1999 September 9
Comet Hale-Bopp Over the Superstition Mountains
Credit & Copyright: William R. Dellinges
Four years ago, Comet Hale-Bopp was discovered out near Jupiter falling toward the inner Solar System. Two years ago, it provided spectacular pictures as it neared its closest approach to the Sun. Still today, spectacular pictures of the brightest comet of the 1990s are surfacing. Above, Comet Hale-Bopp was photographed in 1997 behind the Superstition Mountains in Arizona. Clearly visible are the comets white dust tail that shines by reflected sunlight, and the blue ion tail that shines by glowing gas. Currently, there are several comets visible from the proper location with a small telescope. A comet visible to the unaided eye appears about once every five years.
Comet Hale-Bopp Over the Superstition Mountains
Credit & Copyright: William R. Dellinges
Four years ago, Comet Hale-Bopp was discovered out near Jupiter falling toward the inner Solar System. Two years ago, it provided spectacular pictures as it neared its closest approach to the Sun. Still today, spectacular pictures of the brightest comet of the 1990s are surfacing. Above, Comet Hale-Bopp was photographed in 1997 behind the Superstition Mountains in Arizona. Clearly visible are the comets white dust tail that shines by reflected sunlight, and the blue ion tail that shines by glowing gas. Currently, there are several comets visible from the proper location with a small telescope. A comet visible to the unaided eye appears about once every five years.
1999 September 10
Cassini Images The Moon
Credit: Cassini Imaging Team, University of Arizona, JPL, NASA
On August 18, the Cassini spacecraft flew by the Earth and Moon, then continued on its way to the outer solar system. Near its closest approach to the Moon, a distance of about 377,000 kilometers, controllers tested Cassini's imaging systems on this most familiar celestial body. This composite picture shows three resulting lunar images from the green, blue, and ultraviolet regions of the spectrum (left to right). Prominant in the upper right of each image is the dark, round Mare Crisium (Sea of Crises) at the eastern edge of the Moon's near side. With its cameras clearly functioning well, Cassini's next way-point will be Jupiter in December 2000. It is expected to arrive at its final destination, the Saturnian system, in 2004.
Cassini Images The Moon
Credit: Cassini Imaging Team, University of Arizona, JPL, NASA
On August 18, the Cassini spacecraft flew by the Earth and Moon, then continued on its way to the outer solar system. Near its closest approach to the Moon, a distance of about 377,000 kilometers, controllers tested Cassini's imaging systems on this most familiar celestial body. This composite picture shows three resulting lunar images from the green, blue, and ultraviolet regions of the spectrum (left to right). Prominant in the upper right of each image is the dark, round Mare Crisium (Sea of Crises) at the eastern edge of the Moon's near side. With its cameras clearly functioning well, Cassini's next way-point will be Jupiter in December 2000. It is expected to arrive at its final destination, the Saturnian system, in 2004.
1999 September 11
The Annotated Galactic Center
Credit: W. Keel (U. Alabama, Tuscaloosa), Cerro Tololo, Chile
The sky toward the center of our Galaxy is filled with a wide variety of celestial wonders. Many are easily visible with binoculars. Constellations near the galactic center include Sagittarius, Libra, Scorpius, Scutum, and Ophiuchus. Nebulae include Messier Objects M8, M16, M17, M20 and the Pipe Nebula. Open star clusters include M6, M7, M18, M21, M23, M24, M25. Globular star clusters include M9, M22, M28, M54, M69, M70. And don't forget Baade's Window. Click on the photo to get the un-annotated version.
The Annotated Galactic Center
Credit: W. Keel (U. Alabama, Tuscaloosa), Cerro Tololo, Chile
The sky toward the center of our Galaxy is filled with a wide variety of celestial wonders. Many are easily visible with binoculars. Constellations near the galactic center include Sagittarius, Libra, Scorpius, Scutum, and Ophiuchus. Nebulae include Messier Objects M8, M16, M17, M20 and the Pipe Nebula. Open star clusters include M6, M7, M18, M21, M23, M24, M25. Globular star clusters include M9, M22, M28, M54, M69, M70. And don't forget Baade's Window. Click on the photo to get the un-annotated version.
