Astronomy Picture of the Day Search Results for "Hale-Bopp"

APOD: 2022 April 8 - Hale-Bopp: The Great Comet of 1997
Explanation: Only twenty-five years ago, Comet Hale-Bopp rounded the Sun and offered a dazzling spectacle in planet Earth's night skies. Digitized from the original astrophoto on 35mm color slide film, this classic image of the Great Comet of 1997 was recorded a few days after its perihelion passage on April 1, 1997. Made with a camera and telephoto lens piggy-backed on a small telescope, the 10 minute long, hand-guided exposure features the memorable tails of Hale-Bopp, a whitish dust tail and blue ion tail. Here, the ion tail extends well over ten degrees across the northern sky. In all, Hale-Bopp was reported as visible to the naked eye from late May 1996 through September 1997. Also known as C/1995 O1, Hale-Bopp is recognized as one of the most compositionally pristine comets to pass through the inner Solar System. A visitor from the distant Oort cloud, the comet's next perihelion passage should be around the year 4380 AD. Do you remember Hale-Bopp?

APOD: 2021 December 8 - Comet Hale Bopp Over Val Parola Pass
Explanation: Comet Hale-Bopp, the Great Comet of 1997, became much brighter than any surrounding stars. It was seen even over bright city lights. Away from city lights, however, it put on quite a spectacular show. Here Comet Hale-Bopp was photographed above Val Parola Pass in the Dolomite mountains surrounding Cortina d'Ampezzo, Italy. Comet Hale-Bopp's blue ion tail, consisting of ions from the comet's nucleus, is pushed out by the solar wind. The white dust tail is composed of larger particles of dust from the nucleus driven by the pressure of sunlight, that orbit behind the comet. Comet Hale-Bopp (C/1995 O1) remained visible to the unaided eye for 18 months -- longer than any other comet in recorded history. The large comet is next expected to return around the year 4385. This month, Comet Leonard is brightening and may soon become visible to the unaided eye.

APOD: 2020 July 11 - The Tails of Comet NEOWISE
Explanation: Comet NEOWISE (C/2020 F3) is now sweeping through northern skies. Its developing tails stretch some six degrees across this telescopic field of view, recorded from Brno, Czech Republic before daybreak on July 10. Pushed out by the pressure of sunlight itself, the comet's broad, yellowish dust tail is easiest to see. But the image also captures a fainter, more bluish tail too, separate from the reflective comet dust. The fainter tail is an ion tail, formed as ions from the cometary coma are dragged outward by magnetic fields in the solar wind and fluoresce in the sunlight. In this sharp portrait of our new visitor from the outer Solar System, the tails of comet NEOWISE are reminiscent of the even brighter tails of Hale Bopp, the Great Comet of 1997.

APOD: 2017 April 9 - Comet Hale Bopp Over Val Parola Pass
Explanation: Comet Hale-Bopp, the Great Comet of 1997, became much brighter than any surrounding stars. It was seen even over bright city lights. Away from city lights, however, it put on quite a spectacular show. Here Comet Hale-Bopp was photographed above Val Parola Pass in the Dolomite mountains surrounding Cortina d'Ampezzo, Italy. Comet Hale-Bopp's blue ion tail, consisting of ions from the comet's nucleus, is pushed out by the solar wind. The white dust tail is composed of larger particles of dust from the nucleus driven by the pressure of sunlight, that orbit behind the comet. Comet Hale-Bopp (C/1995 O1) remained visible to the unaided eye for 18 months -- longer than any other comet in recorded history. This year marks the 20th anniversary of Comet Hale-Bopp's last trip to the inner Solar System. The large comet is next expected to return around the year 4385.

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: 2013 November 24 - Comet Hale Bopp Over Indian Cove
Explanation: Comet Hale-Bopp, the Great Comet of 1997, was quite a sight. In the above photograph taken on 1997 April 6, Comet Hale-Bopp was imaged from the Indian Cove Campground in the Joshua Tree National Park in California, USA. A flashlight was used to momentarily illuminate foreground rocks in this six minute exposure. An impressive blue ion tail was visible above a sunlight-reflecting white dust tail. Comet Hale-Bopp remained visible to the unaided eye for over a year before returning to the outer Solar System and fading. As Comet ISON approaches the Sun this week, sky enthusiasts around the Earth are waiting to see if its tails will become even more spectacular than those displayed by Comet Hale-Bopp.

APOD: 2013 October 13 - Hale Bopp: The Great Comet of 1997
Explanation: Sixteen years ago, Comet Hale-Bopp rounded the Sun and offered a dazzling spectacle in planet Earth's night. This stunning view, recorded shortly after the comet's 1997 perihelion passage, features the memorable tails of Hale-Bopp -- a whitish dust tail and blue ion tail. Here, the ion tail extends well over ten degrees across the northern sky, fading near the double star clusters in Perseus, while the head of the comet lies near Almach, a bright star in the constellation Andromeda. Do you remember Hale-Bopp? The photographer's sons do, pictured in the foreground at ages 12 and 15. In all, Hale-Bopp was reported as visible to the naked eye from roughly late May 1996 through September 1997. Currently, sky enthusiasts await Comet ISON's continued brightening in the coming weeks, unsure how interesting its first journey to the inner Solar System will be.

APOD: 2012 December 23 - Comet Hale Bopp Over Val Parola Pass
Explanation: Comet Hale-Bopp, the Great Comet of 1997, became much brighter than any surrounding stars. It was seen even over bright city lights. Away from city lights, however, it put on quite a spectacular show. Here Comet Hale-Bopp was photographed above Val Parola Pass in the Dolomite mountains surrounding Cortina d'Ampezzo, Italy. Comet Hale-Bopp's blue ion tail, consisting of ions from the comet's nucleus, is pushed out by the solar wind. The white dust tail is composed of larger particles of dust from the nucleus driven by the pressure of sunlight, that orbit behind the comet. Observations showed that Comet Hale-Bopp's nucleus spins about once every 12 hours. A comet that may well exceed Hale-Bopp's peak brightness is expected to fall into the inner Solar System next year.

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: 2008 March 2 - Comet Hale Bopp Over Val Parola Pass
Explanation: Comet Hale-Bopp, the Great Comet of 1997, became much brighter than any surrounding stars. It was seen even over bright city lights. Away from city lights, however, it put on quite a spectacular show. Here Comet Hale-Bopp was photographed above Val Parola Pass in the Dolomite mountains surrounding Cortina d'Ampezzo, Italy. Comet Hale-Bopp's blue ion tail, consisting of ions from the comet's nucleus, is pushed out by the solar wind. The white dust tail is composed of larger particles of dust from the nucleus driven by the pressure of sunlight, that orbit behind the comet. Observations showed that Comet Hale-Bopp's nucleus spins about once every 12 hours.

APOD: 2007 March 31 - Hale-Bopp: The Great Comet of 1997
Explanation: Ten short years ago, Comet Hale-Bopp rounded the Sun and offered a dazzling spectacle in planet Earth's night. This stunning view, recorded shortly after the comet's perihelion passage on April 1, 1997, features the memorable tails of Hale-Bopp -- a whitish dust tail and blue ion tail. Here, the ion tail extends well over ten degrees across the northern sky, fading near the double star clusters in Perseus, while the head of the comet lies near Almach, a bright star in the constellation Andromeda. Do you remember Hale-Bopp? The photographer's sons do, pictured in the foreground at ages 12 and 15. In all, Hale-Bopp was reported as visible to the naked eye from roughly late May 1996 through September 1997.

APOD: 2007 January 24 - A Comet Tail Horizon
Explanation: What's happening over the horizon? Many a sky enthusiast who thought they had seen it all had never seen anything like this. To the surprise of many Northern Hemisphere observers, the tail of Comet McNaught remained visible even after the comet's head set ahead of the Sun. What's more, visible were bright but extremely rare filamentary striae from the comet's expansive dust tail. The cause of dust tail striae are not known for sure, but are possibly related to fragmentation of comet's nucleus. The last comet to show prominent striae was Comet Hale-Bopp in 1997. Pictured above, the tail of Comet McNaught was caught just after sunset last Friday above the Carnic Alps of northern Italy.

