Astronomy in English: June 2008

Monday 30 June 2008

A Sky Filled with Leonids

In the early morning hours of November 19, amateur Chen Huang-Ming caught a sky filled with astronomical wonders. With his fisheye camera set up on Ho-Huan Mountain in Taiwan for a half-hour exposure, he started the above image a local time of 2:33 am. First, the many famous stars and nebulas captured are too numerous to count. Planets Jupiter and Saturn are visible, while the plane of our Milky Way Galaxy sweeps diagonally across the image. What makes this image most spectacular, however, are the over 100 bright meteors visible from the 2001 Leonids Meteor Shower. The meteor shower is caused by the Earth plowing through a stream of sand-sized ice particles shed years ago by Comet Tempel-Tuttle. Note that the meteors can all be tracked back to a radiant in the constellation Leo, the direction from which the particles orbit the Sun.

AE Aurigae The Flaming Star

Is star AE Aurigae on fire? Although surrounded by what may look like smoke, the object known as the "flaming star" creates energy primarily by nuclear fusion, like other stars. Fire, typically defined as the rapid molecular acquisition of oxygen, happens only when sufficient oxygen is present and is not important in such high-energy, low-oxygen environments such as stars. The material that appears as smoke is mostly interstellar hydrogen, but does contain smoke-like dark filaments of carbon-rich dust grains. The AE Aurigae region was imaged by the KPNO 0.9-meter telescope and is shown above in false but representative colors. The star AE Aurigae itself is very bright, young, blue, and known as a runaway star since it appears to have been ejected from the Orion Nebula region about 2.7 million years ago.

Dueling Auroras

Will it be curtains for one of these auroras? A quick inspection indicates that it is curtains for both, as the designation curtains" well categorizes the type of aurora pattern pictured. Another (informal) type is the corona.The above auroras resulted from outbursts of ionic particles from the Sun during the last week of September. A polarity change in the solar magnetic field at the Earth then triggered auroras over the next few days.The above picture was taken on October 3 as fleeting space radiation pelted the Earth's atmosphere high above the Yukon in Canada.

Rumors of a Strange Universe

Three years ago results were first presented indicating that most of the energy in our universe is not in stars or galaxies but is tied to space itself. In the language of cosmologists, a large cosmological constant is directly implied by new distant supernovae observations. Suggestions of a cosmological constant (lambda) are not new -- they have existed since the advent of modern relativistic cosmology. Such claims are not usually popular with astronomers, though, because lambda is so unlike known universe components, because lambda's value appears limited by other observations, and because less-strange cosmologies without lambda have previously done well in explaining the data. What is noteworthy here is the seemingly direct and reliable method of the observations and the good reputations of the scientists conducting the investigations. Over the past three years, two independent teams of astronomers have continued to accumulate data that appears to confirm the unsettling result. The above picture of a supernova that occurred in 1994 on the outskirts of a spiral galaxy was taken by one of these collaborations. Still, extraordinary claims require extraordinary evidence, and so cosmologists the world over continue to await more data and confirmation by independent methods.

Neptune's Great Dark Spot Gone But Not Forgotten

When NASA's Voyager 2 spacecraft flew bydistant Neptune in August of 1989 astronomerswere shocked.Since Neptune receives only 3 percentthe sunlight Jupiter does, theyexpected to find a dormant, dark, frigid planet.Instead, the Voyager images revealedevidence of a dynamic and turbulent world.One of the most spectacular discoveries was of the Great Dark Spot, shown here in close-up.Surprisingly, it wascomparable in size and at the same relative southern latitude as Jupiter'sGreat Red Spot, appearing to be asimilar rotating storm system.Winds near the spot were measured up to1500 miles per hour, the strongest recorded on any planet.The Voyager data also revealed that the GreatDark Spot varied significantly in size during the brief flyby.When the HubbleSpace Telescope viewed the planet in 1994, the spot hadvanished -- only to be replaced by another darkspot in the planet's northern hemisphere!

Meteor Storm Sights and Sounds

This dramatic four-frame animation shows a fireball meteor and itsdeveloping persistent "smoke" train, recorded two weeks ago i skies nearSalvador, Brazil.Indeed similar sights are astonishingly familiar world-wide towitnesses of this November's fireball-ric Leonid meteor storm.A few skygazers even discoveredthat some bright Leonid fireballs made faint, gentle,hissing sounds(!), a surprising effect only recentlyappreciated and understood.Accounts of fireballmeteors making noise have long bee viewedwith skepticism, particularly because sounds werereportedly heard just as the meteor was seen overhead.But light travels much faster than sound so, like delaye thunder froma distant lightning stroke, ameteor produced sound should onlybe heard long after th meteor streak was seen Asound explanation supported b laboratorytests is that turbulen plasma created by the meteor's passagegenerates very low frequency radio waves Travelingat light speed the radio waves reach the groundsimultaneously with visible light where they are strong enough to induceoscillating current andaudible vibrations in common objectslike grass, leaves,wire-frame glasses, and perhaps even dry, frizzy hair.

