73P/Schwassmann–Wachmann, also known as Schwassmann–Wachmann 3, is a periodic comet in the Solar System that is in the process of disintegrating. Starting the 2011 perihelion passage the primary component 73P-C was recovered on 28 November 2010 near apparent magnitude 21.3;[6] it came to perihelion (closest approach to the Sun) on 16 October 2011.[3]

Comet Schwassmann–Wachmann 3 was one of the comets discovered by astronomers Arnold Schwassmann and Arno Arthur Wachmann, working at the Hamburg Observatory in Bergedorf, Germany. It began disintegrating on its re-entry to the inner Solar System in 1995, in a reaction triggered by the Sun's heating of the comet as it emerged from the colder regions of the outer Solar System.

Comet 73P is a parent body of meteor shower Tau Herculids.

The comet was discovered as astronomers were exposing photographic plates in search of minor planets for a minor planet survey, on May 2, 1930. The comet was lost after its 1930 apparition, but was observed several more times.

73P/Schwassmann–Wachmann has an orbital period of slightly less than 5 1/3 years so that it comes nearest to the Earth every 16 years. The primary fragment 73P-C has an Earth-MOID of 0.04 AU (6,000,000 km; 3,700,000 mi).[3] 73P was originally estimated to have a core diameter of 1100 meters.

Schwassmann–Wachmann 3
Disrupted comet Schwassmann–Wachmann 3
(as seen from Mt Laguna on April 19, 2006)
Discovered byArnold Schwassmann
Arno Arthur Wachmann
Discovery dateMay 2, 1930
1930 VI; 1979 VIII;
1990 VIII; 1994w
Orbital characteristics A
(JD 2455600.5)
Aphelion5.184 AU
Perihelion0.9426 AU
Semi-major axis3.063 AU
Orbital period5.36 yr
Earth MOID0.014 AU (2,100,000 km)[5]
Last perihelionMarch 16, 2017[1]
October 16, 2011[2][3]
June 6, 2006[2]
Next perihelion2022-Aug-25[4]


In 1995, 73P began to disintegrate.[7] It was seen to break into four large pieces labeled 73P-A, B, C, & D.[8] As of March 2006, at least eight fragments were known: B, C, G, H, J, L, M & N. On April 18, 2006, the Hubble Space Telescope recorded dozens of pieces of fragments B and G. It appears that the comet may eventually disintegrate completely and cease to be observable (as did 3D/Biela in the 19th century), in which case its designation would change from 73P to 73D. It is now known to have split into at least 66 separate objects.[5] Nucleus C is the largest and the presumed principal remnant of the original nucleus.[8]


The fragments were passing the Earth in late April and early May 2006, coming nearest to the Earth around May 12 at a distance of about 11.9 million km (7.4 million miles), a close pass in astronomical terms (0.08 AU) though nothing to be concerned about. In 1930 when it passed the Earth that close, there were meteor showers with as many as 100 meteors per minute. However, analysis by P. A. Wiegert et al.[9] suggested that a recurrence of that spectacle was unlikely.

The comet was to have been visited by the CONTOUR comet nucleus probe on June 18, 2006. Unfortunately, contact with the probe was lost on August 15, 2002 when it fired its Star 30BP solid rocket motor to inject itself into solar orbit.

Image gallery

06-0501 73p martinez fal vcastro IMG 9934

The B, G and R components of 73P, and Tau Coronae Borealis, May 1, 2006.

06-0508 sw3+m57 martinez fal vcastro img 0032

The C component of 73P, and the Ring Nebula, May 8, 2006.

C-73P wiki

This image taken by Andrew Catsaitis of components B and C of Comet 73P/Schwassmann–Wachmann 3 as seen together on 31 May 2006.

Ringcomet nickerson stevens powell new

This image of fragment C passing the ring nebula was taken on 2006.05.07 at St. Francis Xavier University in Antigonish, Nova Scotia, Canada.


Component B as seen by the Hubble Space Telescope. Also available as Video clip

Ring Nebula and 73P-Schwassmann-Wachmann

Comet Schwassmann–Wachmann passes in the field of view of the Ring Nebula on May 7, 2006. Photo by Maynard Pittendreigh.