1999 September 12
Stonehenge: Ancient Monument to the Sun
Credit & Copyright: Clive Ruggles
Stonehenge consists of large carved stones assembled about 4000 years ago. Long before modern England was established, ancient inhabitants somehow moved 25 ton rocks nearly 20 miles to complete it. From similar constructs of the era, people could learn the time of year by watching how the Sun and Moon rose and set relative to accurately placed stones and pits. The placement of the boulders at Stonehenge, however, is not impressively accurate by today's standards, nor even by the standards of that time. Therefore, modern scholars interpret Stonehenge as a colossal monument to the Sun in celebration of the predictability of the seasons.
Stonehenge: Ancient Monument to the Sun
Credit & Copyright: Clive Ruggles
Stonehenge consists of large carved stones assembled about 4000 years ago. Long before modern England was established, ancient inhabitants somehow moved 25 ton rocks nearly 20 miles to complete it. From similar constructs of the era, people could learn the time of year by watching how the Sun and Moon rose and set relative to accurately placed stones and pits. The placement of the boulders at Stonehenge, however, is not impressively accurate by today's standards, nor even by the standards of that time. Therefore, modern scholars interpret Stonehenge as a colossal monument to the Sun in celebration of the predictability of the seasons.
1999 September 13
Supernova Remnant N132D in X-Rays
Credit: Chandra X-ray Observatory, NASA
Thousands of years after a star explodes, an expanding remnant may still glow brightly. Such is the case with N132D, a supernova remnant located in the neighboring Large Magellanic Cloud galaxy. The expanding shell from this explosion now spans 80 light-years and has swept up about 600 Suns worth of mass. The bright regions surrounding the lower right of this X-ray image result from a collision with an even more massive molecular cloud. Towards the upper left, the supernova remnant expands more rapidly into less dense region of space. This image is one of the first ever taken with the High Resolution Camera onboard the orbiting Chandra X-ray Observatory, and records details being analyzed for the first time.
Supernova Remnant N132D in X-Rays
Credit: Chandra X-ray Observatory, NASA
Thousands of years after a star explodes, an expanding remnant may still glow brightly. Such is the case with N132D, a supernova remnant located in the neighboring Large Magellanic Cloud galaxy. The expanding shell from this explosion now spans 80 light-years and has swept up about 600 Suns worth of mass. The bright regions surrounding the lower right of this X-ray image result from a collision with an even more massive molecular cloud. Towards the upper left, the supernova remnant expands more rapidly into less dense region of space. This image is one of the first ever taken with the High Resolution Camera onboard the orbiting Chandra X-ray Observatory, and records details being analyzed for the first time.
1999 September 14
The Colorful Orion Nebula
Credit: Gary Bernstein (U. Michigan); Copyright: U. Michigan, Lucent
The Great Nebula in Orion is a colorful place. Visible to the unaided eye as a fuzzy patch in the constellation of Orion, this image taken with the Big Throughput Camera shows the Orion Nebula to be a busy neighborhood of young stars, hot gas, and dark dust. The power behind much of the Orion Nebula (M42) is the Trapezium - four of the brightest stars in the nebula. The eerie blue glow surrounding the bright stars pictured here is their own starlight reflected by nearby dust. Hot oxygen and hydrogen gases cause the extended green and pink glows, respectively. Dark brown dust filaments cover much of the region. The whole Orion Nebula cloud complex, which includes the Horsehead Nebula, will slowly disperse over the next 100,000 years.
