2003 April 30
A Lenticular Cloud Over New Hampshire
Credit & Copyright: J. D. Rufo, J. Koermer, Plymouth State College
Why does this cloud look so strange? Actually, pictured above are several clouds all stacked up into one striking lenticular cloud. Normally, air moves much more horizontally than it does vertically. Smetimes, however, such as when wind comes off of a mountain or a hill, relatively strong vertical oscillations take place as the air stabilizes. The dry air at the top of an oscillation may be quite stratified in moisture content, and hence forms clouds at each layer where the air saturates with moisture. The result can be a lenticular cloud with a strongly layered appearance. The above picture was taken in 1999 over Plymouth, New Hampshire, USA. The same lenticular cloud also looks strange when photographed from 30 kilometers away.
A Lenticular Cloud Over New Hampshire
Credit & Copyright: J. D. Rufo, J. Koermer, Plymouth State College
Why does this cloud look so strange? Actually, pictured above are several clouds all stacked up into one striking lenticular cloud. Normally, air moves much more horizontally than it does vertically. Smetimes, however, such as when wind comes off of a mountain or a hill, relatively strong vertical oscillations take place as the air stabilizes. The dry air at the top of an oscillation may be quite stratified in moisture content, and hence forms clouds at each layer where the air saturates with moisture. The result can be a lenticular cloud with a strongly layered appearance. The above picture was taken in 1999 over Plymouth, New Hampshire, USA. The same lenticular cloud also looks strange when photographed from 30 kilometers away.
2003 May 1
The Energetic Jet from Centaurus A
Credit: M. J. Hardcastle (Univ. Bristol), et al.
X-ray; Chandra Observatory, NASA / Radio; NRAO, VLA
The center of well-studied active galaxy Centaurus A is hidden from the view of optical telescopes by a cosmic jumble of stars, gas, and dust. But both radio and x-ray telescopes can trace the remarkable jet of high-energy particles streaming from the galaxy's core. With Cen A's central region at the lower right, this composite false-color image shows the radio emission in red and x-rays in blue over the inner 4,000 light-years of the jet. One of the most detailed images of its kind, the picture shows how the x-ray and radio emitting sites are related along the jet, providing a road map to understanding the energetic stream. Extracting its energy from a supermassive black hole at the galaxy's center, the jet is confined to a relatively narrow angle and seems to produce most of its x-rays (bluer colors) at the upper left, farther from the core, where the jet begins to collide with Centaurus A's denser gas.
The Energetic Jet from Centaurus A
Credit: M. J. Hardcastle (Univ. Bristol), et al.
X-ray; Chandra Observatory, NASA / Radio; NRAO, VLA
The center of well-studied active galaxy Centaurus A is hidden from the view of optical telescopes by a cosmic jumble of stars, gas, and dust. But both radio and x-ray telescopes can trace the remarkable jet of high-energy particles streaming from the galaxy's core. With Cen A's central region at the lower right, this composite false-color image shows the radio emission in red and x-rays in blue over the inner 4,000 light-years of the jet. One of the most detailed images of its kind, the picture shows how the x-ray and radio emitting sites are related along the jet, providing a road map to understanding the energetic stream. Extracting its energy from a supermassive black hole at the galaxy's center, the jet is confined to a relatively narrow angle and seems to produce most of its x-rays (bluer colors) at the upper left, farther from the core, where the jet begins to collide with Centaurus A's denser gas.
2003 May 2
Five to Mars
Image Credit: USGS, Viking Project, NASA
Come December 2003 - January 2004, an armada of five new invaders from Earth should arrive on the shores of the Red Planet -- the Japanese ( ISAS) Nozomi orbiter, the European Space Agency's Mars Express orbiter carrying the Beagle 2 lander, and NASA's own two Mars Exploration Rovers. While Nozomi began its interplanetary voyage in 1998, the other spacecraft are scheduled for launch windows beginning this June. Clearly, earthdwellers remain intensely curious about Mars and the tantalizing possibility of past or present martian life, with these robotic missions focussing on investigating the planet's atmosphere and the search for water. This mosaic of over 100 Viking 1 orbiter images of Mars was recorded in 1980 and is projected to show the perspective seen from an approaching spacecraft at a distance of 2,000 kilometers. Exceptional views of Mars will be possible from earthbound telescopes in August and September.
