A comet is coming to sky near you, later this month.
It won’t be a brilliant sight – but we can expect a stunning view of the action from a recycled spacecraft. The story began in 1986, when British astronomer Malcolm Hartley was scanning a photograph of the sky taken by a sky-camera – the UK Schmidt Telescope – in New South Wales, Australia. Among the images of stars, nebulae and galaxies, Hartley spotted a smudge that shouldn’t have been there.
It was a comet, an icy lump of rock traipsing around the Solar System named Comet Hartley 2 (comets are named after their discoverer, and this was Hartley’s second). A mile across, the comet caught Hartley’s eye because it was sweeping close to the Sun’s heat, and its ices were boiling into a fuzzy cocoon of steam and dust. Hartley’s comet swings around the Sun every six years, in an elongated orbit, and its next close approach to the Sun is on 28 October. That’s when its erupting jets of steam and dust will be most active. Coincidentally, Comet Hartley 2 passes unusually close to the Earth on 20 October. As a result, we’ll get to see the comet in our night sky, just visible to the naked eye.
We’ve marked the comet’s position on the chart at 5-day intervals. But don’t hold your breath, as the light of the Moon will tend to drown out the faint and fuzzy comet. You’ll be best waiting until the wee small hours of the morning when the Moon has set and Comet Hartley 2 is much higher in the sky. If you’re not sure it it the comet you are seeing, then binoculars should show it up clearly. And if moonlight, streetlight, the British weather or the need for sleep deprive you of a view, then watch the news. A Nasa spaceprobe – originally used to fire at massive probe at Comet Tempel 1 – is homing in on the comet, and already sending back pictures.
“Star” of the month is the planet Jupiter, shining brilliantly in the south. It is still holding centre-stage in the heavens, having just passed its closest approach to Earth for 47 years. Unlike Jupiter, the stars are putting on a pretty poor show in October. At this stage in Earth’s orbit , we face the “bare” constellations of Pegasus and princess Andromeda, along with the faint, “wet” star patterns of Cetus (the whale), Pisces (the fishes), Aquarius (the water-bearer) and Capricornus (the sea-goat). But one star is making a bid for glory. In the last week of the month, the red star Mira (in Cetus) may achieve prominence. This distended star has difficulty controlling its waistline, and changes in brightness as it swells and shrinks. By the end of October, it could rival the Pole Star in the sky.
1: 4.52am Moon at Last Quarter
7: 7.44pm New Moon
14: 10.27pm Moon at First Quarter
21-31: Mira at maximum
23: 2.36am Full Moon
30: 1.46pm Moon at Last Quarter