The Colorful Orion Nebula
Credit: Gary Bernstein (U. Michigan); Copyright: U. Michigan, Lucent
The Great Nebula in Orion is a colorful place. Visible to the unaided eye as a fuzzy patch in the constellation of Orion, this image taken with the Big Throughput Camera shows the Orion Nebula to be a busy neighborhood of young stars, hot gas, and dark dust. The power behind much of the Orion Nebula (M42) is the Trapezium - four of the brightest stars in the nebula. The eerie blue glow surrounding the bright stars pictured here is their own starlight reflected by nearby dust. Hot oxygen and hydrogen gases cause the extended green and pink glows, respectively. Dark brown dust filaments cover much of the region. The whole Orion Nebula cloud complex, which includes the Horsehead Nebula, will slowly disperse over the next 100,000 years.
1999 September 15
The Big Corona
Credit & Copyright: Fred Espenak (NASA /GSFC)
Most photographs don't adequately portray the magnificence of the Sun's corona. Seeing the corona first-hand during a total solar eclipse is best. The human eye can adapt to see features and extent that photographic film usually cannot. Welcome, however, to the digital age. The above picture is a combination of twenty-two photographs that were digitally processed to highlight faint features. The outer pictures of the Sun's corona were digitally altered to enhance dim, outlying waves and filaments. The inner pictures of the usually dark Moon were enhanced to bring out its faint glow from doubly reflected sunlight. Shadow seekers need not fret, though, since as yet there is no way that digital image processing can mimic the fun involved in experiencing a total solar eclipse.
The Big Corona
Credit & Copyright: Fred Espenak (NASA /GSFC)
Most photographs don't adequately portray the magnificence of the Sun's corona. Seeing the corona first-hand during a total solar eclipse is best. The human eye can adapt to see features and extent that photographic film usually cannot. Welcome, however, to the digital age. The above picture is a combination of twenty-two photographs that were digitally processed to highlight faint features. The outer pictures of the Sun's corona were digitally altered to enhance dim, outlying waves and filaments. The inner pictures of the usually dark Moon were enhanced to bring out its faint glow from doubly reflected sunlight. Shadow seekers need not fret, though, since as yet there is no way that digital image processing can mimic the fun involved in experiencing a total solar eclipse.
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1999 September 16
The Incredible Expanding Cat's Eye
Credit: Arsen R. Hajian (USNO), Yervant Terzian (Cornell)
Watch closely. As this animation blinks between two Hubble Space Telescope images of NGC 6543 - the first from 1994 and the second from 1997 - the intricate filaments of this nebula are seen to shift. The shift is due to the actual expansion of this gaseous shroud shed by a dying star! NGC 6543 is more popularly known as the Cat's Eye Nebula. Classified as a "planetary nebula", its complex, interwoven shells of expanding gas have been castoff by the central star as it evolves from a red giant to its final white dwarf phase. The planetary nebula phase of a star's life is known to be relatively brief, lasting 10,000 years or so. In fact, combined with other data, this nebula's detectable shift over a three year period allows the expansion age of its bright inner shells to be estimated at only around 1,000 years while its distance can be gauged at about 3,000 light-years.
The Incredible Expanding Cat's Eye
Credit: Arsen R. Hajian (USNO), Yervant Terzian (Cornell)
Watch closely. As this animation blinks between two Hubble Space Telescope images of NGC 6543 - the first from 1994 and the second from 1997 - the intricate filaments of this nebula are seen to shift. The shift is due to the actual expansion of this gaseous shroud shed by a dying star! NGC 6543 is more popularly known as the Cat's Eye Nebula. Classified as a "planetary nebula", its complex, interwoven shells of expanding gas have been castoff by the central star as it evolves from a red giant to its final white dwarf phase. The planetary nebula phase of a star's life is known to be relatively brief, lasting 10,000 years or so. In fact, combined with other data, this nebula's detectable shift over a three year period allows the expansion age of its bright inner shells to be estimated at only around 1,000 years while its distance can be gauged at about 3,000 light-years.
