Comet Arend–Roland was discovered on November 6, 1956, by Belgian astronomers
Sylvain Arend
Sylvain Julien Victor Arend (6 August 1902 – 18 February 1992) was a Belgian astronomer born in Robelmont, Luxembourg province, Belgium. His main interest was astrometry.
Together with Georges Roland, he discovered the bright comet C/1956 ...
and Georges Roland on photographic plates. As the eighth
comet
A comet is an icy, small Solar System body that warms and begins to release gases when passing close to the Sun, a process called outgassing. This produces an extended, gravitationally unbound atmosphere or Coma (cometary), coma surrounding ...
found in 1956, it was named Arend–Roland 1956h after its discoverers. Because it was the third comet to pass through
perihelion
An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values.
Apsides perta ...
during 1957, it was then renamed 1957 III. Finally, it received the standard
IAU
The International Astronomical Union (IAU; , UAI) is an international non-governmental organization (INGO) with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach, education, and developmen ...
designation C/1956 R1 (Arend–Roland), with the "C/" indicating that it was a non-periodic comet and the "R1" showing that it was the first comet reported as discovered in the half-month designated by "R". The last is equivalent to the period September 1–15.
Observations
In November 1956, a double astrograph at the
Uccle Observatory
The Royal Observatory of Belgium (; ; ) has been situated in the Uccle municipality of Brussels since 1890. It is part of the institutions of the Belgian Federal Science Policy Office (BELSPO).
The Royal Observatory was first established in Sa ...
in
Brussels
Brussels, officially the Brussels-Capital Region, (All text and all but one graphic show the English name as Brussels-Capital Region.) is a Communities, regions and language areas of Belgium#Regions, region of Belgium comprising #Municipalit ...
was being used for routine investigation of
minor planet
According to the International Astronomical Union (IAU), a minor planet is an astronomical object in direct orbit around the Sun that is exclusively classified as neither a planet nor a comet. Before 2006, the IAU officially used the term ''minor ...
s. On 6 November 1956, the Belgian astronomers Sylvain Arend and Georges Roland discovered a comet on their photographic plates. At that time the comet was at
visual magnitude
Apparent magnitude () is a measure of the brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction of the object's light ca ...
10, with a strong central condensation and a short tail. The early discovery of this comet allowed observing programs and equipment to be prepared well in advance.
The orbital elements for this comet were computed by Michael Philip Candy, who predicted
perihelion
An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. The line of apsides (also called apse line, or major axis of the orbit) is the line connecting the two extreme values.
Apsides perta ...
passage on 8 April 1957. As the comet was already well developed, he predicted that the object would present a prominent display during April in the northern hemisphere. In early December the comet was 2.5
AU from the Sun and 1.7 AU from the Earth. It was in the constellation
Pisces
Pisces may refer to:
*Pisces (astrology), an astrological sign
Astronomy
*Pisces (constellation), a constellation
** Pisces Overdensity, an overdensity of stars in the Milky Way's halo that is situated in the Pisces constellation
** Pisces II, a ...
until February, when it reached magnitude 7.5–8.
During the April perihelion passage, the tail of the comet reached a length of 15° of arc. The appearance of the tail varied, with streamers on April 16 and May 5, and the tail splitting into three beams on April 29. By April 22 the comet also displayed a prominent anomalous tail (or
antitail) spanning 5°. This antitail stretched out to span 12° on April 25, reaching its maximal extent. The antitail had disappeared by 29 April.
Following perihelion on 8 April, the comet began to fade rapidly from its maximal brightness of magnitude −1. At the start of May it was measured at visual magnitude 5.46. By 8 May it had decreased to magnitude 7, well below the sensitivity limit of the unaided human eye. On 29 May it had dropped to magnitude 8.55.
This was the first comet for which attempts were made to detect it at various radio frequencies. However, these efforts were unsuccessful. No comets were successfully detected in the radio band until the 1973 passage of
comet Kohoutek.
Comet Arend–Roland was the subject of the first edition of the
BBC
The British Broadcasting Corporation (BBC) is a British public service broadcaster headquartered at Broadcasting House in London, England. Originally established in 1922 as the British Broadcasting Company, it evolved into its current sta ...
's long-running astronomy program ''
The Sky at Night
''The Sky at Night'' is a documentary television programme on astronomy produced by the BBC. The show had the same permanent presenter, Sir Patrick Moore, from its first monthly broadcast on 24 April 1957 until 7 January 2013. The latter date ...
'' on 24 April 1957.
Astronomer
Carl Sagan
Carl Edward Sagan (; ; November 9, 1934December 20, 1996) was an American astronomer, planetary scientist and science communicator. His best known scientific contribution is his research on the possibility of extraterrestrial life, including e ...
relates an anecdote on page 80 of his 1980 book ''
Cosmos
The cosmos (, ; ) is an alternative name for the universe or its nature or order. Usage of the word ''cosmos'' implies viewing the universe as a complex and orderly system or entity.
The cosmos is studied in cosmologya broad discipline covering ...
'' about being on duty in an observatory near Chicago in 1957 when a late-night phone call from an inebriated man asked what was the "fuzzy thing" they were seeing in the sky. Sagan told the man that it was a comet (Arend–Roland). The man asked what a comet was, and Sagan answered that it was "a snowball, one mile wide". After a long pause, the man said, quoting Sagan: "Lemme talk to a ''real'' 'shtronomer!".
Properties
It was traveling on a
hyperbolic
Hyperbolic may refer to:
* of or pertaining to a hyperbola, a type of smooth curve lying in a plane in mathematics
** Hyperbolic geometry, a non-Euclidean geometry
** Hyperbolic functions, analogues of ordinary trigonometric functions, defined u ...
orbit, that is, traveling fast enough to escape from the Solar System entirely, hence implying that it will never be seen again by earthbound observers. Observations of the comet over a period of 520 days allowed precise orbital elements to be computed. However, the distribution of the orbital elements showed a wavy pattern that suggested a non-gravitational influence. Alternatively, the comet may have originated from interstellar space rather than from the
Oort cloud
The Oort cloud (pronounced or ), sometimes called the Öpik–Oort cloud, is scientific theory, theorized to be a cloud of billions of Volatile (astrogeology), icy planetesimals surrounding the Sun at distances ranging from 2,000 to 200,000 A ...
. When an orbital solution is computed that includes non-gravitational forces that vary as the inverse square of the heliocentric distance, somewhat different values are derived (see the Marsden (1970) column in the table below).
At perihelion, the comet was emitting an estimated (83 tons/s) of dust and was releasing roughly gas molecules per second. It is believed that an outburst of dust occurred on April 2, six days before perihelion. The antitail was formed from particles released between February 6 and 1 March 1957. Estimates of the total amount of dust released into the
zodiac
The zodiac is a belt-shaped region of the sky that extends approximately 8° north and south celestial latitude of the ecliptic – the apparent path of the Sun across the celestial sphere over the course of the year. Within this zodiac ...
al cloud range from to .
References
Notes
Citations
External links
*
C/1956 R1 (Arend–Roland)by Gary W. Kronk
HDR Astrophotography: Simulations Atlas of Past Comets (1900 to 1999)by Nicolas Lefaudeux
{{DEFAULTSORT:Arend-Roland, 1956 R1
Non-periodic comets
Hyperbolic comets
Near-Earth comets
1956 in science
19561108
Great comets