Astronomy Picture of the Day Search Results for "Crab Nebula"

APOD: 2023 December 26 – IC 443: The Jellyfish Nebula
Explanation: Why is this jellyfish swimming in a sea of stars? Drifting near bright star Eta Geminorum, seen at the right, the Jellyfish Nebula extends its tentacles from the bright arcing ridge of emission left of center. In fact, the cosmic jellyfish is part of bubble-shaped supernova remnant IC 443, the expanding debris cloud from a massive star that exploded. Light from the explosion first reached planet Earth over 30,000 years ago. Like its cousin in astronomical waters, the Crab Nebula supernova remnant IC 443 is known to harbor a neutron star -- the remnant of the collapsed stellar core. The Jellyfish Nebula is about 5,000 light-years away. At that distance, the featured image would span about 140 light-years across.

APOD: 2023 November 15 - M1: The Incredible Expanding Crab
Explanation: Cataloged as M1, the Crab Nebula is the first on Charles Messier's famous list of things which are not comets. In fact, the Crab Nebula is now known to be a supernova remnant, an expanding cloud of debris from the death explosion of a massive star. The violent birth of the Crab was witnessed by astronomers in the year 1054. Roughly 10 light-years across, the nebula is still expanding at a rate of about 1,500 kilometers per second. You can see the expansion by comparing these sharp images from the Hubble Space Telescope and James Webb Space Telescope. The Crab's dynamic, fragmented filaments were captured in visible light by Hubble in 2005 and Webb in infrared light in 2023. This cosmic crustacean lies about 6,500 light-years away in the constellation Taurus.

APOD: 2023 November 9 - M1: The Crab Nebula
Explanation: The Crab Nebula is cataloged as M1, the first object on Charles Messier's famous 18th century list of things which are not comets. In fact, the Crab is now known to be a supernova remnant, debris from the death explosion of a massive star witnessed by astronomers in the year 1054. This sharp image from the James Webb Space Telescope’s NIRCam (Near-Infrared Camera) and MIRI (Mid-Infrared Instrument) explores the eerie glow and fragmented strands of the still expanding cloud of interstellar debris in infrared light. One of the most exotic objects known to modern astronomers, the Crab Pulsar, a neutron star spinning 30 times a second, is visible as a bright spot near the nebula's center. Like a cosmic dynamo, this collapsed remnant of the stellar core powers the Crab's emission across the electromagnetic spectrum. Spanning about 12 light-years, the Crab Nebula is a mere 6,500 light-years away in the head-strong constellation Taurus.

APOD: 2023 March 20 – M1: The Expanding Crab Nebula
Explanation: Are your eyes good enough to see the Crab Nebula expand? The Crab Nebula is cataloged as M1, the first on Charles Messier's famous list of things which are not comets. In fact, the Crab is now known to be a supernova remnant, an expanding cloud of debris from the explosion of a massive star. The violent birth of the Crab was witnessed by astronomers in the year 1054. Roughly 10 light-years across today, the nebula is still expanding at a rate of over 1,000 kilometers per second. Over the past decade, its expansion has been documented in this stunning time-lapse movie. In each year from 2008 to 2022, an image was produced with the same telescope and camera from a remote observatory in Austria. The sharp, processed frames even reveal the dynamic energetic emission surrounding the rapidly spinning pulsar at the center. The Crab Nebula lies about 6,500 light-years away toward the constellation of the Bull (Taurus).

APOD: 2023 January 15 – M1: The Crab Nebula from Hubble
Explanation: This is the mess that is left when a star explodes. The Crab Nebula, the result of a supernova seen in 1054 AD, is filled with mysterious filaments. The filaments are not only tremendously complex, but appear to have less mass than expelled in the original supernova and a higher speed than expected from a free explosion. The featured image, taken by the Hubble Space Telescope, is presented in three colors chosen for scientific interest. The Crab Nebula spans about 10 light-years. In the nebula's very center lies a pulsar: a neutron star as massive as the Sun but with only the size of a small town. The Crab Pulsar rotates about 30 times each second.

APOD: 2022 August 21 - The Spinning Pulsar of the Crab Nebula
Explanation: At the core of the Crab Nebula lies a city-sized, magnetized neutron star spinning 30 times a second. Known as the Crab Pulsar, it is the bright spot in the center of the gaseous swirl at the nebula's core. About twelve light-years across, the spectacular picture frames the glowing gas, cavities and swirling filaments near the Crab Nebula's center. The featured picture combines visible light from the Hubble Space Telescope in purple, X-ray light from the Chandra X-ray Observatory in blue, and infrared light from the Spitzer Space Telescope in red. Like a cosmic dynamo the Crab pulsar powers the emission from the nebula, driving a shock wave through surrounding material and accelerating the spiraling electrons. With more mass than the Sun and the density of an atomic nucleus,the spinning pulsar is the collapsed core of a massive star that exploded. The outer parts of the Crab Nebula are the expanding remnants of the star's component gasses. The supernova explosion was witnessed on planet Earth in the year 1054.

APOD: 2022 March 4 - The Multiwavelength Crab
Explanation: The Crab Nebula is cataloged as M1, the first object on Charles Messier's famous list of things which are not comets. In fact, the Crab is now known to be a supernova remnant, expanding debris from massive star's death explosion, witnessed on planet Earth in 1054 AD. This brave new image offers a 21st century view of the Crab Nebula by presenting image data from across the electromagnetic spectrum as wavelengths of visible light. From space, Chandra (X-ray) XMM-Newton (ultraviolet), Hubble (visible), and Spitzer (infrared), data are in purple, blue, green, and yellow hues. From the ground, Very Large Array radio wavelength data is shown in red. One of the most exotic objects known to modern astronomers, the Crab Pulsar, a neutron star spinning 30 times a second, is the bright spot near picture center. Like a cosmic dynamo, this collapsed remnant of the stellar core powers the Crab's emission across the electromagnetic spectrum. Spanning about 12 light-years, the Crab Nebula is 6,500 light-years away in the constellation Taurus.

APOD: 2021 December 24 - M1: The Crab Nebula
Explanation: The Crab Nebula is cataloged as M1, the first object on Charles Messier's famous 18th century list of things which are not comets. In fact, the Crab is now known to be a supernova remnant, debris from the death explosion of a massive star, witnessed by astronomers in the year 1054. This sharp, ground-based telescopic view combines broadband color data with narrowband data that tracks emission from ionized sulfur, hydrogen, and oxygen atoms to explore the tangled filaments within the still expanding cloud. One of the most exotic objects known to modern astronomers, the Crab Pulsar, a neutron star spinning 30 times a second, is visible as a bright spot near the nebula's center. Like a cosmic dynamo, this collapsed remnant of the stellar core powers the Crab's emission across the electromagnetic spectrum. Spanning about 12 light-years, the Crab Nebula is a mere 6,500 light-years away in the constellation Taurus.

APOD: 2021 October 22 - A Comet and a Crab
Explanation: This pretty field of view spans over 2 degrees or 4 full moons on the sky, filled with stars toward the constellation Taurus, the Bull. Above and right of center in the frame you can spot the faint fuzzy reddish appearance of Messier 1 (M1), also known as the Crab Nebula. M1 is the first object in 18th century comet hunter Charles Messier's famous catalog of things which are definitely not comets. Made from image data captured this October 11, there is a comet in the picture though. Below center and left lies the faint greenish coma and dusty tail of periodic comet 67P Churyumov-Gerasimenko, also known as Rosetta's comet. In the 21st century, it became the final resting place of robots from planet Earth. Rosetta's comet is now returning to the inner solar system, sweeping toward its next perihelion or closest approach to the Sun, on November 2. Too faint to be seen by eye alone, the comet's next perigee or closest approach to Earth will be November 12.

