Comet Hale–Bopp
Inclination | 89.3° |
---|---|
Last perihelion | |
Next perihelion | 4385 ± 2.0 AD[7] |
Physical characteristics | |
Dimensions | 40–80 km (25–50 mi)[1] |
Mean diameter | 60 km (37 mi) |
Mean radius | 30 km (19 mi) |
0.01–0.07 |
Comet Hale–Bopp (formally designated C/1995 O1) is a comet that was one of the most widely observed of the 20th century and one of the brightest seen for many decades.
Discovery
The comet was discovered independently on July 23, 1995, by two observers, Alan Hale and Thomas Bopp, both in the United States.[8]
Hale had spent many hundreds of hours searching for comets without success, and was tracking known comets from his driveway in
Bopp did not own a telescope. He was out with friends near Stanfield, Arizona, observing star clusters and galaxies when he chanced across the comet while at the eyepiece of his friend's telescope. He realized he might have spotted something new when, like Hale, he checked his star maps to determine if any other deep-sky objects were known to be near M70, and found that there were none. He alerted the Central Bureau for Astronomical Telegrams through a Western Union telegram. Brian G. Marsden, who had run the bureau since 1968, laughed, "Nobody sends telegrams anymore. I mean, by the time that telegram got here, Alan Hale had already e-mailed us three times with updated coordinates."[12]
The following morning, it was confirmed that this was a new comet, and it was given the designation C/1995 O1. The discovery was announced in International Astronomical Union circular 6187.[9][13]
Early observation
Hale–Bopp's orbital position was calculated as 7.2
Its great distance and surprising activity indicated that comet Hale–Bopp might become very bright when it reached
Perihelion
Hale–Bopp became visible to the naked eye in May 1996, and although its rate of brightening slowed considerably during the latter half of that year,[18] scientists were still cautiously optimistic that it would become very bright. It was too closely aligned with the Sun to be observable during December 1996, but when it reappeared in January 1997 it was already bright enough to be seen by anyone who looked for it, even from large cities with light-polluted skies.[19]
The Internet was a growing phenomenon at the time, and numerous websites that tracked the comet's progress and provided daily images from around the world became extremely popular. The Internet played a large role in encouraging the unprecedented public interest in comet Hale–Bopp.[20]
As the comet approached the Sun, it continued to brighten, shining at 2nd magnitude in February, and showing a growing pair of tails, the blue gas tail pointing straight away from the Sun and the yellowish dust tail curving away along its orbit. On March 9, a solar eclipse in China, Mongolia and eastern Siberia allowed observers there to see the comet in the daytime.[21] Hale–Bopp had its closest approach to Earth on March 22, 1997, at a distance of 1.315 au.[22]
As it passed perihelion on April 1, 1997, the comet developed into a spectacular sight. It shone brighter than any star in the sky except
After perihelion
After its perihelion passage, the comet moved into the
The comet continued to fade as it receded, but was still tracked by astronomers. In October 2007, 10 years after the perihelion and at a distance of 25.7 au from the Sun, the comet was still active as indicated by the detection of the CO-driven coma.[26] Herschel Space Observatory images taken in 2010 suggest comet Hale–Bopp is covered in a fresh frost layer.[27] Hale–Bopp was again detected in December 2010 when it was 30.7 au away from the Sun,[28] and in 2012, at 33.2 au from the Sun.[29] The James Webb Space Telescope observed Hale–Bopp in 2022, when it was 46.2 au from the Sun.[30]
Orbital changes
The comet likely made its previous
Hale–Bopp may have had a near collision with Jupiter in 2215 BC, which probably caused a dramatic change in its orbit, and 2215 BC may have been its first passage through the inner Solar System from the
The estimated probability of Hale-Bopp's striking Earth in future passages through the inner Solar System is remote, about 2.5×10−9 per orbit.[35] However, given that the comet nucleus is around 60 km in diameter,[1] the consequences of such an impact would be apocalyptic. Weissman conservatively estimates the diameter at 35 km; an estimated density of 0.6 g/cm3 then gives a cometary mass of 1.3×1019 g. At a probable impact velocity of 52.5 km/s, impact energy can be calculated as 1.9×1032 ergs, or 4.4×109 megatons, about 44 times the estimated energy of the K-T impact event.[35]
