Astronomy in English: July 2008

Thursday 31 July 2008

The Pencil Nebula Supernova Shockwave

At 500,000 kilometers per hour, a supernova shockwave plows through interstellar space.This shockwave is known as the Pencil Nebula, or NGC 2736, and is part of the Vela supernova remnant, an expanding shell of a star that exploded about 11,000 years ago. Initially the shockwave was moving at millions of kilometersper hour, but the weight of all the gas it has swept up has slowed it considerably Pictured above, the shockwave moves from left to right, as can be discerned by the lack of gas on the left. The above region spans nearly a light year across, asmall part of the 100+ light-year span of the entire Vela supernova remnant. The Hubble Space Telscope ACS captured the above image last October.

Rhea Saturn's Second Largest Moon

Rhea is the second largest moon of Saturn, behind Titan, and the largest without an atmosphere. It is composed mostly of water ice, but has a small rocky core. Rhea's rotation and orbit are locked together (just like Earth's Moon) so that one side always faces Saturn. A consequence of this is that one side always leads the other. Rhea's leading surface is much more heavily cratered than its trailingsurface. The above photograph was taken with the Voyager 1 spacecraft in 1980. NASA's Cassini spacecraft is currently on route to Saturn and will arrive in 2004.

Warped Spiral Galaxy ESO 510-13

How did spiral galax ESO510-13 get bent out of shape?The disks of many spirals ar thin and flat, but not solid.Spiral disks are loose conglomerations ofbillions of stars and diffuse gas al gravitationallyorbiting a galaxy center.A flat diskis thought to be created by sticky collisionsof large gas clouds early in th galaxy's formation. Warped disks are not uncommon, though, and even our own Milky Way Galaxy is thought to havea small warp. The causes of spiral warps are still being investigated, but some warps are thought to result from interactions or even collisions between galaxies. ESO 510-13is about 150 million light years away and about 100,000 lightyears across.

Sun, Moon, Hot Air Balloon

Anticipating the celestia shadow playof a solar eclipse, sky gazers across Germany watched th Sun rise on May 31.In Bonn, astrophotographerThilo Kranz had set up his small refracto telescope and cameraon the Kennedy Bridge acrossthe Rhein river to get a good view to the northeast.The timing of this eclipsemust have seemed ideal for a local balloon flight too, as hot airballoonists alsofavor early morning hours with usually calm surface winds.Kranz and colleagues had noticeda balloon drifting in the hazy sky near the horizon andspeculated about viewin theeclipse fro on board.But when the eclipsed Sun finally emerged into viewthey were delighted to see th lighter-than-aircraft make the occasion a very special show from their ownvantage point.In fact, in the central panel of this montage of Kranz'stelescopic eclipse images, the silhouetted balloon remindsthe APOD editors of a remarkably well-fed exclamation mark!

Ring of Fire from Cape Wrath

If the Moon's apparen diameteris not quite large enough tocover the Sun during a solar eclipse, an annular eclipsecan be the result - aspectacle of silhouetted Moon surrounded by a solar "ring of fire".Just such a view was possible fo observers in the far northernhemisphere as th newMoon slid across the solar disk on May 31st.Still, fo astronomicaladventurers at Cape Wrath on thenorthwestern coast of Scotland, the eastern sky was cloudy oneclipse day.But fortunately the Sun became visible a few minutesprior to the annular phase and determined astronomer HansCoeckelberghs was able to capture this dramatic telescopic imageof theeclipsed Sun'sring of fire looming through a reddened, cloud-streaked sky.Not to be outdone by the north, the far southern hemisphere willhost the next solar eclipse, with the path of totality racingacross Antarctica o November 23rd.

Eclipse in the Mist

The Sun and Moon rose togetherover much of Europe on the mornin ofMay 31st with thefirst solar eclipse of 2003 already in progress.And while sightings of the full annular phase of theeclipse were restricted t far northern regions,early morning risers were still treated t inspiring views of twocelestial bodies which are mos important to life on planet Earth.Following the dawn's spectacle from Charneux,Belgium, astrophotographer Olivier Meeckersrecorded this evocative image of the partially eclipsedSun rising above a primeval apparitio of mists and trees.Last month was indeed a rewarding one fo eclipsewatchers as May's full Moon and (second) new Moon lined up for theirrespectiv lunar an solar eclipses.November 2003 will also host both a total lunar andtotal sola eclipse.