APOD: 2021 May 19 - The Jellyfish and Mars
Explanation: Normally faint and elusive, the Jellyfish Nebula is caught in this alluring scene. In the telescopic field of view two bright yellowish stars, Mu and Eta Geminorum, stand just below and above the Jellyfish Nebula at the left. Cool red giants, they lie at the foot of the celestial twin. The Jellyfish Nebula itself floats below and left of center, a bright arcing ridge of emission with dangling tentacles. In fact, the cosmic jellyfish is part of bubble-shaped supernova remnant IC 443, the expanding debris cloud from a massive star that exploded. Light from that explosion first reached planet Earth over 30,000 years ago. Like its cousin in astrophysical waters the Crab Nebula supernova remnant, the Jellyfish Nebula is known to harbor a neutron star, the remnant of the collapsed stellar core. Composed on April 30, this telescopic snapshot also captures Mars. Now wandering through early evening skies, the Red Planet also shines with a yellowish glow on the right hand side of the field of view. Of course, the Jellyfish Nebula is about 5,000 light-years away, while Mars is currently almost 18 light-minutes from Earth.

APOD: 2021 February 9 - Flashes of the Crab Pulsar
Explanation: It somehow survived an explosion that would surely have destroyed our Sun. Now it is spins 30 times a second and is famous for the its rapid flashes. It is the Crab Pulsar, the rotating neutron star remnant of the supernova that created the Crab Nebula. A careful eye can spot the pulsar flashes in the featured time-lapse video, just above the image center. The video was created by adding together images taken only when the pulsar was flashing, as well as co-added images from other relative times. The Crab Pulsar flashes may have been first noted by an unknown woman attending a public observing night at the University of Chicago in 1957 -- but who was not believed. The progenitor supernova explosion was seen by many in the year 1054 AD. The expanding Crab Nebula remains a picturesque expanding gas cloud that glows across the electromagnetic spectrum. The pulsar is now thought to have survived the supernova explosion because it is composed of extremely-dense quantum-degenerate matter.

APOD: 2020 September 6 - M1: The Crab Nebula from Hubble
Explanation: This is the mess that is left when a star explodes. The Crab Nebula, the result of a supernova seen in 1054 AD, is filled with mysterious filaments. The filaments are not only tremendously complex, but appear to have less mass than expelled in the original supernova and a higher speed than expected from a free explosion. The featured image, taken by the Hubble Space Telescope, is presentedi in three colors chosen for scientific interest. The Crab Nebula spans about 10 light-years. In the nebula's very center lies a pulsar: a neutron star as massive as the Sun but with only the size of a small town. The Crab Pulsar rotates about 30 times each second.

APOD: 2020 January 19 - M1: The Incredible Expanding Crab Nebula
Explanation: Are your eyes good enough to see the Crab Nebula expand? The Crab Nebula is cataloged as M1, the first on Charles Messier's famous list of things which are not comets. In fact, the Crab is now known to be a supernova remnant, an expanding cloud of debris from the explosion of a massive star. The violent birth of the Crab was witnessed by astronomers in the year 1054. Roughly 10 light-years across today, the nebula is still expanding at a rate of over 1,000 kilometers per second. Over the past decade, its expansion has been documented in this stunning time-lapse movie. In each year from 2008 to 2017, an image was produced with the same telescope and camera from a remote observatory in Austria. Combined in the time-lapse movie, the 10 images represent 32 hours of total integration time. The sharp, processed frames even reveal the dynamic energetic emission within the incredible expanding Crab. The Crab Nebula lies about 6,500 light-years away in the constellation Taurus.

APOD: 2019 April 24 - The Shape of the Southern Crab
Explanation: The symmetric, multi-legged appearance of the Southern Crab Nebula is certainly distinctive. About 7,000 light-years distant toward the southern sky constellation Centaurus, its glowing nested hourglass shapes are produced by the remarkable symbiotic binary star system at its center. The nebula's dramatic stellar duo consists of a hot white dwarf star and cool, pulsating red giant star shedding outer layers that fall onto the smaller, much hotter companion. Embedded in a disk of material, outbursts from the white dwarf cause an outflow of gas driven away both above and below the disk resulting in the bipolar hourglass shapes. The bright central shape is about half a light-year across. This new Hubble Space Telescope image celebrates the 29th anniversary of Hubble's launch on April 24, 1990 on board the Space Shuttle Discovery.

APOD: 2019 April 4 - Messier 2
Explanation: After the Crab Nebula, M1, this giant star cluster is the second entry in 18th century astronomer Charles Messier's famous list of things that are not comets. M2 is one of the largest globular star clusters now known to roam the halo of our Milky Way galaxy. Though Messier originally described it as a nebula without stars, this stunning Hubble image resolves stars across the central 40 light-years of M2. Its population of stars numbers close to 150,000, concentrated within a total diameter of around 175 light-years. About 55,000 light-years distant toward the constellation Aquarius, this ancient denizen of the Milky Way, also known as NGC 7089, is 13 billion years old.

APOD: 2019 March 7 - Sharpless 249 and the Jellyfish Nebula
Explanation: Normally faint and elusive, the Jellyfish Nebula is caught in this alluring telescopic field of view. The entire scene is a two panel mosaic constructed using narrowband image data, with emission from sulfur, hydrogen and oxygen atoms shown in red, green and blue hues. It's anchored right and left by two bright stars, Mu and Eta Geminorum, at the foot of the celestial twin. The Jellyfish Nebula itself is right of center, the brighter arcing ridge of emission with dangling tentacles. In fact, the cosmic jellyfish is part of bubble-shaped supernova remnant IC 443, the expanding debris cloud from a massive star that exploded. Light from the explosion first reached planet Earth over 30,000 years ago. Like its cousin in astrophysical waters the Crab Nebula supernova remnant, the Jellyfish Nebula is known to harbor a neutron star, the remnant of the collapsed stellar core. An emission nebula cataloged as Sharpless 249 fills the field at the upper left. The Jellyfish Nebula is about 5,000 light-years away. At that distance, this image would be about 300 light-years across.

APOD: 2018 September 9 - M1: The Crab Nebula from Hubble
Explanation: This is the mess that is left when a star explodes. The Crab Nebula, the result of a supernova seen in 1054 AD, is filled with mysterious filaments. The filaments are not only tremendously complex, but appear to have less mass than expelled in the original supernova and a higher speed than expected from a free explosion. The featured image, taken by the Hubble Space Telescope, is presented in three colors chosen for scientific interest. The Crab Nebula spans about 10 light-years. In the nebula's very center lies a pulsar: a neutron star as massive as the Sun but with only the size of a small town. The Crab Pulsar rotates about 30 times each second.

APOD: 2018 March 23 - Sharpless 249 and the Jellyfish Nebula
Explanation: Normally faint and elusive, the Jellyfish Nebula is caught in this alluring telescopic image. Centered in the scene it's anchored right and left by two bright stars, Mu and Eta Geminorum, at the foot of the celestial twin. The Jellyfish Nebula is the brighter arcing ridge of emission with dangling tentacles. In fact, the cosmic jellyfish is part of bubble-shaped supernova remnant IC 443, the expanding debris cloud from a massive star that exploded. Light from the explosion first reached planet Earth over 30,000 years ago. Like its cousin in astrophysical waters the Crab Nebula supernova remnant, the Jellyfish Nebula is known to harbor a neutron star, the remnant of the collapsed stellar core. An emission nebula cataloged as Sharpless 249 fills the field at the upper left. The Jellyfish Nebula is about 5,000 light-years away. At that distance, this image would be about 300 light-years across.

APOD: 2018 March 17 - The Crab from Space
Explanation: The Crab Nebula is cataloged as M1, the first object on Charles Messier's famous list of things which are not comets. In fact, the Crab is now known to be a supernova remnant, expanding debris from the death explosion of a massive star. This intriguing false-color image combines data from space-based observatories, Chandra, Hubble, and Spitzer, to explore the debris cloud in X-rays (blue-white), optical (purple), and infrared (pink) light. One of the most exotic objects known to modern astronomers, the Crab Pulsar, a neutron star spinning 30 times a second, is the bright spot near picture center. Like a cosmic dynamo, this collapsed remnant of the stellar core powers the Crab's emission across the electromagnetic spectrum. Spanning about 12 light-years, the Crab Nebula is 6,500 light-years away in the constellation Taurus.

