Space rock set to hide bright star

A naked-eye star is expected to blink out briefly early on Sunday morning when a faint asteroid passes in front of it.

Asteroid Gaspra photographed by NASA's Galileo probe
Asteroid Gaspra photographed by NASA’s Galileo probe. Credit: NASA

The rare event is predicted to happen along a narrow track of the UK that is just 16km (ten miles) wide – the estimated diameter of the asteroid, named 502 Sigune, which is only magnitude 14, close to the brightness of Pluto.

The star it will cover, 74 Ophiuchi, is not a very bright one but at magnitude 4.9 it can be spotted with the unaided eye in a clear, dark sky and is easily visible in binoculars.

Experts say they expect it to blink from view for just 1.2 seconds from the centre of the track between 00.18 and 00.20 UT – that is around 1.20am BST.

Jon Harper, Director of the Society for Popular Astronomy’s Occultation Section is appealing for observers to look out for this example of cosmic hide-and-seek.

He says: “Owing to the brightness of the star, an observer on the occultation path, equipped with nothing more than a pair of binoculars and a stop watch, should very easily be able to see the star wink out and come back on again and make a valuable timing of the moment when the occultation takes place.

“The latest predictions indicate a path crossing the UK from east to west, hitting the mainland on the North Sea coast in Yorkshire, between Scarborough and Bridlington.

“The path then proceeds through York, Leeds, Huddersfield, Manchester, Warrington and Chester to Aberystwyth, and leaves the mainland in Cardigan Bay. Remember, though, that with small bodies such as Sigune, predictions as to where the occultation will be seen are not always accurate, and observers living a considerable distance north or south of the predicted path could see the occultation instead.”

Jon is calling for negative observations as well as positive ones to be reported to him. Full details of the event and how to contact Jon can be found here on the SPA site.

The star 74 Ophiuchi lies almost midway between Beta Ophiuchi and Theta Serpentis, close to the Aquila border.

Photo: Not Sigune, but a bigger asteroid called Gaspra as imaged by the Galileo spaceprobe.

Paul Sutherland

Paul Sutherland

I have been a professional journalist for nearly 40 years. I write regularly for science magazines including BBC Sky at Night magazine, BBC Focus, Astronomy Now and Popular Astronomy. I have also authored three books on astronomy and contributed to others.
Paul Sutherland

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Paul Sutherland

I have been a professional journalist for nearly 40 years. I write regularly for science magazines including BBC Sky at Night magazine, BBC Focus, Astronomy Now and Popular Astronomy. I have also authored three books on astronomy and contributed to others.

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