2007 September 20
Northern Cygnus
Credit & Copyright: Robert Gendler
Bright, hot, supergiant star Deneb lies at top center in this gorgeous skyscape. The 20 frame mosaic spans an impressive 12 degrees across the northern end of Cygnus the Swan. Crowded with stars and luminous gas clouds along the plane of our Milky Way Galaxy, Cygnus is also home to the dark, obscuring Northern Coal Sack Nebula, extending from Deneb toward the bottom center of the view. The reddish glow of NGC 7000, the North America Nebula, and IC 5070, the Pelican Nebula, are at the upper left, but many other nebulae and star clusters are identifiable throughout the wide field. Of course, Deneb itself is the alpha star of Cygnus and is also known to northern hemisphere skygazers for its place in two asterisms -- marking the top of the Northern Cross and a vertex of the Summer Triangle.
Northern Cygnus
Credit & Copyright: Robert Gendler
Bright, hot, supergiant star Deneb lies at top center in this gorgeous skyscape. The 20 frame mosaic spans an impressive 12 degrees across the northern end of Cygnus the Swan. Crowded with stars and luminous gas clouds along the plane of our Milky Way Galaxy, Cygnus is also home to the dark, obscuring Northern Coal Sack Nebula, extending from Deneb toward the bottom center of the view. The reddish glow of NGC 7000, the North America Nebula, and IC 5070, the Pelican Nebula, are at the upper left, but many other nebulae and star clusters are identifiable throughout the wide field. Of course, Deneb itself is the alpha star of Cygnus and is also known to northern hemisphere skygazers for its place in two asterisms -- marking the top of the Northern Cross and a vertex of the Summer Triangle.
2007 September 21
Coronet in the Southern Crown
Credit: X-ray: NASA/ CXC/CfA/ J.Forbrich et al.; Infrared: NASA/ SSC/CfA/IRAC GTO Team
X-rays from young stars and infrared light from stars and cosmic dust are combined in this false color image of a star-forming region in Corona Australis, the Southern Crown. The small star grouping is fittingly known as the Coronet Cluster. A mere 420 light-years distant, the Coronet Cluster offers a relatively close-up view of stars and protostars evolving with a wide range of masses. The observations suggest that energetic x-rays come from the hot, extended stellar atmospheres or coronae of the Coronet stars. The tantalizing multi-wavelength view spans about 2 light-years and was produced using data from the orbiting Chandra Observatory (x-ray) and the Spitzer Space Telescope (infrared).
Coronet in the Southern Crown
Credit: X-ray: NASA/ CXC/CfA/ J.Forbrich et al.; Infrared: NASA/ SSC/CfA/IRAC GTO Team
X-rays from young stars and infrared light from stars and cosmic dust are combined in this false color image of a star-forming region in Corona Australis, the Southern Crown. The small star grouping is fittingly known as the Coronet Cluster. A mere 420 light-years distant, the Coronet Cluster offers a relatively close-up view of stars and protostars evolving with a wide range of masses. The observations suggest that energetic x-rays come from the hot, extended stellar atmospheres or coronae of the Coronet stars. The tantalizing multi-wavelength view spans about 2 light-years and was produced using data from the orbiting Chandra Observatory (x-ray) and the Spitzer Space Telescope (infrared).
2007 September 22
Pangea Ultima: Earth in 250 Million Years?
Credit & Copyright: C. R. Scotese (U. Texas at Arlington), PALEOMAP
Is this what will become of the Earth's surface? The surface of the Earth is broken up into several large plates that are slowly shifting. About 250 million years ago, the plates on which the present-day continents rest were positioned quite differently, so that all the landmasses were clustered together in one supercontinent now dubbed Pangea. About 250 million years from now, the plates are again projected to reposition themselves so that a single landmass dominates. The above simulation from the PALEAOMAP Project shows this giant landmass: Pangea Ultima. At that time, the Atlantic Ocean will be just a distant memory, and whatever beings inhabit Earth will be able to walk from North America to Africa.
Pangea Ultima: Earth in 250 Million Years?
