47P/Ashbrook–Jackson

47P/Ashbrook–Jackson
Comet Ashbrook–Jackson photographed by the Hubble Space Telescope on 26 July 2000
Discovery
Discovered byJoseph Ashbrook
Cyril V. Jackson
Discovery siteLowell Observatory, USA
Johannesburg, S. Africa
Discovery date26 August 1948
Designations
P/1948 Q1
P/1955 H1
  • 1948 IX, 1956 II
  • 1963 VI, 1971 III
  • 1978 XIV, 1986 II
  • 1993 XIII
Orbital characteristics
Epoch21 November 2025 (JD 2461000.5)
Observation arc77.41 years
Number of
observations		4,142
Aphelion5.43 AU
Perihelion2.807 AU
Semi-major axis4.12 AU
Eccentricity0.3180
Orbital period8.35 years
Inclination13.039°
356.88°
Argument of
periapsis		357.92°
Mean anomaly2.83°
Last perihelion28 October 2025
Next perihelion4 March 2034
TJupiter2.907
Earth MOID1.811 AU
Jupiter MOID0.016 AU
Physical characteristics
Mean diameter
5.6 km (3.5 mi)
Mean density
0.01±0.01 g/cm3
15.6±0.1 hours
  • (V−R) = 0.45±0.03
  • (R−I) = 0.38±0.03
Comet total
magnitude (M1)		13.5

47P/Ashbrook–Jackson is a Jupiter-family comet with an 8.35-year orbit around the Sun. It is the only comet discovered by Joseph Ashbrook and the third and final one by Cyril V. Jackson.

Observational history

The comet was first spotted by Joseph Ashbrook while examining a photographic plate exposed from the Lowell Observatory while observing the asteroid 1327 Namaqua on the night of 26 August 1948. At the time it was a diffuse, 12th-magnitude object with a tail about a degree in length, located within the constellation Aquarius. It was independently discovered by Cyril V. Jackson from the Yale-Columbia station at Johannesburg just a few hours later.

Orbital calculations by Leland E. Cunningham in 1948 led to the successful recovery of the comet by Michael P. Candy on April 1955. Since then, comet Ashbrook–Jackson was observed on every apparition, with the most recent observations recorded as recently as 2025.

Physical characteristics

Despite a large perihelion distance of 2.81 AU (420 million km), the comet typically reaches magnitude 12 on each observed apparition since 1948, making Ashbrook–Jackson one of the intrinsically brightest short-period comets ever known.

Its nucleus is estimated to have an effective radius of around 2.8 km (1.7 mi), rotating on its axis once every 15.6±0.1 hours.

Notes

  1. ↑ Observation arc from the Minor Planet Center database only covered dates from 7 October 1948 until 21 January 2026 (77.29 years). This figure includes its entire arc up to 26 August 1948.
  2. ↑ Cyril Jackson previously discovered C/1935 M1 and 58P/Jackson–Neujmin in 1935 and 1936, respectively
  3. ↑ Reported initial position upon discovery was: α = 23h 11.9m , δ = –14° 50′

References

  1. ↑ "Comet Names and Designations". International Comet Quarterly. Retrieved 7 August 2025.
  2. ↑ "47P/Ashbrook–Jackson – JPL Small-Body Database Lookup". ssd.jpl.nasa.gov. Jet Propulsion Laboratory. Retrieved 1 March 2010.
  3. 1 2 "47P/Ashbrook–Jackson Orbit". Minor Planet Center. Retrieved 2 March 2017.
  4. ↑ "Horizons Batch for 47P/Ashbrook-Jackson (90000557) on 2034-Mar-04" (Perihelion occurs when rdot flips from negative to positive). JPL Horizons. Retrieved 15 April 2026.
  5. 1 2 P. L. Lamy; I. Toth; Y. R. Fernández; H. A. Weaver (2004). "The Sizes, Shapes, Albedos, and Colors of Cometary Nuclei" (PDF). Comets II. pp. 223–264. JSTOR j.ctv1v7zdq5.22. Archived from the original (PDF) on 9 October 2022. Retrieved 7 August 2025.
  6. 1 2 3 C. Snodgrass; S. C. Lowry; A. Fitzsimmons (2006). "Photometry of cometary nuclei: rotation rates, colours and a comparison with Kuiper Belt Objects". Monthly Notices of the Royal Astronomical Society. 373 (4): 1590–1602. arXiv:astro-ph/0610301. Bibcode:2006MNRAS.373.1590S. doi:10.1111/j.1365-2966.2006.11121.x.
  7. 1 2 R. Kokotanekova; C. Snodgrass; P. Lacerda; S. F. Green; S. C. Lowry; et al. (2017). "Rotation of cometary nuclei: new light curves and an update of the ensemble properties of Jupiter-family comets". Monthly Notices of the Royal Astronomical Society. 471 (3): 2974–3007. arXiv:1707.02133. Bibcode:2017MNRAS.471.2974K. doi:10.1093/mnras/stx1716.
  8. 1 2 3 Kronk, Meyer & Seargent 2009, pp. 304–307.
  9. ↑ Kronk, Meyer & Seargent 2009, pp. 471–472.
  10. ↑ G. W. Kronk. "47P/Ashbrook–Jackson". Cometography.com. Retrieved 26 November 2025.

Bibliography