APOD: 2018 March 15 - Catalog Entry Number 1
Explanation: Every journey has a first step and every catalog a first entry. First entries in six well-known deep sky catalogs appear in these panels, from upper left to lower right in chronological order of original catalog publication. From 1774, Charles Messier's catalog entry number 1 is M1, famous cosmic crustacean and supernova remnant the Crab Nebula. J.L.E. Dreyer's (not so new) New General Catalog was published in 1888. A spiral galaxy in Pegasus, his NGC 1 is centered in the next panel. Just below it in the frame is another spiral galaxy cataloged as NGC 2. In Dreyer's follow-on Index Catalog (next panel), IC 1 is actually a faint double star, though. Now recognized as part of the Perseus molecular cloud complex, dark nebula Barnard 1 begins the bottom row from Dark Markings of the Sky, a 1919 catalog by E.E. Barnard. Abell 1 is a distant galaxy cluster in Pegasus, from George Abell's 1958 catalog of Rich Clusters of Galaxies. The final panel is centered on vdB 1, from Sidney van den Bergh's 1966 study. The pretty, blue galactic reflection nebula is found in the constellation Cassiopeia.

APOD: 2018 January 4 - M1: The Incredible Expanding Crab
Explanation: The Crab Nebula is cataloged as M1, the first on Charles Messier's famous list of things which are not comets. In fact, the Crab is now known to be a supernova remnant, an expanding cloud of debris from the explosion of a massive star. The violent birth of the Crab was witnessed by astronomers in the year 1054. Roughly 10 light-years across today, the nebula is still expanding at a rate of over 1,000 kilometers per second. Over the past decade, its expansion has been documented in this stunning time-lapse movie. In each year from 2008 to 2017, an image was produced with the same telescope and camera from a remote observatory in Austria. Combined in the time-lapse movie, the 10 images represent 32 hours of total integration time. The sharp, processed frames even reveal the dynamic energetic emission within the incredible expanding Crab. The Crab Nebula lies about 6,500 light-years away in the constellation Taurus.

APOD: 2017 May 11 - The Multiwavelength Crab
Explanation: The Crab Nebula is cataloged as M1, the first object on Charles Messier's famous list of things which are not comets. In fact, the Crab is now known to be a supernova remnant, expanding debris from massive star's death explosion, witnessed on planet Earth in 1054 AD. This brave new image offers a 21st century view of the Crab Nebula by presenting image data from across the electromagnetic spectrum as wavelengths of visible light. From space, Chandra (X-ray) XMM-Newton (ultraviolet), Hubble (visible), and Spitzer (infrared), data are in purple, blue, green, and yellow hues. From the ground, Very Large Array radio wavelength data is in shown in red. One of the most exotic objects known to modern astronomers, the Crab Pulsar, a neutron star spinning 30 times a second, is the bright spot near picture center. Like a cosmic dynamo, this collapsed remnant of the stellar core powers the Crab's emission across the electromagnetic spectrum. Spanning about 12 light-years, the Crab Nebula is 6,500 light-years away in the constellation Taurus.

APOD: 2017 January 7 - Sharpless 249 and the Jellyfish Nebula
Explanation: Normally faint and elusive, the Jellyfish Nebula is caught in this alluring telescopic mosaic. The scene is anchored below by bright star Eta Geminorum, at the foot of the celestial twin, while the Jellyfish Nebula is the brighter arcing ridge of emission with tentacles dangling below and left of center. In fact, the cosmic jellyfish is part of bubble-shaped supernova remnant IC 443, the expanding debris cloud from a massive star that exploded. Light from the explosion first reached planet Earth over 30,000 years ago. Like its cousin in astrophysical waters the Crab Nebula supernova remnant, the Jellyfish Nebula is known to harbor a neutron star, the remnant of the collapsed stellar core. An emission nebula cataloged as Sharpless 249 fills the field at the upper right. The Jellyfish Nebula is about 5,000 light-years away. At that distance, this narrowband composite image presented in the Hubble Palette would be about 300 light-years across.

APOD: 2016 September 18 - Starry Night Scavenger Hunt
Explanation: Did you know that van Gogh's painting Starry Night includes Comet Hale-Bopp? Hopefully not, because it doesn't. But the featured image does. Although today's picture may appear at first glance to be a faithful digital reproduction of the original Starry Night, actually it is a modern rendition meant not only to honor one of the most famous paintings of the second millennium, but to act as a scavenger hunt. Can you find, in the featured image, a comet, a spiral galaxy, an open star cluster, and a supernova remnant? Too easy? OK, then find, the rings of Supernova 1987A, the NGC 2392, the Crab Nebula, Thor's Helmet, the Cartwheel Galaxy, and the Ant Nebula. Still too easy? Then please identify any more hidden images not mentioned here -- and there are several -- on APOD's main discussion board: The Asterisk. Finally, the collagist has graciously hidden APOD's 10th anniversary Vermeer photomontage just to honor APOD. (Thanks!)

APOD: 2016 July 8 - The Swirling Core of the Crab Nebula
Explanation: At the core of the Crab Nebula lies a city-sized, magnetized neutron star spinning 30 times a second. Known as the Crab Pulsar, it's actually the rightmost of two bright stars, just below a central swirl in this stunning Hubble snapshot of the nebula's core. Some three light-years across, the spectacular picture frames the glowing gas, cavities and swirling filaments bathed in an eerie blue light. The blue glow is visible radiation given off by electrons spiraling in a strong magnetic field at nearly the speed of light. Like a cosmic dynamo the pulsar powers the emission from the nebula, driving a shock wave through surrounding material and accelerating the spiraling electrons. With more mass than the Sun and the density of an atomic nucleus, the spinning pulsar is the collapsed core of a massive star that exploded. The Crab Nebula is the expanding remnant of the star's outer layers. The supernova explosion was witnessed on planet Earth in the year 1054.

APOD: 2015 August 16 - M1: The Crab Nebula from Hubble
Explanation: This is the mess that is left when a star explodes. The Crab Nebula, the result of a supernova seen in 1054 AD, is filled with mysterious filaments. The filaments are not only tremendously complex, but appear to have less mass than expelled in the original supernova and a higher speed than expected from a free explosion. The featured image, taken by the Hubble Space Telescope, is presented in three colors chosen for scientific interest. The Crab Nebula spans about 10 light-years. In the nebula's very center lies a pulsar: a neutron star as massive as the Sun but with only the size of a small town. The Crab Pulsar rotates about 30 times each second.

APOD: 2014 December 3 - Sharpless 249 and the Jellyfish Nebula
Explanation: Normally faint and elusive, the Jellyfish Nebula is caught in this alluring telescopic mosaic. The scene is anchored right and left by two bright stars, Mu and Eta Geminorum, at the foot of the celestial twin while the Jellyfish Nebula is the brighter arcing ridge of emission with dangling tentacles below and right of center. In fact, the cosmic jellyfish is part of bubble-shaped supernova remnant IC 443, the expanding debris cloud from a massive star that exploded. Light from the explosion first reached planet Earth over 30,000 years ago. Like its cousin in astrophysical waters the Crab Nebula supernova remnant, the Jellyfish Nebula is known to harbor a neutron star, the remnant of the collapsed stellar core. An emission nebula cataloged as Sharpless 249 fills the field at the upper left. The Jellyfish Nebula is about 5,000 light-years away. At that distance, this narrowband composite image would be about 300 light-years across.

APOD: 2014 November 21 - M1: The Crab Nebula
Explanation: The Crab Nebula is cataloged as M1, the first object on Charles Messier's famous 18th century list of things which are not comets. In fact, the Crab is now known to be a supernova remnant, debris from the death explosion of a massive star, witnessed by astronomers in the year 1054. This sharp, ground-based telescopic view uses narrowband data to track emission from ionized oxygen and hydrogen atoms (in blue and red) and explore the tangled filaments within the still expanding cloud. One of the most exotic objects known to modern astronomers, the Crab Pulsar, a neutron star spinning 30 times a second, is visible as a bright spot near the nebula's center. Like a cosmic dynamo, this collapsed remnant of the stellar core powers the Crab's emission across the electromagnetic spectrum. Spanning about 12 light-years, the Crab Nebula is a mere 6,500 light-years away in the constellation Taurus.