Coronal Inflow

The active Sun has thrown a lot our way lately, includin storms of particlesstreaming outward in the solar wind an clouds of plasmawhich triggered awesome auroral displays.Still, a growing body of intriguing observationsfrom the LASCO instrument on board th space-basedSOlar and Heliospheric Observatory SOHO)indicates material also flows back toward the Sun, starting fromover 2 million kilometers above it visible surface.Relatively hard to detect against the outflowin solarcorona, a dark inflowing cloud's relative motion is trackedabove in two highly processed images recorded an hour apart.The solar surface, graphically shown by the yellowquarter circle at the lower right,is blocked from view by a smoot occulting disk.Fighting against solarwind outflow of about 120 kilometers persecond the cloud seems to be moving inward at 50-100 kilometers persecond.Occasionall appearing asoften as once per hour,the clouds, seem to be dragged in by collapsin magnetic field loops rather than gravity alone.Researchers are no workingto relate this surprising inflow to thesolar wind and magneti environmentof the Sun.

Extra Solar Planetary Atmosphere Detected

By directly detecting the atmosphere of a planet outside our Solar System, humanity has taken another small step toward finding extraterrestrial life.The unexpected detection by David Charbonneau Caltech) and associates came from Hubble Space Telescope observations of Sun-like star HD 209458. As an orbiting planet crossed between that star and the Earth, sodium in the planet's atmosphere absorbed starlight at very specific colors. The planet, originally discovered two years ago, has about 70 percent the mass of Jupiter but orbits very close in. A long-term goal of this type of research is the detection of planetary biomarkers that would indicate life, such as oxygen, water, or methane.

Ancient Layered Rocks on Mars

Is this a picture of Mars or Earth? Oddly enough, it is a picture of Mars. What may appear to some as a terrestrial coastline is in fact a formation of ancient layered rocks and wind-blown sand on Mars. The above-pictured region spans about three kilometers in Schiaparelli Crater. What created the layers of sediment is still a topic of research. Viable hypotheses include ancient epochs of deposit either from running water or wind-blown sand. Winds and sandstorms have smoothed and eroded the structures more recently. The "water" that appears near the bottom is actually dark colored sand. The image was taken with the Mars Global Surveyor spacecraft that has now returned over 100,000 images. News: APOD is now also available in Spanish.

Leonids from the Road

Sometimes you just have to stop and watch the meteors. In the early morning hours of November 18, a band of eleven people searched for a flat and cloudless site to see the 2001 Leonids Meteor Shower. Starting in central Iowa, weather satellite images indicated that southern Minnesota might be their best chance, and so off they drove. Although they couldn't shake off all of the clouds, they found a dark gravel road, pulled off, and settled in for the rare celestial light show. "By about 4 am, we were visually counting 1000 per hour. After that they started to increase dramatically." The photographer was just a little too late to catch a really bright fireball, but did catch several other bright Leonid meteors above one of the cars in the convoy. The exposure lasted a few minutes. News: APOD is now also available in Spanish.

M16 Stars from Eagle's EGGs

Newborn stars are forming in the Eagle Nebula. This image, taken with the Hubble Space Telescope in 1995, shows evaporating gaseous globules (EGGs) emerging from pillars of molecular hydrogen gas and dust. The giant pillars are light years in length and are so dense that interior gas contracts gravitationally to form stars. At each pillars' end, the intense radiation of bright young stars causes low density material to boil away, leaving stellar nurseries of dense EGGs exposed. The Eagle Nebula, associated with the open star cluster M16, lies about 7000 light years away.

Mariner's Mercury

Mercury, the closest planet to the Sun, remain the most mysterious of theSolar System's inner planets.Hiding in the Sun's glare it i adifficult target for Earth bound observers.The only spacecraft t explore Mercuryclose-up was Mariner 10 whichexecuted thre flybys of Mercuryin 1974 and 1975, surveying approximately 45percent of its surface Mariner10 deftly manuevered tophotograph part of the sunlithemisphere during each approach, passed behind the planet,and continued to image the sun-facing side as the spacecraft receded.Its highest resolutio photographs recorded featuresapproximately a mile across.A reprocessin of theMariner 10 data has resulted in this dramatic mosaic. Like the Earth's Moon, Mercury's surfaceshows the scars of impact cratering -the smooth vertical band and patches visible above represent regionswhere no image information is available.

Counting Falling Stardust

In the clear, dark and moonless predawn hours o November 18,Greenbelt, Maryland's local baseball field was packed.The crowd stared skyward and occasionally conversed in hushedand reverent tones."How man didyou count?" a man asked.Some had long since lost track ... but others were keeping score countinghundreds o Leonidmeteors in a short hour's worth of skygazing.Farther to the west, near Florence, Arizona recreationalastronomers also gathered to enjo thecelestial show.Taken fro thatlocation, this single, 10 minute, wide-angle exposur captured a dozen or so Leonid meteors.The shooting stars are clearly seen to b streaming from the shower' radiant point in the constellation Leo.

