103P Hartley

Closest to Earth on 2023 Sep 26 at 0.38AU.
Closest to Sun on 2023 Oct 12 at 1.06AU.
Maximum magnitude 7.5 in late October 2023
Orbital period 6.48 years

103P Hartley on 2023 November 3 at 17:15UT




The 103rd periodic comet was discovered by Malcolm Hartley in 1986, using the UK Schmidt telescope at Siding Spring observatory.
It was the flyby target for the EPOXI mission in 2010 when its diameter was estimated to be 1.2 kms and shaped like a bowling pin.
It had a very favourable approach to the earth in October 2010, when it reached 5th magnitude.
(see above photo taken on 2010 November 4.
The 2023 appearance is also very favourable but not as close as in 2010.
Make an effort to see this comet as it won't be this close to Earth for the remainder of our lifetimes.
The comet is expected to reach peak brightness of 7.5, a few weeks after perihelion.
This is not unusual for periodic comets to continue brightening after the perihelion passage.

Night mode chart for 2023

During September 2023, the comet brightened rapidly from magnitude 10 to 8 as it traversed the constellations of Perseus and Auriga.
It situated low in the northern sky at the start of astronomical twilight, therefore favouring northerners.
Moon free period started from September 12 when the comet can be found near Epsilon Peg.
It entered Auriga on the 18th.
On September 22, it was 2 degrees north of star cluster M38, then 3 degrees north of M36 and M37 over the nights following.
Moonlight started to interfere by September 27th.

At the start of October, the magnitude 8.0 comet was situated on the Auriga-Gemini border, in the hour before dawn.
On October 13, a wonderful rendezvous occurred when the comet wa situated adjacent to the Eskimo nebula NGC 2392.
The next 2 weeks were the best period of visibility as it trekked south-eastwards through Gemini and Cancer
The comet was best in late October, shining at magnitude 8.0.

During November, 103P is expected to fade from magnitude 8 to 9 as it treks southwards through Hydra, in the morning sky before dawn.
Moonlight will interfere with observing until November 7, when the comet situates a degree south of Sigma Hydra.
Between November 16 to 18, the comet is within a degree of a galaxy cluster with main group members NGC 2695 and NGC 2708.
On November 21, the comet will be adjacent to 12th mag galaxy NGC 2721.
Moonlight once again interferes from November 24.

During December, 103P is expected to fade from magnitude 9 to 10 as it continues its trek southwards through Hydra, best observed in the morning sky before dawn.
Moonlight interferes until December 6th.
No interesting rendezvous events occur this month.
By new years eve, the comet is now observable during late evening hours, rising in the east.