46P/Wirtanen

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46P/Wirtanen
Credit:ESO
Discovery
Discovered by Carl A. Wirtanen
Discovery date January 17, 1948
Alternative
designations
1961 IV; 1960m;
1967 XIV; 1967k;
1974 XI; 1974i;
1986 VI; 1985q;
1991 XVI; 1991s;
46P/1948 A1;
1947 XIII; 1948b;
46P/1954 R2;
1954 XI;
1954j
Orbital characteristics A
Epoch September 3, 2002 (JDT 2452520.5)
Aphelion 5.129946 AU
Perihelion 1.0587602 AU
Semi-major axis 3.0943529 AU
Eccentricity 0.6578412
Orbital period 5.44 a
Inclination 11.73813°
Last perihelion July 9, 2013[1]
February 2, 2008
Next perihelion 2018-Dec-12

46P/Wirtanen is a small short-period comet with a current orbital period of 5.4 years. It was the original target for close investigation by the Rosetta spacecraft, planned by the European Space Agency. It belongs to the Jupiter family of comets, all of which have aphelia between 5 and 6 AU. Its diameter is estimated at 1.2 kilometres (0.75 mi).

Discovery[edit]

46P/Wirtanen was discovered photographically on January 17, 1948, by the American astronomer Carl A. Wirtanen. The plate was exposed on January 15 during a stellar proper motion survey for the Lick Observatory. Due to a limited number of initial observations, it took more than a year to recognize this object as a short-period comet.

The 2013 perihelion passage is not favorable since between January 23 and September 26, the comet will have an elongation less than 20 degrees from the Sun.

On 16 December 2018 the comet will pass 0.0777 AU (11,620,000 km; 7,220,000 mi) from Earth.[2] (about 32 lunar distances)

Exploration[edit]

Main article: Comet Hopper

The Comet Hopper is a proposed lander to NASA's Discovery Program that, if selected, would orbit and land multiple times on Comet Wirtanen as the comet approaches the Sun. The Comet Hopper mission has three primary science goals over the 7.3 years of its nominal lifetime. At roughly 4.5 AU the spacecraft will rendezvous with Comet Wirtanen and begin to map the spatial heterogeneity of surface solids as well as gas and dust emissions from the coma - the nebulous envelope around the nucleus of a comet. The remote mapping will also allow for any nucleus structure, geologic processes, and coma mechanisms to be determined. After arriving at the comet, the spacecraft will approach and land, then subsequently hop to other locations on the comet. As the comet approaches the sun, the spacecraft will land and hop multiple times.[3] The final landing will occur at 1.5 AU. As the comet approaches the sun and becomes more active, the spacecraft will be able to record surface changes.[4]

Also, 46P/Wirtanen was the original destination of the European Space Agency's Rosetta spacecraft mission, but delays meant that the comet was no longer easily reachable and another periodic comet, 67P/Churyumov–Gerasimenko, was chosen as the mission's target instead.[5][6]

Associated Piscid Meteor Shower[edit]

Russian forecaster Mikhail Maslov had predicted that the Earth's orbit would cross Comet Wirtanen's debris stream as many as 4 times between December 10 and December 14, 2012. As there had not previously been an encounter with this debris stream, it was not certain whether or not a meteor shower would be visible from Earth, but there was speculation that a shower with as many as 30 meteors per hour might occur.[7]

Observers in Australia reported that on the night of December 14, 2012, as many as a dozen meteors were seen emanating from the predicted radiant in the constellation of Pisces.[8]

Targeted[edit]

The comet was the target for the proposed 2016 Comet Hopper mission, which reached the finalist stage in the Discovery program. It was one of only three missions in that selection to have a more detailed study. It was ultimately won by the InSight mission, a Mars lander. The Comet Hopper was designed to use the ASRG, the Advanced Stirling Radioisotope Generator.

References[edit]

  1. ^ Syuichi Nakano (2010-04-09). "46P/Wirtanen (NK 1909)". OAA Computing and Minor Planet Sections. Retrieved 2012-02-18. 
  2. ^ "JPL Close-Approach Data: 46P/Wirtanen". 2008-06-23 last obs. Retrieved 2012-02-22. 
  3. ^ "Maryland scientists vie for NASA missions". Baltimore Sun. Retrieved 2011-06-02. 
  4. ^ "Planetary Science Division Update". NASA. Retrieved 2011-05-23. 
  5. ^ "Comet 67P/Churyumov-Gerasimenko". Rosetta. ESA. 18 December 2013. Retrieved 20 May 2014. 
  6. ^ "Hubble Assists Rosetta Comet Mission" (Press release). Hubble Space Telescope. September 5, 2003. Retrieved May 20, 2014. 
  7. ^ "A New Meteor Shower in December?". NASA. Retrieved 2012-12-13. 
  8. ^ "Comet Wirtanen meteors report". IceInSpace. Retrieved 2012-12-17. 

External links[edit]

Periodic comets (by number)
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