The Milky Way Behind an Eclipsed Moon

What's behind the Moon? Each month, our Moon passes in front of -- and outshines -- many an interesting star field. Exceptions occur during a new Moon and during a total eclipse. In the background of a new Moon is usually the Sun, an even brighter orb that even more easily outshines everything behind it, except during a total solar eclipse. Even the longest total solar eclipse lasts just a few minutes, while the Sun's corona still remains bright. During a total lunar eclipse, however, the full Moon dims and a majestic star field may present itself for an hour or more. Such was the case during the middle of last month, when a rare glimpse of an eclipsed Moon superposed in front of the disk of our home Milky Way Galaxy was captured. Although fully in the Earth's shadow, the eclipsed Moon is still the brightest object on the right. The above image was captured during sub-zero weather from the Teide 2003 expedition to Mirador del Pico Viejo, a mountain in the Canary Islands, Spain, off the northwest coast of Africa.

The Fogs of Mars

Fogs of clouds and dust covered parts of southern Mars during last Martian winter. Giant volcanoes, such as Ascraeus Mons, the central circular feature near the top of the image, were surrounded by large water clouds. Slightly southwest, Pavonis Mons and Arisa Mons also peeked above their water clouds. The rough terrain below center is Labyrinthus Noctis, a maze of deep troughs running over 200 kilometers long. Directly south, a large white dust storm fogs Syria Planum, a large plateau. This image mosaic was taken by the Mars Global Surveyor spacecraft currently orbiting Mars. Soon five more Earth-launched spacecraft should arrive at the Red Planet, named for the Roman god of war.

GRO J1655 40 Evidence for a Spinning Black Hole

In the center of a swirling whirlpool of hot gas is likely a beast that has never been seen directly: a black hole. Studies of the bright light emitted by the swirling gas frequently indicate not only that a black hole is present, but also likely attributes. The gas surrounding GRO J1655-40, for example, has been found to display an unusual flickering at a rate of 450 times a second. Given a previous mass estimate for the central object of seven times the mass of our Sun, the rate of the fast flickering can be explained by a black hole that is rotating very rapidly. What physical mechanisms actually cause the flickering -- and a slower quasi-periodic oscillation (QPO) -- in accretion disks surrounding black holes and neutron stars remains a topic of much research.

NGC 1818 Pick A Star

This is NGC 1818,a youthful, glittering clusterof 20,000 stars residing in th LargeMagellanic Cloud, 180,000 light-years away.Pick a star. Any star Astronomersmight pick the unassuming bluish-white one (circled) whic appearsto be a hot newly formed white dwarf star.What makes it so interesting?The standard astronomical wisdomsuggests that stars over 5 times as massive as thesun rapidly exhausttheir nuclear fuel and end their lives in a spectacula supernova explosion.With less than this critical massthey evolve into red giants, pass through a relatively peaceful planetary nebula phase,and calmly fade away a white dwarf stars like this one.Except that as a member of the NGC 1818 cluster,this new white dwarf would have evolved fro a redgiant star over 7.6 times as massive as thesun -- which should have exploded Its discoverywill likely force astronomers to revise thelimiting mass estimate for supernovae upward.

Ring of Fire Revisited

Early on Saturday,May 31 (UT) the new Moon willonce again slide across the Sun's fiery disk, an once again a annular solar eclipse will be theresult -- since the Moon's apparen diameterwill be a little too small to completel cover the Sun.But this tim celestial geometryhas conspired to produce a broa D-shaped regionfor viewing theannular phase that extends into the far northern hemisphere,rather than creating a thin track racing across land and sea.The characteristic ring of fire will be visible fromnorthern Scotland, Iceland, and parts of Greenland.Otherwise a partial eclipse will be more widely visibleas across Europe, along with parts of Asia and North America,the Moon will appear to take a "bite" out of the Sun.While the northerly observers might certainly expect dramaticview, it will probably not look quit like this one, recorded with a foregroundof palm trees during a 1992 annular eclipse.Want to watch Saturday's eclipse on the web?Check out the planne webcastsfrom Astronet.

Frizion Illume

Scientific images of cosmic dustclouds or even frozen water can be esthetic too.In fact, this picture of thin layers of formin ice crystalsuses a scientific understanding o light's wave propertiessolely for artistic purposes.Titled "Illume" thepicture was created by astrophysicist Peter Wasilewski.To make the picture, the crystals were illuminated by lightshining through a polarizing filter -- a filter thatrestricts the otherwise randomly oriented light wavesto vibrate in only one direction.Whil passing through the ice, different colors o thepolarized light are then refracted andreflected along slightly different paths by the delicatecrystalline layers Viewing the scenewith a second polarizing filter bringsout the wondrous display of structure and color.Painting with "light, th laws of physics,and an attitude" Wasilewsk hascreated a series of these evocative ice images thathe refers to as Frozen Vision o Frizion.