APOD: 2014 July 25 - Cosmic Crab Nebula
Explanation: The Crab Pulsar, a city-sized, magnetized neutron star spinning 30 times a second, lies at the center of this tantalizing wide-field image of the Crab Nebula. A spectacular picture of one of our Milky Way's supernova remnants, it combines optical survey data with X-ray data from the orbiting Chandra Observatory. The composite was created as part of a celebration of Chandra's 15 year long exploration of the high energy cosmos. Like a cosmic dynamo the pulsar powers the X-ray and optical emission from the nebula, accelerating charged particles to extreme energies to produce the jets and rings glowing in X-rays. The innermost ring structure is about a light-year across. With more mass than the Sun and the density of an atomic nucleus, the spinning pulsar is the collapsed core of the massive star that exploded, while the nebula is the expanding remnant of the star's outer layers. The supernova explosion was witnessed in the year 1054.

APOD: 2013 September 5 - M1: The Incredible Expanding Crab
Explanation: The Crab Nebula is cataloged as M1, the first on Charles Messier's famous list of things which are not comets. In fact, the Crab is now known to be a supernova remnant, an expanding cloud of debris from the explosion of a massive star. The violent birth of the Crab was witnessed by astronomers in the year 1054. Roughly 10 light-years across today, the nebula is still expanding at a rate of over 1,000 kilometers per second. Want to watch the Crab Nebula expand? Check out this video (vimeo) animation comparing an image of M1 taken in 1999 at the European Southern Observatory, with this one, taken in 2012 at the Mt. Lemmon Sky Center. Background stars were used to register the two images. The Crab Nebula lies about 6,500 light-years away in the constellation Taurus.

APOD: 2013 January 9 - The Elusive Jellyfish Nebula
Explanation: Normally faint and elusive, the Jellyfish Nebula is caught in this alluring telescopic view. Drifting near bright star Eta Geminorum, at the foot of a celestial twin, the Jellyfish Nebula is seen dangling tentacles from the bright arcing ridge of emission left of center. In fact, the cosmic jellyfish is part of bubble-shaped supernova remnant IC 443, the expanding debris cloud from a massive star that exploded. Light from the explosion first reached planet Earth over 30,000 years ago. Like its cousin in astrophysical waters the Crab Nebula supernova remnant, IC 443 is known to harbor a neutron star, the remnant of the collapsed stellar core. The Jellyfish Nebula is about 5,000 light-years away. At that distance, this image would be about 100 light-years across.

APOD: 2011 December 25 - M1: The Crab Nebula from Hubble
Explanation: This is the mess that is left when a star explodes. The Crab Nebula, the result of a supernova seen in 1054 AD, is filled with mysterious filaments. The filaments are not only tremendously complex, but appear to have less mass than expelled in the original supernova and a higher speed than expected from a free explosion. The above image, taken by the Hubble Space Telescope, is presented in three colors chosen for scientific interest. The Crab Nebula spans about 10 light-years. In the nebula's very center lies a pulsar: a neutron star as massive as the Sun but with only the size of a small town. The Crab Pulsar rotates about 30 times each second.

APOD: 2011 May 23 - An Unexpected Flare from the Crab Nebula
Explanation: Why does the Crab Nebula flare? No one is sure. The unusual behavior, discovered over the past few years, seems only to occur in very high energy light -- gamma rays. As recently as one month ago, gamma-ray observations of the Crab Nebula by the Fermi Gamma Ray Space Telescope showed an unexpected increase in gamma-ray brightness, becoming about five times the nebula's usual gamma-ray brightness, and fading again in only a few days. Now usually the faster the variability, the smaller the region involved. This might indicate that the powerful pulsar at the center of the Crab, a compact neutron star rotating 30 times a second, is somehow involved. Specifically, speculation is centered on the changing magnetic field that surely surrounds the powerful pulsar. Rapid changes in this field might lead to waves of rapidly accelerated electrons which emit the flares, possibly in ways similar to our Sun. The above image shows how the Crab Nebula normally appears in gamma rays, as compared to the Geminga pulsar, and how it then appeared during the recent brightening.

APOD: 2011 April 18 - Visual Effects: Wonders of the Universe
Explanation: What visual effects are depicted in this video? The effects were created by BDH for the BBC television show Wonders of the Universe, but are unlabeled in this version. Even so, some stills in the video are easily identified, such as the Hubble image of the Carina Nebula that occurs at about 2:22, the Crab Nebula at about 7:45, and the Cat's Eye Nebula that occurs at about 8:16. A pan away from a spiral galaxy occurs at about 4:00, and breathtaking vistas of the spiral occur until past 5:00. Pulsars and supernovas seem to take over at about 9:00 and are truly spectacular. Binary star systems containing a pulsar and an accretion disk occur beginning at about 14:30. Past that, the entire computer animated video seems to sparkle with unknown stars, unknown planets, and sequences where unknown gas is flowing toward unknown places. What, for example, is being depicted at 13:00? Please help create a companion explanation for the video by contributing to APOD's discussion page.

APOD: 2010 December 20 - A Lunar Eclipse on Solstice Day
Explanation: Sometime after sunset tonight, the Moon will go dark. This total lunar eclipse, where the entire Moon is engulfed in the shadow of the Earth, will be visible from all of North America, while the partial phase of this eclipse will be visible throughout much of the rest of the world. Observers on North America's east coast will have to wait until after midnight for totality to begin, while west coasters should be able to see a fully darkened moon before midnight. Pictured above is a digital prediction, in image form, for how the Moon and the surrounding sky could appear near maximum darkness. Rolling your cursor over the image will bring up labels. Parts of the Moon entering the circle labeled umbra will appear the darkest since the Sun there will be completely blocked by the Earth. Parts of the Moon entering the circle labeled penumbra will be exposed to some direct sunlight, and so shine by some degree by reflected light. The diminished glare of the normally full Moon will allow unusually good viewings of nearby celestial wonders such as the supernova remnant Simeis 147, the open star cluster M35, and the Crab Nebula M1. By coincidence this eclipse occurs on the day with the shortest amount of daylight in the northern hemisphere -- the Winter Solstice. This solstice eclipse is the first in 456 years, although so far it appears that no one has figured out when the next solstice eclipse will be.

APOD: 2010 June 15 - Starry Night Scavenger Hunt
Explanation: Did you know that Van Gogh's painting Starry Night includes Comet Hale-Bopp? Hopefully not, because it doesn't. But the above image does. Although today's featured picture may appear at first glance to be a faithful digital reproduction of the original Starry Night, actually it is a modern rendition meant not only to honor one of the most famous paintings of the second millennium, but to act as a scavenger hunt. Can you find, in the above image, a comet, a spiral galaxy, an open star cluster, and a supernova remnant? Too easy? OK, then find, the rings of Supernova 1987A, NGC 2392, the Crab Nebula, Thor's Helmet, the Cartwheel Galaxy, and the Ant Nebula. Still too easy? Then please identify any more hidden images not mentioned here -- and there are several -- on APOD's main discussion board: Starship Asterisk. Finally, the collagist has graciously hidden APOD's 10th anniversary Vermeer photomontage to help honor APOD on its 15th anniversary tomorrow.

APOD: 2010 May 15 - The Elusive Jellyfish Nebula
Explanation: Normally faint and elusive, the Jellyfish Nebula is caught in this alluring, false-color, telescopic view. Flanked by two bright stars, Mu and Eta Geminorum, at the foot of a celestial twin, the Jellyfish Nebula is the brighter arcing ridge of emission with dangling tentacles below and right of center. In fact, the cosmic jellyfish is seen to be part of bubble-shaped supernova remnant IC 443, the expanding debris cloud from a massive star that exploded. Light from the explosion first reached planet Earth over 30,000 years ago. Like its cousin in astrophysical waters the Crab Nebula supernova remnant, IC 443 is known to harbor a neutron star, the remnant of the collapsed stellar core. Emission nebula Sharpless 249 fills the field at the upper left. The Jellyfish Nebula is about 5,000 light-years away. At that distance, this image would be about 300 light-years across. The color scheme used in the narrowband composite was made popular in Hubble Space Telescope images, mapping emission from oxygen, hydrogen, and sulfur atoms to blue, green and red colors.