1999 September 17
M3: Half A Million Stars
Credit: Barbara Mochejska (Warsaw University), Andrew Szentgyorgyi (CfA), FLWO
This immense ball of half a million stars older than the sun lies 30,000 light-years above the plane of our Galaxy. Cataloged as M3 (and NGC 5272), it is one of about 250 globular star clusters which roam our galactic halo. Individual stars are difficult to distinguished in the densely packed core but colors are apparent for the bright stars on the cluster's outskirts. M3's many cool "red" giant stars take on a yellowish cast in this lovely composite image while hotter giants and pulsating variable stars look light blue.
M3: Half A Million Stars
Credit: Barbara Mochejska (Warsaw University), Andrew Szentgyorgyi (CfA), FLWO
This immense ball of half a million stars older than the sun lies 30,000 light-years above the plane of our Galaxy. Cataloged as M3 (and NGC 5272), it is one of about 250 globular star clusters which roam our galactic halo. Individual stars are difficult to distinguished in the densely packed core but colors are apparent for the bright stars on the cluster's outskirts. M3's many cool "red" giant stars take on a yellowish cast in this lovely composite image while hotter giants and pulsating variable stars look light blue.
1999 September 18
Mercury Astronauts and a Redstone
Credit: NASA
Space suited project Mercury astronauts John H. Glenn, Virgil I. Grissom, and Alan B. Shepard Jr. (left to right) are posing in front of a Redstone rocket in this vintage 1961 NASA publicity photo. Project Mercury was the first U.S. program designed to put humans in space. It resulted in 6 flights using one-man capsules and Redstone and Atlas rockets. Shortly after the first U.S. manned flight on May 5, 1961, a suborbital flight piloted by Alan Shepard, President Kennedy announced the goal of a manned lunar landing by 1970. This goal was achieved by NASA's Apollo program and Shepard himself walked on the moon as commander of the Apollo 14 mission. Alan Shepard passed away in 1998. Virgil Grissom died in a tragic fire during an Apollo launch pad test in 1967. Senator John Glenn flew again on the 25th voyage of the Space Shuttle Discovery.
Mercury Astronauts and a Redstone
Credit: NASA
Space suited project Mercury astronauts John H. Glenn, Virgil I. Grissom, and Alan B. Shepard Jr. (left to right) are posing in front of a Redstone rocket in this vintage 1961 NASA publicity photo. Project Mercury was the first U.S. program designed to put humans in space. It resulted in 6 flights using one-man capsules and Redstone and Atlas rockets. Shortly after the first U.S. manned flight on May 5, 1961, a suborbital flight piloted by Alan Shepard, President Kennedy announced the goal of a manned lunar landing by 1970. This goal was achieved by NASA's Apollo program and Shepard himself walked on the moon as commander of the Apollo 14 mission. Alan Shepard passed away in 1998. Virgil Grissom died in a tragic fire during an Apollo launch pad test in 1967. Senator John Glenn flew again on the 25th voyage of the Space Shuttle Discovery.
1999 September 19
Interstellar Dust-Bunnies of NGC 891
Credit: C. Howk & B. Savage (Wisconsin); N. Sharp (NOAO)
Copyright: WIYN, Inc., 3.5-m WIYN Telescope
What is going on in NGC 891? This galaxy appeared previously to be very similar to our own Milky Way Galaxy: a spiral galaxy seen nearly edge-on. However, recent high-resolution images of NGC 891's dust show unusual filamentary patterns extending well away from its Galactic disk. This interstellar dust was probably thrown out of the galactic disk toward the halo by stellar supernovae explosions. Because dust is so fragile, its appearance after surviving disk expulsion can be very telling. Newly discovered phenomena, however, sometimes appear so complex that more questions are raised than are answered.