SNR 0103-72.6 Oxygen Supply

A supernova explosion,a massive star's inevitable an spectacular demise,blasts back into space debris enriched in the heavy element forgedin it stellar core.Incorporated into future stars and planets, these are theelements ultimately necessary for life Seen here ina false-color x-ray image, supernova remnantSNR 0103-72.6 is revealed to be just such an expanding debriscloud in neighboring galaxy, th SmallMagellanic Cloud.Judging from the measured size of the expanding outer ring ofshock-heated gas, about 150 light-years, light fromthe original supernova explosion would have first reachedEarth about 10,000 years ago.Hundreds of supernova remnantshave been identified asmuch sought after astronomical laboratories for studying thecycle o element synthesisand enrichment, but th x-ray data also showthat the hot gas at the center of thisparticular supernova remnant is exceptionally richin neon and oxygen.

A Mercury Transit Sequence

Earlier this month, the planet Mercury crossed the face of the Sun, as seen from Earth. Because the plane of Mercury's orbit is not exactly coincident with the plane of Earth's orbit, Mercury usually appears to pass over or under the Sun. The above time-lapse sequence, superimposed on a single frame,was taken from a balcony in Belgium on May 7 and shows the entire transit. The solar crossing lasted over five hours, so that the above 23 images were taken roughly 15 minutes apart. The north pole of the Sun, the Earth, Mercury's orbit, although all different, all occur in directions slightly above the left of the image.Near the center and on the far right, sunspots are visible.

The Earth and Moon from Mars

What does Earth look like from Mars? The first image of Earth from the red planet was captured earlier this month by the camera onboard the Mars Global Surveyor spacecraft currently orbiting Mars. Features visible on Earth include the Pacific Ocean, clouds, much of South America, and part of North America. Earth's Moon is visible on the upper right, with the crater Tycho brightening the lower part. Previously, Earth has been imaged from the Moon and spacecraft across the Solar System.

Spiral Galaxy NGC 253 Almost Sideways

NGC 253 is a normal spiral galaxy seen here almost sideways. It is the largest member of the Sculptor Group of Galaxies, the nearest group to our own Local Group of Galaxies. NGC 253 pictured above, appears visually as one of the brightest spirals on the sky, and is easily visible in southern hemisphere with a good pair of binoculars. The type Sc galaxy is about 10 million light years distant. NGC 253 is considered a starburst galaxy because of high star formation rates and dense dust clouds in its nucleus. The energetic nuclear region is seen to glow in X-ray and gamma-ray light.

M74 The Perfect Spiral

If not perfect, then thi spiralgalaxy is at least one of the most photogenic.An island universe of about 100 billion stars,30 million light-years away toward th constellation Pisces,NGC 628 or M74 presents a gorgeou face-on viewto earthbound astronomers Classifiedas an Sc galaxy, the grand designof M74's graceful spiralarms traced by bright bluestar clusters and dar cosmic dust lanes,is similar in many respects to our own home galaxy, th Milky Way.Recorded with a 28 millio pixeldetector array, this impressiv image celebrated first light forthe Gemini Multi-Object Spectrograph GMOS), a state-of-the-art instrumentoperational at the 8-mete Gemini North telescope.The Gemini North Observatory gazes into the skies abov Mauna Kea,Hawaii, USA, while its twin observatory Gemini South,operates fromCerro Pachn in central Chile.

Eclipsed Moon and Stars

Half-shadowed by the Earth,the Moon takes ona remarkable appearance against a field ofstars in this intriguing telephoto picture recorded duringa partial phase of last week' lunareclipse.The picture is not a composite, butit has been digitally enhanced to bring out features coveringa large range in brightness.On the Moon itself,surface details are visible in both thebright uneclipsed portion in direct sunlight, and the very much dimme copper-colored, eclipsed region.Also much fainter than th Moon'ssunlit surface, thebackground star field, along with the unusual lighting,seems to contribute to an eerie "3D" perception of the lunar orb.Canadian astrophotographer Jay Ouellet took the picture froml'Observatoire de la Decouverte in Val Belair, a suburb of Quebec City,where about 200 skygazers gathered to enjoy th celestial exposition.

Eclipsed Moon Montage

After watching this month's lunar eclipse, amateur astronomerSebastien Gauthier carefully composed this montage oftelescopic images of th Moon sliding throughplanet Earth's shadow.While the deepest part of the total eclipse corresponds tothe central exposure, the play of light acros thelunar surface nicely demonstrates that the planet's shadow is notuniformly dark as it extends into space.In fact, lunar maria and montes arestill visible in the dimmed, reddened sunlight scattered intothe cone-shapedshadow region, or umbra, by Earth's atmosphere.For this eclipse, th Moon's trajectory took it North of theumbra's darker core, seen here cast over th Moon's crateredsouthern highlands.Gauthier's telescope and camera equipment were set up near theTrois-Rivieres Colleg Champlain Observatoryin Quebec, Canada.

