Comet 103P/Hartley, known as Hartley 2, reached perihelion - the point in its orbit nearest the Sun - on 12 October.
Comet Hartley 2 is a morning object during October 2023, its month track beginning in Auriga but quickly passing into Gemini.
Find out what comets and asteroids are in the sky tonight and our pick of the greatest comets of recent times.
Comet 103P/Hartley's discovery
Comet 103P Hartley was discovered by Malcolm Hartley on 15 March 1986 at Siding Spring Observatory in Australia.
It was discovered using the observatory's Schmidt Telescope, and found to be about 1 mile in diameter.
Hartley 2 is about 1 mile in diameter and takes around 6.5 years to orbit the Sun, making it a periodic comet (hence the 'P' in its name).
Observing Comet 103p/Hartley
Find our more about Comet 103P/Hartley in our video below.
Key dates
Based on previous apparitions, Hartley 2 is expected to remain close to peak brightness throughout October.
5 - 11 October: Comet Hartley 2 crossed the main form of the stick-figure twins, lying very close to mag. +3.5 Wasat (Delta (δ) Geminorum) on the night of 10/11 October.
As this coincides with the comet approaching peak brightness, the early hours of 11 October and onwards should be a good time to look for it.
The only negative is the Moon in Leo, 9° east of Venus.
This shouldn’t be too much of an issue, though, as it will be at a slender 11%-lit waning phase.
Observing before 03:00 BST (02:00 UT) puts the comet at a decent altitude and the Moon below the horizon.
The Moon rises around 03:30 BST (02:30 UT) on this date.
19 October: After its close pass of Wasat on 10/11 October, Hartley 2 heads southeast to eventually cross the border with Cancer.
27 October: The comet's track takes it very close to Altarf (Beta (β) Cancri) in the morning
The period up to 27 October is optimal for observing Hartley 2 as this will allow you to view the comet without the Moon spoiling the view.
Be aware that the Moon does set just as astronomical dawn is about to start on 27 October.
Have you managed to observe Comet 103P/Hartley? Let us know by emailing contactus@skyatnightmagazine.com