APOD: 2006 August 13 - The Comet and the Galaxy
Explanation: The Moon almost ruined this photograph. During late March and early April 1997, Comet Hale-Bopp passed nearly in front of the Andromeda Galaxy. Here the Great Comet of 1997 and the Great Galaxy in Andromeda were photographed together on 1997 March 24th. The problem was the brightness of the Moon. The Moon was full that night and so bright that long exposures meant to capture the tails of Hale-Bopp and the disk of M31 would capture instead only moonlight reflected off the Earth's atmosphere. By the time the Moon would set, this opportunity would be gone. That's why this picture was taken during a total lunar eclipse.

APOD: 2005 September 4 - Comet Hale Bopp Over Val Parola Pass
Explanation: Comet Hale-Bopp became much brighter than any surrounding stars. It was seen even over bright city lights. Out away from city lights, however, it put on quite a spectacular show. Here Comet Hale-Bopp was photographed above Val Parola Pass in the Dolomite mountains surrounding Cortina d'Ampezzo, Italy. Comet Hale-Bopp's blue ion tail was created when fast moving particles from the solar wind struck expelled ions from the comet's nucleus. The white dust tail is composed of larger particles of dust and ice expelled by the nucleus that orbit behind the comet. Observations showed that Comet Hale-Bopp's nucleus spins about once every 12 hours.

APOD: 2005 May 22 - The Dust and Ion Tails of Comet Hale-Bopp
Explanation: In 1997, Comet Hale-Bopp's intrinsic brightness exceeded any comet since 1811. Since it peaked on the other side of the Earth's orbit, however, the comet appeared only brighter than any comet in two decades. Visible above are the two tails shed by Comet Hale-Bopp. The blue ion tail is composed of ionized gas molecules, of which carbon monoxide particularly glows blue when reacquiring electrons. This tail is created by the particles from the fast solar wind interacting with gas from the comet's head. The blue ion tail points directly away from the Sun. The light colored dust tail is created by bits of grit that have come off the comet's nucleus and are being pushed away by the pressure of light from the Sun. This tail points nearly away from the Sun. The above photograph was taken in March 1997.

APOD: 2004 October 3 - Comet Hale Bopp and the North America Nebula
Explanation: Comet Hale-Bopp's 1997 encounter with the inner Solar System allowed many breath-taking pictures. Above, Comet Hale-Bopp was photographed crossing the constellation of Cygnus, sporting spectacular yellow dust and blue ion tails. Visible on the right in red is the North America Nebula, a bright emission nebula observable from a dark location with binoculars. The North America Nebula is about 1500 light-years away, much farther than the comet, which was only about 8 light minutes away. Several bright blue stars from the open cluster M39 are visible just above the comet's blue ion tail.

APOD: 2004 April 20 - Comet Hale Bopp Over Indian Cove
Explanation: Comet Hale-Bopp, the Great Comet of 1997, was quite a sight. No comets of comparable brightness have graced the skies of Earth since then. During this next month, however, even besides the fleeting Comet Bradfield, two comets have a slight chance of rivaling Hale-Bopp and a good chance of putting on a memorable sky show. Unfortunately, most of the show will be confined to sky gazers in Earth's southern hemisphere. Both comets are already visible to the unaided eye from there. The first, Comet C/2002 T7 (LINEAR), should be at its best before dawn during the first weeks of May from the south. The second, Comet C/2001 Q4 (NEAT), should be visible in early May from all over the Earth. Both comets appear to be approaching the inner Solar System for the first time and so it is very hard to predict how bright each will become. In the above photograph taken 1997 April 6, Comet Hale-Bopp was imaged from the Indian Cove Campground in the Joshua Tree National Forest in California, USA. A flashlight was used to momentarily illuminate foreground rocks during this six minute exposure.

APOD: 2004 March 14 - Comet Hale Bopp Over Val Parola Pass
Explanation: Comet Hale-Bopp became much brighter than any surrounding stars. It was seen even over bright city lights. Out away from city lights, however, it put on quite a spectacular show. Here Comet Hale-Bopp was photographed above Val Parola Pass in the Dolomite mountains surrounding Cortina d'Ampezzo, Italy. Comet Hale-Bopp's blue ion tail was created when fast moving particles from the solar wind struck expelled ions from the comet's nucleus. The white dust tail is composed of larger particles of dust and ice expelled by the nucleus that orbit behind the comet. Observations showed that Comet Hale-Bopp's nucleus spins about once every 12 hours.

APOD: 2002 November 16 - Tempel-Tuttle: The Leonid Comet
Explanation: Star trails streak this composite time exposure of comet Tempel-Tuttle recorded by Tim Puckett on January 26, 1998. Then passing through the inner solar system on its 33 year orbit around the Sun, Tempel-Tuttle brightened unexpectedly, but binoculars or small telescopes were still required to visually observe it. Tempel-Tuttle is also called "the Leonid Comet" as the yearly Leonid meteor shower results when the Earth crosses this comet's orbital plane and encounters a trail of cometary dust. So, while not rivaling spectacular naked-eye comets like Hyakutake or Hale-Bopp, Tempel-Tuttle still puts on a show. The Earth is now approaching relatively dense regions of Tempel-Tuttle's orbiting debris trail, so in the next few days, skywatchers will be searching for leonid meteors. An extremely active meteor shower is expected to be visible over Europe and North America in the early morning hours of Tuesday, November 19, despite interference from a glaring full moon.

APOD: 2001 May 27 - Comet Hale-Bopp Over Val Parola Pass
Explanation: Comet Hale-Bopp became much brighter than any surrounding stars. It was seen even over bright city lights. Out away from city lights, however, it put on quite a spectacular show. Here Comet Hale-Bopp was photographed above Val Parola Pass in the Dolomite mountains surrounding Cortina d'Ampezzo, Italy. Comet Hale-Bopp's blue ion tail was created when fast moving particles from the solar wind struck expelled ions from the comet's nucleus. The white dust tail is composed of larger particles of dust and ice expelled by the nucleus that orbit behind the comet. Observations showed that Comet Hale-Bopp's nucleus spins about once every 12 hours.

APOD: 2001 March 26 - Comet Hale Bopp in the Outer Solar System
Explanation: Whatever became of Comet Hale-Bopp? The brightest comet in recent years has continued into the outer Solar System and is now farther from the Sun than Saturn. To the surprise of many, Comet Hale-Bopp is still active, continuing to spew gas, ice and dust particles out into space. Pictured above earlier this month, Comet Hale-Bopp can be seen in the Southern Hemisphere with a moderate sized-telescope. The continued activity of Comet Hale-Bopp may be due to the large size of its nucleus - estimated to be about 50 kilometers across. The unusual dotted appearance of most stars in the above image is due to the 14 discrete exposures that were centered on the comet and not the stars.

APOD: 2000 December 27 - The Dust and Ion Tails of Comet Hale Bopp
Explanation: In 1997, Comet Hale-Bopp's intrinsic brightness exceeded any comet since 1811. Since it peaked on the other side of the Earth's orbit, however, the comet appeared only brighter than any comet in two decades. Visible above are the two tails shed by Comet Hale-Bopp. The blue ion tail is composed of ionized gas molecules, of which carbon monoxide particularly glows blue when reacquiring electrons. This tail is created by the particles from the fast solar wind interacting with gas from the comet's head. The blue ion tail points directly away from the Sun. The white dust tail is created by bits of grit that have come off the comet's nucleus and are being pushed away by the pressure of light from the Sun. This tail points nearly away from the Sun. The above photograph was taken in March 1997.

APOD: 2000 July 27 - Tails Of Comet LINEAR
Explanation: Comet C/1999 S4 LINEAR is only one of many comets discovered with the Lincoln Near Earth Asteroid Research (LINEAR) telescope operating near Soccoro, New Mexico, USA. Traveling steadily southward through Earth's night sky, C/1999 S4 passed perihelion (closest approach to the Sun) yesterday on what is likely its first trip through the inner solar system. Now fading, comet LINEAR became no brighter than about 6th magnitude, but is still easily visible with binoculars in northern hemisphere skies. While the memorable comets Hale-Bopp and Hyakutake were much brighter, comet LINEAR is displaying delightful tails evident in this false-color composite image from the Crni Vrh Observatory in Slovenia. The combined series of exposures made on July 22nd are registered on the comet. In the resulting picture, stars appear as rows of dots, but the faint structures in the comet's tail are beautifully recorded. Presently seen moving from Ursa Major to Leo this comet LINEAR will begin to shine in southern hemisphere skies in August.