Copper Moon, Golden Gate

When the Moon rose overSan Francisco's GoldenGate Bridge on May 15, both bridge and Moon were in alread in Earth's shadow.Of course, the bridge is in the Earth's shadow nightly, whilethe Moon only has that opportunity abouttwice a year, during a lunar eclipse.And even though in western North America the total phase of the lunareclipse began before moonrise, many in areas with clear skies came outto enjoy the spectacle.For this eclipse, skygazers reported a darker than normal,copper-colore Moon during totality.The dramatic color is evident in this multiple exposure of th reddened Moonrising, taken by astrophotographer Evad Damast.Damast viewed the eclipse from the Marin Headlands north and west ofthe famousbridge, looking back toward the bay and the citylights.

A Primordial Quasar

What did the first quasars look like? The nearest quasars are now known to be supermassive black holes in the centers of galaxies. Gas and dust that falls toward a quasar glows brightly, sometimes outglowing the entire home galaxy. The quasars that formed in the first billion years of the universe are more mysterious, though, with even the nature of the surrounding gas still unknown. Above, an artist's impression shows a primordial quasar as it might have been, surrounded by sheets of gas, dust, stars, and early star clusters. Exacting observations of three distant quasars now indicate emission of very specific colors of the element iron. These Hubble Space Telescope observations, which bolster recent results from the WMAP mission, indicate that a whole complete cycle of stars was born, created this iron, and died within the first few hundred million years of the universe.

The Andromeda Deep Field

What can you learn from looking into the depths of space? In an effort to find out true ages of stars in neighboring Andromeda galaxy's halo, astronomers stared into the galaxy giant with the new Advanced Camera for Surveys through the Hubble Space Telescope. The resulting exposure of over three days, shown above, is the deepest exposure in visible light ever taken, although shorter in duration than the multi-wavelength effort toward the Hubble Deep Field. The final image illuminated not only Andromeda (M31) but the distant universe. Andromeda's halo stars turned out to be have a wider range of ages than our Milky Way's halo stars, likely indicating more encounters with small neighboring galaxies. Visible on the above left is one of Andromeda's globular star clusters, while literally thousands of background galaxies are seen in the distance universe, far beyond M31.

The Holographic Principle

Is this image worth a thousand words? According to the Holographic Principle, the mostinformation you can get from this image is about 3 x 10⁶⁵ bits for a normal sized computer monitor. The Holographic Principle, yet unproven, states that there is a maximum amount of information content held by regions adjacent to any surface. Therefore, counter-intuitively, the information content inside a room depends not on the volume of the room but on the area of the bounding walls. The principle derives from the idea that the Planck length, the length scale where quantum mechanics begins to dominate classical gravity, is one side of an area that can hold only about one bit of information. The limit was first postulated by physicist Gerard 't Hooft in 1993. It can arise from generalizations from seemingly distant speculation that the information held by a black hole is determined not by its enclosed volume but by the surface area of its event horizon. The term "holographic" arises from a hologram analogy where three-dimension images are created by projecting light though a flat screen. Beware, other people looking at the above image may not claim to see 3 x 10⁶⁵ bits -- they might claim to see a teapot.

Dark Sky, Bright Sun

In low Earth orbit there is no enough atmosphereto diffuse and scatter sunlight,so shadows are black an the sky isdark - even when the Sun shines.The harsh lighting produced thi dramatic effectas mission specialist Gregory Harbaughphotographed colleague Joseph Tanner duringtheir second spacewalk t service the HubbleSpace Telescope in February 1997.The aft section of th Space Shuttle Discovery isvisible in the background withthe Sun hanging over a delicate crescent o the Earth's limb.A checklist is attached to Tanner's left arm, andHarbaugh's reflectionis just visible in Tanner's visor.

A Tale of Two Nebulae

Thi colorfultelescopic view towards the northern constellatio Lyra reveals dim outer regions around M57,popularly known as the Ring Nebula.While modern astronomers stil referto M57 as a planetary nebula,at one light-year across M57 is not a planetbut the gaseous shroud of a dying sun-like star.Roughly the same apparent size as M57, the fainter, ofte overlookedbarred spiral galaxy IC1296 is at the lower right andwould have been referred to in th early 20th century as spiral nebula.By chance the pair are in the same field of view, and while theyappear to have similar sizes they are actually veryfar apart.M57 lies at a distance of a mere 2,00 light-years, well within our ownMilky Way galaxy Extragalactic IC1296 is morelike 200,000,000 light-years distant or about 100,000 times farther away.Since they appear roughly similar in size, spiral nebula IC1296must also be about 100,00 times larger than planetary nebula M57.