Fireball, Smoke Trail, Meteor Storm

Returning from orbit,space shuttles enter the atmosphere atabout 8 kilometers per second as friction heats their protectiveceramic tiles to over 1,400 degrees Celsius.By contrast, the bits of comet dust which became th Leonid meteorsseen on November 18, were moving at 70 kilometers per second,completely vaporizing at altitudes of around 100 kilometers In thissingle 5 minute time exposure, three Leoni meteors areshootin through skies above Spruce Knob,West Virginia, USA Background starsare near the constellation Orion.The brightest meteor, afireball, dramatically changes colors along itspath and leaves a smoke persistant trail driftingin high-altitude winds.From that extremely dark site, at an elevation of 1,200 meters astrophotographerJerry Lodriguss reports, "We observed a zenithalhourly rate] of about 3,600 at 10:30 UT andvery high rates from 9:30 UT until well into the startof astronomical twilight at 10:50 UT. It was quite spectacular storm,with bolides going off like flashbulbs,green and red fireballs and other fainter Leonids in all parts ofthe sky."

The Galactic Ring of NGC 6782

Do spiral galaxies look the same in every color? NGC 6782 demonstrates colorfully that they do not. In visible light, NGC 6782 appears to be a normal spiral galaxy with a bright bar across its center. In ultraviolet light, however, the central region blossoms into a spectacular and complex structure highlighted by a circumnuclear ring, as shown in the above representative color Hubble Space Telescope image. Many of the young stars that formed in a recent burst of star formation emit the ultraviolet light. Astronomers are studying possible relationships between the central bar and the ring. Light we see today from NGC 6782 left about 180 million years ago, while dinosaurs roamed the Earth. The galaxy spans about 80,000 light-years and can be seen with a telescope toward the constellation of Pavo.

A Leonids Star Field

As meteor after meteor streaked across a moonless sky, photographers across the world snapped pictures of the 2001 Leonids Meteor Shower. Many recognized this as the best meteor shower they had ever seen. In fact, the 2001 Leonids was the most active meteor shower since the mid-1960s. The above photo captures three Leonid meteors crossing a photogenic star-field. On the far right is the Pleiades star cluster. The brightest meteor crosses right in front of the Hyades star cluster, situated below the image center. Just left of center is the bright plane Saturn, and the bright star belowSaturn is Aldebaran. The ten-minute exposure was taken near Victoria, British Columbia, Canada at 2:45 am PST on 2001 November 18.

A 2001 Leonids Meteor Shower Fireball

The 2001 Leonids Meteor Shower gave quite a show to many parts of the world yesterday during the early morning hours. Many sleepy observers venturing into their own backyards were treated to several bright meteors per minute streaking across the sky. This rate made the 2001 Leonids the most active meteor shower in over three decades. Pictured above is a bright Leonid fireball that briefly lit up Hawaii yesterday morning. A CONCAM nighttime all-sky monitor on Mauna Kea, a dormant volcano, caught the bright meteor, seen as the very bright streak across the lower part of the fisheye image. The meteor track crossed the Galactic plane (the faint glow that runs from the lower left to upper right), passed below the planet Jupiter, and through the constellation Orion. CONCAMs in Hawaii, Arizona, and California all recorded numerous bright meteors during this year's Leonids.

A Leonid Meteor Explodes

Last night and tonight, a lucky few may see a meteor explode. As our Earth passes unusually close to debris expelled from Comet Tempel-Tuttle, many sand-sized particles from this comet areentering and burning up in the Earth's atmosphere. This yearl phenomenon is known as the Leonids Meteor Shower, but the location the Earth passes through this year holds promise to provide relatively high activity. In particular, the 1998 Leonids was noteworthy for its many bright meteors. In the above slow-loading sequence, a 1998 Leonid was caught exploding over Los Alamos, New Mexico. In the last one-minute exposure, another Leonid streaks past.

Catching Falling Stardust

This carrot-shaped track is actually little more than 5 hundredthsof an inch long.It is the trail of a meteroid through the high-tec substance aerogelexposed to space by the shuttle launche EURECA(European Recoverable Carrier) spacecraft Like those i the ongoing Leonid meteor shower, thismeteoroid is about a thousandth of an inch in diameter.It is visible where it came to rest, justbeyond the tip of the carrot at the far right.Chemical analyses o interplanetary dust particles similarto this one suggest that some of them may b bitsof comets and thus represent samples of material fro theearly stages of the formation of the Solar System.

