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Saturday, June 30, 2007

Venus and Saturn in close encounter

Two bright planets are closing in for a spectacular rendezvous in the evening sky this weekend. Ringed wonder Saturn and the more brilliant Venus will be just two-thirds of a degree apart - a little more than the width of the Moon - at their closest.

Chart showing Venus and Saturn in LeoCatch the pair in the darkening twilight.

You will find them just to the west of the sickle shape that forms the head of the Zodiacal constellation Leo.

The sky map here, produced with Starry Night Pro, shows the grouping from mid-northern latitudes at 21.25 UT on June 30. Saturn will lie just to the upper left of Venus, as seen in northern skies.

If you have a short-focus telescope that gives a wide-angle view at low powers, you might be able to see Saturn's rings and the crescent phase of Venus in the same field of view.

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Friday, June 22, 2007

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 from Galileo in 1991The 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.



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