Interstellar Dust-Bunnies of NGC 891
Credit: C. Howk & B. Savage (Wisconsin); N. Sharp (NOAO)
Copyright: WIYN, Inc., 3.5-m WIYN Telescope
What is going on in NGC 891? This galaxy appeared previously to be very similar to our own Milky Way Galaxy: a spiral galaxy seen nearly edge-on. However, recent high-resolution images of NGC 891's dust show unusual filamentary patterns extending well away from its Galactic disk. This interstellar dust was probably thrown out of the galactic disk toward the halo by stellar supernovae explosions. Because dust is so fragile, its appearance after surviving disk expulsion can be very telling. Newly discovered phenomena, however, sometimes appear so complex that more questions are raised than are answered.
1999 September 20
Io in True Color
Credit: Galileo Project, JPL, NASA
The strangest moon in the Solar System is bright yellow. This recently released picture, showing Io's true colors, was taken in July by the Galileo spacecraft currently orbiting Jupiter. Io's colors derive from sulfur and molten silicate rock. The unusual surface of Io is kept very young by its system of active volcanoes. The intense tidal gravity of Jupiter stretches Io and damps wobbles caused by Jupiter's other Galilean moons. The resulting friction greatly heats Io's interior, causing molten rock to explode through the surface. Io's volcanoes are so active that they are effectively turning the whole moon inside out. Some of Io's volcanic lava is so hot it glows in the dark.
Io in True Color
Credit: Galileo Project, JPL, NASA
The strangest moon in the Solar System is bright yellow. This recently released picture, showing Io's true colors, was taken in July by the Galileo spacecraft currently orbiting Jupiter. Io's colors derive from sulfur and molten silicate rock. The unusual surface of Io is kept very young by its system of active volcanoes. The intense tidal gravity of Jupiter stretches Io and damps wobbles caused by Jupiter's other Galilean moons. The resulting friction greatly heats Io's interior, causing molten rock to explode through the surface. Io's volcanoes are so active that they are effectively turning the whole moon inside out. Some of Io's volcanic lava is so hot it glows in the dark.
1999 September 21
The Quintuplet Star Cluster
Credit: Don Figer (STScI) et al., NASA
Bright clusters of stars form and disperse near the center of our Galaxy. Four million years ago the Quintuplet Cluster, pictured above, formed and is now slowly dispersing. The Quintuplet Cluster is located within 100 light-years of the Galactic center, and is home to the brightest star yet cataloged in our Galaxy: the Pistol Star. Objects near our Galactic center are usually hidden from view by opaque dust. This recently-released picture was able to capture the cluster in infrared light, though, with the NICMOS camera onboard the orbiting Hubble Space Telescope. The young Quintuplet Cluster is one of the most massive open clusters yet discovered, but still much less massive than the ancient globular clusters that orbit in the distant halo. Some of the bright white stars visible above may be on the verge of blowing themselves up in a spectacular supernova.
The Quintuplet Star Cluster
Credit: Don Figer (STScI) et al., NASA
Bright clusters of stars form and disperse near the center of our Galaxy. Four million years ago the Quintuplet Cluster, pictured above, formed and is now slowly dispersing. The Quintuplet Cluster is located within 100 light-years of the Galactic center, and is home to the brightest star yet cataloged in our Galaxy: the Pistol Star. Objects near our Galactic center are usually hidden from view by opaque dust. This recently-released picture was able to capture the cluster in infrared light, though, with the NICMOS camera onboard the orbiting Hubble Space Telescope. The young Quintuplet Cluster is one of the most massive open clusters yet discovered, but still much less massive than the ancient globular clusters that orbit in the distant halo. Some of the bright white stars visible above may be on the verge of blowing themselves up in a spectacular supernova.
1999 September 22
Halos Around the Ring Nebula
Credit: Subaru 8.3-m Telescope, NAOJ
What's happened to the Ring Nebula? The familiar Ring that can be seen with a small back-yard telescope takes on a new look when viewed in dim light. The above recently-released, false-color image taken by the giant Subaru Telescope shows details of giant halos of diffuse gas that are seen to envelop the entire structure. The Ring Nebula, also known as M57, is an elongated planetary nebula, a type of nebula that is created when a Sun-like star evolves to throw off its outer atmosphere and becomes a white dwarf. The Ring Nebula is about 2000 light-years away, and the main ring spans about one light-year. The origin and future evolution of the Ring Nebula's outer halos is still being investigated.