Five to Mars
Image Credit: USGS, Viking Project, NASA
Come December 2003 - January 2004, an armada of five new invaders from Earth should arrive on the shores of the Red Planet -- the Japanese ( ISAS) Nozomi orbiter, the European Space Agency's Mars Express orbiter carrying the Beagle 2 lander, and NASA's own two Mars Exploration Rovers. While Nozomi began its interplanetary voyage in 1998, the other spacecraft are scheduled for launch windows beginning this June. Clearly, earthdwellers remain intensely curious about Mars and the tantalizing possibility of past or present martian life, with these robotic missions focussing on investigating the planet's atmosphere and the search for water. This mosaic of over 100 Viking 1 orbiter images of Mars was recorded in 1980 and is projected to show the perspective seen from an approaching spacecraft at a distance of 2,000 kilometers. Exceptional views of Mars will be possible from earthbound telescopes in August and September.
2003 May 3
Denizen of the Tarantula Nebula
Credit: Hubble Heritage Team (AURA / STScI/ NASA)
The star cluster at lower right, cataloged as Hodge 301, is a denizen of the Tarantula Nebula. An evocative nebula in the southern sky, the sprawling cosmic Tarantula is an energetic star forming region some 168,000 light-years distant in our neighboring galaxy the Large Magellanic Cloud. The stars within Hodge 301 formed together tens of millions of years ago and as the massive ones quickly exhaust their nuclear fuel they explode. In fact, the giant stars of Hodge 301 are rapidly approaching this violent final phase of stellar evolution - known as a supernova. These supernova blasts send material and shock waves back into the nebular gas to create the Tarantula's glowing filaments also visible in this Hubble Space Telescope Heritage image. But these spectacular stellar death explosions signal star birth as well, as the blast waves condense gas and dust to ultimately form the next generation of stars inside the Tarantula Nebula.
Denizen of the Tarantula Nebula
Credit: Hubble Heritage Team (AURA / STScI/ NASA)
The star cluster at lower right, cataloged as Hodge 301, is a denizen of the Tarantula Nebula. An evocative nebula in the southern sky, the sprawling cosmic Tarantula is an energetic star forming region some 168,000 light-years distant in our neighboring galaxy the Large Magellanic Cloud. The stars within Hodge 301 formed together tens of millions of years ago and as the massive ones quickly exhaust their nuclear fuel they explode. In fact, the giant stars of Hodge 301 are rapidly approaching this violent final phase of stellar evolution - known as a supernova. These supernova blasts send material and shock waves back into the nebular gas to create the Tarantula's glowing filaments also visible in this Hubble Space Telescope Heritage image. But these spectacular stellar death explosions signal star birth as well, as the blast waves condense gas and dust to ultimately form the next generation of stars inside the Tarantula Nebula.
2003 May 4
A Sonic Boom
Credit: Ensign John Gay, USS Constellation, US Navy
Many people have heard a sonic boom, but few have seen one. When an airplane travels at a speed faster than sound, density waves of sound emitted by the plane cannot precede the plane, and so accumulate in a cone behind the plane. When this shock wave passes, a listener hears all at once the sound emitted over a longer period: a sonic boom. As a plane accelerates to just break the sound barrier, however, an unusual cloud might form. The origin of this cloud is still debated. A leading theory is that a drop in air pressure at the plane described by the Prandtl-Glauert Singularity occurs so that moist air condenses there to form water droplets. Above, an F/A-18 Hornet was photographed just as it broke the sound barrier. Large meteors and the space shuttle frequently produce audible sonic booms before they are slowed below sound speed by the Earth's atmosphere.
A Sonic Boom
Credit: Ensign John Gay, USS Constellation, US Navy
Many people have heard a sonic boom, but few have seen one. When an airplane travels at a speed faster than sound, density waves of sound emitted by the plane cannot precede the plane, and so accumulate in a cone behind the plane. When this shock wave passes, a listener hears all at once the sound emitted over a longer period: a sonic boom. As a plane accelerates to just break the sound barrier, however, an unusual cloud might form. The origin of this cloud is still debated. A leading theory is that a drop in air pressure at the plane described by the Prandtl-Glauert Singularity occurs so that moist air condenses there to form water droplets. Above, an F/A-18 Hornet was photographed just as it broke the sound barrier. Large meteors and the space shuttle frequently produce audible sonic booms before they are slowed below sound speed by the Earth's atmosphere.