Credit & Copyright: C. R. Scotese (U. Texas at Arlington), PALEOMAP
Is this what will become of the Earth's surface? The surface of the Earth is broken up into several large plates that are slowly shifting. About 250 million years ago, the plates on which the present-day continents rest were positioned quite differently, so that all the landmasses were clustered together in one supercontinent now dubbed Pangea. About 250 million years from now, the plates are again projected to reposition themselves so that a single landmass dominates. The above simulation from the PALEAOMAP Project shows this giant landmass: Pangea Ultima. At that time, the Atlantic Ocean will be just a distant memory, and whatever beings inhabit Earth will be able to walk from North America to Africa.
2007 September 23
The Equal Night
Credit: STS-68 Crew, NASA
Today, the Sun crosses the celestial equator heading south at 0951 UT. Known as the equinox, the astronomical event marks the first day of autumn in the northern hemisphere and spring in the south. Equinox means equal night and with the Sun on the celestial equator, Earth dwellers will experience nearly 12 hours of daylight and 12 hours of darkness. Of course, for those in the south, the days will grow longer with the Sun marching higher in the sky as summer approaches. A few weeks after the September Equinox of 1994, the Crew of the shuttle orbiter Endeavour recorded this image of the Sun poised above the Earth's limb. Glare illuminates Endeavour's vertical tail (pointing toward the Earth) along with radar equipment in the payload bay.
The Equal Night
Credit: STS-68 Crew, NASA
Today, the Sun crosses the celestial equator heading south at 0951 UT. Known as the equinox, the astronomical event marks the first day of autumn in the northern hemisphere and spring in the south. Equinox means equal night and with the Sun on the celestial equator, Earth dwellers will experience nearly 12 hours of daylight and 12 hours of darkness. Of course, for those in the south, the days will grow longer with the Sun marching higher in the sky as summer approaches. A few weeks after the September Equinox of 1994, the Crew of the shuttle orbiter Endeavour recorded this image of the Sun poised above the Earth's limb. Glare illuminates Endeavour's vertical tail (pointing toward the Earth) along with radar equipment in the payload bay.
2007 September 24
A Galactic Star Forming Region in Infrared
Credit: S. Carey (SSC/Caltech), JPL-Caltech, NASA
How do stars form? To help study this complex issue, astronomers took a deep image in infrared light of an active part of our Milky Way Galaxy where star formation is rampant. In IRDC G11.11-0.11, thick clouds of dust and gas are congealing into stars that are so dark that humans living there would see an empty night sky. The image, though, taken last year by the Spitzer Space Telescope in infrared light, shows vast glowing fields of gas and dust, indicating that much of this dust is heated by forming stars. The centers of some clouds, such as the snake-like structure on the upper left, are so thick and cold that they are dark even in infrared light. Many of the red dots are glowing dust shrouds centered on very young newly formed stars. The unusual red sphere below the snake is actually a supernova remnant, the glowing shell of a young star so massive it evolved rapidly and exploded. The region spans about 150 light years and lies about 10,000 light years away toward the constellation of Sagittarius.
A Galactic Star Forming Region in Infrared
Credit: S. Carey (SSC/Caltech), JPL-Caltech, NASA
How do stars form? To help study this complex issue, astronomers took a deep image in infrared light of an active part of our Milky Way Galaxy where star formation is rampant. In IRDC G11.11-0.11, thick clouds of dust and gas are congealing into stars that are so dark that humans living there would see an empty night sky. The image, though, taken last year by the Spitzer Space Telescope in infrared light, shows vast glowing fields of gas and dust, indicating that much of this dust is heated by forming stars. The centers of some clouds, such as the snake-like structure on the upper left, are so thick and cold that they are dark even in infrared light. Many of the red dots are glowing dust shrouds centered on very young newly formed stars. The unusual red sphere below the snake is actually a supernova remnant, the glowing shell of a young star so massive it evolved rapidly and exploded. The region spans about 150 light years and lies about 10,000 light years away toward the constellation of Sagittarius.
2007 September 25
Zodiacal Light and the False Dawn
Credit & Copyright: Yuri Beletsky (ESO)
An unusual triangle of light will be particularly bright near the eastern horizon before sunrise during the next two months for observers in Earth's northern hemisphere. Once considered a false dawn, this triangle of light is actually Zodiacal Light, light reflected from interplanetary dust particles. The triangle is clearly visible toward the left of the frame taken from the Paranal Observatory in Chile in July. Zodiacal dust orbits the Sun predominantly in the same plane as the planets: the ecliptic. Zodiacal light is so bright this time of year because the dust band is oriented nearly vertical at sunrise, so that the thick air near the horizon does not block out relatively bright reflecting dust. Zodiacal light is also bright for people in Earth's northern hemisphere in March and April just after sunset.