Halos Around the Ring Nebula
Credit: Subaru 8.3-m Telescope, NAOJ
What's happened to the Ring Nebula? The familiar Ring that can be seen with a small back-yard telescope takes on a new look when viewed in dim light. The above recently-released, false-color image taken by the giant Subaru Telescope shows details of giant halos of diffuse gas that are seen to envelop the entire structure. The Ring Nebula, also known as M57, is an elongated planetary nebula, a type of nebula that is created when a Sun-like star evolves to throw off its outer atmosphere and becomes a white dwarf. The Ring Nebula is about 2000 light-years away, and the main ring spans about one light-year. The origin and future evolution of the Ring Nebula's outer halos is still being investigated.
1999 September 23
Equinox and Eruptive Prominence
Credit: SOHO - EIT Consortium, ESA, NASA
Today, the Sun crosses the celestial equator and seasons change from Summer to Fall in the north and Winter to Spring in the southern hemisphere. Defined by the Sun's position in sky the event is known as an equinox - the length of daylight is equal to the length of night. Just last week the active Sun produced the dramatic eruptive prominence seen in this extreme ultraviolet picture from the space-based SOHO observatory. The hot plasma is lofted above the solar surface by twisting magnetic fields. How big is the prominence? Click on the image to view the larger full-sun picture. At the same scale, planet Earth would likely still appear smaller than your cursor.
Equinox and Eruptive Prominence
Credit: SOHO - EIT Consortium, ESA, NASA
Today, the Sun crosses the celestial equator and seasons change from Summer to Fall in the north and Winter to Spring in the southern hemisphere. Defined by the Sun's position in sky the event is known as an equinox - the length of daylight is equal to the length of night. Just last week the active Sun produced the dramatic eruptive prominence seen in this extreme ultraviolet picture from the space-based SOHO observatory. The hot plasma is lofted above the solar surface by twisting magnetic fields. How big is the prominence? Click on the image to view the larger full-sun picture. At the same scale, planet Earth would likely still appear smaller than your cursor.
1999 September 24
Cometary Globules In Orion
Credit: David Theil (CASA), IRAS
Intense ultraviolet light from massive, hot stars in the Orion region has sculpted and compressed clouds of dust and gas in to distinctively shaped Cometary Globules. Seen in this IRAS infrared image recorded at a wavelength sensitive to emission from dust, the elongated globules are easily visible along with a bright region which corresponds to the Trapezium star cluster. Otherwise known as the Witch Head Nebula, IC 2118 is the string of globules near the middle right. Suggestively similar to comets in general appearance only, Cometary Globules are interstellar condensations on a vastly different scale. These are likely related to star formation episodes in the Orion molecular cloud. Besides those indicated by the arrows, more comet-shaped clouds or globules are present in this image.
Cometary Globules In Orion
Credit: David Theil (CASA), IRAS
Intense ultraviolet light from massive, hot stars in the Orion region has sculpted and compressed clouds of dust and gas in to distinctively shaped Cometary Globules. Seen in this IRAS infrared image recorded at a wavelength sensitive to emission from dust, the elongated globules are easily visible along with a bright region which corresponds to the Trapezium star cluster. Otherwise known as the Witch Head Nebula, IC 2118 is the string of globules near the middle right. Suggestively similar to comets in general appearance only, Cometary Globules are interstellar condensations on a vastly different scale. These are likely related to star formation episodes in the Orion molecular cloud. Besides those indicated by the arrows, more comet-shaped clouds or globules are present in this image.