2003 May 5
NGC 1275: A Galactic Collision
Credit: Hubble Heritage Team (STScI/AURA), M. Donahue (STScI) & J. Trauger (JPL), NASA
In NGC 1275, one galaxy is slicing through another. The disk of the dusty spiral galaxy near the image center is cutting through a large elliptical galaxy, visible predominantly on the lower left. Galaxies can change significantly during a collision like this, with gravitational tides distorting each galaxy and gas clouds being compressed and lighting up with new star formation. Galaxy collisions occur in slow motion to the human eye, with a single pass taking as much as 100 million years. NGC 1275 is a member of the Perseus cluster of galaxies that lies about 230 million light years away toward the constellation of Perseus. Each galaxy spans about 50,000 light years across. The above picture is a composite of images taken by the Hubble Space Telescope in 1995 and 2001.
NGC 1275: A Galactic Collision
Credit: Hubble Heritage Team (STScI/AURA), M. Donahue (STScI) & J. Trauger (JPL), NASA
In NGC 1275, one galaxy is slicing through another. The disk of the dusty spiral galaxy near the image center is cutting through a large elliptical galaxy, visible predominantly on the lower left. Galaxies can change significantly during a collision like this, with gravitational tides distorting each galaxy and gas clouds being compressed and lighting up with new star formation. Galaxy collisions occur in slow motion to the human eye, with a single pass taking as much as 100 million years. NGC 1275 is a member of the Perseus cluster of galaxies that lies about 230 million light years away toward the constellation of Perseus. Each galaxy spans about 50,000 light years across. The above picture is a composite of images taken by the Hubble Space Telescope in 1995 and 2001.
2003 May 6
A Chicago Meteorite Fall
Credit & Copyright: Ivan and Colby Navarro
If you wait long enough, a piece of outer space itself will come right to you. As Colby Navarro worked innocently on the computer, a rock from space crashed through the roof, struck the printer, banged off the wall, and came to rest near the filing cabinet. This occurred around midnight on March 26 in Park Forest, Illinois, USA, near Chicago. The meteorite, measuring about 10 cm across, was one of several that fell near Chicago that day as part of a tremendous fireball. Pictured above is the resulting hole in the ceiling, while the inset image shows the wall dent and the meteorite itself. Although the vast majority of meteors is much smaller and burn up in the Earth's atmosphere, the average homeowner should expect to repair direct meteor damage every hundred million years.
A Chicago Meteorite Fall
Credit & Copyright: Ivan and Colby Navarro
If you wait long enough, a piece of outer space itself will come right to you. As Colby Navarro worked innocently on the computer, a rock from space crashed through the roof, struck the printer, banged off the wall, and came to rest near the filing cabinet. This occurred around midnight on March 26 in Park Forest, Illinois, USA, near Chicago. The meteorite, measuring about 10 cm across, was one of several that fell near Chicago that day as part of a tremendous fireball. Pictured above is the resulting hole in the ceiling, while the inset image shows the wall dent and the meteorite itself. Although the vast majority of meteors is much smaller and burn up in the Earth's atmosphere, the average homeowner should expect to repair direct meteor damage every hundred million years.
2003 May 7
The Southern Sky from the International Space Station
Credit: Don Pettit, ISS Expedition 6, NASA
Look up from Earth's South Pole, and this stellar starscape is what you might see. Alternatively, this patch of sky is also visible from many southern locations as well as the orbiting International Space Station, where the above image was recently recorded. To the left of the photograph's center are the four stars that mark the boundaries of the famous Southern Cross. The band of stars, dust, and gas crossing the middle of the photograph is part our Milky Way Galaxy. At the lower left is the dark Coal Sack Nebula, and the bright nebula on the far right is the Carina Nebula. The Southern Cross is such a famous constellation that it is depicted on the national flag of Australia.
The Southern Sky from the International Space Station
Credit: Don Pettit, ISS Expedition 6, NASA
Look up from Earth's South Pole, and this stellar starscape is what you might see. Alternatively, this patch of sky is also visible from many southern locations as well as the orbiting International Space Station, where the above image was recently recorded. To the left of the photograph's center are the four stars that mark the boundaries of the famous Southern Cross. The band of stars, dust, and gas crossing the middle of the photograph is part our Milky Way Galaxy. At the lower left is the dark Coal Sack Nebula, and the bright nebula on the far right is the Carina Nebula. The Southern Cross is such a famous constellation that it is depicted on the national flag of Australia.