Zodiacal Light and the False Dawn
Credit & Copyright: Yuri Beletsky (ESO)
An unusual triangle of light will be particularly bright near the eastern horizon before sunrise during the next two months for observers in Earth's northern hemisphere. Once considered a false dawn, this triangle of light is actually Zodiacal Light, light reflected from interplanetary dust particles. The triangle is clearly visible toward the left of the frame taken from the Paranal Observatory in Chile in July. Zodiacal dust orbits the Sun predominantly in the same plane as the planets: the ecliptic. Zodiacal light is so bright this time of year because the dust band is oriented nearly vertical at sunrise, so that the thick air near the horizon does not block out relatively bright reflecting dust. Zodiacal light is also bright for people in Earth's northern hemisphere in March and April just after sunset.
2007 September 26
Saguaro Moon
Credit & Copyright: Stefan Seip (Astro Meeting)
A Full Moon rising can be a dramatic celestial sight, and Full Moons can have many names. For example, tonight's Full Moon, the one nearest the autumnal equinox in the northern hemisphere, is popularly called the Harvest Moon. According to lore the name is a fitting one because farmers could work late into the night at the end of the growing season harvesting crops by moonlight. In the same traditions, the Full Moon following the Harvest Moon is the Hunter's Moon. But, recorded on a trip to the American southwest, this contribution to compelling images of moonrise is appropriately titled Saguaro Moon.
Saguaro Moon
Credit & Copyright: Stefan Seip (Astro Meeting)
A Full Moon rising can be a dramatic celestial sight, and Full Moons can have many names. For example, tonight's Full Moon, the one nearest the autumnal equinox in the northern hemisphere, is popularly called the Harvest Moon. According to lore the name is a fitting one because farmers could work late into the night at the end of the growing season harvesting crops by moonlight. In the same traditions, the Full Moon following the Harvest Moon is the Hunter's Moon. But, recorded on a trip to the American southwest, this contribution to compelling images of moonrise is appropriately titled Saguaro Moon.
2007 September 27
Hole in the Sun
Credit: SOHO - EIT Consortium, ESA, NASA
The dark expanse below the equator of the Sun is a coronal hole -- a low density region extending above the surface where the solar magnetic field opens freely into interplanetary space. Shown in false color, the picture was recorded on September 19th in extreme ultraviolet light by the EIT instrument onboard the space-based SOHO observatory. Studied extensively from space since the 1960s in ultraviolet and x-ray light, coronal holes are known to be the source of the high-speed solar wind, atoms and electrons that flow outward along the open magnetic field lines. The solar wind streaming from this coronal hole triggered colorful auroral displays on planet Earth begining late last week, enjoyed by spaceweather watchers at high latitudes.
Hole in the Sun
Credit: SOHO - EIT Consortium, ESA, NASA
The dark expanse below the equator of the Sun is a coronal hole -- a low density region extending above the surface where the solar magnetic field opens freely into interplanetary space. Shown in false color, the picture was recorded on September 19th in extreme ultraviolet light by the EIT instrument onboard the space-based SOHO observatory. Studied extensively from space since the 1960s in ultraviolet and x-ray light, coronal holes are known to be the source of the high-speed solar wind, atoms and electrons that flow outward along the open magnetic field lines. The solar wind streaming from this coronal hole triggered colorful auroral displays on planet Earth begining late last week, enjoyed by spaceweather watchers at high latitudes.
2007 September 28
A Hole in Mars Close Up
Credit: HiRISE, MRO, LPL (U. Arizona), NASA
In a close-up from the HiRISE instrument onboard the Mars Reconnaissance Orbiter, this mysterious dark pit, about 150 meters across, lies on the north slope of ancient martian volcano Arsia Mons. Lacking raised rims and other impact crater characteristics, this pit and others like it were originally identified in visible light and infrared images from the Mars Odyssey and Mars Global Surveyor spacecraft. While the visible light images showed only darkness within, infrared thermal signatures indicated that the openings penetrated deep under the martian surface and perhaps were skylights to underground caverns. In this later image, the pit wall is partially illuminated by sunlight and seen to be nearly vertical, though the bottom, at least 78 meters below, is still not visible. The dark martian pits are thought to be related to collapse pits in the lava flow, similar to Hawaiian volcano pit craters.