  1. ^ Syuichi Nakano (2011-01-07). "73P/Schwassmann-Wachmann 3 - C (NK 2021)". OAA Computing and Minor Planet Sections. Retrieved 2012-02-18.
  2. ^ a b 73P past, present and future orbital elements
  3. ^ a b c "JPL Small-Body Database Browser: 73P/Schwassmann–Wachmann 3-C". Jet Propulsion Laboratory. Retrieved 2011-05-05. 2011-02-23 last obs
  4. ^ "73P/Schwassmann-Wachmann Orbit". Minor Planet Center. Retrieved 2017-04-07.
  5. ^ a b "JPL Small-Body Database Browser: 73P/Schwassmann–Wachmann (66 objects)". Retrieved 2008-10-25. 2006-05-24 last obs of main body 3-C
  6. ^ "MPEC 2010-Y12 : OBSERVATIONS AND ORBITS OF COMETS". IAU Minor Planet Center. 2010-12-18. Retrieved 2011-06-26.
  7. ^ Whitney Clavin (2006-05-10). "Spitzer Telescope Sees Trail of Comet Crumbs". Spitzer Space Telescope at Caltech. Retrieved 2008-10-25.
  8. ^ a b "Hubble Provides Spectacular Detail of a Comet's Breakup". Hubblesite (News Release Number: STScI-2006-18). 2006-04-27. Retrieved 2008-10-25.
  9. ^ Monthly Notices of the Royal Astronomical Society, Volume 361, p. 638 The τ Herculid meteor shower and Comet 73P/Schwassmann–Wachmann 3 P. A. Wiegert, P. G. Brown, J. Vaubaillon and H. Schijns

External links

Numbered comets
73P/Schwassmann–Wachmann Next

2022 (MMXXII)

will be a common year starting on Saturday of the Gregorian calendar, the 2022nd year of the Common Era (CE) and Anno Domini (AD) designations, the 22nd year of the 3rd millennium, the 22nd year of the 21st century, and the 3rd year of the 2020s decade.


276P/Vorobjov (previously P/2012 T7 (VOROBJOV)) is a Jupiter-family comet discovered on 15 October 2012 by Tomáš Vorobjov on three 120-s images taken remotely using the 0.81-m f/7 Ritchey-Chretien Schulman Telescope located at the Mt. Lemmon SkyCenter via the Sierra Stars Observatory Network in the course of a minor-planet search survey undertaken as part of the International Astronomical Search Collaboration (IASC) school campaigns. After posting on the Minor Planet Center's NEOCP webpage, other observers have commented on the object's cometary appearance. The discovery was announced by the Minor Planet Center on 18 October, three days after the discovery.


72P/Denning–Fujikawa is a periodic comet discovered on 4 October 1881 by William Frederick Denning. The comet was not seen at another apparition until recovered by Shigehisa Fujikawa in 1978. From 29 December 1978 until 17 June 2014, the comet was lost. On 17 June 2014 the comet was recovered by Hidetaka Sato.Repeated failures to recover the comet during perihelion even in cases where it is estimated that it should have been magnitude 8 or, as in 1987 and 1996, it was being actively looked for suggest it is only occasionally active. This has resulted in it being classified as a transitional comet.


74P/Smirnova–Chernykh is a periodic comet in the Solar System. It fits the definition of an Encke-type comet with (TJupiter > 3; a < aJupiter), and is a Quasi-Hilda comet. It was discovered in late March 1975 by Tamara Mikhajlovna Smirnova while examining exposures from the Crimean Astrophysical Observatory. In the discovery images the comet had an apparent magnitude of ~15. In the year of discovery, the comet came to perihelion on August 6, 1975.The comet had been photographed during 1967, but was identified as an asteroid and assigned the designation 1967 EU.The comet is estimated at about 4.46 km in diameter, and currently has an orbit contained completely inside of the orbit of Jupiter.

Arno Arthur Wachmann

Arno Arthur Wachmann (March 8, 1902 – July 24, 1990) was a German astronomer and discoverer of comets and minor planets, who worked for many years at the Bergedorf Observatory in Hamburg.With Arnold Schwassmann he co-discovered the periodic comets 29P/Schwassmann–Wachmann, 31P/Schwassmann–Wachmann and 73P/Schwassmann–Wachmann. The Minor Planet Center credits him with the discovery of 3 asteroids during 1938–1939.The inner main-belt asteroid 1704 Wachmann was named in his honor (M.P.C. 3933).

C/2012 E2 (SWAN)

Comet C/2012 E2 (SWAN) was a Kreutz group sungrazing comet discovered by Vladimir Bezugly in publicly available images taken by the SWAN instrument (Solar Wind ANisotropies) on board the SOHO spacecraft. It is recognized for being the first Kreutz sungrazer observed in SWAN imagery.

C/2015 F3

Comet C/2015 F3 (SWAN) was discovered in March 2015 by Rob Matson, Vladimir Bezugly and Michael Matiazzo in near real time images taken by the SWAN instrument aboard the SOHO spacecraft. At discovery the comet was already shining at around 10th magnitude as it was already near perihelion

. Orbital studies revealed C/2015 F3 to be a related fragment to long periodic comets C/1988 A1 (Liller) and C/1996 Q1 (Tabur), which were already thought to have broken off each other at a previous perihelion passage. As of May 2015, Comet SWAN was fading rapidly, as both C/1988 A1 and C/1996 Q1 ultimately did. .