Leonid Watching

Will the Leonids storm this year?The annual Leonid meteor shower should pea this weekend and somepredictions suggest that "storm" rates of a thousand or more meteorsper hour are possible for observers located in eastern Northand Central Americaduring the early morning hours of Sunday, November 18.Similar high rates are also anticipated for the western Pacific regionon the morning of November 19th.In any event, th 2001 Leonidshower should be dramatic an easy to watch, as were th Leonids of recent years.From top left to bottom right above are spectacula examples ofbright fireball meteors from the 1998 Leonid shower as recorded b V. Winter and J. Dudley Lorenzo Lovato, an Wally Pacholka.A 1998 image from the Puckett Observatory at lower leftfeatures the source of th debris stream which suppliesthe Leonid meteors comet Tempel-Tuttle.

Recycling Columbia

Twenty years ago this week, th Space Shuttle Columbia becamethe first reusable spaceship Its second trip to low Earth orbit and back again beganon November 12, 1981, following it maiden voyage by only seven months.Seen above Columbia, 56 meters (184 feet) long with a24 meter (78 foot) wingspan, is launched mated to anexternal fuel tank and two solid rocket boosters producingdramatic exhaust plumes.The solid rocket boosters,one on each side of the external tank, provide most of the thrust inthe first 2 minutes after launch and are then jettisoned forlater recovery.Supplying the main shuttle engines during liftoff, th external fuel tank separates after about 8 minutes.The largest shuttle element not recycled for a futureflight, the external tank falls backtoward Earth breaking up and descending into a remote ocean area.Still the oldest operating shuttle, Columbia i pictured herein June of 1992 rocketing toward a cloud bank o its twelfth flight.Officially designated OV-102, Columbia i fittingly named after the 18thcentury sailing vessel which became the firs Americanship to circumnavigate planet Earth.

Auroras Over Both Earth Poles

Auroras in the north and south can be nearly mirror images of each other. Such mirroring had been suspected for centuries but dramatically confirmed only last month by detailed images from NASA's orbiting Polar spacecraft. Pictured above, a time-lapse movie shows simultaneous changes in aurora borealis, at the top, and aurora australis, at the bottom. A cloud of electrons and ions moving out from the Sun on October 22 created the auroras. The solar explosion that released the particles occurred about three days earlier.

A Gravity Map of Earth

Is gravity the same over the surface of the Earth? No -- it turns out that in some places you will feel slightly heavier than others. The above relief map shows in exaggerated highs and lows where the gravitational field of Earth is relatively strong and weak. A low spot can be seen just off the coast of India, while a relative high occurs in the South Pacific Ocean. The cause of these irregularities is unknown since present surface features do not appear dominant. Scientists hypothesize that factors that are more important lay in deep underground structures and may be related to the Earth's appearance in the distant past. To better map Earth's gravity and hence better understand its interior and past, NASA plans to launch the Gravity Recovery and Climate (GRACE) satellite in February.

Is Mystery Object an Orphan Afterglow

What is that unusual object? Astronomers can identify most objects that are imaged on the sky, but not all. Pictured above is one that currently defies classification. Attributes of the object include that it has unusual colors, appears to be fading as months go by, and appears to be associated with a distant galaxy. Its discoverers hold hope that they have uncovered the first known orphan afterglow, an explosion that would have been classified as a gamma-ray burst if the gamma-rays were beamed in our direction. Orphan afterglows, if they exist, could have unparalleled brightness, and hence be visible so far away that they yield key information about the early years of our universe.A bit of caution might be merited, however, as the last well-publicized mystery object turned out not to be a new member of the astronomical zoo, but rather an unusual type of quasar. Follow-up observations and analysis over the next year may find more objects like this and/or solve this mystery.

An Annotated Leonid

The 1998 Leonids Meteor Shower was one of the most photographed meteor events in history. Patient observers saw bright meteors streak across dark skies every few minutes, frequently leaving fading trails stretching across the sky. High above the Anza-Borrego Desert, a meteor was photographed streaking up from the radiant constellation of the Leonids: Leo. This meteor train covered over 40 degrees, and changed colors from green to red. The intensity of the Leonid Meteor Shower in 2001 is uncertain but may approach one per second for somelocations on November 18.

Lunar Dust and Duct Tape

Why is the Moon dusty?On Earth, rocks are weathered by wind and water, creating soil and sand.On the Moon, the long history o micrometeorite bombardmenthas blasted away at the rocky surface creating a layer of powder lunar soil or regolith.This lunar regolith could be scientific an industrial bonanza.But for the Apollo astronauts an their equipment,the pervasive, fine, gritty dust was definitely a problem Onthe lunar surface in December 1972 Apollo 17 astronautsHarrison Schmitt and Eugene Cernan needed to repair one of theirlunar rover's fender in an effort to keep the"rooster tails" of dust away from themselves and their gear This picture reveals the wheel andfender of their dust covere rover along withthe ingenious application of spare maps,clamps, and a grey strip of "duct tape".