Moon Slide Slim

No special filters - or even a telescope - are required to enjoy leisurelylunar eclipse.In fact, watched from all over the night side of planet Earth, thes regularcelestial performances have entertained many casual skygazers.Still, this eye-catching picture of a lunar eclipse may lookunfamiliar.To make it, astrophotographer Doug Murray set his cameraon a tripod and locked the shutter open during the total lunareclipse of January 2000 Theresulting image records th trail of the Moonsliding through the night, steadily progressing towardthe total eclipse phase as seen from Florida, USA Haunting red hues of diminished moonlight,common during the total phase of a lunar eclipse,are evident at the far right, along the slimmer portionof the trail.At least part o tonight's lunar eclipse will be visible i clearnight skies over the Americas, Europe, and Africa.The eclipse should lastover three hours fro start to finish, withabout 53 minutes of totality. Lunar eclipse: Times

The North Pole of Venus

If you could look down on the North Pole of Venus what would you see? The Magellan probe that orbited Venus from 1990 to 1994 was able to peer through the thick Venusian clouds and build up the above image by emitting and re-detecting cloud-penetrating radar. Visible as the bright patch below central North is Venus' highest mountain Maxwell Montes. Other notable features include numerous mountains, coronas, impact craters, tessera, ridges, and lava flows. Although the size and mass of Venus are similar to the Earth, its thick carbon-dioxide atmosphere has trapped heat so efficiently that surface temperature usually exceeds 700 kelvins, hot enough to melt lead. News: Are you ready for tomorrow's lunar eclipse Times

Mercury Transits the Sun

How big is the Sun? The Sun is not only larger than any planet, it is larger than all of the planets put together. The Sun accounts for about 99.9 percent of all the mass in its Solar System. Merely stating the Sun's diameter is about 1,400,000 kilometers does not do it justice. Last week a chance to gain visual size perspective occurred when planet Mercury made a rare crossing in front to Sun. Mercury, a planet over a third of the diameter of our Earth, is the dark dot on the upper right. In comparison to the Sun, Mercury is so small it is initially hard to spot. Also visible on the Sun are dark circular sunspots, bright plages, and dark elongated prominences -- many of which are larger than Mercury. The above contrast-enhanced picture was captured last week from France.

In the Vicinity of the Cone Nebula

Strange shapes and textures can be found in neighborhood of the Cone Nebula.The unusual shapes originate from fine interstellar dust reacting in complex ways with the energetic light and hot gas being expelled by the young stars. The brightest star on the right of the above picture is S Mon,while the region just above it has been nicknamed the Fox Fur Nebula for its color and structure. The blue glow directly surrounding S Mon results from reflection, where neighboring dust reflects light from the bright star. The orange glow that encompasses the whole region results not only fromdust reflection but also emission from hydrogen gas ionized by starlight.S Mon is part of a young open cluster of stars named NGC 2264, located about 2500 light years away toward the constellation of Monoceros. The origin of the mysterious geometric Cone Nebula, visible on the far left, remains a mystery.

M83 The Southern Pinwheel Galaxy from VLT

M83 is one ofthe closest and brightes spiral galaxies onthe sky.Visible with binoculars in the constellation o Hydra, majestic spiral armshave prompted its nickname as the Southern Pinwheel.Although discovered 250 years ago, onlymuch later was it appreciated that M83 was not a nearby gas cloud, but a barredspiral galaxy much like our own Milky Way Galaxy. M83, pictured above in a photograph from VeryLarge Telescope, is a prominent member of a group of galaxies that includes Centaurus A and NGC 5253, all of which lie about 15 million light years distant. To date, six supernova explosions have been recorded in M83. An intriguing doublecircumnuclear ring has been discovered at the center of M83.

Wednesday 30 July 2008

NGC 7293 The Helix Nebula

Will our Sun look like this one day? The Helix Nebula is the closest example of a planetary nebula created at the end of the life of a Sun-like star. The outer gasses of the star expelled into space appear from our vantage point as if we are looking down a helix. The remnant central stellar core, destined to become a white dwarf star, glows in light so energetic it causes the previously expelled gas to fluoresce. The Helix Nebula, given a technical designation of NGC 7293, lies about 650 light-years away towards the constellation of Aquarius and spans about 2.5 light-years. The above picture is a composite of newly released images from the ACS instrument on the Hubble Space Telescope and wide-angle images from the Mosaic Camera on the WIYN 0.9-m Telescope at Kitt Peak National Observatory. A close-up of the inner edge of the Helix Nebula shows complex gas knots of unknown origin. News: Today is Astronomy Day!