APOD: 2009 October 25 -M1: The Crab Nebula from Hubble
Explanation: This is the mess that is left when a star explodes. The Crab Nebula, the result of a supernova seen in 1054 AD, is filled with mysterious filaments. The filaments are not only tremendously complex, but appear to have less mass than expelled in the original supernova and a higher speed than expected from a free explosion. The above image, taken by the Hubble Space Telescope, is presented in three colors chosen for scientific interest. The Crab Nebula spans about 10 light-years. In the nebula's very center lies a pulsar: a neutron star as massive as the Sun but with only the size of a small town. The Crab Pulsar rotates about 30 times each second.

APOD: 2009 May 14 - Elusive Jellyfish Nebula
Explanation: Normally faint and elusive, the Jellyfish Nebula is caught in this alluring wide-field telescopic view. Flanked by two yellow-tinted stars, Mu and Eta Geminorum, at the foot of a celestial twin, the Jellyfish Nebula is the brighter arcing ridge of emission with dangling tentacles right of center. In fact, the cosmic jellyfish is seen to be part of bubble-shaped supernova remnant IC 443, the expanding debris cloud from a massive star that exploded. Light from the explosion first reached planet Earth over 30,000 years ago. Like its cousin in astrophysical waters the Crab Nebula supernova remnant, IC 443 is known to harbor a neutron star, the remnant of the collapsed stellar core. Emission nebula Sharpless 249 fills the field at the upper left. The Jellyfish Nebula is about 5,000 light-years away. At that distance, this image would be almost 200 light-years across.

APOD: 2008 December 27 - Crab Pulsar Wind Nebula
Explanation: The Crab Pulsar, a city-sized, magnetized neutron star spinning 30 times a second, lies at the center of this remarkable image from the orbiting Chandra Observatory. The deep x-ray image gives the first clear view of the convoluted boundaries of the Crab's pulsar wind nebula. Like a cosmic dynamo the pulsar powers the x-ray emission. The pulsar's energy accelerates charged particles, producing eerie, glowing x-ray jets directed away from the poles and an intense wind in the equatorial direction. Intriguing edges are created as the charged particles stream away, eventually losing energy as they interact with the pulsar's strong magnetic field. With more mass than the Sun and the density of an atomic nucleus, the spinning pulsar itself is the collapsed core of a massive star. The stellar core collapse resulted in a supernova explosion that was witnessed in the year 1054. This Chandra image spans just under 9 light-years at the Crab's estimated distance of 6,000 light-years.

APOD: 2008 February 17 - M1: The Crab Nebula from Hubble
Explanation: This is the mess that is left when a star explodes. The Crab Nebula, the result of a supernova seen in 1054 AD, is filled with mysterious filaments. The filaments are not only tremendously complex, but appear to have less mass than expelled in the original supernova and a higher speed than expected from a free explosion. The above image, taken by the Hubble Space Telescope, is presented in three colors chosen for scientific interest. The Crab Nebula spans about 10 light-years. In the nebula's very center lies a pulsar: a neutron star as massive as the Sun but with only the size of a small town. The Crab Pulsar rotates about 30 times each second.

APOD: 2006 October 26 - Composite Crab
Explanation: The Crab Nebula is cataloged as M1, the first object on Charles Messier's famous list of things which are not comets. In fact, the Crab is now known to be a supernova remnant, expanding debris from the death explosion of a massive star. This intriguing false-color image combines data from space-based observatories, Chandra, Hubble, and Spitzer, to explore the debris cloud in x-rays (blue-purple), optical (green), and infrared (red) light. One of the most exotic objects known to modern astronomers, the Crab Pulsar, a neutron star spinning 30 times a second, is the bright spot near picture center. Like a cosmic dynamo, this collapsed remnant of the stellar core powers the Crab's emission across the electromagnetic spectrum. Spanning about 12 light-years, the Crab Nebula is 6,500 light-years away in the constellation Taurus.

APOD: 2005 December 2 - Crab Nebula Mosaic from HST
Explanation: The Crab Nebula is cataloged as M1, the first object on Charles Messier's famous list of things which are not comets. In fact, the cosmic Crab is now known to be a supernova remnant, an expanding cloud of debris from the death explosion of a massive star. Light from that stellar catastrophe was first witnessed by astronomers on planet Earth in the year 1054. Composed of 24 exposures taken in October 1999, January 2000, and December 2000, this Hubble Space Telescope mosaic spans about twelve light years. Colors in the intricate filaments trace the light emitted from atoms of hydrogen, oxygen, and sulfur in the debris cloud. The spooky blue interior glow is emitted by high-energy electrons accelerated by the Crab's central pulsar. One of the most exotic objects known to modern astronomers, the pulsar is a neutron star, the spinning remnant of the collapsed stellar core. The Crab Nebula lies about 6,500 light-years away in the constellation Taurus.

APOD: 2005 September 20 - M1: The Crab Nebula from NOT
Explanation: This is the mess that is left when a star explodes. The Crab Nebula, the result of a supernova seen in 1054 AD, is filled with mysterious filaments. The filaments are not only tremendously complex, but appear to have less mass than expelled in the original supernova and a higher speed than expected from a free explosion. The above image, taken by the Nordic Optical Telescope (NOT), is in three colors chosen for scientific interest. The Crab Nebula spans about 10 light-years. In the nebula's very center lies a pulsar: a neutron star as massive as the Sun but with only the size of a small town. The Crab Pulsar rotates about 30 times each second.

APOD: 2005 March 26 - Composite Crab
Explanation: The Crab Pulsar, a city-sized, magnetized neutron star spinning 30 times a second, lies at the center of this composite image of the inner region of the well-known Crab Nebula. The spectacular picture combines optical data (red) from the Hubble Space Telescope and x-ray images (blue) from the Chandra Observatory, also used in the popular Crab Pulsar movies. Like a cosmic dynamo the pulsar powers the x-ray and optical emission from the nebula, accelerating charged particles and producing the eerie, glowing x-ray jets. Ring-like structures are x-ray emitting regions where the high energy particles slam into the nebular material. The innermost ring is about a light-year across. With more mass than the Sun and the density of an atomic nucleus, the spinning pulsar is the collapsed core of a massive star that exploded, while the nebula is the expanding remnant of the star's outer layers. The supernova explosion was witnessed in the year 1054.

APOD: 2004 April 29 - Titan's X-Ray
Explanation: This June's rare and much heralded transit of Venus will feature our currently brilliant evening star in silhouette, as the inner planet glides across the face of the Sun. But on January 5, 2003 an even rarer transit took place. Titan, large moon of ringed gas giant Saturn, crossed in front of the Crab Nebula, a supernova remnant some 7,000 light-years away. During Titan's transit, the orbiting Chandra Observatory's x-ray detectors recorded the shadowing of cosmic x-rays generated by the Crab's amazing pulsar nebula, pictured above, in a situation analogous to a medical x-ray. The resulting image (inset at left) probes the extent of Titan's atmosphere. So, how rare was Titan's transit of the Crab? While Saturn itself passes within a few degrees of the Crab Nebula every 30 years, the next similar transit is reportedly due in 2267. And since the stellar explosion which gave birth to the Crab was seen in 1054, the 2003 Titan transit may have been the first to occur ... ever.

APOD: 2004 April 8 - Elusive Jellyfish Nebula
Explanation: Normally faint and elusive, the Jellyfish Nebula is caught in the net of this spectacular wide-field telescopic view. Flanked by two yellow-tinted stars at the foot of a celestial twin - Mu and Eta Geminorum - the Jellyfish Nebula is the brighter arcing ridge of emission with dangling tentacles just right of center. Here, the cosmic jellyfish is seen to be part of bubble-shaped supernova remnant IC 443, the expanding debris cloud from an exploded star some 5,000 light-years away. Also in view, emission nebula IC 444 nearly fills the field to the upper left, dotted with small blue reflection nebulae. Like its cousin in astrophysical waters, the Crab Nebula, IC 443 is known to harbor a neutron star, the collapsed core of the massive star that exploded over 30,000 years ago.