SOHO Comet 367 Sungrazer

The most prolific comet discovering instrumentin history rides aboard th sun-staringSOHO spacecraft, 1.5 million kilometers sunward of planet Earth.Of course, most of these SOHOcomets have bee sungrazers -like the one illustrated in the dramatic montage above.Three frames taken hours apart on October 23rd, showbright SOHO comet number 367plunging toward the fiery solar surface its tail streaming awayfrom the Sun located just beyond the left hand border.Each panel spans about one million kilometers a the distance o the Sun.From bottom to top, the comet's tail grows as the intensifyingsolar radiation heats the frozen comet material and increases theoutflow of gas and dust.Because of their orbits sungrazersare believed to belong to afamily of comets produced by the breakup of a single much largercomet.Coincidentally, this sungrazer wa discoveredshortly after solar active regionsblasted out clouds of energetic particles, like those thattriggered the recent spectacula auroralstorms.And like all SOH sungrazers so far,comet number 367 was not seen to survive its close solar encounter.

Under A Sunspot

At the Sun's surface, sunspots are known to be dark planet-sized regions ofintense magnetic fields.But what lies below?Using observations from th MichelsonDoppler Imager (MDI) instrument aboard the space-base SOHOobservatory, astronomers have derive thispremier picture of the flowof material just beneath visible sunspot.The MDI data indicate that immediatel underthe sunspot a strong inflowing current exists, shown aboveby the dark arrows.This converging undertowpulls near-surface material toward the spot and preventsthe concentrated magnetic fields from flying apart,like repelling poles o ironmagnets.Such a configuration appears to divert the normal flo of plasmabubbling up from the solar interior, creating self-sustainingsunspot.The MDI instrument can explore the properties of the solar interiorby detecting motions produced b sound wavesas they interact at the solar surface.

Sunday 29 June 2008

A Sun Pillar in Red and Violet

Sometimes the unknown is beautiful. In 2000 February near Lake Tahoe, Nevada, two amateur photographers noticed an unusual red column of light rise mysteriously from a setting sun. During the next few minutes, they were able to capture the pillar and a photogenic sunset on film. Pictured above, the red column is seen above a serene Lake Tahoe and snow-capped mountains across fro Lake Tahoe-Nevada State Park. The mysterious column, they learned later, is a Sun Pillar, a phenomenon where sunlight reflects off of distant falling ice crystals.

In the Center of Spiral Galaxy M83

What's happening at the center of spiral galaxy M83? Just about everything, from the looks of it. M83, visible in the inset image on the upper left, is one of the closest spiral galaxies to our own Milky Way Galaxy and from a distance of 15 million light-years, appears to be relatively normal. Zooming in on M83's nucleus with the latest telescopes, however, shows the center to be an energetic and busy place. Visible in the above image from the Hubble Space Telescope are bright, newly formed stars and giant lanes of dark dust. An image with similar perspective from the Chandra X-ray Observatory shows the region is also rich in very hot gas and small bright sources. Observations with the large ground-based VLT telescopes show the very center likely has two separate nuclei.

Aurora Over Winnipeg

What's happening above that city? The city is Winnipeg, Canada, and the phenomenon is aurora. These past few months have been active ones for our Sun, producing several coronal mass ejections (CMEs) of particles that have swept past our Earth and caused many spectacular auroras. Specifically in this case, a CME that occurred on October 9 impacted the Earth on October 11 and 12, causing nearly 12 hours of auroras. The above-pictured aurora had to be very bright to be seen over the lights of Winnipeg, the city well below and in front of the cascading atmospheric airglow. Lights reflecting off of a slight haze cause an unrelated glow that emanates from some of the buildings.

Leonids from Leo

Is Leo leaking? Leo, the famous sky constellation visible on the left of the above all-sky photograph, appears to be the source of all the meteors seen in 1998's Leonids Meteor Shower. That Leonids point back to Leo is not a surprise - it is the reason that this November meteor shower is called the Leonids. Sand-sized debris expelled from Comet Tempel-Tuttle follows a well-defined orbit about our Sun, and the part of the orbit that approaches Earth is superposed in front of the constellation Leo. Therefore, when Earth crosses this orbit, the radiant point of falling debris appears in Leo. Over 150 meteorscan be seen in the above four-hour effort. The intensity of the Leonid Meteor Shower in 2001 is uncertain but may approach one per second for some locations on November 18.

Bright Stars, Dim Galaxy

These two clusters of bright, newly formed star surrounded bya glowing nebula lie 10 million light-years away in the dim,irregular galaxy cataloged as NGC 2366.The HubbleSpace Telescope image shows that the youngest cluster,the bottom one at about 2 million years old,is still surrounded by the gas and dust cloud it condensed from, whil powerful stellar winds from the starsin the older cluster at the top (4-5 million years old),have begun to clear away its central areas giving the entire nebulaan apparent inverted hook shape.Compared to the sun, the stars in these cluster are massive an short lived.The brightest one, near the tip of the hook, is a rare Luminous Blue Variablewith 30 to 60 times the mass of the sun - similar to the erruptiv Eta Carinae in our own Milky Way.Stars this massiv are extremely variable.A comparison with ground based images indicates that in threeyears this star's brightness increased by about 40 times making it currentlythe brightest star i this dim galaxy.