C/2015 F5 (SWAN-XingMing)

Comet C/2015 F5 (SWAN-XingMing) was discovered on March 29, 2015 in near real time SWAN images of the SOHO spacecraft, by Szymon Liwo and Worachate Boonplod. It was also independently discovered on April 4, 2015 by Guoyou Sun and Gao Xing at the XingMing observatory near Ürümqi, China. At discovery, the comet had just passed perihelion and was only 0,35 AU from the Sun, shining at about +10 mag. As of May 2015 the comet had faded below mag +13. The comet is periodic with an orbital period of about 61 years .


The COmet Nucleus TOUR (CONTOUR) was a NASA Discovery-class space probe that failed shortly after its July 2002 launch. It had as its primary objective close flybys of two comet nuclei with the possibility of a flyby of a third known comet or an as-yet-undiscovered comet.

The two comets scheduled to be visited were Encke and Schwassmann-Wachmann-3, and the third target was d'Arrest. It was hoped that a new comet would have been discovered in the inner Solar System between 2006 and 2008, in which case the spacecraft trajectory would have been changed if possible to rendezvous with the new comet. Scientific objectives included imaging the nuclei at resolutions of up to 4 meters (13 ft), performing spectral mapping of the nuclei at resolutions of up to 100 meters (330 ft), and obtaining detailed compositional data on gas and dust in the near-nucleus environment, with the goal of improving knowledge of the characteristics of comet nuclei.

After the solid rocket motor intended to inject the spacecraft into solar orbit was ignited on August 15, 2002, contact with the probe could not be re-established. Ground-based telescopes later found three objects along the course of the satellite, leading to the speculation that it had disintegrated. Attempts to contact the probe were ended on December 20, 2002. The probe thus accomplished none of its primary scientific objectives, but did prove some spaceflight technologies, such as the APL-developed non-coherent spacecraft navigation technique, which was later used on the New Horizons spacecraft.

Comet nucleus

The nucleus is the solid, central part of a comet, popularly termed a dirty snowball or an icy dirtball. A cometary nucleus is composed of rock, dust, and frozen gases. When heated by the Sun, the gases sublimate and produce an atmosphere surrounding the nucleus known as the coma. The force exerted on the coma by the Sun's radiation pressure and solar wind cause an enormous tail to form, which points away from the Sun. A typical comet nucleus has an albedo of 0.04. This is blacker than coal, and may be caused by a covering of dust.Results from the Rosetta and Philae spacecraft show that the nucleus of 67P/Churyumov–Gerasimenko has no magnetic field, which suggests that magnetism may not have played a role in the early formation of planetesimals. Further, the ALICE spectrograph on Rosetta determined that electrons (within 1 km (0.62 mi) above the comet nucleus) produced from photoionization of water molecules by solar radiation, and not photons from the Sun as thought earlier, are responsible for the degradation of water and carbon dioxide molecules released from the comet nucleus into its coma. On 30 July 2015, scientists reported that the Philae spacecraft, that landed on comet 67P/Churyumov-Gerasimenko in November 2014, detected at least 16 organic compounds, of which four (including acetamide, acetone, methyl isocyanate and propionaldehyde) were detected for the first time on a comet.

Friedrich Karl Arnold Schwassmann

Friedrich Karl Arnold Schwassmann (25 March 1870 – 19 January 1964) was a German astronomer and a discoverer of 22 minor planets and 4 comets, who worked at AOP in Potsdam and at Bergedorf Observatory in Hamburg.He was co-discoverer with Arno Arthur Wachmann of the periodic comets 29P/Schwassmann–Wachmann, 31P/Schwassmann–Wachmann and 73P/Schwassmann–Wachmann, and with Arno Arthur Wachmann and Leslie Peltier of the non-periodic comet C/1930 D1 (Peltier–Schwassmann–Wachmann). The main-belt asteroid 989 Schwassmannia, discovered by himself in 1922, was later named in his honor (H 94).

Ivano Bertini

Ivano Bertini (born April, 1968, in Milan, Italy) is an Italian astronomer at the University of Padua.

List of missions to comets

As of 2013, the United States, Soviet Union, Japan and the European Space Agency have conducted missions to comets.

List of numbered comets

This is a list of periodic comets that were numbered by the Minor Planet Center after having been observed on at least two occasions. As of October 2018 there are 375 numbered comets (1P–375P), most of them being members of the Jupiter-family (JFC). There are also 27 Encke-type comets (ETCs), 14 Halley-type comets (HTCs), 4 Chiron-type comets (CTCs), and one long-period comet (i.e. 153P). Many of these bodies are also near-Earth comets (NECs). In addition, 8 numbered comets are principally classified as minor planets – five main-belt comets, two centaurs (CEN), and one Apollo asteroid – and display characteristics of both an asteroid and a comet.