APOD: 2004 January 28 - The Crab Nebula from CFHT
Explanation: This is the mess that is left when a star explodes. The Crab Nebula, the result of a supernova seen in 1054 AD, is filled with mysterious filaments. The filaments are not only tremendously complex, but appear to have less mass than expelled in the original supernova and a higher speed than expected from a free explosion. The above image, taken by the Canada-France-Hawaii Telescope (CFHT), is in three colors chosen for scientific interest. The Crab Nebula spans about 10 light-years. In the nebula's very center lies a pulsar: a neutron star as massive as the Sun but with only the size of a small town. The Crab Pulsar rotates about 30 times each second.

APOD: 2003 September 14 - The Crab Nebula from VLT
Explanation: The Crab Nebula, filled with mysterious filaments, is the result of a star that was seen to explode in 1054 AD. This spectacular supernova explosion was recorded by Chinese and (quite probably) Anasazi Indian astronomers. The filaments are mysterious because they appear to have less mass than expelled in the original supernova and higher speed than expected from a free explosion. In the above picture taken recently from a Very Large Telescope, the color indicates what is happening to the electrons in differentparts of the Crab Nebula. Red indicates the electrons are recombining with protons to form neutral hydrogen, while blue indicates the electrons are whirling around the magnetic field of the inner nebula. In the nebula's very center lies a pulsar: a neutron star rotating, in this case, 30 times a second.

APOD: 2003 September 4 - Composite Crab
Explanation: The Crab Pulsar, a city-sized, magnetized neutron star spinning 30 times a second, lies at the center of this composite image of the inner region of the well-known Crab Nebula. The spectacular picture combines optical data (red) from the Hubble Space Telescope and x-ray images (blue) from the Chandra Observatory, also used in the popular Crab Pulsar movies. Like a cosmic dynamo the pulsar powers the x-ray and optical emission from the nebula, accelerating charged particles and producing the eerie, glowing x-ray jets. Ring-like structures are x-ray emitting regions where the high energy particles slam into the nebular material. The innermost ring is about a light-year across. With more mass than the Sun and the density of an atomic nucleus, the spinning pulsar is the collapsed core of a massive star that exploded, while the nebula is the expanding remnant of the star's outer layers. The supernova explosion was witnessed in the year 1054.

APOD: 2003 January 10 - The Crab that Played with the Planet
Explanation: Wandering through the constellation Taurus, Saturn made its closest approach to planet Earth last month, tilting its lovely rings toward appreciative skygazers while rising high in midnight skies. On January 4th and 5th, Saturn also crossed in front of the high and far-off Crab Nebula (M1), a cosmic cloud of debris from a stellar explosion and first on the list of astronomer Charles Messier's celestial sights. But Saturn and the Crab made poor playmates, as light from the bright planet overwhelmed the the diffuse nebula, all but hiding the Crab during the transit. Taken on January 2nd, a few days before their closest encounter, this composite digital image illustrates the problem. The subtle nebula is just visible at the right, while on the left, light from a drastically over-exposed Saturn overflows its pixels. Composited into the image is a correctly exposed picture of ringed Saturn with the Saturnian moons labeled. The well-exposed Saturn image was also taken on January 2nd, but captured with an exposure lasting only a fraction of a second, in contrast with the tens of seconds of exposure time required to reveal the Crab.

APOD: 2002 September 20 - The Crab Nebula Pulsar Shrugs
Explanation: How does a city-sized neutron star power the vast Crab Nebula? The expulsion of wisps of hot gas at high speeds appears to be at least part of the answer. Yesterday time-lapse movies taken from both the Chandra X-ray Observatory and the Hubble Space Telescope were released showing a wisp of gas moving out at about half the speed of light. Wisps like this likely result from tremendous electric voltages created by the central pulsar, a rapidly rotating, magnetized, central neutron star. The hot plasma strikes existing gas, causing it glow in colors across the electromagnetic spectrum. Pictured above is a composite image of the center of the Crab Nebula where red represents radio emission, green represents visible emission, and blue represents X-ray emission. The dot at the very center is the hot pulsar spinning 30 times per second.

APOD: 2002 July 14 - The Crab Nebula from VLT
Explanation: The Crab Nebula, filled with mysterious filaments, is the result of a star that was seen to explode in 1054 AD. This spectacular supernova explosion was recorded by Chinese and (quite probably) Anasazi Indian astronomers. The filaments are mysterious because they appear to have less mass than expelled in the original supernova and higher speed than expected from a free explosion. In the above picture taken recently from a Very Large Telescope, the color indicates what is happening to the electrons in different parts of the Crab Nebula. Red indicates the electrons are recombining with protons to form neutral hydrogen, while blue indicates the electrons are whirling around the magnetic field of the inner nebula. In the nebula's very center lies a pulsar: a neutron star rotating, in this case, 30 times a second.

APOD: 2001 December 27 - The Incredible Expanding Crab
Explanation: The Crab Nebula is cataloged as M1, the first on Charles Messier's famous list of things which are not comets. In fact, the Crab is now known to be a supernova remnant, an expanding cloud of debris from the explosion of a massive star. The violent birth of the Crab was witnessed by astronomers in the year 1054. Roughly 10 light-years across today, the nebula is still expanding at a rate of over 1,000 kilometers per second. Flipping between two images made nearly 30 years apart, this animation clearly demonstrates the expansion. The smaller Crab was recorded as a photographic image made in 1973 using the Kitt Peak National Observatory 4-meter telescope in 1973. The expanded Crab was made this year with the Kitt Peak Visitor Center's 0.4-meter telescope and digital camera. Background stars were used to register the two images.

APOD: 2001 September 13 - X-Rays and the Circinus Pulsar
Explanation: A bizarre stellar corpse 19,000 light-years from Earth, pulsar PSR B1509-58 beckons from the small southern constellation of Circinus. Like its cousin at the heart of the Crab nebula, the Circinus pulsar is a rapidly spinning, magnetized neutron star. Seen in this false-color Chandra Observatory image, the environment surrounding this cosmic powerhouse glows in high energy x-rays. The Circinus pulsar itself, thought to generate more than 7 quadrillion volts (7 followed by 15 zeros), lies within the knot of bright emission near the center of the picture. Stretching toward the bottom left, x-ray emission traces a jet of particles almost 20 light-years long that seems to arise from the pulsar's south pole, while the arc of bright emission above the central knot is likely a shockwave produced by particles driven from the pulsar's equator. Near the top of the picture, lower energy x-ray emission shown in green is from gas shock-heated to millions of degrees Celsius. The shocked gas was produced by debris blasted out from the stellar explosion that created the Circinus pulsar.

APOD: 2001 June 2 - The Pulsar Powered Crab
Explanation: In the Summer of 1054 A.D. Chinese astronomers reported that a star in the constellation of Taurus suddenly became as bright as the full Moon. Fading slowly, it remained visible for over a year. It is now understood that a spectacular supernova explosion - the detonation of a massive star whose remains are now visible as the Crab Nebula- was responsible for the apparition. The core of the star collapsed to form a rotating neutron star or pulsar, one of the most exotic objects known to modern astronomers. Like a cosmic lighthouse, the rotating Crab pulsar generates beams of radio, visible, x-ray and gamma-ray energy which, as the name suggests, produce pulses as they sweep across our view. Using a stunning series of visible light images taken with the Hubble Space Telescope (HST) in 1995, astronomers have discovered spectacular pulsar powered motions within the Crab nebula. Highlights of this HST Crab "movie" show wisps of material moving away from the pulsar at half the speed of light, a scintillating halo, and an intense knot of emission dancing, sprite-like, above the pulsar's pole. Only 10 kilometers wide but more massive than the sun, the pulsar's energy drives the dynamics and emission of the nebula itself which is more than 10 light-years across.