Over many orbits, the cumulative effect of gravitational perturbations on comets with high orbital
Scientific results
Due to the massive size of its nucleus, Comet Hale–Bopp was observed intensively by
Hale–Bopp showed the highest ever linear polarization detected for any comet. Such polarization is the result of solar radiation getting scattered by the dust particles in the coma of the comet and depends on the nature of the grains. It further confirms that the dust grains in the coma of comet Hale–Bopp were smaller than inferred in any other comet.[40]
Sodium tail
One of the most remarkable discoveries was that the comet had a third type of tail. In addition to the well-known gas and dust tails, Hale–Bopp also exhibited a faint sodium tail, only visible with powerful instruments with dedicated filters. Sodium emission had been previously observed in other comets, but had not been shown to come from a tail. Hale–Bopp's sodium tail consisted of neutral atoms (not ions), and extended to some 50 million kilometres in length.[41]
The source of the sodium appeared to be the inner
While the comet's dust tail roughly followed the path of the comet's orbit and the gas tail pointed almost directly away from the Sun, the sodium tail appeared to lie between the two. This implies that the sodium atoms are driven away from the comet's head by radiation pressure.[41]
Deuterium abundance
The abundance of deuterium in comet Hale–Bopp in the form of heavy water was found to be about twice that of Earth's oceans. If Hale–Bopp's deuterium abundance is typical of all comets, this implies that although cometary impacts are thought to be the source of a significant amount of the water on Earth, they cannot be the only source.[44]
Deuterium was also detected in many other
Organics
Spectroscopic observations of Hale–Bopp revealed the presence of many organic chemicals, several of which had never been detected in comets before. These complex molecules may exist within the cometary nucleus, or might be synthesised by reactions in the comet.[45]
Detection of argon
Hale–Bopp was the first comet where the noble gas argon was detected.[46] Noble gases are chemically inert and vary from low to high volatility. Since different noble elements have different sublimation temperatures, and don't interact with other elements, they can be used for probing the temperature histories of the cometary ices. Krypton has a sublimation temperature of 16–20 K and was found to be depleted more than 25 times relative to the solar abundance,[47] while argon with its higher sublimation temperature was enriched relative to the solar abundance.[46] Together these observations indicate that the interior of Hale–Bopp has always been colder than 35–40 K, but has at some point been warmer than 20 K. Unless the solar nebula was much colder and richer in argon than generally believed, this suggests that the comet formed beyond Neptune in the Kuiper belt region and then migrated outward to the Oort cloud.[46]
Rotation
Comet Hale–Bopp's activity and outgassing were not spread uniformly over its nucleus, but instead came from several specific jets. Observations of the material streaming away from these jets[48] allowed astronomers to measure the rotation period of the comet, which was found to be about 11 hours 46 minutes.[49]
Binary nucleus question
In 1997 a paper was published that hypothesised the existence of a binary nucleus to fully explain the observed pattern of comet Hale–Bopp's dust emission observed in October 1995. The paper was based on theoretical analysis, and did not claim an observational detection of the proposed satellite nucleus, but estimated that it would have a diameter of about 30 km, with the main nucleus being about 70 km across, and would orbit in about three days at a distance of about 180 km.[50] This analysis was confirmed by observations in 1996 using Wide-Field Planetary Camera 2 of the Hubble Space Telescope which had taken images of the comet that revealed the satellite.[51]
Although observations using
UFO claims
In November 1996, amateur astronomer Chuck Shramek of
Several astronomers, including Alan Hale, stated that the object was simply the 8.5-magnitude star SAO141894.
