The new astronomical year

Each January brings some of our finest evening skies of any month. We must wait until the late evening, though, to see Jupiter, our first bright planet of the night, rise in the E in Leo. Mars, following in the early hours, stands to the left of Spica in Virgo before dawn when Venus is alongside Saturn and low in the SE. Jupiter’s opposition on 8 March is followed by those of Mars on 22 May and Saturn 12 days later, both low down in Britain’s sky.

As we look to the astronomical year ahead, the stand-out event is
probably the transit of the planet Mercury across the Sun’s disc on 9 May. Usually Mercury glides invisibly above or below the Sun as it sweeps around the near side of its orbit. Occasionally, though, it is seen as a small inky dot against the dazzling solar surface.

This is its first transit since 2006 and, unlike that one, it is visible in its entirety from western Europe, eastern North America and much of South America

More spectacular, but less rare, is the total eclipse of the Sun on 9 March. Its narrow path of totality crosses Sumatra and Borneo before speeding eastwards over the Pacific. An annular solar eclipse, with the Moon too small to hide the Sun completely, occurs on 1 September across Central Southern Africa.

Penumbral lunar eclipses, in which the Moon hardly dims at all, occur on 23 March and 16 September – only the end-stage of the latter being visible from Britain.

Every year opens with the potential for unexpected astronomical sights, be they spectacular fireballs, comets, novae or, dare I say, supernovae.

At this moment, though, the brightest comet we know of for 2016 is beginning to make its pass between the Plough and Polaris, the Pole Star, over the coming weeks. Our chart plots the path of what is officially called Comet 2013 US10 Catalina, and looks between the N and NE at about 22:00 at present.

The comet’s unusual name stems from the fact that it was catalogued as an asteroid by astronomers of the Catalina Sky Survey in 2013 before its true nature was revealed. It reached perihelion, 123m km from the Sun, on 15 November and is closest to the Earth (108m km) on 17 January. Earlier hopes that it might be a bright naked-eye comet evaporated when it emerged from the Sun’s glare as a sixth magnitude binocular object, though photographs showed its two tails, one of gas and the other of dust, appeared at quite divergent angles – a result of our viewing perspective.

At present, Comet Catalina is still close to magnitude 6.5 and appears as a round greenish fuzz, about one third as large as the Moon. Binoculars should show it easily in a dark sky, particularly as it passes near Alkaid, the star at the end of the Plough’s handle, on the nights of the 14th and 15th. By the time it leaves our chart in early February, it may well be as dim as the 8th magnitude.