2003 May 8
Mercury Spotting
Credit: SOHO - EIT Consortium, ESA, NASA
Can you spot the planet? The diminutive disk of Mercury, the solar system's innermost planet, spent about five hours crossing in front of the enormous solar disk yesterday (Wednesday, May 7th), as viewed from the general vicinity of planet Earth. The Sun was above the horizon during the entire transit for observers in Europe, Africa, Asia, or Australia, and the horizon was certainly no problem for the sun-staring SOHO spacecraft. Seen as a dark spot, Mercury progresses from left to right (top panel to bottom) in these four images from SOHO's extreme ultraviolet camera. The panels' false-colors correspond to different wavelengths in the extreme ultraviolet which highlight regions above the Sun's visible surface. This is the first of 14 transits of Mercury which will occur during the 21st century, but the next similar event will be a transit of Venus in June of 2004. Need help spotting Mercury? Just click on the picture.
Mercury Spotting
Credit: SOHO - EIT Consortium, ESA, NASA
Can you spot the planet? The diminutive disk of Mercury, the solar system's innermost planet, spent about five hours crossing in front of the enormous solar disk yesterday (Wednesday, May 7th), as viewed from the general vicinity of planet Earth. The Sun was above the horizon during the entire transit for observers in Europe, Africa, Asia, or Australia, and the horizon was certainly no problem for the sun-staring SOHO spacecraft. Seen as a dark spot, Mercury progresses from left to right (top panel to bottom) in these four images from SOHO's extreme ultraviolet camera. The panels' false-colors correspond to different wavelengths in the extreme ultraviolet which highlight regions above the Sun's visible surface. This is the first of 14 transits of Mercury which will occur during the 21st century, but the next similar event will be a transit of Venus in June of 2004. Need help spotting Mercury? Just click on the picture.
2003 May 9
International Space Station in Transit
Credit & Copyright: Tom Laskowski
A stunning telescopic image of the International Space Station crossing in front of an eight day old Moon, this picture was captured on April 11th. But while Wednesday's leisurely transit of Mercury across the Sun entertained observers all over the dayside of planet Earth, the audience for this lunar transit was more restricted. Like other satellites in low Earth orbit, the space station moves quickly through the sky. Glinting in the sunlight near sunset and sunrise, its path strongly depends on the observer's longitude and latitude. So, well-placed astronomer Tom Laskowski tracked the orbiting space station from a site near South Bend, Indiana, USA and recorded a digital movie of the fleeting, dramatic event. This single frame from the movie has been enhanced to bring out detail in the space station. Seen below the lunar terminator at the lower left, the International Space Station appears here at a distance of just over 400 kilometers, with the Moon nearly 400,000 kilometers away.
International Space Station in Transit
Credit & Copyright: Tom Laskowski
A stunning telescopic image of the International Space Station crossing in front of an eight day old Moon, this picture was captured on April 11th. But while Wednesday's leisurely transit of Mercury across the Sun entertained observers all over the dayside of planet Earth, the audience for this lunar transit was more restricted. Like other satellites in low Earth orbit, the space station moves quickly through the sky. Glinting in the sunlight near sunset and sunrise, its path strongly depends on the observer's longitude and latitude. So, well-placed astronomer Tom Laskowski tracked the orbiting space station from a site near South Bend, Indiana, USA and recorded a digital movie of the fleeting, dramatic event. This single frame from the movie has been enhanced to bring out detail in the space station. Seen below the lunar terminator at the lower left, the International Space Station appears here at a distance of just over 400 kilometers, with the Moon nearly 400,000 kilometers away.
2003 May 10
NGC 7293: The Helix Nebula
Credit: NASA, WIYN, NOAO, ESA, Hubble Helix Nebula Team, M. Meixner (STScI), & T. A. Rector (NRAO)
Will our Sun look like this one day? The Helix Nebula is the closest example of a planetary nebula created at the end of the life of a Sun-like star. The outer gasses of the star expelled into space appear from our vantage point as if we are looking down a helix. The remnant central stellar core, destined to become a white dwarf star, glows in light so energetic it causes the previously expelled gas to fluoresce. The Helix Nebula, given a technical designation of NGC 7293, lies about 650 light-years away towards the constellation of Aquarius and spans about 2.5 light-years. The above picture is a composite of newly released images from the ACS instrument on the Hubble Space Telescope and wide-angle images from the Mosaic Camera on the WIYN 0.9-m Telescope at Kitt Peak National Observatory. A close-up of the inner edge of the Helix Nebula shows complex gas knots of unknown origin.