THEMIS of Mars

Not an ancient Greek goddess, THEMIS i modern acronese fo THermal EMission Imaging System.Above is this remarkable instrument' premier infrared image ofMars, from the newly orbitin Mars Odyssey spacecraft.Taken on October 30th, the sharp infrared picture covers the indicatedswath of the martian southern hemisphere and showssurface temperatures in false-colors ranging from red, a warm 0 degreesCelsius, to cool purple shades of -120 degrees C.The striking, cold circular feature i Mars' south polar ice cap.Composed of froze carbon dioxide, the ice cap is about 900 kilometers wid and shrinkingduring the onslaught of southern hemispher summer.Temperatures are also seen to drop as the bottom portionof the THEMIS image sweep beyondthe terminator or shadow line, into the martia night.A thin, light blue crescent along the upper edge of the planet is th martian atmosphere. The THEMIS image data was recorded a a test ofthe camera systemfrom an altitude of about 22,000 kilometers .

M87's Energetic Jet

Anenergetic jet from the core ofgiant elliptical galaxy M87 stretches outward for 5,000 light-years.This monstrous je appearsin the panels above to be a knotted and irregular structure, dectecte across the spectrum, fromx-ray to optical t radio wavelengths.In all these bands,the observed emission is likely created as high energyelectrons spiral along magnetic field lines, so calle synchrotron radiation.But what powers this cosmic blowtorch?Ultimately, the jet is thought to be produce as matter near the center of M87swirls toward a spinning, supermassive black hole.Strong electromagnetic forces are generated and eject materialaway fro the black hole alongthe axis of rotation in a narrow jet Galaxy M87is about 50 million light-years away and reigns asthe large central elliptical galaxy in th Virgocluster.

Halloween and the Ghost Head Nebula

Halloween's origin is ancient and astronomical. Since the fifth century BC, Halloween has been celebrated as a cross-quarter day, a day halfway between an equinox (equal day / equal night) and a solstice (minimum day / maximum night in the northern hemisphere). With our modern calendar, however, the real cross-quarter day will occur next week. Another cross-quarter day is Groundhog's Day Halloween'smodern celebration retains historic roots in dressing to scare away the spirits of the dead. A perhaps-fitting modern tribute to this ancient holiday is the above-pictured Ghost Head Nebula taken with the Hubble Space Telescope. Appearing similar to the icon of a fictional ghost, NGC 2080 is actually a star forming region in the Large Magellanic Cloud, a satellite galaxy of our own Milky Way Galaxy. The Ghost Head Nebula spans about 50 light-years and is shown in representative colors.

Anticrepuscular Rays Over Colorado

What's happening over the horizon? Although the scene may appear somehow supernatural, nothing more unusual is occurring than a setting Sun and some well placed clouds. Pictured above are anticrepuscular rays. To understand them, start by picturing common crepuscular rays that are seen any time that sunlight pours though scattered clouds. Now although sunlight indeed travels along straight lines, the projections of these lines onto the spherical sky are great circles. Therefore, the crepuscular rays from a setting (or rising) sun will appear to re-converge on the other side of the sky. At the anti-solar point 180 degrees around from the Sun, they are referred to as anticrepuscular rays. Pictured above is a particularly striking set of anticrepuscular rays photographed earlier this month from a moving car just outside of Boulder, Colorado, USA.

Spinning Black Holes and MCG 6 30 15

What makes the core of galaxy MCG-6-30-15 so bright? Some astronomers believe the answer is a massive spinning black hole. If so, this would be the first observational indication that it is possible to make a black hole act like a battery -- and tap into its rotational energy. MCG-6-30-15 is a distant galaxy that has recently been observed with the orbiting XMM-Newton satellite in X-ray light. These observations show the galaxy's nucleus not only to be very bright but also to show evidence that much of the light is climbing out of a deep gravitational well. A spinning black hole could explain both effects. A strong magnetic field could be the mediator transferring rotational energy from the black hole to the surrounding gas. Pictured above is an artist's illustration of a black hole surrounded by an accretion disk. For clarity, the illustration does not include distorting gravitational lens effects.

NGC 2346 A Butterfly-Shaped Planetary Nebula

It may look like a butterfly, but it's bigger than our Solar System. NGC 2346 is a planetary nebula made of gas and dust that has evolved into a familiar shape. At the heart of the bipolar planetary nebula is a pair of close stars orbiting each other once every sixteen days. The tale of how the butterfly blossomed probably began millions of years ago, when the stars were farther apart. The more massive star expanded to encompass its binary companion, causing the two to spiral closer and expel rings of gas. Later, bubbles of hot gas emerged as the core of the massive red giant star became uncovered. In billions of years, our Sun will become a red giant and emit a planetary nebula - but probably not in the shape of a butterfly, because the Sun has no binary star companion.