1999 September 25
Twistin' By The Lagoon
Credit: A. Caulet (ST-ECF, ESA), NASA
The awesome spectacle of starbirth produces extreme stellar winds and intense energetic starlight -- bombarding dusty molecular clouds inside the Lagoon Nebula (M8). At least two long funnel shaped clouds, each roughly half a light-year long, have apparently been formed by this activity. They extend from the upper left of this close-up of the bright area of the Lagoon known as 'the Hour Glass'. Are these interstellar funnel clouds actually swirling, twisting analogs to Earthly tornados? It's possible. As energy from nearby young hot stars, like the one at lower right, pours into the cool dust and gas, large temperature differences in adjoining regions can be created generating shearing winds. This picture is a reprocessed HST image made in 1995 as researchers explored this nearby (5,000 light-year distant) star forming region which lies in the direction of Sagittarius.
Twistin' By The Lagoon
Credit: A. Caulet (ST-ECF, ESA), NASA
The awesome spectacle of starbirth produces extreme stellar winds and intense energetic starlight -- bombarding dusty molecular clouds inside the Lagoon Nebula (M8). At least two long funnel shaped clouds, each roughly half a light-year long, have apparently been formed by this activity. They extend from the upper left of this close-up of the bright area of the Lagoon known as 'the Hour Glass'. Are these interstellar funnel clouds actually swirling, twisting analogs to Earthly tornados? It's possible. As energy from nearby young hot stars, like the one at lower right, pours into the cool dust and gas, large temperature differences in adjoining regions can be created generating shearing winds. This picture is a reprocessed HST image made in 1995 as researchers explored this nearby (5,000 light-year distant) star forming region which lies in the direction of Sagittarius.
1999 September 26
M83: A Barred Spiral Galaxy
Credit: David Malin (AAO), AATB
M83 is a bright spiral galaxy that can be found with a small telescope in the constellation of Hydra. It takes light about 15 million years to reach us from M83. M83 is quite a typical spiral - much like our own Milky Way Galaxy. Spiral galaxies contains many billions of stars, the youngest of which inhabit the spiral arms and glow strongly in blue light. Dark dust lanes are mixed in with the stars and help define M83's marked spiral structure. The space between the spiral arms is also filled with stars - but stars that are typically more dim and red. The stars and gas in spiral arms seem to be responding to much more mass than is visible here, implying that galaxies are predominantly composed of some sort of dark matter. Finding the nature of this dark matter remains one of the great challenges of modern science.
M83: A Barred Spiral Galaxy
Credit: David Malin (AAO), AATB
M83 is a bright spiral galaxy that can be found with a small telescope in the constellation of Hydra. It takes light about 15 million years to reach us from M83. M83 is quite a typical spiral - much like our own Milky Way Galaxy. Spiral galaxies contains many billions of stars, the youngest of which inhabit the spiral arms and glow strongly in blue light. Dark dust lanes are mixed in with the stars and help define M83's marked spiral structure. The space between the spiral arms is also filled with stars - but stars that are typically more dim and red. The stars and gas in spiral arms seem to be responding to much more mass than is visible here, implying that galaxies are predominantly composed of some sort of dark matter. Finding the nature of this dark matter remains one of the great challenges of modern science.
1999 September 27
Our Galaxy in Stars, Gas, and Dust
Credit & Copyright: John P. Gleason, Celestial Images
The disk of our Milky Way Galaxy is home to hot nebulae, cold dust, and billions of stars. The red nebulae visible in the above contrast-enhanced picture are primarily emission nebulae, glowing clouds of hydrogen gas heated by nearby, bright, young stars. The blue nebulae are primarily reflection nebulae, clouds of gas and fine dust reflecting the light of nearby bright stars. Perhaps the most striking, though, are the areas of darkness, including the Pipe Nebula visible on the image top left. These are lanes of thick dust, many times containing relatively cold molecular clouds of gas. Dust is so plentiful that it obscures the Galactic Center in visible light, hiding its true direction until discovered early this century. The diffuse glow comes from billions of older, fainter stars like our Sun, which are typically much older than any of the nebulae. Most of the mass of our Galaxy remains in a form currently unknown.