International Space Station in Transit

A stunning telescopic image of th InternationalSpace Stationcrossing in front of an eight day old Moon, this picturewas captured on April 11th.But while Wednesday's leisurel transitof Mercury across the Sunentertained observers all over th dayside of planet Earth, theaudience for this lunar transit was more restricted Like other satellitesin low Earth orbit, the spacestation moves quicklythrough the sky.Glinting in the sunlight nearsunset and sunrise,its path strongly depends on the observer's longitude and latitude.So, well-placed astronomer Tom Laskowski tracked theorbiting space stationfrom a site near South Bend, Indiana, USA an recorded a digital movieof the fleeting, dramatic event.This single frame from the movie has been enhanced tobring out detai inthe space station.Seen below the lunar terminator at the lower left,the International Space Station appears here at a distanceof just over 400 kilometers,with the Moon nearly 400,000 kilometers away.

Mercury Spotting

Can you spot the planet?The diminutive disk of Mercury, the solar system' innermost planet,spent about five hours crossing in front of the enormous solar diskyesterday (Wednesday, May 7th) asviewed from the general vicinity of planet Earth.The Sun was above the horizon durin the entire transit for observersin Europe, Africa, Asia, or Australia, and the horizon wa certainlyno problem for the sun-staring SOHO spacecraft.Seen as a dark spot,Mercury progresses from left to right(top panel to bottom) in these four images from SOHO's extremeultraviolet camera.The panels' false-colors correspond to different wavelengths inthe extreme ultraviolet which highlight regions above the Sun'svisible surface Thisis the firstof 14 transits of Mercury whichwill occur during the 21s century,but the next similar event will be transitof Venus in June of 2004.Need help spotting Mercury?Just click on the picture.

The Southern Sky from the International Space Station

Look up from Earth's South Pole, and this stellar starscape is what you might see. Alternatively, this patch of sky is also visible from many southern locations as well as the orbiting International Space Station, where the above image was recently recorded. To the left of the photograph's center are the four stars that mark the boundaries of the famous Southern Cross. The band of stars, dust, and gas crossing the middle of the photograph is part our Milky Way Galaxy. At the lower left is the dark Coal Sack Nebula, and the bright nebula on the far right is the Carina Nebula. The Southern Cross is such a famous constellation that it is depicted on the national flag of Australia.

A Chicago Meteorite Fall

If you wait long enough, a piece of outer space itself will come right to you. As Colby Navarro worked innocently on the computer, a rock from space crashed through the roof, struck the printer, banged off the wall, and came to rest near the filing cabinet. This occurred around midnight on March 26 in Park Forest, Illinois, USA, near Chicago. The meteorite, measuring about 10 cm across, was one of several that fell near Chicago that day as part of a tremendous fireball. Pictured above is the resulting hole in the ceiling, while the inset image shows the wall dent and th meteorite itself. Although the vast majority of meteors is much smaller and burn up in the Earth's atmosphere, the average homeowner should expect to repair direct meteor damage every hundred million years.

NGC 1275 A Galactic Collision

In NGC 1275, one galaxy is slicing through another. The disk of the dusty spiral galaxy near the image center is cutting through a large elliptical galaxy, visible predominantly on the lower left. Galaxies can change significantly during a collision like this, with gravitational tides distorting each galaxy and gas clouds being compressed and lighting up with new star formation. Galaxy collisions occur in slow motion to the human eye, with a single pass taking as much as 100 million years. NGC 1275 is a member of the Perseus cluster of galaxies that lies about 230 million light years away toward the constellation of Perseus. Each galaxy spans about 50,000 light years across. The above picture is a composite of images taken by the Hubble Space Telescope in 1995 and 2001.

A Sonic Boom

Many people have heard a sonic boom, but few have seen one.When an airplane travels at a speed faster than sound, density waves of sound emitted by the plane cannot precede the plane, and so accumulate in a cone behind the plane. When this shock wave passes, a listener hears all at once the sound emitted over a longer period: a sonic boom. As a plane accelerates to just break the sound barrier, however, an unusual cloud might form. The origin of this cloud is still debated. A leading theory is that a drop in air pressure at the planedescribed by the Prandtl-Glauert Singularity occurs so that moist air condenses there to form water droplets. Above, an F/A-18 Hornet was photographed just as it broke the sound barrier. Large meteors and the space shuttle frequently produce audible sonic booms before they are slowed below sound speed by the Earth's atmosphere.