Sher 25 A Pending Supernova

No supernova has ever been predicted.These dramatic stellar explosions that destroy stars and disperse elements that compos people and planetsare not so well understood that astronomers can accurately predict when a star will explode - yet.Perhaps Sher25 will be the first.Sher 25, designated by the arrow, is a blu supergiant star located just outside the star cluster and emission nebul NGC 3603.Sher 25 lies in the center of an hourglass shaped nebula much like the one that surrounds the last bright supernova visible from Earth: SN1987a.Now the hourglass shaped rings around SN1987a were emitted before that blue supergiant exploded. Maybe Sher 25 has expelled these bipolar rings in a stepthat closely precedes a supernova. If so, Sher 25 may be withina few thousand years of its spectacular finale.

Elements in the Aftermath

Massive starsspend their brie lives furiously burning nuclear fuel Through fusionat extreme temperatures and densities surrounding thestellar core, nuclei of light element like Hydrogen and Helium are combined to heavie elements likeCarbon, Oxygen, etc. in a progression which ends with Iron.And so a supernova explosion,a massive star's inevitable and spectacular demise,blasts back into space debri enriched inheavier elements to be incorporated into other stars and planets (an people!).This detaile false-color x-ray imagefrom the orbiting ChandraObservatory shows such a hot, expanding stella debriscloud about 36 light-years across.Cataloged as G292.0+1.8, this young supernova remnantin the southern constellatio Centaurus resulted froma massive star which exploded an estimated 1,600 years ago.Bluish colors highlight filaments of the mulitmillion degree gaswhich are exceptionall rich in Oxygen, Neon, and Magnesium.Just below and left of center, a point like object in the Chandra imagesuggests tha theenriching supernova also produced a pulsar inits aftermath, a rotating neutron star remnant of the collapsed stellarcore.

Odyssey at Mars

After an interplanetaryjourney lasting 200 days, the Mars Odyssey spacecraf hasentered orbit around the Red Planet.This latest success is welcome as in the past, Mars has often seemed adifficult planet to visit Beginning with the firstSoviet attempts in 1960, around 30 missions havetried while only 10 or so have gone without serious mishap.Now tha Mars Odysseyhas arrived, its immediate future will involv aerobraking.Cautiously dipping into th martian atmosphere, the spacecraft willgradually adjust its present wide and elliptical 20-hourorbit to a circular 2-hour orbit only 400 kilometers above th planet's surface.Then, its instruments an cameras will focus on exploringthe climate and geologic histor of Mars, including th search for waterand evidence of life-sustainin environments.In the artist's conception above, the spacecraft with wing-like solar panelsis imagined firing its rocket engine fo Mars orbit insertion over terrain seenin natural and false-color.

The Matter of Galaxy Clusters

Situated over 2,000,000,000 two billion)light-years from Earth, galaxies in cluster Abell 2390 (top) andMS2137.3-2353 (bottom are seen in the right hand panels above,false-color images from th HubbleSpace Telescope.Corresponding panels on the left reveal each cluster' x-rayappearance in images from the Chandra X-ray Observatory.While the Hubble images record the cluster's star-filled galaxies,the x-ray images show no galaxies at all ... onlymulti-million degree hot intracluster ga which glows in high energy x-rays.But there lies a profound mystery.The total mass in the galaxies on the right, plus themass of the hot gas on the left, falls far short of providing enough gravityto confine the hot gas withi the galaxy clusters.In fact the best accounting to datecan only find 13 per cent (!)of the total matter necessary Gravitational lensarcs visible in the deep Hubble imagesalso indicate these clusters have much more mass than directly identifiablein the Chandra and Hubble data.Astronomers conclude that most of the cluster matter i dark matter,invisible even to the combined far-seeing eyes of these orbitin astrophysical observatories.What is thenature of this cosmic dark matter?

Emission and Reflection in NGC 6559

Bright gas and dark dust permeate the space between stars in a nebula known as NGC 6559. The gas, primarily hydrogen, is responsible for the diffuse red glow of the emission nebula. As energetic light from neighboring stars ionizes interstellar hydrogen, protons and electrons recombine to emit light of very specific colors, including the red hue observed. Small dust particles reflect blue starlight efficiently and so creates the blue reflection nebulosity seen near two of the bright stars. Dust also absorbs visible light, causing the dark clouds and filaments visible. NGC 6559 lies about 5000 light-years away toward the constellation of Sagittarius.