APOD: 2000 June 11 - Sirius: The Brightest Star in the Night
Explanation: Sirius is the brightest star in the night sky. Sirius is visible on the far left of the above photograph, to the left of the constellation of Orion and Comet Hale-Bopp. Intrinsically, Sirius is over 20 times brighter than our Sun and over twice as massive. As Sirius is 8.7 light years distant, it is not the closest star system - the Alpha Centauri system holds this distinction. Sirius is called the Dog Star because of its prominence in the constellation of Canis Majoris (Big Dog). In 1862, Sirius was discovered to be a binary star system with a companion star, Sirius B, 10,000 times dimmer than the bright primary, Sirius A. Sirius B was the first white dwarf star discovered, a type of star first understood by Subrahmanyan Chandrasekhar in 1930. While studying Sirius in 1718, Edmond Halley discovered that stars move with respect to each other. There is conflicting evidence that Sirius appeared more red only 2000 years ago.

APOD: 2000 April 13 - Exploring Comet Tails
Explanation: Comets are known for their tails. In the spring of 1997 and 1996 Comet Hale-Bopp (above) and Comet Hyakutake gave us stunning examples as they passed near the Sun. These extremely active comets were bright, naked-eye spectacles offering researchers an opportunity to telescopically explore the composition of primordial chunks of our solar system by studying their long and beautiful tails. But it has only recently been discovered that surprising readings from experiments on-board the interplanetary Ulysses probe which lasted for several hours on May 1, 1996, indicate the probe passed through comet Hyakutake's tail! Ulysses experiments were intended to study the Sun and solar wind and the spacecraft-comet encounter was totally unanticipated. Relative positions of Ulysses and Hyakutake on that date indicate that this comet's ion tail stretched an impressive 360 million miles or about four times the Earth-Sun distance. This makes Hyakutake's tail the longest ever recorded and suggests that comet tails are much longer than previously believed.

APOD: November 13, 1999 - Tempel Tuttle: The Leonid Comet
Explanation: Star trails streak this composite time exposure of Comet Tempel-Tuttle recorded by T. Puckett on January 26, 1998. Then passing through the inner solar system on its 33 year orbit around the Sun, Tempel-Tuttle brightened unexpectedly, but binoculars or small telescopes were still required to visually observe it. Tempel-Tuttle is also called "the Leonid Comet" as the yearly Leonid meteor shower results when the Earth crosses this comet's orbital plane and encounters cometary dust. So, while not rivaling spectacular naked-eye comets like Hyakutake or Hale-Bopp, Tempel-Tuttle still puts on a show. When the Earth plunges through Tempel-Tuttle's debris tail in November of this year, many sky-watchers are anticipating an extremely active meteor shower to result, perhaps even a meteor storm!

APOD: September 9, 1999 - Comet Hale Bopp Over the Superstition Mountains
Explanation: Four years ago, Comet Hale-Bopp was discovered out near Jupiter falling toward the inner Solar System. Two years ago, it provided spectacular pictures as it neared its closest approach to the Sun. Still today, spectacular pictures of the brightest comet of the 1990s are surfacing. Above, Comet Hale-Bopp was photographed in 1997 behind the Superstition Mountains in Arizona. Clearly visible are the comets white dust tail that shines by reflected sunlight, and the blue ion tail that shines by glowing gas. Currently, there are several comets visible from the proper location with a small telescope. A comet visible to the unaided eye appears about once every five years.

APOD: August 8, 1999 - Comet Hale-Bopp Over Val Parola Pass
Explanation: Comet Hale-Bopp became much brighter than any surrounding stars. It was seen even over bright city lights. Out away from city lights, however, it put on quite a spectacular show. Here Comet Hale-Bopp was photographed above Val Parola Pass in the Dolomite mountains surrounding Cortina d'Ampezzo, Italy. Comet Hale-Bopp's blue ion tail was created when fast moving particles from the solar wind struck expelled ions from the comet's nucleus. The white dust tail is composed of larger particles of dust and ice expelled by the nucleus that orbit behind the comet. Observations showed that Comet Hale-Bopp's nucleus spins about once every 12 hours.

APOD: July 2, 1999 - Shadow Of A Comet
Explanation: Hale-Bopp, the Great Comet of 1997, may have been the most viewed comet in history - visible even from bright metropolitan skies. Astronomers are now reporting that this magnificent comet also cast a shadow against the glare of the solar system's ultraviolet haze. This false-color image represents a slice of the sky viewed by the SWAN (Solar Wind ANisotropy) instrument aboard the space-based SOHO observatory. Recorded on March 8, 1997 it shows a general haze of solar ultraviolet light scattered by interstellar hydrogen. The sun itself is positioned below the bottom center of the cropped image and the large bright spot is ultraviolet sunlight scattered by the cloud of hydrogen gas surrounding Hale-Bopp's nucleus. Just above and to the left is a broad, diffuse, dark streak - the 150 million kilometer long shadow produced by the denser regions of this hydrogen envelope. Why are comets surrounded by hydrogen? The hydrogen comes from the breakup of water (H20) vapor released as the comet nucleus approaches the sun. These observations indicate that Hale-Bopp's nucleus was producing about 300 tons of water per second.

APOD: March 14, 1999 - The Comet and the Galaxy
Explanation: The Moon almost ruined this photograph. During late March and early April 1997, Comet Hale-Bopp passed nearly in front of the Andromeda Galaxy. Here the Great Comet of 1997 and the Great Galaxy in Andromeda were photographed together on 1997 March 24th. The problem was the brightness of the Moon. The Moon was full that night and so bright that long exposures meant to capture the tails of Hale-Bopp and the disk of M31 would capture instead only moonlight reflected off the Earth's atmosphere. By the time the Moon would set, this opportunity would be gone. That's why this picture was taken during a lunar eclipse.

APOD: August 23, 1998 - Vega
Explanation: Vega is a bright blue star 25 light years away. Vega is the brightest star in the Summer Triangle, a group of stars easily visible summer evenings in the northern hemisphere. The name Vega derives from Arabic origins, and means "stone eagle." 4,000 years ago, however, Vega was known by some as "Ma'at" - one example of ancient human astronomical knowledge and language. 14,000 years ago, Vega, not Polaris, was the north star. Vega is the fifth brightest star in the night sky, and has a diameter almost three times that of our Sun. Life bearing planets, rich in liquid water, could possibly exist around Vega. The above picture, taken in January 1997, finds Vega, the Summer Triangle, and Comet Hale-Bopp high above Victoria, British Columbia, Canada.

APOD: July 9, 1998 - Hale-Bopp: The Crowd Pleaser Comet
Explanation: In 1997, the bright comet Hale-Bopp may have become the most viewed comet in history -- visible even to casual skywatchers in light polluted cities around the globe. In this picture, taken by photographer Joe Orman on the evening of May 8, 1997, Hale-Bopp easily competes with near twilight skies and a shining, over-exposed, crescent moon above Mobile, Arizona, USA. Where is Hale-Bopp now? Still visible to telescopic observers in the Southern Hemisphere, the comet is outbound, presently about 537 million miles from the Sun. (Jupiter orbits at about 480 million miles.) The long lead time provided by the early discovery of Hale-Bopp has allowed extensive observing campaigns producing a bonanza of information about this primordial chunk of our Solar System.

APOD: June 28, 1998 - Comet Hale Bopp Over Val Parola Pass
Explanation: In 1997, Comet Hale-Bopp became much brighter than any surrounding stars. It could be seen even over bright city lights. Out away from city lights, however, it put on quite a spectacular show. Here Comet Hale-Bopp was photographed last March above Val Parola Pass in the Dolomite mountains surrounding Cortina d'Ampezzo, Italy. Comet Hale-Bopp's blue ion tail was created when fast moving particles from the solar wind strike ions expelled from the comet's nucleus. The white dust tail was composed of larger particles of dust and ice expelled by the nucleus that orbit behind the comet. Observations have shown that Comet Hale-Bopp's nucleus spins about once every 12 hours. Comet Hale-Bopp is still visible to those in the right place with a good telescope.