APOD: 2001 March 25 - The Crab Nebula from VLT
Explanation: The Crab Nebula, filled with mysterious filaments, is the result of a star that was seen to explode in 1054 AD. This spectacular supernova explosion was recorded by Chinese and (quite probably) Anasazi Indian astronomers. The filaments are mysterious because they appear to have less mass than expelled in the original supernova and higher speed than expected from a free explosion. In the above picture taken recently from a Very Large Telescope, the color indicates what is happening to the electrons in different parts of the Crab Nebula. Red indicates the electrons are recombining with protons to form neutral hydrogen, while blue indicates the electrons are whirling around the magnetic field of the inner nebula. In the nebula's very center lies a pulsar: a neutron star rotating, in this case, 30 times a second.

APOD: 2000 July 11 - The Crab Nebula in Blue and White
Explanation: The Crab Nebula is a complex shell of expanding gas. The Crab Nebula formed from a star that was seen to explode in a supernova about 1000 years ago. This two color composite image taken with the WIYN 3.5-meter telescope shows in great detail filamentary structure of the glowing hydrogen gas. Also known as M1, the center is home to a dense neutron star, a star as massive as our Sun but only the size of a city. The neutron star is a pulsar that spins thirty times a second and spits out energy that powers the nebula. The nebula is named from its likeness to a crab in an early drawing. The Crab Nebula still presents mysteries today as the total mass of the nebula and pulsar appears much less than the mass of the original pre-supernova star!

APOD: 2000 June 9 - Vela Pulsar: Neutron Star-Ring-Jet
Explanation: This stunning image from the orbiting Chandra X-ray Observatory is centered on the Vela pulsar -- the collapsed stellar core within the Vela supernova remnant some 800 light-years distant. The Vela pulsar is a neutron star. More massive than the Sun, it has the density of an atomic nucleus. About 12 miles in diameter it spins 10 times a second as it hurtles through the supernova debris cloud. The pulsar's electric and magnetic fields accelerate particles to nearly the speed of light, powering the compact x-ray emission nebula revealed in the Chandra picture. The cosmic crossbow shape is over 0.2 light-years across, composed of an arrow-like jet emanating from the polar region of the neutron star and bow-like inner and outer arcs believed to be the edges of tilted rings of x-ray emitting high energy particles. Impressively, the swept back compact nebula indicates the neutron star is moving up and to the right in this picture, exactly along the direction of the x-ray jet. The Vela pulsar (and associated supernova remnant) was created by a massive star which exploded over 10,000 years ago. Its awesome x-ray rings and jet are reminiscent of another well-known pulsar powered system, the Crab Nebula.

APOD: 2000 June 5 - In the Heart of the Crab
Explanation: The supernova explosion that formed the Crab Nebula was first seen on the year 1054. Last week, astronomers released a new image of the still-evolving center of the explosion. The above representative-color photograph was taken in colors emitted by specific elements including hydrogen (orange), nitrogen (red), sulfur (pink), and oxygen (green), with the result appearing oddly similar to a Jackson Pollock painting. Visible is a complex array of gas filaments rushing out at over 5 million kilometers per hour. Even at these tremendous speeds, though, it takes a filament over 600 years to cross the 3 light year wide frame. The rapidly spinning neutron star remnant of this ancient cataclysm is visible as the lower of the two bright stars just above the photograph center. The Crab Nebula (M1) is located 6,500 light-years away towards the constellation of Taurus.

APOD: 2000 March 11 - Messier Marathon
Explanation: Gripped by an astronomical spring fever, it's once again time for many amateur stargazers to embark on a Messier Marathon! The Vernal Equinox occurs March 20, marking the first day of Spring for the Northern Hemisphere. It also marks a favorable celestial situation for potentially viewing all the objects in 18th century French astronomer Charles Messier's catalog in one glorious dusk to dawn observing run. This year a bright full moon will interfere with dark skies near the actual equinox, so good nights near new moon for weekend marathoners are March 11/12 and April 1/2. (As an added bonus all the planets in the solar system can be viewed on these dates.) Astronomer Paul Gitto has created this masterful Messier Marathon grid with 11 rows and 10 columns of Messier catalog objects. In numerical order, the grid begins with M1, the Crab Nebula, at upper left and ends with M110, a small elliptical galaxy in Andromeda (lower right). Gitto's images were made with a digital camera and a 10-inch diameter reflecting telescope.

APOD: November 22, 1999 - The Crab Nebula from VLT
Explanation: The Crab Nebula, filled with mysterious filaments, is the result of a star that was seen to explode in 1054 AD. This spectacular supernova explosion was recorded by Chinese and (quite probably) Anasazi Indian astronomers. The filaments are mysterious because they appear to have less mass than expelled in the original supernova and higher speed than expected from a free explosion. In the above picture taken recently from a Very Large Telescope, the color indicates what is happening to the electrons in different parts of the Crab Nebula. Red indicates the electrons are recombining with protons to form neutral hydrogen, while blue indicates the electrons are whirling around the magnetic field of the inner nebula. In the nebula's very center lies a pulsar: a neutron star rotating, in this case, 30 times a second.

APOD: September 29, 1999 - The Crab Nebula in X Rays
Explanation: 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.

APOD: March 18, 1999 - Messier Marathon
Explanation: Gripped by an astronomical spring fever, this week many amateur stargazers embark on a Messier Marathon. The Vernal Equinox occurs Saturday, March 20, marking the first day of Spring for the Northern Hemisphere. It also marks a favorable celestial situation for potentially viewing all the objects in 18th century French astronomer Charles Messier's catalog in one glorious dusk to dawn observing run. This year, interference from bright moonlight will be minimal as the the moon is near its dark or new phase. Astronomer Paul Gitto has created this masterful Messier Marathon grid with 11 rows and 10 columns of Messier catalog objects. In numerical order, the grid begins with M1, the Crab Nebula, at upper left and ends with M110, a small elliptical galaxy in Andromeda (lower right). Gitto's images were made with a digital camera and a 10-inch diameter reflecting telescope.

APOD: November 22, 1998 - The High Energy Crab Nebula
Explanation: This is the mess that is left when a star explodes. The Crab Nebula is so energetic that it glows in every kind of light known. Shown above are images of the Crab Nebula from visible light to the X-ray band. NUV stands for "near ultraviolet" light, FUV means "far ultraviolet" light, and VIS means visible light. In the center of the Crab Nebula lies the powerful Crab pulsar - a spinning neutron star with mass comparable to our Sun but with the diameter of only a small town. The pulsar expels particles and radiation in a beam that sweeps past the Earth 30 times a second. The supernova that created the Crab Nebula was seen by ancient Chinese astronomers and possibly even the Anasazi Indians -- in 1054 AD, perhaps glowing for a week as bright as the full moon. The Crab still presents mysteries today as the total mass of the nebula and pulsar appears much less than the mass of the original pre-supernova star!

APOD: September 5, 1998 - The Pulsar Powered Crab
Explanation: In the Summer of 1054 A.D. Chinese astronomers reported that a star in the constellation of Taurus suddenly became as bright as the full Moon. Fading slowly, it remained visible for over a year. It is now understood that a spectacular supernova explosion - the detonation of a massive star whose remains are now visible as the Crab Nebula- was responsible for the apparition. The core of the star collapsed to form a rotating neutron star or pulsar, one of the most exotic objects known to 20th century astronomy. Like a cosmic lighthouse, the rotating Crab pulsar generates beams of radio, visible, x-ray and gamma-ray energy which, as the name suggests, produce pulses as they sweep across our view. Using a stunning series of visible light images taken with the Hubble Space Telescope (HST), astronomers have discovered spectacular pulsar powered motions within the Crab nebula. Highlights of this HST Crab "movie" show wisps of material moving away from the pulsar at half the speed of light, a scintillating halo, and an intense knot of emission dancing, sprite-like, above the pulsar's pole. Only 6 miles wide but more massive than the sun, the pulsar's energy drives the dynamics and emission of the nebula itself which is more than 10 lightyears across. In this HST image, the pulsar is the left most of the two bright central stars.

