7784 Watterson

7784 Watterson
Discovery [1]
Discovered byT. B. Spahr
Discovery siteCatalina Stn.
Discovery date5 August 1994
(7784) Watterson
Named after
Bill Watterson
1994 PL
main-belt · Phocaea[3][4]
Orbital characteristics[1]
Epoch 4 September 2017 (JD 2458000.5)
Uncertainty parameter 0
Observation arc63.56 yr (23,217 days)
Aphelion2.8025 AU
Perihelion1.7348 AU
2.2686 AU
3.42 yr (1,248 days)
Physical characteristics
Dimensions5.53 km (calculated)[3]
5.556±0.070 km[5][6]
2.539±0.001 h[a]
0.23 (assumed)[3]
13.5[1][3] · 13.7[5]

7784 Watterson, provisional designation 1994 PL, is a stony Phocaea asteroid from the inner regions of the asteroid belt, approximately 6 kilometers in diameter. It was discovered by American astronomer Timothy Spahr at the U.S. Catalina Station, Arizona, on 5 August 1994.[2] The asteroid was named after cartoonist Bill Watterson.[2]

Orbit and classification[]

The S-type asteroid is a member of the Phocaea family (701),[4] a group of asteroids with similar orbital characteristics. It orbits the Sun in the inner main-belt at a distance of 1.7–2.8 AU once every 3 years and 5 months (1,248 days). Its orbit has an eccentricity of 0.24 and an inclination of 23° with respect to the ecliptic.[1]

Physical characteristics[]

In 2011, a photometric lightcurve analysis by astronomer Brian Skiff gave a rotation period of 2.539 hours with a relatively low brightness amplitude of 0.10 magnitude, indicative of a nearly spheroidal shape (U=3-).[a]

According to the surveys carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer (WISE), Watterson has an albedo of 0.19 and a diameter of 5.6 kilometers.[5] The Collaborative Asteroid Lightcurve Link agrees with WISE's observations and assumes a slightly higher albedo of 0.23 and calculates a diameter of 5.5 kilometers.[3]


This minor planet is named after Bill Watterson (born 1958), cartoonist of the daily comic strip Calvin and Hobbes. Syndicated from 1985 to 1995, this strip is fondly remembered and treasured by the discoverer, and helped him stay awake and sane on long observing nights and during the trials and tribulations of graduate school.[2]


  1. ^ a b Skiff (2011) web: rotation period 2.539±0.001 hours with a brightness amplitude of 0.10 mag. CALL assigns a Quality Code of 3-, which denotes a slightly less than secure result within the precision given and no ambiguity. Summary figures for (7784) Watterson at Collaborative Asteroid Lightcurve Link (CALL)


  1. ^ a b c d "JPL Small-Body Database Browser: 7784 Watterson (1994 PL)" (2017-05-02 last obs.). Jet Propulsion Laboratory. Retrieved 22 June 2017.
  2. ^ a b c d "7784 Watterson (1994 PL)". Minor Planet Center. Retrieved 6 February 2016.
  3. ^ a b c d e f "LCDB Data for (7784) Watterson". Asteroid Lightcurve Database (LCDB). Retrieved 6 February 2016.
  4. ^ a b "Asteroid 7784 Watterson – Nesvorny HCM Asteroid Families V3.0". Small Bodies Data Ferret. Retrieved 27 October 2019.
  5. ^ a b c d Mainzer, A.; Grav, T.; Masiero, J.; Hand, E.; Bauer, J.; Tholen, D.; et al. (November 2011). "NEOWISE Studies of Spectrophotometrically Classified Asteroids: Preliminary Results". The Astrophysical Journal. 741 (2): 25. arXiv:1109.6407. Bibcode:2011ApJ...741...90M. doi:10.1088/0004-637X/741/2/90. Retrieved 6 February 2016.
  6. ^ a b Masiero, Joseph R.; Mainzer, A. K.; Grav, T.; Bauer, J. M.; Cutri, R. M.; Dailey, J.; et al. (November 2011). "Main Belt Asteroids with WISE/NEOWISE. I. Preliminary Albedos and Diameters". The Astrophysical Journal. 741 (2): 20. arXiv:1109.4096. Bibcode:2011ApJ...741...68M. doi:10.1088/0004-637X/741/2/68. Retrieved 11 March 2017.

External links[]