NGC 7293: The Helix Nebula
Credit: NASA, WIYN, NOAO, ESA, Hubble Helix Nebula Team, M. Meixner (STScI), & T. A. Rector (NRAO)
Will our Sun look like this one day? The Helix Nebula is the closest example of a planetary nebula created at the end of the life of a Sun-like star. The outer gasses of the star expelled into space appear from our vantage point as if we are looking down a helix. The remnant central stellar core, destined to become a white dwarf star, glows in light so energetic it causes the previously expelled gas to fluoresce. The Helix Nebula, given a technical designation of NGC 7293, lies about 650 light-years away towards the constellation of Aquarius and spans about 2.5 light-years. The above picture is a composite of newly released images from the ACS instrument on the Hubble Space Telescope and wide-angle images from the Mosaic Camera on the WIYN 0.9-m Telescope at Kitt Peak National Observatory. A close-up of the inner edge of the Helix Nebula shows complex gas knots of unknown origin.
2003 May 11
M83: The Southern Pinwheel Galaxy from VLT
Credit: FORS Team, 8.2-meter VLT, ESO
M83 is one of the closest and brightest spiral galaxies on the sky. Visible with binoculars in the constellation of Hydra, majestic spiral arms have prompted its nickname as the Southern Pinwheel. Although discovered 250 years ago, only much later was it appreciated that M83 was not a nearby gas cloud, but a barred spiral galaxy much like our own Milky Way Galaxy. M83, pictured above in a photograph from a Very Large Telescope, is a prominent member of a group of galaxies that includes Centaurus A and NGC 5253, all of which lie about 15 million light years distant. To date, six supernova explosions have been recorded in M83. An intriguing double circumnuclear ring has been discovered at the center of M83.
M83: The Southern Pinwheel Galaxy from VLT
Credit: FORS Team, 8.2-meter VLT, ESO
M83 is one of the closest and brightest spiral galaxies on the sky. Visible with binoculars in the constellation of Hydra, majestic spiral arms have prompted its nickname as the Southern Pinwheel. Although discovered 250 years ago, only much later was it appreciated that M83 was not a nearby gas cloud, but a barred spiral galaxy much like our own Milky Way Galaxy. M83, pictured above in a photograph from a Very Large Telescope, is a prominent member of a group of galaxies that includes Centaurus A and NGC 5253, all of which lie about 15 million light years distant. To date, six supernova explosions have been recorded in M83. An intriguing double circumnuclear ring has been discovered at the center of M83.
2003 May 12
In the Vicinity of the Cone Nebula
Credit & Copyright: T. A. Rector (NRAO), NOAO, AURA, NSF
Strange shapes and textures can be found in neighborhood of the Cone Nebula. The unusual shapes originate from fine interstellar dust reacting in complex ways with the energetic light and hot gas being expelled by the young stars. The brightest star on the right of the above picture is S Mon, while the region just above it has been nicknamed the Fox Fur Nebula for its color and structure. The blue glow directly surrounding S Mon results from reflection, where neighboring dust reflects light from the bright star. The orange glow that encompasses the whole region results not only from dust reflection but also emission from hydrogen gas ionized by starlight. S Mon is part of a young open cluster of stars named NGC 2264, located about 2500 light years away toward the constellation of Monoceros. The origin of the mysterious geometric Cone Nebula, visible on the far left, remains a mystery.
In the Vicinity of the Cone Nebula
Credit & Copyright: T. A. Rector (NRAO), NOAO, AURA, NSF
Strange shapes and textures can be found in neighborhood of the Cone Nebula. The unusual shapes originate from fine interstellar dust reacting in complex ways with the energetic light and hot gas being expelled by the young stars. The brightest star on the right of the above picture is S Mon, while the region just above it has been nicknamed the Fox Fur Nebula for its color and structure. The blue glow directly surrounding S Mon results from reflection, where neighboring dust reflects light from the bright star. The orange glow that encompasses the whole region results not only from dust reflection but also emission from hydrogen gas ionized by starlight. S Mon is part of a young open cluster of stars named NGC 2264, located about 2500 light years away toward the constellation of Monoceros. The origin of the mysterious geometric Cone Nebula, visible on the far left, remains a mystery.