Our Galaxy in Stars, Gas, and Dust
Credit & Copyright: John P. Gleason, Celestial Images
The disk of our Milky Way Galaxy is home to hot nebulae, cold dust, and billions of stars. The red nebulae visible in the above contrast-enhanced picture are primarily emission nebulae, glowing clouds of hydrogen gas heated by nearby, bright, young stars. The blue nebulae are primarily reflection nebulae, clouds of gas and fine dust reflecting the light of nearby bright stars. Perhaps the most striking, though, are the areas of darkness, including the Pipe Nebula visible on the image top left. These are lanes of thick dust, many times containing relatively cold molecular clouds of gas. Dust is so plentiful that it obscures the Galactic Center in visible light, hiding its true direction until discovered early this century. The diffuse glow comes from billions of older, fainter stars like our Sun, which are typically much older than any of the nebulae. Most of the mass of our Galaxy remains in a form currently unknown.
1999 September 28
Mystery Object Explained
Credit: S. G. Djorgovski et al., DPOSS Team, Palomar Observatory
Explorers often discover the unexpected. Such was the case when the Second Palomar Observatory Sky Survey chanced upon the unusual object circled in the above photograph. The so-called mystery object appeared star-like but displayed colors unlike most stars or quasars. Further investigation has now revealed the object to be a Broad Absorption Line (BAL) quasar, a relatively rare type of active center of a distant galaxy. Different atoms and molecules in the absorbing gas surrounding the BAL quasar's center probably cause the unusual colors. We are fortunate enough to live in the fascinating age when much of the universe is being investigated for the first time, so exciting - and often unexpected - discoveries are sure to continue.
Mystery Object Explained
Credit: S. G. Djorgovski et al., DPOSS Team, Palomar Observatory
Explorers often discover the unexpected. Such was the case when the Second Palomar Observatory Sky Survey chanced upon the unusual object circled in the above photograph. The so-called mystery object appeared star-like but displayed colors unlike most stars or quasars. Further investigation has now revealed the object to be a Broad Absorption Line (BAL) quasar, a relatively rare type of active center of a distant galaxy. Different atoms and molecules in the absorbing gas surrounding the BAL quasar's center probably cause the unusual colors. We are fortunate enough to live in the fascinating age when much of the universe is being investigated for the first time, so exciting - and often unexpected - discoveries are sure to continue.
1999 September 29
The Crab Nebula in X-Rays
Credit: Chandra X-ray Observatory, NASA
Why does the Crab Nebula still glow? In the year 1054 A.D. a supernova was observed that left a nebula that even today glows brightly in every color possible, across the entire electromagnetic spectrum. At the nebula's center is an ultra-dense neutron star that rotates 30 times a second. The power liberated as this neutron star slows its rotation matches the power radiated by the Crab Nebula. The above picture by the recently launched Chandra X-Ray Observatory shows new details of the nebula's center in X-ray light, yielding important clues to how the neutron star powers the nebula. Visible are rings of high-energy particles that are being flung outward near light-speed from the center, and powerful jets emerging from the poles. Astrophysicists continue to study and learn from this unusual engine which continually transfers 30 million times more power than lightning at nearly perfect efficiency.
The Crab Nebula in X-Rays
Credit: Chandra X-ray Observatory, NASA
Why does the Crab Nebula still glow? In the year 1054 A.D. a supernova was observed that left a nebula that even today glows brightly in every color possible, across the entire electromagnetic spectrum. At the nebula's center is an ultra-dense neutron star that rotates 30 times a second. The power liberated as this neutron star slows its rotation matches the power radiated by the Crab Nebula. The above picture by the recently launched Chandra X-Ray Observatory shows new details of the nebula's center in X-ray light, yielding important clues to how the neutron star powers the nebula. Visible are rings of high-energy particles that are being flung outward near light-speed from the center, and powerful jets emerging from the poles. Astrophysicists continue to study and learn from this unusual engine which continually transfers 30 million times more power than lightning at nearly perfect efficiency.