Comet Finlay is a periodic comet with an orbital period of 6 years discovered by William Henry Finlay (Royal Observatory, Cape of Good Hope, South Africa) on September 26, 1886. The next perihelion passage is July 13, 2021 when the comet will have a solar elongation of 54 degrees at approximately apparent magnitude 10.[6] It last came to perihelion on December 27, 2014,[2] at around magnitude 10.[6] Of the numbered periodic comets, the orbit of 15P/Finlay has one of the smallest minimum orbit intersection distances with the orbit of Earth (E-MOID).[7] In 2060 the comet will pass about 6 million km from Earth.

Discovered byWilliam Henry Finlay
Discovery dateSeptember 26, 1886
1886 S1; 1886 VII;
1886e; 1893 K1;
1893 III; 1893a;
1906 V; 1906d;
1919 II; 1919d;
1926 V; 1926d;
1953 VII; 1953i;
1960 VIII; 1960d;
1967 IX; 1967g;
1974 X; 1974d;
1981 XII; 1981e;
1988 IX; 1988f
Orbital characteristics A
(JD 2457000.5)
Aphelion6.019 AU
Perihelion0.976 AU
Semi-major axis3.488 AU
Orbital period6.51 a
Earth MOID0.009 AU (1.3 million km)[4]
Jupiter MOID0.16 AU (24 million km)[4]
Dimensions1.8 km (uncertain)[5]
Last perihelionJuly 13, 2021[1]
December 27, 2014[1][2]
June 22, 2008
Next perihelion2028-Feb-09[3]


Perihelion distance
at different epochs
Epoch Perihelion
1866 1.0
1906 0.96
1919 1.0
1981 1.1
2008 0.97
2021 0.99

When the first orbit calculations were made in 1886, there was a similarity between this orbit and that of Francesco de Vico's lost periodic comet of 1844 (54P/de Vico-Swift-NEAT). Lewis Boss (Dudley Observatory, Schenectady, United States) noted large discrepancies between the orbits and after further observations concluded that de Vico's comet could not be the same as Finlay's.[8]

During the 1906 apparition the comet brightened to magnitude 6. In 1910 a close pass with Jupiter increased the orbital period, in 1919 the path was off predictions and a new comet discovered by Sasaki (Kyoto Observatory, Japan) on October 25, 1919, was discovered to be Finlay's.

The magnitude of the comet declined after 1926, and it was not until 1953 that it has been observed on every return.


During the 2014 perihelion passage the comet outburst on 16 December 2014 from magnitude 11 to magnitude 9 becoming bright enough to be seen in common binoculars with a 50 mm objective lens.[9] On December 23, 2014, 15P and Mars were only 1/6 of a degree apart in the sky after sunset.[9] But by December 23, 2014, the comet had dimmed considerably since the outburst. On 16 January 2015, the comet outburst to magnitude 8.[10]


15P/Finlay currently has an Earth-MOID of 0.009 AU (1,300,000 km; 840,000 mi).[4] The comet will come to perihelion seven more times and then between October 26–28, 2060, the comet will pass roughly 0.04 AU (6.0 million km; 3.7 million mi) from the Earth with an uncertainty region of about ±2.5 million km.[4] This will be one of the closest comet approaches to Earth.[11]


  1. ^ a b c "15P/Finlay Orbit". Minor Planet Center. Retrieved 2014-06-21.
  2. ^ a b Syuichi Nakano (2011-11-05). "15P/Finlay (NK 2161)". OAA Computing and Minor Planet Sections. Retrieved 2012-02-18.
  3. ^ Goto JPL Horizons
    Observer Location: @sun
    (Perihelion occurs when deldot flips from negative to positive)
  4. ^ a b c d "JPL Close-Approach Data: 15P/Finlay" (last observation: 2015-04-20). Retrieved 2014-11-01.
  5. ^ M. Festou; H. U. Keller; Harold A. Weaver (2004). Comets II. University of Arizona Press. p. 242. ISBN 978-0-8165-2450-1.
  6. ^ a b Seiichi Yoshida (2016-06-11). "15P/Finlay". Seiichi Yoshida's Comet Catalog. Retrieved 2020-07-20.
  7. ^ "JPL Small-Body Database Search Engine: numbered comets". JPL Solar System Dynamics. Retrieved 2020-07-27.
  8. ^ Kronk, Gary W. "15P/Finlay". Cometography. Retrieved 2007-01-31.
  9. ^ a b Bob King (2014-12-18). "Comet Finlay in Bright Outburst, Visible in Small Telescopes". Universe Today. Retrieved 2014-12-20.
  10. ^ Michael Mattiazzo. "24324Re: [comets-ml] Re: Possible another outburst of 15P/Finlay?". Yahoo: comet-ml. Retrieved 2015-01-17.
  11. ^ Comet Close Approaches to the Earth

External linksEdit

Numbered comets
15P/Finlay Next