APOD: May 20, 1998 - Discovery Image: Comet SOHO (1998 J1)
Explanation: Staring at the Sun from a vantage point in space (Kids, don't try this at home!), the Solar and Heliospheric Observatory (SOHO) has enabled the discovery of much about our closest star. It has also been used to discover about 50 comets. While not competing with Hale-Bopp, one of SOHO's recently discovered comets has proved to be bright enough to see with the unaided eye. The May 4th discovery image is shown above with an enlarged inset of the comet. This colorized image is from SOHO's solar coronagraph (LASCO) which views the region around the Sun by blocking out the overwhelming sunlight with an occulting disk. The disk is visible near the bottom left, with the Sun's size and position indicated by the white circle. Bright solar wind regions can also be seen along with the the planet Mars and a background of stars. The comet itself is just entering the field of view at the upper right. Observers report that Comet SOHO (1998 J1) has now been seen low in the western sky following sunset and is moving south and east becoming more visible as this month progresses, particularly from the Southern Hemisphere.

APOD: February 20, 1998 - Hale Bopp: A Continuing Tail
Explanation: Where is Hale-Bopp now? The Great Comet of 1997, one of the largest and most active comets ever, is outbound about 400 million miles from the sun. Too faint for viewing without telescopes or binoculars, Hale-Bopp is presently positioned in the very southerly constellation of Pictor. This "negative" image (black stars against white sky) of Hale-Bopp is the result of a 1 hour time exposure using the 1-metre European Southern Observatory Schmidt telescope on January 5. Clearly the comet still has a substantial tail, blown by the solar wind, that points generally away from the sunward direction. But look closely. A spiky "anti-tail" is also visible pointing toward the sun! It is likely that this anti-tail is composed of dust grains released from the comet nucleus which are too large to be easily pushed by the solar wind. As Hale-Bopp recedes from the sun its activity will subside but astronomers are still uncertain as to how long its tails will last. After a swing through the outer solar system and the Oort cloud, Hale-Bopp will pass through the inner solar system again ... around the year 5400.

APOD: January 30, 1998 - Tempel-Tuttle: The Leonid Comet
Explanation: Star trails streak this composite time exposure of Comet Tempel-Tuttle recorded by T. Puckett on January 26. Presently passing through the inner solar system on its 33 year orbit around the Sun, Tempel-Tuttle has brightened unexpectedly, but binoculars or small telescopes are still required to visually observe it. Tempel-Tuttle is also called "the Leonid Comet" as the yearly Leonid meteor shower results when the Earth crosses this comet's orbital plane and encounters cometary dust. So, while not currently rivaling the spectacle of a Hyakutake or Hale-Bopp, Tempel-Tuttle may still put on a show. When the Earth plunges through Tempel-Tuttle's debris tail in November of this year, many sky-watchers are anticipating an extremely active meteor shower to result, perhaps even a meteor storm!

APOD: December 25, 1997 - A Hale Bopp Holiday
Explanation: Seen from the Pik Terskol Observatory in the northern Caucasus mountains, comet Hale-Bopp and the bright stars of the constellation Perseus hang above the snowy, moon-lit landscape. Although it reminds Northern Hemisphere dwellers of an idyllic Winter scene, this picture was actually recorded in the spring - on April 13th of this year. Seasons Greetings and Best Wishes from APOD!

APOD: December 15, 1997 - A Farewell to Tails
Explanation: As 1997 fades, so does the Great Comet of 1997: Comet Hale-Bopp. Discovered even before the Great Comet of 1996, Comet Hale-Bopp became the brightest comet since 1976. Many will remember Comet Hale-Bopp as a comet with a coma so bright it could be seen by eye even when near the Moon. Others will remember spectacular photographs that appeared in magazines and on the web. Amateurs, inspired by the beauty of the comet, took most of these photographs. In particular, today APOD salutes Wally Pacholka, who took the above famous photograph. Mr. Pacholka reports that he repeatedly drove 150 miles to a national park, stayed up half the night, and took hundreds of photos while carefully waving a flashlight to momentarily illuminate the foreground. His equipment consisted only of a standard 35-mm camera which, for pointing accuracy, he piggybacked on a telescope bought at age 12 with money earned from a paper route.

APOD: November 25, 1997 - The Comet and the Galaxy
Explanation: The Moon almost ruined this photograph. During late March and early April, Comet Hale-Bopp passed nearly in front of the Andromeda Galaxy. Here the Great Comet of 1997 and the Great Galaxy in Andromeda were photographed together on March 24th. The problem was the brightness of the Moon. The Moon was full that night and so bright that long exposures meant to capture the tails of Hale-Bopp and the disk of M31 would capture instead only moonlight reflected off the Earth's atmosphere. By the time the Moon would set, this opportunity would be gone. That's why this picture was taken during the lunar eclipse.

APOD: October 11, 1997 - Floating Free in Space
Explanation: NASA astronauts can float free in space without any connection to a spaceship. Here astronaut Bruce McCandless maneuvers outside the Space Shuttle Challenger by firing nitrogen gas thrusters on his manned maneuvering unit (MMU). This picture was taken in 1984 and records this first untethered spacewalk. The MMU was developed because astronauts found tethers restrictive.

APOD: October 9, 1997 - Hale Bopp and the North American Nebula
Explanation: Comet Hale-Bopp's recent encounter with the inner Solar System allowed many breath-taking pictures. Above, Comet Hale-Bopp was photographed on March 8th in the constellation of Cygnus. Visible on the right in red is the North American Nebula, a bright emission nebula observable from a dark location with binoculars. The North American Nebula is about 1500 light years away, much farther than the comet, which was about 8 light minutes away. Several bright blue stars from the open cluster M39 are visible just above the comet's blue ion tail.

APOD: September 10, 1997 - Comet Hale-Bopp Outbound
Explanation: Hale-Bopp, the Comet of the Century, is leaving the inner Solar System. Outbound at about 12 miles per second it is presently nearing the main asteroid belt between Mars and Jupiter. This false-color image represents a recent view from low Earth orbit showing the comet surrounded by its shrinking coma against a background of stars. It was constructed from a fraction of the data taken aboard the Space Shuttle Discovery in August by a small innovative telescopic camera known as the Southwest Ultraviolet Imaging System or SWUIS. SWUIS (sounds like "swiss") images will be particularly interesting to astronomers who wish to continue to follow the Great Comet's interaction with the Solar Wind. The once bright Hale-Bopp has faded below 4th magnitude but is still visible to Earthbound observers south of 35 degrees north latitude.

APOD: August 25, 1997 - A Fisheye View of Comet Hale-Bopp
Explanation: Thousands of stars, several constellations, a planet and a comet all graced the western horizon over Ujue, Spain just after sunset on April 4th, 1997. Because the picture was taken with a fisheye lens, much of the whole night sky is visible. Comet Hale-Bopp, with both tails blazing, appears right of center. The brightest star is Sirius near the edge, well to the left of the constellation Orion. The red star above the belt of Orion is Betelgeuse, while the red star near the center is Aldebaran, just to the left of the bright Pleaides star cluster. Many other interesting astronomical objects are visible, including zodiacal light, which is the diffuse triangular glow in the center. Even the planet Mercury appears just over the horizon.

APOD: August 6, 1997 - Hale-Bopp from Indian Cove
Explanation: Good cameras were able to obtain impressive photographs of Comet Hale-Bopp when at its brightest earlier this year. In the above photograph taken April 5th, Comet Hale-Bopp was imaged from the Indian Cove Campground in the Joshua Tree National Forest in California, USA. A flashlight was used to momentarily illuminate foreground rocks in this 30 second exposure. Comet Hale-Bopp is still visible to the unaided eye in Earth's Southern Hemisphere, with observers there reporting it to be about 4th magnitude. The comet is now passing nearly in front of the star Sirius, and shows only a slight dust tail.

APOD: July 28, 1997 - Help Aldebaran Map the Moon
Explanation: Turn on your camcorder, go outside, and become an astronomer. How?. Tomorrow morning, our Moon will pass directly in front of Aldebaran, the brightest star in this picture and in entire constellation of Taurus. Aldebaran is visible to the left and below Comet Hale-Bopp in the above photograph, which was taken on April 30th in Tenerife, Spain. This occultation is valuable because disappearance times from different locations can be used to map the height of the lunar terrain at the occultation points. You can help by clicking here, where a site will detail how to tape a familiar cable channel and then take your still-running camcorder outside to tape the occultation of Aldebaran by the Moon. You can then donate your VCR tape to science by mailing it to this address. Leave yourself plenty of time for a practice run and be sure to check the weather before going to a lot of trouble!