A Hole in Mars Close Up
Credit: HiRISE, MRO, LPL (U. Arizona), NASA
In a close-up from the HiRISE instrument onboard the Mars Reconnaissance Orbiter, this mysterious dark pit, about 150 meters across, lies on the north slope of ancient martian volcano Arsia Mons. Lacking raised rims and other impact crater characteristics, this pit and others like it were originally identified in visible light and infrared images from the Mars Odyssey and Mars Global Surveyor spacecraft. While the visible light images showed only darkness within, infrared thermal signatures indicated that the openings penetrated deep under the martian surface and perhaps were skylights to underground caverns. In this later image, the pit wall is partially illuminated by sunlight and seen to be nearly vertical, though the bottom, at least 78 meters below, is still not visible. The dark martian pits are thought to be related to collapse pits in the lava flow, similar to Hawaiian volcano pit craters.
2007 September 29
Dawn Launch Mosaic
Credit & Copyright: Randy Pollock
Shortly after sunrise on Thursday at Cape Canaveral Air Force Station, the Dawn spacecraft began its journey to the asteroid belt, arcing eastward into a blue and cloudy sky. Dawn's voyage began on a conventional, chemically fueled Delta II rocket, but will continue with an innovative ion propulsion system. The spacecraft's extremely efficient ion engines will use electricity derived from solar power to ionize xenon atoms and generate a gentle but continuous thrust. After a four year interplanetary cruise, Dawn will orbit two small worlds, first Vesta and then Ceres. Vesta is one of the largest main belt asteroids, while nomenclature introduced by the International Astronomical Union in 2006 classifies nearly spherical Ceres as a dwarf planet.
Dawn Launch Mosaic
Credit & Copyright: Randy Pollock
Shortly after sunrise on Thursday at Cape Canaveral Air Force Station, the Dawn spacecraft began its journey to the asteroid belt, arcing eastward into a blue and cloudy sky. Dawn's voyage began on a conventional, chemically fueled Delta II rocket, but will continue with an innovative ion propulsion system. The spacecraft's extremely efficient ion engines will use electricity derived from solar power to ionize xenon atoms and generate a gentle but continuous thrust. After a four year interplanetary cruise, Dawn will orbit two small worlds, first Vesta and then Ceres. Vesta is one of the largest main belt asteroids, while nomenclature introduced by the International Astronomical Union in 2006 classifies nearly spherical Ceres as a dwarf planet.
2007 September 30
A Milky Way Band
Credit & Copyright: John P. Gleason, Celestial Images
Most bright stars in our Milky Way Galaxy reside in a disk. Since our Sun also resides in this disk, these stars appear to us as a diffuse band that circles the sky. The above panorama of a northern band of the Milky Way's disk covers 90 degrees and is a digitally created mosaic of several independent exposures. Scrolling right will display the rest of this spectacular picture. Visible are many bright stars, dark dust lanes, red emission nebulae, blue reflection nebulae, and clusters of stars. In addition to all this matter that we can see, astronomers suspect there exists even more dark matter that we cannot see.
A Milky Way Band
Credit & Copyright: John P. Gleason, Celestial Images
Most bright stars in our Milky Way Galaxy reside in a disk. Since our Sun also resides in this disk, these stars appear to us as a diffuse band that circles the sky. The above panorama of a northern band of the Milky Way's disk covers 90 degrees and is a digitally created mosaic of several independent exposures. Scrolling right will display the rest of this spectacular picture. Visible are many bright stars, dark dust lanes, red emission nebulae, blue reflection nebulae, and clusters of stars. In addition to all this matter that we can see, astronomers suspect there exists even more dark matter that we cannot see.
2007 October 1
The Small Cloud of Magellan
Credit & Copyright: St�phane Guisard
Portuguese navigator Ferdinand Magellan and his crew had plenty of time to study the southern sky during the first circumnavigation of planet Earth. As a result, two celestial wonders easily visible for southern hemisphere skygazers are known as the Clouds of Magellan. These cosmic clouds are now understood to be dwarf irregular galaxies, satellites of our larger spiral Milky Way Galaxy. The Small Magellanic Cloud pictured above actually spans 15,000 light-years or so and contains several hundred million stars. About 210,000 light-years distant in the constellation Tucana, it is the fourth closest of the Milky Way's known satellite galaxies, after the Canis Major and Sagittarius Dwarf galaxies and the Large Magellanic Cloud. This gorgeous view also includes two foreground globular star clusters NGC 362 (bottom right) and 47 Tucanae. Spectacular 47 Tucanae is a mere 13,000 light-years away and seen here to the left of the Small Magellanic Cloud.
