Comet 103P Hartley: what time and how to observe it?

This month of October 2023 is marked by the return of a well-known visitor: Comet 103P Hartley. We tell you everything about this fascinating object visible since the end of September in the night sky.

Discovered in 1986, comet Hartley 2, also called 103P Hartley, is a periodic comet that visits us approximately every 6 and a half years. This year, the comet has been visible in the night sky since September. It will reach its closest point to the Sun this October 12 and can be observed from the northern hemisphere to the south. using a pair of binoculars or a telescope.

To see the comet, you will have to direct your gaze towards the constellation Gemini in which it is located. This emerges from the western horizon a little before midnight around mid-October and increasingly earlier in the evening as it progresses. as the days pass. To easily identify the Gemini constellation, you can use a sky map like the one offered on the Stelvision website or a mobile application like Sky Tonight (available on the App Store and on Google Play). The comet is therefore visible all night for amateur astronomers equipped with binoculars or a telescope.

A so-called “comet” is visible all night long. hyperactive periodic" well known

In 2010, the Deep Impact probe designed by NASA set out to explore the world. the encounter of this comet while it was located at proximity of the earth. The machine was thus able to fly over the object at a low angle. a distance of only 700 kilometers, the opportunity to carry out a certain number of observations and to carry out multiple measurements. We thus learned that Hartley is a so-called “hyperactive” comet, which means that its activity is very active. is much larger than one would expect from a comet of this size. Its peanut-shaped core contains carbon dioxide which vaporizes under the effect of the heat, expelling the dust found inside it. the surface of the comet. This mission also made it possible to obtain some spectacular photos of the comet revealing its astonishing shape and the jets of gas escaping from one of its ends. ;s.

Photograph of comet 103P Hartley captured by the Deep Impact probe (NASA) during its flyby in 2010 © AP/SIPA (published 09/10/2023) < p>The object of a participatory science experiment

The passage of Hartley is the opportunity for the French Astronomy Association (AFA) to propose a collaborative science campaign which all volunteers are invited to attend. participate. The objective of the project is to measure the increase then the decrease in brightness. of the comet throughout its passage. All budding astronomers who wish can therefore bring their camera, telescope or telescope to photograph the bolide and measure its luminosity. The AFA is implementing provides a tutorial which explains how to carry out this measurement and share it on its site.