APOD: July 23, 1997 - A Hale-Bopp Triple Crown
Explanation: It was truly a busy sky. In one of the more spectacular photos yet submitted to Astronomy Picture of the Day, Don Cooke of Lyme, New Hampshire caught the Sun, Moon, Earth, night sky, Pleiades star cluster, and Comet Hale-Bopp all in one frame. The first leg of this "triple crown" exposure was of the Sun, taken at 6:55 pm on April 10th 1997. Through a dark filter, the Sun appears as the bright dot on the lower right of the image. A second filtered exposure was then taken after the Sun had set, one hour and 40 minutes later - this time featuring the Moon. The Moon appears as a crescent superimposed on an odd-shaped dark circle protruding into the left of the image. This shadow is actually a silhouette of a driveway reflector mounted on an aluminum rod used to block out the bright moon - so as to allow a third exposure, this time unfiltered, of the background night sky. And what a beautiful sky it is. Highlights include Comet Hale-Bopp, on the right, and the Pleiades star cluster, near the center. But what, you may wonder, is that bright light near the center of the picture? Don't worry if you can't guess: it's a porch light from a house across the river!

APOD: July 15, 1997 - Vega
Explanation: Vega is a bright blue star 25 light years away. Vega is the brightest star in the Summer Triangle, a group of stars easily visible summer evenings in the northern hemisphere. The name Vega derives from Arabic origins, and means "stone eagle." 4,000 years ago, however, Vega was known by some as "Ma'at" - one example of ancient human astronomical knowledge and language. 14,000 years ago, Vega, not Polaris, was the north star. Vega is the fifth brightest star in the night sky, and has a diameter almost three times that of our Sun. Life bearing planets, rich in liquid water, could possibly exist around Vega. The above picture, taken in January, finds Vega, the Summer Triangle, and Comet Hale-Bopp high above Victoria, British Columbia, Canada.

APOD: June 10, 1997 - Hale-Bopp Above the Cinqui Torri Mountains
Explanation: Hale-Bopp may be the most photographed comet in history. Above, our photogenic giant flying snowball appeared last month as a backdrop to the "Cinque Torri" Mountains near Contina d'Ampezzo, Italy. Although the comet is still fairly bright, it is fading as it recedes from the Sun, and is now more easily visible from Earth's southern hemisphere. Having shed a few meters of ice and rock from its surface, Comet Hale-Bopp will coast to the outer Solar System, and return again in another 2400 years.

APOD: May 26, 1997 - Old Faithful Meets Hale-Bopp
Explanation: As Comet Hale-Bopp leaves our Northern Skies, it provides us with yet another burst of joy. On May 11th the fading comet was photographed behind the famous "Old Faithful" water geyser of Yellowstone National Park, Wyoming, USA, Planet Earth. Perhaps more familiar to Earth Dwellers than the dark geysers on Neptune's moon Triton, the gas geysers on Jupiter's moon Io, and the dirty water geysers hypothesized on Jupiter's moon Europa, Earth's Old Faithful is also reliable - every 60-80 minutes it gushes a plume of water and steam high into the air. Comet Hale-Bopp will continue to be visible to observers in the Southern Hemisphere as it moves away from the Sun towards the outer Solar System.

APOD: May 15, 1997 - Hale-Bopp: Climbing Into Southern Skies
Explanation: Fighting the glow of the setting sun and the city lights of Cape Town, South Africa, comet Hale-Bopp is just visible near the center of this panoramic view - photographed on May 3rd. In the foreground is the Strand beach front, about 50 km East of Cape Town, while the Cape Peninsula mountain ranges can be seen at the left along the horizon. The bright star visible above and to the left of the comet is the red giant Aldebaran in the constellation Taurus. As Hale-Bopp continues its outbound journey during the month of May it will climb higher into evening southern skies. Still a bright comet it is now providing an enjoyable and much anticipated showing for Southern Hemisphere observers.

APOD: May 14, 1997 - Hale-Bopp's Fickle Ion Tail
Explanation: What's happening to Comet Hale-Bopp's blue ion tail? The comet's ion tail is fluctuating more rapidly as it passes a region of changing solar wind. As the comet passes from north to south, it crosses the plane of the Sun's equator, where the solar magnetic field changes direction. Ions from the solar wind, which cause Comet Hale-Bopp's ion tail, act unpredictably here. Therefore, Comet Hale-Bopp's ion tale may show unusual structure or even a disconnection - where the tail appears to break off and then reestablish itself later. The above picture, taken April 30th, indeed shows unusual structure in the blue ion tail.

APOD: May 8, 1997 - Detailing Hale-Bopp
Explanation: This enhanced composite image detailing structure in the coma and dust tail of Hale-Bopp was recorded May 5 - one day before the comet's passage from north to south across the plane of Earth's orbit. As the comet descends into murky twilight for northern hemisphere observers it will become increasingly easy to view from the south. Along with Southern Hemisphere observers, astronomers and a fleet of spacecraft of the International Solar-Terrestrial Physics program have been anxiously awaiting this north/south crossing. The comet's interaction with the changing equatorial solar wind and magnetic field during this crossing is expected to produce distortions and disconnections of Hale-Bopp's ion tail. Whisker-like structures, probably part of the ion tail, are visible above extending from the lower left of the bright coma.

APOD: May 5, 1997 - Sunset with Hale-Bopp at Keck
Explanation: A famous star cluster and observatory highlight this picture of Comet Hale-Bopp. Taken last week from the observatory summit of Hawaii's Mauna Kea Volcano, the dome of the new 10-meter Keck II telescope appears silhouetted on the lower left. Comet Hale-Bopp is visible on the upper right, and the Pleiades star cluster is visible below the comet. Normally sunset and clouds are to be avoided when making astronomical observations, but Comet Hale-Bopp is not a normal astronomical object. In fact, were it cloudless, Professor Keel would be inside NASA's nearby IRTF dome preparing to observe something else. Comet Hale-Bopp continues to look impressive, although it is fading and moving towards the south.

APOD: April 29, 1997 - Hale-Bopp and Orion
Explanation: Comet Hale-Bopp is still brighter than most constellations. In fact, Comet Hale-Bopp may now hold the record for staying bright the longest. Last week the comet was photographed above in the same field as the constellation Orion, visible in the photograph's center, as well as with Sirius, the brightest star in the night, visible on the far left. Just below Comet Hale-Bopp on the right is the volcanic caldera known as White Mountain.. As the comet heads south, it has become visible to most of the world, now including many observers in the Earth's Southern Hemisphere.

APOD: April 25, 1997 - Hale-Bopp Polarized
Explanation: Light polarization is familiar to many outdoor enthusiasts who use polarizing sunglasses to cut the glare of reflected light. These two views of comet Hale-Bopp also demonstrate the effect of polarization. At left is an "ordinary intensity image" of Hale-Bopp's coma taken April 14, while on the right a similar image made with polarizing filters represents the intensity of polarized light. The arcs visible in the polarized view probably correspond to concentrations of ejected cometary dust that produce polarization by reflecting sunlight. Any sort of reflection - from clumps of comet dust or the surface of your favorite lake or ski slope - can polarize light by causing the light waves to vibrate in a plane defined by the reflecting surface.

APOD: April 21, 1997 - Big Sky Comet
Explanation: On April 17^th, "Big Sky" country sure lived up to its name. The dark skies over the US states of Wyoming, Montana and the Dakotas were quite busy, as shown by this photograph featuring Comet Hale-Bopp. In the foreground is the Absaroka Mountain Range in Wyoming, lit by reflected moonlight. Just to the left of Jim Mountain's peak is Comet Hale-Bopp. The unusual colors visible on the far right are aurora, remnants of the recent solar storm recorded on the Sun. Across the middle of the photo are numerous bright stars, and across the top of the picture are clouds.

APOD: April 16, 1997 - A Star Cluster Through Hale-Bopp's Tail
Explanation: Comet Hale-Bopp continues to look impressive. The photograph above captured the comet on April 7^th passing nearly in front of M34, a star cluster in the constellation of Perseus. Many of the stars in this open cluster can be seen through Comet Hale-Bopp's white dust tail. The bright blue ion tail now shows several streams. Now receding from both the Sun and the Earth, Comet Hale-Bopp should still remain an impressive sight for weeks to come as it slowly fades.

