trick on cosmic scale,hiding a central powerful source of x-rays -- likely supermassive black hole -- from direct view X-rays arestill scattered into our line-of-sightthough, by a dense torus of material surrounding the black hole The scenario issupported by x-ray data from th Chandra Observatory combined with a Hubble SpaceTelescope optical image i thisfalse-color composite picture.Optical data in red shows spiral structure across NGC 1068'sinner 7 thousand light-years with the x-ray data overlaid in blueand green.A hot wind of gas streaming from the galaxy's coreis seen as the broad swath of x-ray emission while materia lit upby the hidden black hole source is within the centralcloud of more intense x-rays Also well knownas M77, NGC 1068 lies a mere 50 millionlight-years away toward the constellation Cetus.

Dust Storm Over Northern Mars

Dust Storm Over Northern Mars



Almoston cue, as Mars nears its closest approach to planetEarth in recorded history, ominou seasonal dust storms are beginning to kick up Observers worry that the activity maypresage the development of planet wide dust storm, frustratingattempts to view Mars in the coming months,a situation similar to the Red Planet' uncooperative behavior in 2001 In this example,recorded in mid-May by the Mars Global Surveyorspacecraft camera, a dust storm the size of a continent sweepsnorth and east (toward the upper right) across Mars' northernAcidalia Planitia Meanwhile,interplanetary robotic explorer Mars Express Beagle 2 Nozomi, and the twi Mars ExplorationRovers Opportunity andSpirit, are all bound for Mars and should arrive byearly January 2004.

HD70642 A Star with Similar Planets

HD70642 A Star with Similar Planets



Astronomers have discovered a planetary system more similar to our own Solar System than any known previously. The bright star HD70642, visible with binoculars toward the constellation of Puppis, was already known to be a star like our Sun. Now a planet with twice Jupiter's mass has been discovered in a nearly circular orbit at approximately half the orbital distance of Jupiter.Such an orbit allows the possibility of habitable Earth-type planets orbiting further in, a possibility not likely with all previously discovered planetary systems with massive planets occupying disruptive closer elliptical orbits.The above illustration indicates what the HD70642 planetary system might look like from a hypothetical moon orbiting the newly discovered planet. At only 90 light years distant, extremely faint early radio broadcasts from Earth are now passing this planetary system.

Mt Anatahan Erupts

Mt Anatahan Erupts



Nobody suspected that this volcano would erupt. Mt. Anatahan has not erupted in recorded history. Nevertheless, on May 10, the small volcano in the Northern Mariana Islands of the western Pacific Ocean shot ash 10,000 meters into the air. Explosions from Mt. Anatahan continued every few minutes for two days.The airborne ash was so bad that some flights were cancelled from downwind Guam.Although meter-sized rocks were catapulted through the air, nobody was hurt, as a seismology team that coincidentally installed detectors on the island a few days before had already left. Fortunately, the team was not too far away to get the above picture.

At the Edge of the Sun

At the Edge of the Sun



Dramatic prominences can sometimes be seen looming just beyond the edge of the sun. A solar prominence is a cloud of solar gas held just above the surface by the Sun's magnetic field. The Earth would easily fit below the prominence on the left. A quiescent prominence typically lasts about a month, and may erupt in a Coronal Mass Ejection (CME) expelling hot gas into the Solar System. Although very hot, prominences typically appear dark when viewed against the Sun, since they are slightly cooler than the surface. The above image in false color was taken on June 1 from Stuttgart, Germany with an amateur telescope and camera.

Fractal Interstellar Dust Up Close

Fractal Interstellar Dust Up Close



Our universe is a very dusty place. Dust usually shows its presence by blocking out light emitted from stars or nebulae behind it, sometimes creating the illusion of a horse's head or a sombrero hat. But nobody really knows what a typical interstellar dust grain looks like. By studying how dust absorbs, emits, and reflects light, astronomers do know that interstellar dust is much different than the cell and lint based dust found around a typical house. Interstellar dust grains are composed mostly of carbon, silicon, and oxygen and are usually less than about 1/1000 of a millimeter across. Recent work indicates that most dust grains are not spherical. The above picture shows the result of a fractal adhesion model for dust grains involving random conglomerates of spherical compounds of different properties, here artificially highlighted by different colors.

Centaurus A X-Rays from an Active Galaxy

Centaurus A X-Rays from an Active Galaxy



Its core hiddenfrom optical view by a thick lane of dust, the giant elliptica galaxyCentaurus A was among the first objectsobserved by the orbiting Chandra X-ray Observatory.Astronomers were not disappointed, as Centaurus A'sappearance in x-rays makes its classification as a active galaxy easy to appreciate.Perhaps the most striking feature o thisChandra false-color x-ray viewis the jet, 30,000 light-years long.Blasting toward the upper left corner of the picture the jetseems to arise from the galaxy's bright central x-ray source --suspected of harboring a black hole with a million or so timesthe mass of the Sun Centaurus Ais also seen to be teeming with otherindividual x-ray sources and a pervasive, diffus x-ray glow.Most of these individual sources are likely to be neutron starsor solar mass black holes accreting material from their lessexotic binary companion stars.The diffuse high-energy glowrepresents gas throughout the galaxyheated to temperatures of million of degrees C.At 11 million light-years distant in the constellatio Centaurus,Centaurus A (NGC 5128) is the closes active galaxy.

N49's Cosmic Blast

N49's Cosmic Blast



Scattered debris from a cosmic supernova explosio lights up the skyin this gorgeous composited image based on data from theHubble Space Telescope.Cataloged as N49, these glowing filaments of shocked ga span about30 light-years in our neighboring galaxy, th Large Magellanic Cloud.Light from the original exploding star reached Earth thousandsof years ago, but N49 also marks the location of anotherenergetic outburst -- an extremely intenseblast of gamma-raysdetected by satellites o March5, 1979.That date was the beginning of a exciting journey in astrophysicswhich led researchers to the understanding of an exotic new class ofstars.The source of the "March 5th Event" is now attributed t amagnetar - a highly magnetized, spinning neutron star alsoborn in the ancient stellar explosion which created supernovaremnant N49.The magnetar hurtlesthrough the supernov debris cloud at over 1,200 kilometersper second.

The Vela Pulsar's Dynamic Jet

The Vela Pulsar's Dynamic Jet



The Vela pulsar is a neutron star born over 10,000 years agoin a massive supernova explosion.Above, false-colo x-ray images from th ChandraObservatory reveal details of this remnant pulsar' x-ray bright nebulaalong with emission from a spectacular jet ofhigh-energy particles.In this time-lapse seriesof pictures, the je seems to dancearound very much like an out-of-control firehose,shooting along the pulsar'sdirection of motion (toward the top right corner)to a length of about half a light-year whilewhipping back and forth at about half the speed of light.Highly magnetized and spinning over 10 times a second,the Vela pulsar is thought of as cosmichigh-voltage generator, powering the x-ray nebula anddynamic cosmic jet.A mere 800 light-years away thepulsar itself is located nearthe lower left corner in the four panels.

Aurora Over Cape Cod

Aurora Over Cape Cod



Active pillars of colorful aurora were captured dancing over a serenely smooth and nearly colorless Cape Cod Bay last month. North is straight ahead so that the town lights near the center originate from Provincetown, Massachusetts, USA. The unusual red colors in the aurora slightly reflect off the ocean inlet. Several familiar constellations are visible in the sky, including the famous stellar W of Cassi opeia on the far right.