Occasionally, comets will break up into multiple chunks, as volatiles coming off the comet may cause it to break into two or more pieces. An extreme example of this is 73P/Schwassmann–Wachmann, which broke into over 50 pieces during its 1995 perihelion.

For a larger list of periodic Jupiter-family and Halley-type comets including unnumbered bodies, see list of periodic comets.

Lost comet

A comet is "lost" when it has been missed at its most recent perihelion passage. This generally happens when data is insufficient to reliably calculate the comet's orbit and predict its location. The D/ designation is used for a periodic comet that no longer exists or is deemed to have disappeared.Lost comets can be compared to lost minor planets, although calculation of comet orbits differs because of nongravitational forces, such as emission of jets of gas from the nucleus. Some astronomers have specialized in this area, such as Brian G. Marsden, who successfully predicted the 1992 return of the once-lost periodic comet Swift–Tuttle.

Lulin Observatory

Lulin Observatory (Chinese: 鹿林天文台; pinyin: Lùlín Tiānwéntái; literally: 'Deer Forest Astronomical Observatory', obs. code: D35) is an astronomical observatory operated by the Institute of Astronomy, National Central University in Taiwan.

It is located at the summit of Mount Lulin in Xinyi Township, Nantou County. In 2007, Comet Lulin (C/2007 N3), was found by this observatory, and became the first comet discovered by a Taiwanese researcher. The minor planet 147918 Chiayi was also discovered here.The Lulin 1 meter had its first light in September 2002, after 10 years of development.

Potentially hazardous object

A potentially hazardous object (PHO) is a near-Earth object – either an asteroid or a comet – with an orbit that can make exceptionally close approaches to the Earth and large enough to cause significant regional damage in the event of impact.Most of these objects are potentially hazardous asteroids (PHAs), defined as having a minimum orbital intersection distance with Earth of less than 0.05 astronomical units (19.5 lunar distances) and an absolute magnitude of 22 or brighter. As of January 2018 there are 1,885 known PHAs (about 11% of the total near-Earth population), of which 157 are estimated to be larger than one kilometer in diameter (see list of largest PHAs below). Most of the discovered PHAs are Apollo asteroids (1,601) and fewer belong to the group of Aten asteroids (169).A potentially hazardous object can be known not to be a threat to Earth for the next 100 years or more, if its orbit is reasonably well determined. Potentially hazardous asteroids with some threat of impacting Earth in the next 100 years are listed on the Sentry Risk Table. Potentially hazardous asteroids are normally only a hazard on a time scale of hundreds of years as the known orbit becomes more divergent. After several astronomical surveys, the number of known PHAs has increased tenfold since the end of the 1990s (see bar charts below). The Minor Planet Center's website List of the Potentially Hazardous Asteroids also publishes detailed information for these objects.

Radar astronomy

Radar astronomy is a technique of observing nearby astronomical objects by reflecting microwaves off target objects and analyzing the reflections. This research has been conducted for six decades. Radar astronomy differs from radio astronomy in that the latter is a passive observation and the former an active one. Radar systems have been used for a wide range of solar system studies. The radar transmission may either be pulsed or continuous.

The strength of the radar return signal is proportional to the inverse fourth-power of the distance. Upgraded facilities, increased transceiver power, and improved apparatus have increased observational opportunities.

Radar techniques provide information unavailable by other means, such as testing general relativity by observing Mercury and providing a refined value for the astronomical unit. Radar images provide information about the shapes and surface properties of solid bodies, which cannot be obtained by other ground-based techniques.

Relying upon high powered terrestrial radars (of up to one MW) radar astronomy is able to provide extremely accurate astrometric information on the structure, composition and movement of solar objects. This aids in forming long-term predictions of asteroid-Earth impacts, as illustrated by the object 99942 Apophis. In particular, optical observations measure where an object appears in the sky, but cannot measure the distance with great accuracy (relying on Parallax becomes more difficult when objects are small or poorly illuminated). Radar, on the other hand, directly measures the distance to the object (and how fast it is changing). The combination of optical and radar observations normally allows the prediction of orbits at least decades, and sometimes centuries, into the future.

There are two radar astronomy facilities that are in regular use, the Arecibo Planetary Radar and the Goldstone Solar System Radar.


There are several comets named Schwassmann–Wachmann, the discovery of which is co-credited to German astronomers Arnold Schwassmann and Arno Arthur Wachmann:

29P/Schwassmann–Wachmann (29P/1927 V1, Schwassmann–Wachmann 1)

31P/Schwassmann–Wachmann (31P/1929 B1, Schwassmann–Wachmann 2)

73P/Schwassmann–Wachmann (73P/1930 J1, Schwassmann–Wachmann 3)

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