Comet Boethin (officially 85D/Boethin) was a periodic

Jupiter-family comet A comet is an icy, small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process that is called outgassing. This produces a visible atmosphere or Coma (cometary), coma, and sometimes also a Comet ta ...

discovered in 1975 by Leo Boethin. It appeared again in January 1986 as expected. Although the comet was next expected at perihelion in April 1997, no observations were reported, and the comet is thought to have disintegrated. It has not been observed since March 1986. The comet might have come to perihelion in late July 2020, but the uncertainty in the comet's position is hundreds of millions of km. The old orbit would have the comet next coming to perihelion around November 2031.

Discovery circumstances

The comet was discovered under unusual circumstances. Comet 85D/Boethin was the first comet discovered by an observer in the

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. Leo Boethin (1912-1998), who was assigned as

Reverend The Reverend is an style (manner of address), honorific style most often placed before the names of Christian clergy and Minister of religion, ministers. There are sometimes differences in the way the style is used in different countries and c ...

of the

Abra province Abra, officially the Province of Abra ( ilo, Probinsia ti Abra; tl, Lalawigan ng Abra), is a 3rd class province in the Cordillera Administrative Region of the Philippines. Its capital is the municipality of Bangued. It is bordered by Ilocos No ...

in 1949, had taken advantage of the exceptionally dark skies of

Luzon Luzon (; ) is the largest and most populous island in the Philippines. Located in the northern portion of the Philippines archipelago, it is the economic and political center of the nation, being home to the country's capital city, Manila, as ...

to observe comets and meteor showers. In January 1973, he found his first suspected comet at

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

9.5, but he saw it fading after a few nights down to magnitude 13 before he could send a

telegram Telegraphy is the long-distance transmission of messages where the sender uses symbolic codes, known to the recipient, rather than a physical exchange of an object bearing the message. Thus flag semaphore is a method of telegraphy, whereas p ...

with his observations to Brian Marsden at the

Central Bureau for Astronomical Telegrams The Central Bureau for Astronomical Telegrams (CBAT) is the official international clearing house for information relating to transient astronomical events. The CBAT collects and distributes information on comets, natural satellites, novae, supern ...

. Marsden, sceptical of the report, responded that a short-lived outburst was possible, but that the discovery could not be confirmed. Following his first observations of comet 85D/Boethin on January 4-7, 1975, Boethin sent a Special Delivery letter to Marsden, reporting the discovery of a possible new comet of magnitude 12, using his 8-inch telescope. Before the invention of

email Electronic mail (email or e-mail) is a method of exchanging messages ("mail") between people using electronic devices. Email was thus conceived as the electronic ( digital) version of, or counterpart to, mail, at a time when "mail" meant ...

, telegrams were expensive, and Boethin had chosen to send a letter this time. The report took ten days to reach Marsden, and by that time the full Moon made observations impossible. Marsden responded that the delay was unfortunate, and that Boethin should try to

cable Cable may refer to: Mechanical * Nautical cable, an assembly of three or more ropes woven against the weave of the ropes, rendering it virtually waterproof * Wire rope, a type of rope that consists of several strands of metal wire laid into a hel ...

future reports instead of sending letters, which could take weeks to arrive from the remote Abra province. Marsden was not optimistic that the comet could be recovered. Defying the odds, Boethin was able to observe his comet again in late January and early February, and he sent a telegram to the Central Bureau for Astronomical Telegrams. Using the new report, Marsden was able to calculate an

ephemeris In astronomy and celestial navigation, an ephemeris (pl. ephemerides; ) is a book with tables that gives the trajectory of naturally occurring astronomical objects as well as artificial satellites in the sky, i.e., the position (and possibly vel ...

for the comet, and it was quickly confirmed by other observers. Marsden sent his congratulations, saying that the discovery circumstances had been "quite incredible" and that such a delay of confirmation was unheard of since the breakdown of international communication in

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. Comet 85D/Boethin was quite faint for a visual discovery, which had been made possible only by the very dark skies of Abra province. Observers with telescopes much larger than Boethin's had difficulties to see the object. Marsden noted that this was also true for Boethin's earlier reports from 1973, probably contributing to the unsuccessful confirmation in that case. He offered a free subscription to the IAU Circulars, expressing his hope that Boethin could use the money saved from the subscription to pay for telegrams in case of future discoveries. Boethin never found a new comet again. In 2003,

Gary Kronk Gary W. Kronk (born 1956) is an American amateur astronomer and writer. Biography Kronk was born in Granite City, Illinois, United States, on March 23, 1956. He developed an interest in space at an early age, during the time of the first manned ...

and Brian Marsden noticed that the object that Leo Boethin observed in 1973 was actually 104P/Kowal 2, which had not been officially discovered until 1979. From Boethin's report, it was apparent that comet Kowal 2 had been in a short, major outburst in 1973.

Orbit

85D/Boethin was a

with an orbital period of 11.81 years and a moderate inclination of 4.3°. It had been captured in a 1:1

orbital resonance In celestial mechanics, orbital resonance occurs when orbiting bodies exert regular, periodic gravitational influence on each other, usually because their orbital periods are related by a ratio of small integers. Most commonly, this relationsh ...

with Jupiter for at least the last couple of centuries. At the time of its discovery, it was only the second object known to be in such resonance, after 56P/Slaughter–Burnham. It has been suggested that comets in this resonance might originate from the

Jupiter trojans The Jupiter trojans, commonly called trojan asteroids or simply trojans, are a large group of asteroids that share the planet Jupiter's orbit around the Sun. Relative to Jupiter, each trojan librates around one of Jupiter's stable Lagrange poin ...

. 85D/Boethin came within 0.63 AU of Jupiter in August 1995.

Target of EPOXI mission, loss of comet

It was to be a target of

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding t ...

EPOXI ''EPOXI'' was a compilation of NASA Discovery program missions led by the University of Maryland and principal investigator Michael A'Hearn, with co-operation from the Jet Propulsion Laboratory and Ball Aerospace. ''EPOXI'' uses the '' Deep Impa ...

comet-exploration mission in December 2008; however, the comet was not recovered in time to set up the trajectory for the flyby with sufficient accuracy, and EPOXI switched to its backup target Hartley 2. It is thought that 85D/Boethin may have broken into pieces too small for visual detection. As a result, its

designation Designation may refer to: * Designation (law), the process of determining an incumbent's successor * Professional certification * Designation (landmarks), an official classification determined by a government agency or historical society * Designa ...

was changed from 85P to 85D on 9 June 2017, signifying that it has been lost and has possibly broken up.MPC 104935
/ref>

References

External links

Orbital simulation
from JPL (Java)
Horizons Ephemeris

– Seiichi Yoshida @ aerith.net

Destination: Missing--Comet Once Targeted by NASA Mission Vanished
(Scientific American – October 23, 2012)

(from space.com, July 14, 2005) {{DEFAULTSORT:Boethin, 085P Periodic comets 0085 Lost comets 085P 19750104