Denizen of the Tarantula Nebula

The star cluster at lower right catalogedas Hodge 301, is a denizen o the Tarantula Nebula.An evocative nebula in the southern sky,the sprawling cosmic Tarantula is an energeti starforming region some 168,000 light-years distantin our neighboring galaxy the Large Magellanic Cloud.The stars within Hodge 301 formed together tens of millions of years agoand as the massive ones quickly exhaust their nuclear fuel theyexplode.In fact, the giant stars o Hodge 301are rapidly approaching this violent final phase of stellar evolution knownas a supernova.These supernova blasts send material an shockwaves back into the nebulargas to create the Tarantula's glowing filaments also visible in thisHubble Space Telescop Heritage image.But these spectacular stellar death explosions signal star birthas well, as the blast waves condense gas and dust to ultimatelyform the next generation of star inside the Tarantula Nebula.

Five to Mars

Come December 2003 - January 2004, an armada o fivenew invaders from Earth should arrive on theshores of the Red Planet -- the Japanese ISAS Nozomi orbiter,the European Space Agency' Mars Expressorbiter carrying th Beagle 2lander, and NASA's own tw Mars Exploration Rovers.While Nozomi began its interplanetaryvoyage in 1998,the other spacecraft are scheduled for launch windowsbeginning this June.Clearly, earthdwellers remain intensely curious about Mars andthe tantalizing possibility o past or present martian life,with these robotic missions focussing on investigating the planet'satmosphere and th searchfor water This mosaicof over 100 Viking 1 orbiter image of Marswas recorded in 1980 and isprojected to show the perspective seen from an approaching spacecraftat a distance of 2,000 kilometers Exceptional views of Mars will be possiblefrom earthbound telescopes in August and September.

The Energetic Jet from Centaurus A

The center of well-studied active galax Centaurus Ais hidden from the view of opticaltelescopes by a cosmic jumble of stars, gas, and dust.But both radio an x-raytelescopes can trace th remarkable jetof high-energy particles streaming from the galaxy's core.With Cen A's central region at the lower right,this composite false-color image shows theradio emission in red and x-rays in blue overthe inner 4,000 light-years of the jet.One of the most detailed images of its kind thepicture shows how the x-rayand radio emitting sites are related along thejet, providinga road map to understanding the energetic stream Extractingits energy from a supermassive black hole at thegalaxy's center, the jet is confined to a relatively narrow angleand seems to produce most of its x-rays (bluer colors) at the upper left,farther from the core, where the jet begins to collide wit Centaurus A'sdenser gas.

A Lenticular Cloud Over New Hampshire

Why does this cloud look so strange? Actually, pictured above are several clouds all stacked up into one striking lenticular cloud. Normally, air moves much more horizontally than it does vertically. Sometimes, however, such as when wind comes off of a mountain or a hill, relatively strong vertical oscillations take place as the air stabilizes. The dry air at the top of an oscillation may bequite stratified in moisture content, and hence forms clouds at each layer where the air saturates with moisture.The result can be a lenticular cloud with a strongly layered appearance. The above picture was taken in 1999 over Plymouth, New Hampshire, USA. The same lenticular cloud also looks strange when photographed from 30 kilometers away.

In the Center of the Rosette Nebula

In the heart of the Rosette Nebula lies a bright open cluster of stars that lights up the nebula. The stars of NGC 2244 formed from the surrounding gas only a few million years ago. This just-released image taken by the CFHT's new MegaPrime camera shows the region in unprecedented detail. Although the emission nebula is dominated by red hydrogen light, the above image has exaggerated the effect of green light emitted primarily by small amounts of oxygen.A hot wind of particles streams away from the cluster stars and contributes to an already complex menagerie of gas and dust filaments while slowly evacuating the cluster center. The Rosette Nebula's center measures about 50 light-years across, lies about 4500 light-years away, and is visible with binoculars towards the constellation of Monoceros.

Rollout of a Soyuz TMA 2 Rocket

It takes a big rocket to go into space. Last weekend, this huge Russian rocket was launched toward Earth-orbiting International Space Station (ISS), carrying two astronauts who will make up the new Expedition 7 crew. Seen here during rollout at the Baikonur Cosmodrome, the rocket's white top is actually a Soyuz TMA-2, the most recent version of the longest serving type of human spacecraft. The base is a Russian R7 rocket, originally developed as a prototype Intercontinental Ballistic Missile in 1957. The rocket spans the width of a football field and has a fueled mass of about half a million kilograms. Russian rockets like this will be primary transportation system to the ISS while NASA studies the underlying reasons behind the recent tragic break-up of the Space Shuttle Columbia.