Thirty-nine members of the Heaven's Gate cult committed mass suicide in March 1997 with the intention of teleporting to a spaceship which they believed was flying behind the comet.[60]
Nancy Lieder, who claims to receive messages from aliens through an implant in her brain, stated that Hale–Bopp was a fiction designed to distract the population from the coming arrival of "Nibiru" or "Planet X", a giant planet whose close passage would disrupt the Earth's rotation, causing global cataclysm.[61] Her original date for the apocalypse was May 2003, which passed without incident, but various conspiracy websites continued to predict the coming of Nibiru, most of whom tied it to the 2012 phenomenon.[62] Lieder and others' claims of the planet Nibiru have been repeatedly debunked by scientists.[63]
Legacy
Hale–Bopp was a record-breaking comet—the farthest comet from the Sun discovered by amateurs,
Carolyn Shoemaker and her husband Gene, both famous for co-discovering comet Shoemaker–Levy 9, were involved in a car crash after photographing the comet. Gene died in the crash and his ashes were sent to the Moon aboard NASA's Lunar Prospector mission along with an image of Hale–Bopp, "the last comet that the Shoemakers observed together".[65]
See also
- Comet Hyakutake
- Hale Bopp (Waterhouse), a 1997 string orchestra composition
- Lists of comets
References
- ^ a b c d e f g "JPL Small-Body Database Browser: C/1995 O1 (Hale–Bopp)" (2022-07-09 last obs). Retrieved September 18, 2022.
- ^ a b "JPL SBDB Epoch 1996". Archived from the original on July 30, 2021.
- ^ barycenter. "PR = 8.763E+05 / 365.25 days" = 2399 years)
- ^ Syuichi Nakano (February 12, 2008). "OAA computing section circular NK 1553". OAA Computing and Minor Planet Sections. Retrieved December 17, 2009.
- ^ a b Marsden, B. G. (1995). "Comet C/1995 O1 (Hale-Bopp)". Minor Planet Electronic Circular. 1995-P01.
- ^ S2CID 121368997.
- ^ a b "Solex 10 estimate for Next Perihelion of C/1995 O1 (Hale-Bopp)". Archived from the original on August 10, 2012. Retrieved December 18, 2009.
- Bibcode:2000JBAA..110..311S.
- ^ a b c Hale, A.; Bopp, T.; Stevens, J. (July 23, 1995). "IAU Circular No. 6187". IAU. Retrieved July 5, 2011.
- ISBN 978-3319006093
- ^ a b Lemonick, Michael D. (March 17, 1997). "Comet of the decade Part II". Time. Archived from the original on November 30, 2008. Retrieved October 30, 2008.
- ^ Newcott, William (December 1997). "The Age of Comets". National Geographic Society. Archived from the original on August 29, 2017. Retrieved December 7, 2009.
Nobody sends telegrams anymore...
- S2CID 117124838.
- S2CID 121572975.
- ^ McNaught, R. H.; West, R. M. (August 2, 1995). "Circular No. 6198". IAU. Retrieved July 5, 2011.
- S2CID 4342525.
- ^ S2CID 189899565.
- ^ S2CID 120776226.
- ^ Browne, Malcolm R. (March 9, 1997). "Comet Holds Clues to Birth of Time". The New York Times.
- ^ "The Trail of Hale-Bopp". Scientific American. March 17, 1997. Retrieved October 23, 2008.
- Bibcode:1997JBAA..107..112M.
- ^ a b c "Comet Hale-Bopp". Stardust. Jet Propulsion Laboratory, NASA. November 26, 2003. Retrieved October 9, 2008.
- ^ West, Richard M. (April 13, 1997). "Comet Hale-Bopp (April 13, 1997)". European Southern Observatory. Archived from the original on May 24, 2011. Retrieved November 23, 2008.
- Bibcode:1997BASI...25..155S.