APOD: February 11, 1998 - Ultra Fast Pulsar
Explanation: Pulsars are rotating neutron stars, born in the violent crucibles of supernova explosions. Like cosmic lighthouses, beams of radiation from surface hotspots sweep past our viewpoint creating pulses which reveal the rotation rates of these incredibly dense stellar corpses. The most famous pulsar of all is found in the nearby supernova remnant, the Crab Nebula. The Crab's young pulsar is fast. Rotating at 33 times a second, its radiation energizes the surrounding gaseous stellar debris. But using archival observations from orbiting X-ray telescopes, astronomers have recently identified another "Crab-like" pulsar that is even faster. Located in the Large Magellanic Cloud (LMC), X-ray pulses from this newly discovered pulsar, in the supernova remnant N157B, indicate an even faster rotation rate - 62 times a second - making it the fastest known pulsar associated with a supernova remnant. This contoured, false color X-ray image of a portion of the LMC shows the location of N157B along with the core of the nearby hot star cluster R136, and the site of another Crab-like pulsar in SNR 0540-69.3 (rotating a mere 20 times a second). The image is about 1,500 light-years across.

APOD: February 8, 1998 - M1: Filaments of the Crab Nebula
Explanation: The Crab Nebula, filled with mysterious filaments, is the result of a star that exploded in 1054 AD. This spectacular supernova explosion was recorded by Chinese and (quite probably) Anasazi Indian astronomers. The filaments are mysterious because they appear to have less mass than expelled in the original supernova and higher speed than expected from a free explosion. In the above picture, the color indicates what is happening to the electrons in different parts of the Crab Nebula. Red indicates the electrons are recombining with protons to form neutral hydrogen, while green indicates the electrons are whirling around the magnetic field of the inner nebula. In the nebula's very center lies a pulsar: a neutron star rotating, in this case, 30 times a second.

APOD: February 7, 1997 - M1: Filaments of the Crab Nebula
Explanation: The Crab Nebula is filled with mysterious filaments. The Crab Nebula is the result of a star that exploded in 1054 AD. This spectacular supernova explosion was recorded by Chinese and (quite probably) Anasazi Indian astronomers. The filaments are mysterious because they appear to have less mass than expelled in the original supernova and higher speed than expected from a free explosion. In the above picture, the color indicates what is happening to the electrons in different parts of the Crab Nebula. Red indicates the electrons are recombining with protons to form neutral hydrogen, while green indicates the electrons are whirling around the magnetic field of the inner nebula. In the nebula's very center lies a pulsar: a neutron star rotating, in this case, 30 times a second.

APOD: September 9, 1996 - The High Energy Crab Nebula
Explanation: This is the mess that is left when a star explodes. The Crab Nebula is so energetic that it glows in every kind of light known. Shown above are images of the Crab Nebula from visible light to the X-ray band. NUV stands for "near ultraviolet" light, FUV means "far ultraviolet" light, and VIS means visible light. In the center of the Crab Nebula lies the powerful Crab pulsar - a spinning neutron star with mass comparable to our Sun but with the diameter of only a small town. The pulsar expels particles and radiation in a beam that sweeps past the Earth 30 times a second. The supernova that created the Crab Nebula was seen by ancient Chinese astronomers and possibly even the Anasazi Indians -- in 1054 AD, perhaps glowing for a week as bright as the full moon. The Crab still presents mysteries today as the total mass of the nebula and pulsar appears much less than the mass of the original pre-supernova star!

APOD: June 26, 1996 - Happy Birthday Charles Messier: M1
Explanation: French astronomer Charles Messier was born on June 26, 1730. Inspired by childhood sightings of comets and a solar eclipse visible from his home town of Badonvillier, he became an astronomer and comet hunter who kept careful records of his observations. While hunting for comets in the skies above France he made a now famous list of the positions of about 100 fuzzy, diffuse looking objects which appeared at fixed positions in the sky. Although these objects looked like comets, Messier knew that since they did not move with respect to the background stars they could not be the comets he was searching for. These objects are now well known to modern astronomers to be among the brightest and most striking nebulae, star clusters, and galaxies. Objects on Messier's list are still referred to by their "Messier number". The first object in his catalog, M1 pictured above - also known as the Crab Nebula, was recorded during his search for the return of comet Halley in 1758. Messier died in his home in Paris in 1817.

APOD: May 31, 1996 - The Pulsar Powered Crab
Explanation: In the Summer of 1054 A.D. Chinese astronomers reported that a star in the constellation of Taurus suddenly became as bright as the full Moon. Fading slowly, it remained visible for over a year. It is now understood that a spectacular supernova explosion - the detonation of a massive star whose remains are now visible as the Crab Nebula- was responsible for the apparition. The core of the star collapsed to form a rotating neutron star or pulsar, one of the most exotic objects known to 20th century astronomy. Like a cosmic lighthouse, the rotating Crab pulsar generates beams of radio, visible, x-ray and gamma-ray energy which, as the name suggests, produce pulses as they sweep across our view. Using a stunning series of visible light images taken with the Hubble Space Telescope (HST), astronomers have recently discovered spectacular pulsar powered motions within the Crab nebula. Highlights of this HST Crab "movie" show wisps of material moving away from the pulsar at half the speed of light, a scintillating halo, and an intense knot of emission dancing, sprite-like, above the pulsar's pole. Only 6 miles wide but more massive than the sun, the pulsar's energy drives the dynamics and emission of the nebula itself which is more than 10 lightyears across. In the HST image above, the pulsar is the left most of the two bright central stars.

APOD: November 23, 1995 - M1: Polarization of the Crab
Explanation: The Crab Nebula resulted from a star that exploded - a supernova. Although the stellar explosion that caused the Crab Nebula was seen over 900 years ago, the nebula itself still expands and shines. Much of the emitted light has been found to be polarized. Light waves with the same polarization vibrate in the same plane. Light waves can be polarized by reflection from a surface, an effect familiar to sunglass wearing fishermen and skiers. Polarized light can also be emitted by regions that contain strong magnetic fields. Areas of different polarization above are highlighted by different colors. Mapping the polarization helps astronomers decipher which physical processes create the observed light.

APOD: November 22, 1995 - M1: The Exploding Crab Nebula
Explanation: The Crab Nebula resulted from a star that exploded - a supernova. The outer layers of the star were thrown violently into space, while the inner core collapsed to form a neutron star. This neutron star is visible to us today as a pulsar - a rotating star at the center of the nebula that emits visible flashes of light. The Crab Pulsar flashes about 30 times every second. Although the stellar explosion that caused the Crab Nebula was seen over 900 years ago, the nebula itself still expands and shines. How the nebula obtains the energy needed to shine was a mystery eventually solved by noting that this energy could be released by the slowing of the pulsar's rotation.

APOD: July 25, 1995 - M1: The Crab Nebula
Explanation: In the year 1054 a star in the constellation of Taurus exploded in a spectacular supernova so bright it appeared to dominate the sky except for the Sun and Moon for many days. It left behind one of the most brilliant nebulae, listed first in Charles Messier's list of nebulous sky objects. Today we know that the center of the nebula houses the remnant of the explosion: a spinning neutron star called a pulsar. The Crab pulsar is visible in almost every part of the electromagnetic spectrum, and has been a useful astronomical tool. It is still unclear how the the pulsar emits the light that we see.

APOD: June 24, 1995 - Gamma Ray Crab, Geminga
Explanation: What if you could "see" in gamma-rays? If you could, these two spinning neutron stars or pulsars would be among the brightest objects in the sky. This computer processed image shows the Crab Nebula pulsar (below and right of center) and the Geminga pulsar (above and left of center) in the "light" of gamma-rays. Gamma-ray photons are more than 10,000 times more energetic than visible light photons and are blocked from the Earths's surface by the atmosphere. This image was produced by the high energy gamma-ray telescope "EGRET" on board NASA's orbiting Compton Observatory satellite.