APOD: April 15, 1997 - Hale-Bopp and the Plateau de Bure Interferometer
Explanation: Comet Hale-Bopp is being observed by many different telescopes. Here the comet is pictured behind the array of radio telescopes which compose the Plateau de Bure Interferometer. These telescopes are being used to detect the presence of different molecules in the coma and tail of Comet Hale-Bopp. Molecules detected in the comet include carbon monoxide and sulfur dioxide. The abundance of different types of molecules in Comet Hale-Bopp's coma give clues to its composition and history, as well as clues to the composition and history of our Solar System. Comet Hale-Bopp has now rounded the Sun and is headed back out. It can still be seen by northern observers for several weeks in the northwest sky after sunset.

APOD: April 14, 1997 - Hale-Bopp's Hoods
Explanation: Comet Hale-Bopp is spinning. The nucleus of the comet is a dirty snowball about 25 miles in diameter that spins about once every 12 hours. As Comet Hale-Bopp spins, parts of the comet's surface shoot away in jets. Ejected material therefore makes rings, which appear in above photograph as "hoods" in the coma. Even though the central part of Comet Hale-Bopp's coma is quite condensed, the nucleus is not visible. Comet Hale-Bopp is now headed south, away from the Sun, and is getting dimmer. At its brightest last week, it was even brighter than Comet Hyakutake was last year, although with a less prominent tail. Comet Hale-Bopp will still be easily visible to northern observers for several weeks in the northwest sky after sunset.

APOD: April 8, 1997 - Comet Hale-Bopp Over New York City
Explanation: What's that point of light above the World Trade Center? It's Comet Hale-Bopp! Both faster than a speeding bullet and able to "leap" tall buildings in its single orbit, Comet Hale-Bopp is also bright enough to be seen even over the glowing lights of one of the world's premier cities. In the foreground lies the East River, while much of New York City's Lower Manhattan can be seen between the river and the comet. Comet Hale-Bopp is now moving away from both the Sun and the Earth. It should, however, should remain visible even in northern cities for at least a month. To find Comet Hale-Bopp, look for the brightest object in the northwest sky just after sunset - or wait for its return in 2400 years.

APOD: April 4, 1997 - Hale-Bopp in Stereo
Explanation: This stereo pair of Hale-Bopp images combines two pictures from slightly different viewing angles. Simulating stereo vision, the difference was generated by the comet's apparent motion as it cruised through the inner Solar System. The camera was located in the Shoshone National Forest, Wyoming, USA, Planet Earth, and the two pictures were taken about 45 minutes apart on March 25. Digitized versions were then carefully cropped and adjusted so that the background stars matched. The product of an internet collaboration between J. Modjallal and M. Frost, this pair is meant to be viewed from a comfortable distance by gently crossing your eyes until the images merge.

APOD: April 3, 1997 - Earth, Clouds, Sky, Comet
Explanation: Does a comet's dust tail always orbit behind it? Since comets rotate, they shed gas and dust in all directions equally. Small ice and dust particles expelled by the comet, however, are literally pushed around by sunlight. The smaller the particle, the greater the effect. When the comet is headed inward, sunlight slows down small particles so they orbit behind the comet. When the comet is headed back out though, sunlight speeds them up, so small particles orbit in front of the comet. Comet Hale-Bopp itself is too big to have its orbit affected by the momentum of sunlight. Therefore, since Comet Hale-Bopp started back out to the outer Solar System two days ago, we can expect the dramatic dust tail shown above to shift in front in the coming days.

APOD: April 1, 1997 - Hale-Bopp and Andromeda
Explanation: Which is closer: the comet or the galaxy? Answer: the comet. In its trek through the inner Solar System, Comet Hale-Bopp has passed nearly in front of the Andromeda Galaxy (M31), seen on the lower left. At the time of this picture, March 27^th, Comet Hale-Bopp was about 10 light-minutes from the Earth, while M31 remained about 3 million light-years distant. By contrast, light can cross the Earth in about 1/20^th of a second, and light takes about one second to reach Earth's Moon. Comet Hale-Bopp is one of the largest comets ever recorded, and although its' nucleus has never been photographed, it is estimated from brightness and spin measurements to be about 40 kilometers across. In contrast, Comet Halley in 1987 was measured to be 15 km, and Comet Hyakutake in 1996 was estimated to be no more than 10 km.

APOD: March 28, 1997 - A Comet In The Sky
Explanation: It has been suggested that Comet Hale-Bopp will become the most viewed comet in Human history. Presently, for denizens of the Earth's northern hemisphere, this bright comet is certainly a lovely and inspiring sight -- visible here crowning the sky above Cortina d'Ampezzo, Italy on March 20. Based on orbital calculations, this comet's last passage through the inner Solar System was approximately 4,200 years ago. Principally because of changes caused by the gravitational influence of Jupiter, Hale-Bopp should pass this way again in a mere 2,380 years. Comets come from the outer reaches of the Solar System where they reside, frozen and preserved. Astronomers analyzing their structure and composition as comets swing near the Sun seek a glimpse of the conditions during the Solar System's formative years.

APOD: March 27, 1997 - Comet Country
Explanation: Moonlight illuminates the landscape and lends a painterly quality to this beautiful photograph of the Absaroka mountain range, located along the Montana-Wyoming border near the USA's Yellowstone National Park. In the foreground lies the North Fork of the Shoshone River. The snow-covered peak rising 10,500 feet on the left is Jim Mountain, while Comet Hale-Bopp graces the western sky. Inspired by painters of the American West, like Fredric Remington, Charles Russell, and George "Dee" Smith, photographer Dewey Vanderhoff of Cody, Wyoming has taken advantage of the double blessings of a bright Moon and a bright comet to produce this breathtaking image.

APOD: March 26, 1997 - The City Comet
Explanation: Undaunted by the artificial glow from one of the most famous urban skylines on Earth, comet Hale-Bopp shines above the city of New York, USA. Photographed on March 23rd, this view from New Jersey shows the Hudson River in the foreground, the Empire State Building at the right, the George Washington Bridge at the left, and the comet with a visible tail above. The comet lies at a distance of about 120 million miles from New York. As bright as this comet has turned out to be, it might have been even brighter. On May 6, Hale-Bopp's orbit will take it within about 10 million miles of the point in the Earth's orbit which was occupied by planet Earth itself in early January. If the comet had also reached this point in January, it would have come almost as close to Earth as comet Hyakutake did last year. At that distance, Hale-Bopp might have been 100 times brighter than it is now, reaching -5th or -6th magnitude!

APOD: March 25, 1997 - Hale-Bopp Brightest Comet This Century
Explanation: A comet as bright as Comet Hale-Bopp is very rare indeed. No comet has emitted or reflected this much light since possibly the Great Comet of 1811. However, since Comet Hale-Bopp is across the inner Solar System from us, it does not appear as bright as Comet West did in 1975. The Great Comet of 1996, Comet Hyakutake, was relatively dim but also appeared bright since it passed close to the Earth. Above, Comet Hale-Bopp was photographed high over the town of Las Palmas of the Spanish Canary Islands, on March 11^th.

APOD: March 20, 1997 - Springtime Comet Fever
Explanation: Today marks the Vernal Equinox, the first day of Spring for planet Earth's northern hemisphere. Despite recent attempts by other spectacular and dramatic celestial events to take center stage, Comet Hale-Bopp remains the most popular object in the sky (according to APOD access logs!) and is likely to make this spring memorable for many. Gorgeous pictures of the comet with its delightful tails - this one taken March 16 - make this outbreak of "comet fever" understandable. Will the Earth pass through the lovely tails of Hale-Bopp? No, but the Earth has made similar journeys in the past. In fact, tales are often told of our planet's 1910 passage through comet Halley's tail. Anticipation of this event caused hysteria as it followed close on the heels of the spectroscopic detection of CN, poisonous cyanide, as a gaseous constituent of cometary tails. However, stretching for millions of miles, awe-inspiring comet tails are actually an extremely tenuous, nearly perfect vacuum and don't pose a danger to life on Earth.