The Small Cloud of Magellan
Credit & Copyright: St�phane Guisard
Portuguese navigator Ferdinand Magellan and his crew had plenty of time to study the southern sky during the first circumnavigation of planet Earth. As a result, two celestial wonders easily visible for southern hemisphere skygazers are known as the Clouds of Magellan. These cosmic clouds are now understood to be dwarf irregular galaxies, satellites of our larger spiral Milky Way Galaxy. The Small Magellanic Cloud pictured above actually spans 15,000 light-years or so and contains several hundred million stars. About 210,000 light-years distant in the constellation Tucana, it is the fourth closest of the Milky Way's known satellite galaxies, after the Canis Major and Sagittarius Dwarf galaxies and the Large Magellanic Cloud. This gorgeous view also includes two foreground globular star clusters NGC 362 (bottom right) and 47 Tucanae. Spectacular 47 Tucanae is a mere 13,000 light-years away and seen here to the left of the Small Magellanic Cloud.
2007 October 2
Tutulemma: Solar Eclipse Analemma
Credit & Copyright: Tunc Tezel and Cenk E. Tezel
If you went outside at exactly the same time every day and took a picture that included the Sun, how would the Sun appear to move? With great planning and effort, such a series of images can be taken. The figure-8 path the Sun follows over the course of a year is called an analemma. With even greater planning and effort, the series can include a total eclipse of the Sun as one of the images. Pictured is such a total solar eclipse analemma or Tutulemma - a term coined by the photographers based on the Turkish word for eclipse. The composite image sequence was recorded from Turkey starting in 2005. The base image for the sequence is from the total phase of a solar eclipse as viewed from Side, Turkey on 2006 March 29. Venus was also visible during totality, toward the lower right.
Tutulemma: Solar Eclipse Analemma
Credit & Copyright: Tunc Tezel and Cenk E. Tezel
If you went outside at exactly the same time every day and took a picture that included the Sun, how would the Sun appear to move? With great planning and effort, such a series of images can be taken. The figure-8 path the Sun follows over the course of a year is called an analemma. With even greater planning and effort, the series can include a total eclipse of the Sun as one of the images. Pictured is such a total solar eclipse analemma or Tutulemma - a term coined by the photographers based on the Turkish word for eclipse. The composite image sequence was recorded from Turkey starting in 2005. The base image for the sequence is from the total phase of a solar eclipse as viewed from Side, Turkey on 2006 March 29. Venus was also visible during totality, toward the lower right.
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2007 October 3
Comet Encke's Tail Ripped Off
Credit: Angelos Vourlidas (NRL) et al., SECCHI / STEREO, NASA
Swinging inside the orbit of Mercury, on April 20th periodic comet Encke encountered a blast from the Sun in the form of a Coronal Mass Ejection (CME). When CMEs, enormous clouds of energetic particles ejected from the Sun, slam into Earth's magnetosphere, they often trigger auroral displays. But in this case, the collison carried the tail of the comet away. The tail was likely ripped off by interacting magnetic fields rather than the mechanical pressure of the collision. Clicking on the two panel image will play a movie gif of the remarkable event as recorded by the Heliospheric Imager onboard the STEREO A spacecraft. In the movie, the time between frames is about 45 minutes, while the frames span about 14x20 million kilometers at the distance of the comet. Of course, similar collisions have happened before as the ancient comet loops through its 3.3 year solar orbit. So don't worry, Encke's tail grows back!
