15P/Finlay

15P/Finlay
Discovery
Discovered by	William Henry Finlay
Discovery date	September 26, 1886
Designations
Alternative designations	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
Epoch	2014-Dec-09; (JD 2457000.5)
Aphelion	6.019 AU
Perihelion	0.976 AU
Semi-major axis	3.488 AU
Eccentricity	0.7202
Orbital period	6.51 a
Inclination	6.799°
Last perihelion	July 13, 2021; December 27, 2014; June 22, 2008
Next perihelion	2028-Feb-09; 2034-Sep-08; 2041-Apr-03; 2047-Oct-25; 2054-May-02; 2060-Oct-03
Earth MOID	0.009 AU (1.3 million km)
Jupiter MOID	0.16 AU (24 million km)
Physical characteristics
Dimensions	1.8 km (uncertain)

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.^[7] It last came to perihelion on December 27, 2014,^[2] at around magnitude 10.^[7] 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).^[8] In October 2060 the comet will pass about 5 million km from Earth.

Description

Epoch	Perihelion (AU)
Perihelion distance at different epochs^[1]
1866	1.0
1906	0.96
1919	1.0
1981	1.1
2008	0.97
2021	0.99
2028	1.0^[3]

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.^[9]

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.

2014–2015

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.^[10] On December 23, 2014, 15P and Mars were only 1/6 of a degree apart in the sky after sunset.^[10] But by December 23, 2014, the comet had dimmed considerably since the outburst. On 16 January 2015, the comet outburst to magnitude 8.^[11]

2060

15P/Finlay currently has an Earth-MOID of 0.009 AU (1,300,000 km; 840,000 mi).^[5] The comet will come to perihelion six more times and then on October 22, 2060, the comet will pass roughly 0.0334 AU (5.00 million km; 3.10 million mi) from Earth with an uncertainty region of about ±2300 km.^[5]^[12] This will be one of the closest comet approaches to Earth.^[13]

Arids meteor shower

Debris ejected during the 1995 perihelion passage generated a meteor shower on 29–30 September 2021 radiating from the southern constellation of Ara.^[14] More outbursts are expected on 7 October 2021 from the 2008 and 2014 streams.