2003 May 13
Mercury Transits the Sun
Credit & Copyright: Thierry Legault
How big is the Sun? The Sun is not only larger than any planet, it is larger than all of the planets put together. The Sun accounts for about 99.9 percent of all the mass in its Solar System. Merely stating the Sun's diameter is about 1,400,000 kilometers does not do it justice. Last week a chance to gain visual size perspective occurred when planet Mercury made a rare crossing in front to Sun. Mercury, a planet over a third of the diameter of our Earth, is the dark dot on the upper right. In comparison to the Sun, Mercury is so small it is initially hard to spot. Also visible on the Sun are dark circular sunspots, bright plages, and dark elongated prominences -- many of which are larger than Mercury. The above contrast-enhanced picture was captured last week from France.
Mercury Transits the Sun
Credit & Copyright: Thierry Legault
How big is the Sun? The Sun is not only larger than any planet, it is larger than all of the planets put together. The Sun accounts for about 99.9 percent of all the mass in its Solar System. Merely stating the Sun's diameter is about 1,400,000 kilometers does not do it justice. Last week a chance to gain visual size perspective occurred when planet Mercury made a rare crossing in front to Sun. Mercury, a planet over a third of the diameter of our Earth, is the dark dot on the upper right. In comparison to the Sun, Mercury is so small it is initially hard to spot. Also visible on the Sun are dark circular sunspots, bright plages, and dark elongated prominences -- many of which are larger than Mercury. The above contrast-enhanced picture was captured last week from France.
2003 May 14
The North Pole of Venus
Credit: SSV, MIPL, Magellan Team, NASA
If you could look down on the North Pole of Venus what would you see? The Magellan probe that orbited Venus from 1990 to 1994 was able to peer through the thick Venusian clouds and build up the above image by emitting and re-detecting cloud-penetrating radar. Visible as the bright patch below central North is Venus' highest mountain Maxwell Montes. Other notable features include numerous mountains, coronas, impact craters, tessera, ridges, and lava flows. Although the size and mass of Venus are similar to the Earth, its thick carbon-dioxide atmosphere has trapped heat so efficiently that surface temperature usually exceeds 700 kelvins, hot enough to melt lead.
The North Pole of Venus
Credit: SSV, MIPL, Magellan Team, NASA
If you could look down on the North Pole of Venus what would you see? The Magellan probe that orbited Venus from 1990 to 1994 was able to peer through the thick Venusian clouds and build up the above image by emitting and re-detecting cloud-penetrating radar. Visible as the bright patch below central North is Venus' highest mountain Maxwell Montes. Other notable features include numerous mountains, coronas, impact craters, tessera, ridges, and lava flows. Although the size and mass of Venus are similar to the Earth, its thick carbon-dioxide atmosphere has trapped heat so efficiently that surface temperature usually exceeds 700 kelvins, hot enough to melt lead.
2003 May 15
Moon Slide Slim
Credit & Copyright: Doug Murray
No special filters - or even a telescope - are required to enjoy a leisurely lunar eclipse. In fact, watched from all over the night side of planet Earth, these regular celestial performances have entertained many casual skygazers. Still, this eye-catching picture of a lunar eclipse may look unfamiliar. To make it, astrophotographer Doug Murray set his camera on a tripod and locked the shutter open during the total lunar eclipse of January 2000. The resulting image records the trail of the Moon sliding through the night, steadily progressing toward the total eclipse phase as seen from Florida, USA. Haunting red hues of diminished moonlight, common during the total phase of a lunar eclipse, are evident at the far right, along the slimmer portion of the trail. At least part of tonight's lunar eclipse will be visible in clear night skies over the Americas, Europe, and Africa. The eclipse should last over three hours from start to finish, with about 53 minutes of totality.
Moon Slide Slim
Credit & Copyright: Doug Murray
No special filters - or even a telescope - are required to enjoy a leisurely lunar eclipse. In fact, watched from all over the night side of planet Earth, these regular celestial performances have entertained many casual skygazers. Still, this eye-catching picture of a lunar eclipse may look unfamiliar. To make it, astrophotographer Doug Murray set his camera on a tripod and locked the shutter open during the total lunar eclipse of January 2000. The resulting image records the trail of the Moon sliding through the night, steadily progressing toward the total eclipse phase as seen from Florida, USA. Haunting red hues of diminished moonlight, common during the total phase of a lunar eclipse, are evident at the far right, along the slimmer portion of the trail. At least part of tonight's lunar eclipse will be visible in clear night skies over the Americas, Europe, and Africa. The eclipse should last over three hours from start to finish, with about 53 minutes of totality.