Comet Encke's Tail Ripped Off
Credit: Angelos Vourlidas (NRL) et al., SECCHI / STEREO, NASA
Swinging inside the orbit of Mercury, on April 20th periodic comet Encke encountered a blast from the Sun in the form of a Coronal Mass Ejection (CME). When CMEs, enormous clouds of energetic particles ejected from the Sun, slam into Earth's magnetosphere, they often trigger auroral displays. But in this case, the collison carried the tail of the comet away. The tail was likely ripped off by interacting magnetic fields rather than the mechanical pressure of the collision. Clicking on the two panel image will play a movie gif of the remarkable event as recorded by the Heliospheric Imager onboard the STEREO A spacecraft. In the movie, the time between frames is about 45 minutes, while the frames span about 14x20 million kilometers at the distance of the comet. Of course, similar collisions have happened before as the ancient comet loops through its 3.3 year solar orbit. So don't worry, Encke's tail grows back!
2007 October 4
50th Anniversary of Sputnik: Traveling Companion
Photo Credit: Courtesy NSSDC, NASA
Sputnik means "traveling companion". Despite the innocuous sounding name, the launch of planet Earth's first artificial moon, Sputnik 1, by the Soviet Union on October 4, 1957, changed the world and set in motion events which resulted in the creation of NASA and the race to the Moon. Sputnik 1 was a 184 pound, 22 inch diameter sphere with four whip antennas connected to battery powered transmitters. The transmitters broadcast a continuous "beeping" signal to an astounded earthbound audience for 23 days. A short month later, on November 3, the Soviet Union followed this success by launching a dog into orbit aboard Sputnik 2.
50th Anniversary of Sputnik: Traveling Companion
Photo Credit: Courtesy NSSDC, NASA
Sputnik means "traveling companion". Despite the innocuous sounding name, the launch of planet Earth's first artificial moon, Sputnik 1, by the Soviet Union on October 4, 1957, changed the world and set in motion events which resulted in the creation of NASA and the race to the Moon. Sputnik 1 was a 184 pound, 22 inch diameter sphere with four whip antennas connected to battery powered transmitters. The transmitters broadcast a continuous "beeping" signal to an astounded earthbound audience for 23 days. A short month later, on November 3, the Soviet Union followed this success by launching a dog into orbit aboard Sputnik 2.
2007 October 5
Starburst Cluster in NGC 3603
Credit: NASA, ESA, Hubble Heritage (STScI/AURA)-ESA/ Hubble Collaboration
Acknowledgment: J. Maiz Apellaniz (Inst. Astrofisica Andalucia) et al., & Davide de Martin (skyfactory.org)
A mere 20,000 light-years from the Sun lies NGC 3603, a resident of the nearby Carina spiral arm of our Milky Way Galaxy. NGC 3603 is well known to astronomers as one of the Milky Way's largest star-forming regions. The central open star cluster contains thousands of stars more massive than our Sun, stars that likely formed only one or two million years ago in a single burst of star formation. In fact, nearby NGC 3603 is thought to contain a convenient example of the massive star clusters that populate much more distant starburst galaxies. Surrounding the cluster are natal clouds of glowing interstellar gas and obscuring dust, sculpted by energetic stellar radiation and winds. Recorded by the Hubble's Advanced Camera for Surveys, the image spans about 17 light-years.
Starburst Cluster in NGC 3603
Credit: NASA, ESA, Hubble Heritage (STScI/AURA)-ESA/ Hubble Collaboration
Acknowledgment: J. Maiz Apellaniz (Inst. Astrofisica Andalucia) et al., & Davide de Martin (skyfactory.org)
A mere 20,000 light-years from the Sun lies NGC 3603, a resident of the nearby Carina spiral arm of our Milky Way Galaxy. NGC 3603 is well known to astronomers as one of the Milky Way's largest star-forming regions. The central open star cluster contains thousands of stars more massive than our Sun, stars that likely formed only one or two million years ago in a single burst of star formation. In fact, nearby NGC 3603 is thought to contain a convenient example of the massive star clusters that populate much more distant starburst galaxies. Surrounding the cluster are natal clouds of glowing interstellar gas and obscuring dust, sculpted by energetic stellar radiation and winds. Recorded by the Hubble's Advanced Camera for Surveys, the image spans about 17 light-years.
2007 October 6
X-ray Stars of Orion
Credit: E.Feigelson & K.Getman (PSU) et al., CXO, NASA
The stars of Orion shine brightly in visible light in planet Earth's night sky. The constellation harbors the closest large stellar nursery, the Great Nebula of Orion, a mere 1,500 light-years away. In fact, the apparently bright clump of stars near the center of this false color Chandra x-ray telescope picture are the massive stars of the Trapezium - the young star cluster which powers much of the nebula's visible-light glow. The stars shown in blue and orange are young sun-like stars; prodigious sources of x-rays thought to be produced in hot stellar coronae and surface flares in a young star's strong magnetic field. Our middle-aged Sun itself was probably thousands of times brighter in x-rays when, like the Trapezium stars, it was only a few million years old. The x-ray image spans about 2.5 light-years across the central region of the Orion Nebula.