Venus' Once Molten Surface

If you could look at Venus with radar eyes - this is what you might see.This computer reconstruction of the surface of Venus was created from data from the Magellan spacecraft. Magellan orbited Venus and used radar to map our neighboring planet's surface between 1990 and 1994 Magellan found many interesting surface features, including the large circular domes, typically 25-kilometers across, that are depicted above. Volcanism is thought to have created the domes, although the precise mechanism remains unknown. Venus' surface is so hot and hostile that no surface probe has lasted more than a few minutes.

Big Blue Marble Earth

Thi reconstructed digital portrait of our planetis reminiscent of th Apollo-era pictures of the "big blue marble Earthfrom space Tocreate it, researchers at Goddard Space Flight Center' Laboratoryfor Atmospheres combined dat from aGeostationary Operational Environmental Satellite GOES),the Sea-viewing Wide Field-of-view Sensor SeaWiFS), and thePolar Orbiting Environmental Satellites POES) with USGSelevation model of Earth' topography.Stunningl detailed, the planet's western hemisphere iscast so that heavy vegetation is green and sparse vegetation is yellow,while the heights of mountains and depths of valleyshave been exaggerated by 50 times to makevertical relief visible. HurricaneLinda is the dramatic storm off North America's west coast.And what abou the Moon?The lunar image was reconstructed from GOES data an artistically rescaled for thi visualization.

M17 A Hubble Close-Up

Sculpted by stellar winds and radiation, these fantastic, undulatingshapes lie within th stellarnursery know as M17,the Omega Nebula, some 5,500 light-years away in th nebula-rich constellation Sagittarius.The lumpy featuresin the dense cold gas and dust are illuminatedby stars off the upper left of the image and may themselvesrepresent sites of future star formation.Colors in the fog of surrounding hotter material indicat M17'schemical make up.The predominately green glow corresponds to abundant hydrogen,with trace sulfur and oxygen atoms contributing red and blue hues.The picture spans about 3 light-years and wa releasedto celebratethe thirteenth year of th Hubble Space Telescope'scosmic voyage of exploration.

Earth at Twilight

No sudden, sharp boundary marks the passage of da into night i this gorgeous viewof ocean and clouds over ou fairplanet Earth.Instead, the shadow line o terminator isdiffuse and showsthe gradual transition to darkness we experience as twilight.With the Sun illuminating the scene from the right,the cloud tops reflect gently reddene sunlight filteredthrough the dusty troposphere, the lowest layer of the planet's nurturin atmosphere.A clear high altitude layer,visible along the dayside's upper edge scatters bluesunlight and fades into the blackness of space.This pictur actually is a single digitalphotograph taken in Juneof 2001 from the International Space Statio orbiting at analtitude of 21 nautical miles.

The Stars of NGC 1705

Some 2,000 light-years across, NGC 1705 is small as galaxies go,similar to our Milky Way's own satellite galaxies the Magellanic Clouds.At a much larger distance of 17 million light-years, th starsof NGC 1705 are still easily resolved i this beautiful imageconstructed from data taken in 1999 and 2000 with the Hubble SpaceTelescope.Most of the younger, hot, bluestars in the galaxy areseen to be concentrated in a large central star cluster with th older, cooler,red stars more evenly distributed.Possibly 13 billion years old NGC 1705 could well have beenforming stars through out its lifetime while light from its most recentburst of star formation reached Earth only 30 million years ago.This gradually evolving dwarf irregular galaxylack organized structures like spiral arms andis thought tobe a nearby analog to th firstgalaxies to formin the early Universe.

Springtime on Mars

Vast canyons, towering volcanoes, sprawling fields of ice, deep craters, and high clouds can all be seen in this image of the Solar System's fourth planet: Mars. The orbiting robot Mars Global Surveyor spacecraft took the above mosaic of images as springtime dawned in Northern Mars in 2002 May. Sprawled across the image bottom is Valles Marinaris, a canyon three times the length of Earth's Grand Canyon, and four times as deep. On the left are several volcanoes including Olympus Mons, a volcano three times higher than Earth's Mt. Everest. At the top is the North Polar Cap made of thawing water and carbon-dioxide based ice. Swirling white clouds and circular impact craters are also visible around Mars. Two rovers will be launched to Mars this summer and should arrive in 2004 January.

A Halo Around the Moon

Have you ever seen a halo around the Moon? This fairly common sight occurs when high thin clouds containing millions of tiny ice crystals cover much of the sky. Each ice crystal acts like a miniature lens. Because most of the crystals have a similar elongated hexagonal shape, light entering one crystal face and exiting through the opposing face refracts 22 degrees, which corresponds to the radius of the Moon Halo. A similar Sun Halo may be visible during the day. The picture was taken in Lansdowne, Pennsylvania, USA.The distant planet Jupiter appears by chance just to the left of the Moon. Exactly how ice-crystals form in clouds remains under investigation.

Thursday 31 July 2008

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