2003 May 16
A Tale of Two Nebulae
Credit & Copyright: Brian Lula
This colorful telescopic view towards the northern constellation Lyra reveals dim outer regions around M57, popularly known as the Ring Nebula. While modern astronomers still refer to M57 as a planetary nebula, at one light-year across M57 is not a planet but the gaseous shroud of a dying sun-like star. Roughly the same apparent size as M57, the fainter, often overlooked barred spiral galaxy IC1296 is at the lower right and would have been referred to in the early 20th century as a spiral nebula. By chance the pair are in the same field of view, and while they appear to have similar sizes they are actually very far apart. M57 lies at a distance of a mere 2,000 light-years, well within our own Milky Way galaxy. Extragalactic IC1296 is more like 200,000,000 light-years distant or about 100,000 times farther away. Since they appear roughly similar in size, spiral nebula IC1296 must also be about 100,000 times larger than planetary nebula M57.
A Tale of Two Nebulae
Credit & Copyright: Brian Lula
This colorful telescopic view towards the northern constellation Lyra reveals dim outer regions around M57, popularly known as the Ring Nebula. While modern astronomers still refer to M57 as a planetary nebula, at one light-year across M57 is not a planet but the gaseous shroud of a dying sun-like star. Roughly the same apparent size as M57, the fainter, often overlooked barred spiral galaxy IC1296 is at the lower right and would have been referred to in the early 20th century as a spiral nebula. By chance the pair are in the same field of view, and while they appear to have similar sizes they are actually very far apart. M57 lies at a distance of a mere 2,000 light-years, well within our own Milky Way galaxy. Extragalactic IC1296 is more like 200,000,000 light-years distant or about 100,000 times farther away. Since they appear roughly similar in size, spiral nebula IC1296 must also be about 100,000 times larger than planetary nebula M57.
2003 May 17
Dark Sky, Bright Sun
Credit: STS-82 Crew, NASA
In low Earth orbit there is not enough atmosphere to diffuse and scatter sunlight, so shadows are black and the sky is dark - even when the Sun shines. The harsh lighting produced this dramatic effect as mission specialist Gregory Harbaugh photographed colleague Joseph Tanner during their second spacewalk to service the Hubble Space Telescope in February 1997. The aft section of the Space Shuttle Discovery is visible in the background with the Sun hanging over a delicate crescent of the Earth's limb. A checklist is attached to Tanner's left arm, and Harbaugh's reflection is just visible in Tanner's visor.
Dark Sky, Bright Sun
Credit: STS-82 Crew, NASA
In low Earth orbit there is not enough atmosphere to diffuse and scatter sunlight, so shadows are black and the sky is dark - even when the Sun shines. The harsh lighting produced this dramatic effect as mission specialist Gregory Harbaugh photographed colleague Joseph Tanner during their second spacewalk to service the Hubble Space Telescope in February 1997. The aft section of the Space Shuttle Discovery is visible in the background with the Sun hanging over a delicate crescent of the Earth's limb. A checklist is attached to Tanner's left arm, and Harbaugh's reflection is just visible in Tanner's visor.
2003 May 18
The Holographic Principle
Image Credit & Copyright: E. Winfree, K. Fleischer, A. Barr et al. (Caltech)
Is this image worth a thousand words? According to the Holographic Principle, the most information you can get from this image is about 3 x 10^65 bits for a normal sized computer monitor. The Holographic Principle, yet unproven, states that there is a maximum amount of information content held by regions adjacent to any surface. Therefore, counter-intuitively, the information content inside a room depends not on the volume of the room but on the area of the bounding walls. The principle derives from the idea that the Planck length, the length scale where quantum mechanics begins to dominate classical gravity, is one side of an area that can hold only about one bit of information. The limit was first postulated by physicist Gerard 't Hooft in 1993. It can arise from generalizations from seemingly distant speculation that the information held by a black hole is determined not by its enclosed volume but by the surface area of its event horizon. The term "holographic" arises from a hologram analogy where three-dimension images are created by projecting light though a flat screen. Beware, other people looking at the above image may not claim to see 3 x 10^65 bits -- they might claim to see a teapot.