X-ray Stars of Orion
Credit: E.Feigelson & K.Getman (PSU) et al., CXO, NASA
The stars of Orion shine brightly in visible light in planet Earth's night sky. The constellation harbors the closest large stellar nursery, the Great Nebula of Orion, a mere 1,500 light-years away. In fact, the apparently bright clump of stars near the center of this false color Chandra x-ray telescope picture are the massive stars of the Trapezium - the young star cluster which powers much of the nebula's visible-light glow. The stars shown in blue and orange are young sun-like stars; prodigious sources of x-rays thought to be produced in hot stellar coronae and surface flares in a young star's strong magnetic field. Our middle-aged Sun itself was probably thousands of times brighter in x-rays when, like the Trapezium stars, it was only a few million years old. The x-ray image spans about 2.5 light-years across the central region of the Orion Nebula.
2007 October 7
Two Million Galaxies
Credit & Copyright: S. Maddox (Nottingham U.) et al. APM Survey, Astrophys. Dept. Oxford U.
Our universe is filled with galaxies. Galaxies -- huge conglomerations of stars, gas, dust -- and mysterious dark matter are the basic building blocks of the large-scale universe. Although distant galaxies move away from each other as the universe expands, gravity attracts neighboring galaxies to each other, forming galaxy groups, clusters of galaxies, and even larger expansive filaments. Some of these structures are visible on one of the most comprehensive maps of the sky ever made in galaxies: the APM galaxy survey map completed in the early 1990s. Over 2 million galaxies are depicted above in a region 100 degrees across centered toward our Milky Way Galaxy's south pole. Bright regions indicate more galaxies, while bluer colors denote larger average galaxies. Dark ellipses have been cut away where bright local stars dominate the sky. Many scientific discoveries resulted from analyses of the map data, including that the universe was surprisingly complex on large scales.
Two Million Galaxies
Credit & Copyright: S. Maddox (Nottingham U.) et al. APM Survey, Astrophys. Dept. Oxford U.
Our universe is filled with galaxies. Galaxies -- huge conglomerations of stars, gas, dust -- and mysterious dark matter are the basic building blocks of the large-scale universe. Although distant galaxies move away from each other as the universe expands, gravity attracts neighboring galaxies to each other, forming galaxy groups, clusters of galaxies, and even larger expansive filaments. Some of these structures are visible on one of the most comprehensive maps of the sky ever made in galaxies: the APM galaxy survey map completed in the early 1990s. Over 2 million galaxies are depicted above in a region 100 degrees across centered toward our Milky Way Galaxy's south pole. Bright regions indicate more galaxies, while bluer colors denote larger average galaxies. Dark ellipses have been cut away where bright local stars dominate the sky. Many scientific discoveries resulted from analyses of the map data, including that the universe was surprisingly complex on large scales.
2007 October 8
Galaxy NGC 474: Cosmic Blender
Credit & Copyright: Mischa Schirmer
What's happening to galaxy NGC 474? The multiple layers of emission appear strangely complex and unexpected given the relatively featureless appearance of the elliptical galaxy in less deep images. The cause of the shells is currently unknown, but possibly tidal tails related to debris left over from absorbing numerous small galaxies in the past billion years. Alternatively the shells may be like ripples in a pond, where the ongoing collision with the spiral galaxy to the right of NGC 474 is causing density waves to ripple though the galactic giant. Regardless of the actual cause, the above image dramatically highlights the increasing consensus that the outer halos of most large galaxies are not really smooth but have complexities induced by frequent interactions with -- and accretions of -- smaller nearby galaxies. The halo of our own Milky Way Galaxy is one example of such unexpected complexity. NGC 474 spans about 250,000 light years and lies about 100 million light years distant toward the constellation of the Fish Pisces.