- ^ West, Richard M. (March 7, 1997). "Comet Hale-Bopp (March 7, 1997)". European Southern Observatory. Archived from the original on May 24, 2011. Retrieved November 25, 2008.
- S2CID 13344162.
- S2CID 119197339.
- S2CID 119113598.
- ^ Dave Herald (August 7, 2012). "Comet Hale-Bopp C/1995 O1 - observed tonite". Yahoo Groups. Archived from the original on January 5, 2013. Retrieved August 9, 2012.
- ^ MPEC 2022-S20 : Observations and Orbits of Comets and A/ Objects (2022 September 18)
- ^ a b Yeomans, Don (April 10, 1997). "Comet Hale-Bopp Orbit and Ephemeris Information". JPL/NASA. Retrieved October 23, 2008.
- ISBN 0-297-81847-3, page 198
- barycenter. "AD = 5.24E+02 and PR = 1.5536E+06 / 365.25 days" = 4254 years)
- ^ Williams, David R. (December 23, 2005). "Comet Fact Sheet". NASA (National Space Science Data Center). Retrieved December 5, 2008. (pre-perturbation orbit: semi-major axis 250 au; period 4000yr)
- ^ ISBN 978-0-521-86345-2.
- .
- S2CID 120740179.
- S2CID 43229796.
- doi:10.1086/319039.
- .
- ^ S2CID 119405749.
- S2CID 129323918.
- S2CID 118693620.
- ^ S2CID 34317575.
- .
- ^ S2CID 16759616.
- PMID 9278508.
- ^ "Bergeron Comet Hale-Bopp Animation". Stardust. Jet Propulsion Laboratory, NASA. Retrieved October 14, 2008.
- .
- S2CID 122481110.
- S2CID 122481110.
- Bibcode:1999A&A...349..985M. Archived from the original(PDF) on October 31, 2008. Retrieved October 29, 2008.
- .
- .
- Bibcode:1997A&A...318L...5S.
- ^ Jaroff, Leon; Willwerth, James (April 14, 1997). "The man who spread the myth". Time. Archived from the original on November 21, 2005. Retrieved October 30, 2008.
- ^ Hale, Alan (1997). "Hale-Bopp Comet Madness". Skeptical Inquirer. 21 (2): 25–28. Archived from the original on February 8, 2010. Retrieved December 6, 2009.
- ISBN 978-0-521-64600-0.
- ^ Tholen, David J. (January 15, 1997). "Fraudulent use of an IfA/UH picture". European Organisation for Astronomical Research in the Southern Hemisphere. Archived from the original on September 30, 2007. Retrieved October 14, 2008.
- .
- ^ George Johnson (March 28, 1997). "Comets Breed Fear, Fascination and Web Sites". The New York Times. Retrieved September 27, 2009.
- ^ David Morrison. "The Myth of Nibiru and the End of the World in 2012". Skeptical Inquirer. Archived from the original on April 21, 2009. Retrieved April 28, 2009.
- ^ "Nibiru: The Nonexistent Planet". Space.com. December 4, 2018. Retrieved July 17, 2020.
- ^ Aguirre, Edwin L. (July 1997). "The Great Comet of 1997". Sky and Telescope. Archived from the original on January 16, 2009. Retrieved July 5, 2017.
- ^ "Eugene Shoemaker Ashes Carried on Lunar Prospector". www2.jpl.nasa.gov.
External links
- CometBase: Comet Hale-Bopp
- Cometography.com: Comet Hale-Bopp
- NASA Hale-Bopp page
- Shadow and Substance.com: Static orbital diagram
- Comet Nucleus Animation
- Kramer, Emily A.; Fernandez, Yanga R.; Lisse, Carey M.; Kelley, Michael S.P.; Woodney, Laura M. (2014). "A dynamical analysis of the dust tail of Comet C/1995 O1 (Hale–Bopp) at high heliocentric distances". Icarus. 236: 136–145. S2CID 119201510.
- Hale-Bopp at the JPL Small-Body Database