The First Rocket Launch from Cape Canaveral

A new chapter in space flight began on 1950 July with the launch of the first rocket from Cape Canaveral, Florida: the Bumper 2. Shown above, the Bumper 2 was an ambitious two-stage rocket program that topped a V-2 missile base with a WAC Corporal rocket. The upper stage was able to reach then-record altitudes of almost 400 kilometers, higher than even modern Space Shuttles fly today. Launched under the direction of the General Electric Company, the Bumper 2 was used primarily for testing rocket systems and for research on the upper atmosphere. Bumper 2 rockets carried small payloads that allowed them to measure attributes including air temperature and cosmic ray impacts. Seven years later, the Soviet Union launched Sputnik I and Sputnik II, the first satellites into Earth orbit. In response, in 1958, the US created NASA.

The Sombrero Galaxy from VLT

Why does the Sombrero Galaxy look like a hat? Reasons include the Sombrero's unusually large and extended central bulge of stars, and dark prominent dust lanes that appear in a disk that we see nearly edge-on. Billions of old stars cause the diffuse glow of the extended central bulge. Close inspection of the bulge in the above photograph shows many points of light that are actually globular clusters.M104's spectacular dust rings harbor many younger and brighter stars, and show intricate details astronomers don't yet fully understand. The very center of the Sombrero glows across the electromagnetic spectrum, and is thought to house a large black hole. Fifty million-year-old light from the Sombrero Galaxy can be seen with a small telescope towards the constellation of Virgo.

The Radio Sky Tuned to 408MHz

Tune your radio telescope to 408MHz(408 million cycles per second) and check out the Radio Sky!You should find that frequency on you dial somewhere betweenUS broadcast television channels 13 and 14.In the 1970s large dish antennas atthree radio observatories, Jodrell Bank MPIfR, an Parkes Observatory,were used to do just that the data were combined to map the entire sky.Near this frequency,cosmic radio waves are generated by high energy electrons spiralingalong magnetic fields.In the resulting false color image, the galactic planeruns horizontally through the center, but n stars are visible.Instead, many of the bright sources near the planeare distant pulsars, star forming regions,and supernova remnants, while the gran looping structuresare pieces o bubbles blown by local stellar activity.External galaxies lik Centaurus A, located above the plane to theright of center, an the LMC (below and right)also shine in the Radio Sky.

Saturday 28 June 2008

X-Ray Stars and Winds in the Rosette Nebula

This mosaic of x-ray imagescuts a swath across the photogenicRosette Nebula, a stellar nursery 5,000 light-years from Earthin the constellation Monoceros theUnicorn.Constructed from data recorded by the orbitin Chandra X-ray Observatory,the mosaic spans less than 100 light-years and is colorcoded to show low energies in red and high energy x-rays in blue.At the upper right is the young star cluste NGC 2244, central tothe Rosette Nebula itself.The hot outer layers of the massive stars are seen to be copioussources of x-rays, but a diffuse x-ray glowalso pervades this cluster of newborn stars.Since these stars are so young (less than few million years old!) the diffusex-ray emission is thought to be powered by energetic collidingstellar winds ratherthan remnants of supernovae explosions,a final act in th life cycleof a massive star.Moving away from the center, south and east across the nebula(upper right to lower left),the hot, blustery environment gives way todense molecular gas, absorbing low energy x-rayswhile revealing the penetrating high energy x-rays from embedded stars.

Pluto New Horizons

Pluto'shorizon spans the foreground in this artist's vision,gazing sunward across that distant an not yet explored world.Titled New Horizons, the painting als depicts Pluto'scompanion, Charon, as a darkened, ghostly apparition witha luminou crescentagainst a starry background.Beyon Charon,the diminished Sun is immersed ina flattened cloud of zodiacal dust.Here, Pluto's ruddy colors are based on existin astronomicalobservations while imagined bu scientifically tenable detailsprovided by the artist include high atmospheric cirrus anddark plumes from surface vents, in analogy to Neptune's large moo Tritonexplored by th Voyager2 spacecraft in 1989.Craters suggest bombardment b KuiperBelt objects, a newly understoo population ofouter solar system bodies likel related to th Pluto-Charon system.NASA is now considering a future robotic reconnaissanc missionto Pluto-Charon and the Kuiper Belt which could reach the distantworlds late in the next decade.

Mars Engulfed

For months now Marshas been engulfed by a great dust storm, the biggestseen raging across th Red Planet i decades.As a result, these two Hubble Space Telescop stormwatch images from late June andearly September offer dramatically contrasting view of the martian surface.At left, the onset of smaller "seed" storms can be seen nearthe Hellas basin(lower right edge of Mars) and th northern polar cap.A similar surface view at right, taken over two months later,shows the fully developed extent of the obscuring global dust storm.The storm is reported to be waning, but planet-wide effects such as thewarming of the uppe martianatmosphere and cooling of the surface arestill being monitored daily b instruments on board the Mars GlobalSurveyor spacecraft.The present condition of the martian atmosphere i alsoimportant to the aerobraking MarsOdyssey spacecraft, scheduled to arriveat the Red Planet next week.

Monday 30 June 2008

Sunday 29 June 2008

Saturday 28 June 2008

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