APOD: March 17, 1997 - Comet Hale-Bopp Over Val Parola Pass
Explanation: Comet Hale-Bopp is now much brighter than any surrounding stars. It can be seen even over bright city lights. Out away from city lights, however, it is putting on quite a spectacular show. Here Comet Hale-Bopp was photographed last week above Val Parola Pass in the Dolomite mountains surrounding Cortina d'Ampezzo, Italy. Comet Hale-Bopp's blue ion tale is created when fast moving particles from the solar wind strike recently expelled ions from the comet's nucleus. The white dust tail is composed of larger particles of dust and ice expelled by the nucleus that orbit behind the comet. Recent observations show that Comet Hale-Bopp's nucleus spins about once every 12 hours. Comet Hale-Bopp is now visible in both the early morning and early evening sky, and will continue to brighten this week.

APOD: March 14, 1997 - Comet Hale-Bopp's Developing Tail
Explanation: Comet Hale-Bopp is living up to its expectations. Besides the brightness of its coma, a comet is typically remembered by the length of its tails. As visible in the above picture taken last week, Comet Hale-Bopp's blue ion tail shows a dramatic extension, with current reports of about 20 degrees from dark locations. The comet's white dust tail has so far shown a more modest extent but appears to be growing significantly. Comet Hale-Bopp's closest approach to the Sun occurs in about two weeks, and although it will not get much closer to the Sun than does our Earth, Comet Hale-Bopp is likely to tell even more spectacular tails then.

APOD: March 13, 1997 - Hale-Bopp Brightest Comet This Decade
Explanation: The Great Comet of 1997 is now brighter than the Great Comet of 1996 ever was. In fact, it is brighter than almost every star in the sky. Yet Comet Hale-Bopp is still about two weeks away from maximum light. Comet Hale-Bopp is now well north of the plane of the Earth's orbit and on the same side of the sky as the Sun. Therefore, Comet Hale-Bopp is visible from Earth's Northern Hemisphere both just after sunset and just before sunrise. The above picture of Comet Hale-Bopp was taken last week in Italy. Many Milky Way stars and nebulae are visible. To the left is a rock face partly illuminated by artificial light.

APOD: March 7, 1997 - Comet Hale-Bopp Enters the Evening Sky
Explanation: You no longer have to wake-up early to see Comet Hale-Bopp. From many northern locations, you can now go outside just after sunset and see Comet Hale-Bopp above the north-western horizon. Both writer/editors of APOD are impressed by how bright Comet Hale-Bopp has become, and how easily visible it is. The central coma is now visible from almost any location - even from a bright city. The blue ion tale is visible from a dark location. Comet Hale-Bopp's coma now rivals even last year's Comet Hyakutake, and the tail appears to be increasing in length daily.

APOD: February 27, 1997 - Comet Hale-Bopp is That Bright
Explanation: What's that fuzzy star? It's not a star, it's Comet Hale-Bopp. Not only has Comet Hale-Bopp become easy to see in the morning sky, it has become hard not to see it. It's that bright. Any morning just before sunrise, look towards the east. Comet Hale-Bopp is one of the brightest objects up. Its dominating presence is shown dramatically by this photo taken just west of Williston, North Carolina, USA. Here Comet Hale-Bopp shines above the telephone poles lining Highway 70. Too tired to get up in the morning to see the comet? Don't worry, in less than a month it will also be visible in the evening sky, just before sunset. And it will have a longer tail. From the Space Shuttle, Dr. Steven Hawley says, "Hale-Bopp looks great."

APOD: February 20, 1997 - Comet Hale-Bopp and the Dumbbell Nebula
Explanation: Comet Hale-Bopp is now slowly moving across the morning sky. During its trip to our inner Solar System, the comet passes in front of several notable objects. Here Comet Hale-Bopp was photographed on February 11th superposed nearly in front of the picturesque Dumbbell Nebula, visible on the upper right. Comet Hale-Bopp is now first magnitude - one of the brightest objects in the morning sky. APOD, always in search of interesting and accurate astronomy pictures, issues the following informal challenge: that Comet Hale-Bopp be photographed in color with both easily recognizable foreground and background objects. For instance, in late March, it might be possible to photograph the comet with the Eiffel Tower in the foreground and the Andromeda galaxy (M31) in the background. Such superpositions would not only contrast human and cosmic elements, but give angular perspective on the size of the comet's tail.

APOD: February 13, 1997 - More Jets from Comet Hale-Bopp
Explanation: Comets become fountains of gas and dust as they get near the Sun. Solar heat vaporizes the outer layers of these spectacular orbiting icebergs, exposing caverns of pressurized gas that erupt into jets. The above digitally enhanced image of Comet Hale-Bopp was taken on January 29^th and highlights several of these dust jets. Here, background stars appear as faint raised streaks. Comet Hale-Bopp is currently brighter than most stars, and is visible in the morning sky. Comet Hale-Bopp will continue to brighten and develop an extended tail until April.

APOD: February 12, 1997 - Comet Hale-Bopp Develops a Tail
Explanation: Comet Hale-Bopp has quite a tail to tell already. This remarkable comet was first discovered in 1995, even before Comet Hyakutake. Since then, this erupting snowball continues to fall into our inner Solar System and is starting to put on quite a show. Comets have been known throughout history to show tails that spread across the sky. In the above picture, the blue stream is the ion tail which consists of ions pushed away from the comet's head by the solar wind. The ion tail always points directly away from the Sun. Comet Hale-Bopp is now visible in the morning sky, moving a few degrees each day. Comet Hale-Bopp is expected to be at its best and brightest in late March and early April.

APOD: February 6, 1997 - Comet Hale-Bopp Returns
Explanation: Comet Hale-Bopp has returned from behind the Sun. In December and early January, Comet Hale-Bopp was too near the Sun to be easily visible from Earth. Now the comet graces the morning sky and is visible from dark locations even without binoculars. The above photo was taken on January 31^st and shows the two emerging tails of Comet Hale-Bopp. The blue wisp pointing up is the ion tale, while the white fuzz is the dust tail. On its trip to the inner Solar System, Comet Hale-Bopp is once again showing signs it could brighten in the next few months to become the most spectacular comet in modern times.

APOD: December 19, 1996 - Comet Hale-Bopp Inbound
Explanation: Headed toward the inner Solar System, the much anticipated Comet Hale-Bopp has promised to put on a big show next spring. The comet's apparent brightness is currently approaching 4th magnitude and its inbound journey has been closely followed by many observers. But because it is now so near the Sun's position in the sky it is a difficult target for large ground based optical telescopes as well as the orbiting Hubble Space Telescope (HST). This series of HST images hints at the comet's evolution during the last year, illustrating active and quiescent phases. Hidden from direct view by the dusty cometary coma, Hale-Bopp's nucleus is centered in each frame. A single telescopic image of the comet has recently caused substantial activity on the internet based on false claims of the existence of a mysterious companion. However, the mystery guest turned out to be an 8th magnitude star! Many predict that by next spring telescopes large or small will not be needed to appreciate the true spectacle of Hale-Bopp as it blossoms into a naked-eye astronomical wonder.

APOD: December 10, 1996 - Comet Halley's Nucleus
Explanation: Here is what a comet nucleus really looks like. For all active comets except Halley, it was only possible to see the surrounding opaque gas cloud called the coma. During Comet Halley's most recent pass through the inner Solar System in 1986, however, spacecraft Giotto was able to go right up to the comet and photograph its nucleus. The above image is a composite of hundreds of these photographs. Although the most famous comet, Halley achieved in 1986 only 1/10th the brightness that Comet Hyakutake did last year, and a similar comparison is likely with next year's pass of Comet Hale-Bopp. Every 76 years Comet Halley comes around again, and each time the nucleus sheds about 6 meters of ice and rock into space. This debris composes Halley's tails and leaves an orbiting trail that, when falling to Earth, are called the Orionids Meteor Shower.

APOD: November 13, 1996 - Seven Jets from Comet Hale-Bopp
Explanation: Comet Hale-Bopp is turning out to be quite unusual. One reason is the great amount of jet activity at such a large distance from the Sun. In the above false-color image, no less than seven jets can be seen emanating from Hale-Bopp's coma. As a comet nears the Sun, it's surface warms causing jets of previously trapped gas and dust to stream away from the nucleus. Astronomers continue to study Comet Hale-Bopp's unusual jet activity and wonder how much about the early Solar System Hale-Bopp will teach them, and how bright Hale-Bopp will ultimately become.