Galaxy NGC 474: Cosmic Blender
Credit & Copyright: Mischa Schirmer
What's happening to galaxy NGC 474? The multiple layers of emission appear strangely complex and unexpected given the relatively featureless appearance of the elliptical galaxy in less deep images. The cause of the shells is currently unknown, but possibly tidal tails related to debris left over from absorbing numerous small galaxies in the past billion years. Alternatively the shells may be like ripples in a pond, where the ongoing collision with the spiral galaxy to the right of NGC 474 is causing density waves to ripple though the galactic giant. Regardless of the actual cause, the above image dramatically highlights the increasing consensus that the outer halos of most large galaxies are not really smooth but have complexities induced by frequent interactions with -- and accretions of -- smaller nearby galaxies. The halo of our own Milky Way Galaxy is one example of such unexpected complexity. NGC 474 spans about 250,000 light years and lies about 100 million light years distant toward the constellation of the Fish Pisces.
2007 October 9
Aurora, Stars, Meteor, Lake, Alaska
Credit & Copyright: Bud Kuenzli
Sometimes, after your eyes adapt to the dark, a spectacular sky appears. In this case, a picturesque lake lies in front of you, beautiful green aurora flap high above you, brilliant stars shine far in the distance, and, for a brief moment, a bright meteor streaks by. This digitally fused breathtaking panorama was captured late last month across one of the Chena Lakes in North Pole, Alaska, USA, and includes the Pleiades open cluster of stars on the image right. The shot is unusual not only for the many wonders it has captured simultaneously, but because lakes this far north tend to freeze and become non-reflecting before a sky this dark can be photographed.
Aurora, Stars, Meteor, Lake, Alaska
Credit & Copyright: Bud Kuenzli
Sometimes, after your eyes adapt to the dark, a spectacular sky appears. In this case, a picturesque lake lies in front of you, beautiful green aurora flap high above you, brilliant stars shine far in the distance, and, for a brief moment, a bright meteor streaks by. This digitally fused breathtaking panorama was captured late last month across one of the Chena Lakes in North Pole, Alaska, USA, and includes the Pleiades open cluster of stars on the image right. The shot is unusual not only for the many wonders it has captured simultaneously, but because lakes this far north tend to freeze and become non-reflecting before a sky this dark can be photographed.
2007 October 10
The Strange Trailing Side of Saturn's Iapetus
Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA
What has happened to Saturn's moon Iapetus? Vast sections of this strange world are dark as coal, while others are as bright as ice. The composition of the dark material is unknown, but infrared spectra indicate that it possibly contains some dark form of carbon. Iapetus also has an unusual equatorial ridge that makes it appear like a walnut. To help better understand this mysterious moon, NASA directed the robotic Cassini spacecraft orbiting Saturn to swoop within 2,000 kilometers just last month. Pictured above, from about 75,000 kilometers out, Cassini's trajectory allowed unprecedented imaging of the hemisphere of Iapetus that is always trailing. A huge impact crater seen in the south spans a tremendous 450 kilometers and appears superposed on an older crater of similar size. The dark material is seen increasingly coating the easternmost part of Iapetus, darkening craters and highlands alike. Close inspection indicates that the dark coating typically faces the moon's equator. Whether Iapetus' colors are the result of unusual episodes of internal volcanism or external splattering remains unknown. This and other images from Cassini's Iapetus flyby are being studied for even greater clues.
The Strange Trailing Side of Saturn's Iapetus
Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA
What has happened to Saturn's moon Iapetus? Vast sections of this strange world are dark as coal, while others are as bright as ice. The composition of the dark material is unknown, but infrared spectra indicate that it possibly contains some dark form of carbon. Iapetus also has an unusual equatorial ridge that makes it appear like a walnut. To help better understand this mysterious moon, NASA directed the robotic Cassini spacecraft orbiting Saturn to swoop within 2,000 kilometers just last month. Pictured above, from about 75,000 kilometers out, Cassini's trajectory allowed unprecedented imaging of the hemisphere of Iapetus that is always trailing. A huge impact crater seen in the south spans a tremendous 450 kilometers and appears superposed on an older crater of similar size. The dark material is seen increasingly coating the easternmost part of Iapetus, darkening craters and highlands alike. Close inspection indicates that the dark coating typically faces the moon's equator. Whether Iapetus' colors are the result of unusual episodes of internal volcanism or external splattering remains unknown. This and other images from Cassini's Iapetus flyby are being studied for even greater clues.