The Holographic Principle
Image Credit & Copyright: E. Winfree, K. Fleischer, A. Barr et al. (Caltech)
Is this image worth a thousand words? According to the Holographic Principle, the most information you can get from this image is about 3 x 10^65 bits for a normal sized computer monitor. The Holographic Principle, yet unproven, states that there is a maximum amount of information content held by regions adjacent to any surface. Therefore, counter-intuitively, the information content inside a room depends not on the volume of the room but on the area of the bounding walls. The principle derives from the idea that the Planck length, the length scale where quantum mechanics begins to dominate classical gravity, is one side of an area that can hold only about one bit of information. The limit was first postulated by physicist Gerard 't Hooft in 1993. It can arise from generalizations from seemingly distant speculation that the information held by a black hole is determined not by its enclosed volume but by the surface area of its event horizon. The term "holographic" arises from a hologram analogy where three-dimension images are created by projecting light though a flat screen. Beware, other people looking at the above image may not claim to see 3 x 10^65 bits -- they might claim to see a teapot.
2003 May 19
The Andromeda Deep Field
Credit: T. M. Brown (STScI) et al., ESA, NASA
What can you learn from looking into the depths of space? In an effort to find out true ages of stars in neighboring Andromeda galaxy's halo, astronomers stared into the galaxy giant with the new Advanced Camera for Surveys through the Hubble Space Telescope. The resulting exposure of over three days, shown above, is the deepest exposure in visible light ever taken, although shorter in duration than the multi-wavelength effort toward the Hubble Deep Field. The final image illuminated not only Andromeda (M31) but the distant universe. Andromeda's halo stars turned out to be have a wider range of ages than our Milky Way's halo stars, likely indicating more encounters with small neighboring galaxies. Visible on the above left is one of Andromeda's globular star clusters, while literally thousands of background galaxies are seen in the distance universe, far beyond M31.
The Andromeda Deep Field
Credit: T. M. Brown (STScI) et al., ESA, NASA
What can you learn from looking into the depths of space? In an effort to find out true ages of stars in neighboring Andromeda galaxy's halo, astronomers stared into the galaxy giant with the new Advanced Camera for Surveys through the Hubble Space Telescope. The resulting exposure of over three days, shown above, is the deepest exposure in visible light ever taken, although shorter in duration than the multi-wavelength effort toward the Hubble Deep Field. The final image illuminated not only Andromeda (M31) but the distant universe. Andromeda's halo stars turned out to be have a wider range of ages than our Milky Way's halo stars, likely indicating more encounters with small neighboring galaxies. Visible on the above left is one of Andromeda's globular star clusters, while literally thousands of background galaxies are seen in the distance universe, far beyond M31.
2003 May 20
A Primordial Quasar
Drawing Credit: Wolfram Freudling et al. (STECF), ESO, ESA, NASA
What did the first quasars look like? The nearest quasars are now known to be supermassive black holes in the centers of galaxies. Gas and dust that falls toward a quasar glows brightly, sometimes outglowing the entire home galaxy. The quasars that formed in the first billion years of the universe are more mysterious, though, with even the nature of the surrounding gas still unknown. Above, an artist's impression shows a primordial quasar as it might have been, surrounded by sheets of gas, dust, stars, and early star clusters. Exacting observations of three distant quasars now indicate emission of very specific colors of the element iron. These Hubble Space Telescope observations, which bolster recent results from the WMAP mission, indicate that a whole complete cycle of stars was born, created this iron, and died within the first few hundred million years of the universe.
A Primordial Quasar
Drawing Credit: Wolfram Freudling et al. (STECF), ESO, ESA, NASA
What did the first quasars look like? The nearest quasars are now known to be supermassive black holes in the centers of galaxies. Gas and dust that falls toward a quasar glows brightly, sometimes outglowing the entire home galaxy. The quasars that formed in the first billion years of the universe are more mysterious, though, with even the nature of the surrounding gas still unknown. Above, an artist's impression shows a primordial quasar as it might have been, surrounded by sheets of gas, dust, stars, and early star clusters. Exacting observations of three distant quasars now indicate emission of very specific colors of the element iron. These Hubble Space Telescope observations, which bolster recent results from the WMAP mission, indicate that a whole complete cycle of stars was born, created this iron, and died within the first few hundred million years of the universe.