APOD: November 12, 1996 - Comet Hale-Bopp Passes M14
Explanation: Comet Hale-Bopp continues its slow trek across the night sky, and can now be seen superposed near the bright globular cluster M14. Will Comet Hale-Bopp become as bright in early 1997 as Comet Hyakutake did in early 1996? It is still too early to tell. Currently Hale-Bopp is curiously holding at about 5^th magnitude - just barely bright enough to see without binoculars from a dark location. Because of the size of coma, some speculate that the nucleus of Hale-Bopp is unusually large. The actual nucleus is obscured, however, and recent speculation includes that the nucleus is comparable in size to Comet Halley - about 10-15 km across.

APOD: September 17, 1996 - Comet Hale-Bopp Fades
Explanation: Comet Hale-Bopp has faded in the past few weeks. For Hale-Bopp, promised as the Great Comet of 1997, this was a bit of a disappointment -- but not entirely unexpected. Comet Hale-Bopp continues to approach the Sun - making the comet itself brighten, but now the Earth is moving away from it - making the comet appear to dim. Experts disagree on just how bright Hale-Bopp will become. Optimists hope it will eventually outshine Comet Hyakutake, but some pessimists now expect no better than 3rd magnitude - hardly visible from well-lit cities. Comet Hale-Bopp still appears to be, however, a very large comet, and is sure to show much activity as it nears the Sun. The comet should reach peak brightness in March 1997. This image was taken on August 18th and shows gas shed from the nucleus of the comet.

APOD: July 29, 1996 - A Dust Jet From Hale-Bopp
Explanation: Approaching the inner Solar System, comet Hale-Bopp's icy nucleus is heated by sunlight, accelerating its production of dust and gas. Shrouded in the resulting cloud, known as the coma, the cometary nucleus remains hidden from direct view. However, astronomers using a 2.2 meter telescope at the European Southern Observatory in May, were able to detect an enormous jet of dust extending northward (up) from the nuclear region as seen in this false color image. Dust jets may arise from vents on the surface of the nucleus. Early estimates of the size of Hale-Bopp's nucleus have indicated that it could be as large as 40 kilometers (24 miles) in diameter -- several times larger than comet Halley's. Hale-Bopp's copious dust production bodes well for it becoming a bright naked-eye comet in the spring of 1997.

APOD: July 25, 1996 - Hale-Bopp on Schedule
Explanation: Late March and early April of 1996 marked a banner season for viewing the spectacular naked-eye comet Hyakutake. The spring of 1997 could well offer a similar cometary wonder, Comet Hale-Bopp. Discovered last year while approaching the inner solar sytem Hale-Bopp has been eagerly watched for signs that it will indeed brighten spectacularly. So far, things look good! This recent image of the comet was made on May 14 at the European Southern Observatory when the comet about 340 million miles from Earth. It is shown here using false colors to indicate relative brightness. Stars are visible through the expanding coma. Recent reports are that its level of activity, the rate of dust and gas production from the solar heating of the icy nucleus is as expected. An analysis of its orbit indicates that this comet will approach to within nearly 120 million miles of Earth on March 22, 1997. The orbital calculations also reveal that Hale-Bopp has visited the inner solar system before ... about 4200 years ago.

APOD: July 23, 1996 - Hale-Bopp, Jupiter, and the Milky Way
Explanation: Shining brightly, the mighty Jupiter rules this gorgeous Kodacolor photo of the Milky Way near Sagittarius. Astronomer Bill Keel took the picture earlier this month (July 7) while standing near the summit of Hawaii's Mauna Kea contemplating the sky in the direction of the center of the Galaxy (right of picture center). In addition to the gas giant planet, which is well placed for evening viewing, the image contains an impressive sampler of celestial goodies. Many famous emission nebulae are visible as reddish patches - M16, the Eagle nebula, is just above and right of center, with the Horseshoe nebula, M17, just below it and farther to the right. Also, look for the Lagoon Nebula, M8, as the brightest red patch at the right of the picture with the Trifid Nebula, M20, just above it and to the left. The milky glow of distant unresolved stars in the plane of our Galaxy (thus the term Milky Way) runs through the image cut by dark, absorbing, interstellar dust clouds. The much anticipated comet Hale-Bopp is also clearly visible. Where's the comet? Click on the picture to view the comet's location flanked by superposed vertical lines. The comet was discovered while still beyond the orbit of Jupiter a year ago today independently by Alan Hale and Thomas Bopp. Astronomers monitoring Hale-Bopp's activity report that having now brightened to almost 6th magnitude it is still on track for becoming an extremely bright naked-eye comet in early 1997.

APOD: February 19, 1996 - Periodic Comet Swift-Tuttle
Explanation: Comet Swift-Tuttle, shown above in false color, is the largest object known to make repeated passes near the Earth. It is also one of the oldest known periodic comets with sightings spanning two millennia. Last seen in 1862, its reappearance in 1992 was not spectacular, but the comet did become bright enough to see from many locations with binoculars. To create this composite telescopic image, four separate exposures have been combined, compensating for the motion of the comet. As a result, the stars appear slightly trailed. The inset shows details of the central coma. The unseen nucleus itself is essentially a chunk of dirty ice about ten kilometers in diameter. Comets usually originate in the Oort cloud in the distant Solar System - well past Pluto, most never venturing into the inner Solar System. When perturbed - perhaps by the gravity of a nearby star - a comet may fall toward the Sun. As a comet approaches the Sun, rocks, ice-chunks, gas, and dust boil away, sometimes creating impressive looking tails. In fact, debris from Comet Swift-Tuttle is responsible for the Perseids meteor shower visible every July and August. Comet Swift-Tuttle is expected to make an impressive pass near the earth in the year 2126, possibly similar to Comet Hyakutake this year or Comet Hale-Bopp next year.

APOD: February 8, 1996 - Hyakutake: The Great Comet of 1996?
Explanation: Get ready for one of the most impressive but least anticipated light shows in modern astronomical history. Next month, newly discovered Comet Hyakutake will pass closer to the Earth than any recent comet. Unknown before its discovery by Yuji Hyakutake on 30 January 1996, the fuzzy spot in the above photograph is a comet now predicted to become bright enough to see without a telescope. Although comets act in such diverse ways that predictions are frequently inaccurate, even conservative estimates indicate that this comet is likely to impress. For example, even if Comet Hyakutake remains physically unchanged, its close pass near the Earth in late March 1996 should cause it to appear to brighten to about 3rd magnitude - still bright enough to see with the unaided eye. In the next two months, though, the comet will continue to approach the Sun and hence should become brighter still. Optimistic predictions include that Comet Hyakutake will change physically, develop a larger coma and tail, brighten dramatically, move noticeably in the sky during a single night, and may ultimately become known as the "The Great Comet of 1996." Move over Hale-Bopp!

APOD: October 30, 1995 - Comet Hale-Bopp Update
Explanation: Will comet Hale-Bopp become the brightest comet of the Century in early 1997? Since its discovery in July this year, Hale-Bopp has caused much speculation. Even though it is still beyond the orbit of Jupiter it is astonishingly bright and expected to get much brighter as it plunges inward, toward the Sun. In this latest Hubble Space Telescope image a bright clump of material (above center) has apparently been ejected by evaporation and the rotation of the icy nucleus (below center). Astronomers are using this and other observations to try to figure out if Hale-Bopp is really a giant comet or a smaller object which will fizzle out sooner than expected as it approaches the Sun.

APOD: August 26, 1995 - Two Tails of Comet West
Explanation: Here Comet West is seen showing two enormous tails that wrap around the sky. The ion tale of a comet usually appears more blue and always points away from the Sun. The dust tail trailing the comet's nucleus is the most prominent. Comet West was a visually spectacular comet, reaching its most picturesque in March of 1976. A comet this bright occurs only about once a decade. Comets are really just large dirty snowballs that shed material when they reach the inner solar-system. Many astronomers are hopeful that Comet Hale-Bopp will look as spectacular as this in the spring of 1997.

APOD: August 20, 1995 - Announcing Comet Hale-Bopp
Explanation: The pictured fuzzy patch may become one of the most spectacular comets this century. Although it is very hard to predict how bright a comet will become, Comet Hale-Bopp, named for its discoverers, was spotted farther from the Sun than any previous comet - a good sign that it could become very bright, easily visible to the naked eye. This picture was taken on July 25th 1995, only two days after its discovery. A comet bright enough to see without a telescope occurs only about once a decade. The large coma and long tail of bright comets are so unusual and impressive that they have been considered omens of change by many cultures. A comet does not streak by in few seconds - but it may change its position and structure noticeably from night to night.