On Monday, 9 May just after midday BST, suitably equipped observers in the British Isles can witness the start of a 7½-hour spectacle that hasn’t been seen for almost a decade — the silhouette of innermost planet Mercury crossing the face of the Sun. Here’s our online guide to observing this fascinating and comparatively rare event in complete safety.
On Monday, 9 May there will be a rare transit of Mercury, when the innermost planet in our solar system will pass directly between the Earth and the Sun. The last time this happened was in 2006. With a properly filtered telescope and fine weather, the entire 7½-hour event can be seen from the British Isles.
Have you ever seen Mercury with the naked eye? If not, now is the time to check the elusive innermost planet off your list. Mercury reaches greatest easterly elongation from the Sun on Monday, 18 April, the highlight of a very favourable dusk apparition in the west-northwest for observers in Western Europe and the British Isles.
Sprawling across Pluto’s icy landscape is an unusual geological feature that resembles a giant spider. This enhanced colour image, obtained by NASA’s New Horizons spacecraft on 14 July 2015, consists of at least six extensional fractures (arrowed) converging to a point near the centre. Curiously, the spider’s “legs” expose red deposits below Pluto’s surface.
Scientists have long been puzzled about what makes Mercury’s surface so dark. The innermost planet reflects much less sunlight than the Moon, a body on which surface darkness is controlled by the abundance of iron-rich minerals. These are known to be rare at Mercury’s surface, so what is the “darkening agent” there?
All five of the bright naked-eye planets are observable in the pre-dawn sky from about the third week of January 2016, particularly if one lives south of the equator. But even from the UK, you can get to view the spectacle if you time it right — and the weather obliges! The last time that Mercury, Venus, Mars, Jupiter and Saturn appeared in the same sky was 11 years ago.
The planet Mercury is being pelted regularly by bits of dust from an ancient comet, a new study has concluded. Comet Encke has the shortest period of any comet, returning to perihelion every 3.3 years. The dust from the comet affects Mercury’s tenuous atmosphere and may lead to a new understanding on how these airless bodies maintain their ethereal envelopes.
In the small hours of Friday, 16 October, innermost planet Mercury reaches its greatest westerly elongation from the Sun. For those of you in the UK with a flat, unobscured eastern horizon and willing to get up an hour before sunrise, the next few days provide your best opportunity to see Mercury from the Northern Hemisphere during 2015.
Now that planet Saturn is effectively lost in the dusk twilight for UK-based observers, you may be wondering what has happened to the other four bright naked-eye planets. Far from disappearing, they have just transferred to the morning sky. From 8—11 October, the waning crescent Moon acts as a guide to Venus, Mars, Jupiter then Mercury in the eastern dawn sky.