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Venus dominates the evening sky in January, visible in the west after sunset and at magnitude -4.2 more than ten times brighter than any star in the sky. The planet reaches greatest eastern elongation, when it is farthest from the Sun in the sky, on the 14th but it will brighten slightly as the month goes on as it swings past the Earth.

Venus was for a long time a source of frustration for Earth-bound astronomers, who struggled to see any detail on its brilliant disc. Controversy for most of the 19th century centred on the mysterious “ashen light”, a glow occasionally recorded on Venus’s dark side. Explanations included lightning in the planet’s atmosphere and the glow from Venusian street lighting.

The mystery was resolved only by the European Space Agency’s Venus Express spacecraft in the past two years; the ashen light may be the glow of the roasting surface of Venus, seen through the planet’s thick atmosphere. No alien cities, therefore, but Venus remains a spectacular sight.

Early in the evening on New Year’s Day, Venus is joined by the crescent Moon and by Jupiter and Mercury, which are in a close conjunction. The best time to catch the show is about 16.45, half an hour after sunset, when they will both be due southwest. If you have trouble finding them, draw a line from the Moon through Venus and down to the horizon; Mercury and Jupiter lie on this line, only 7 degrees above the horizon. Mercury reaches greatest eastern elongation on the 4th, and remains visible for much of the first fortnight of 2009 before conjunction on the 20th. Jupiter also vanishes quickly, reaching its conjunction (when it lies on the opposite side of the Sun to the Earth) on the 24th. Mars is also absent, but the fifth naked-eye planet, Saturn, is now well placed, moving through the stars of Leo. It is now rising well before midnight, at about 20.30 by the end of the month.

January’s stellar sky is dominated by the celestial hunter, Orion. One of the most recognisable constellations in the sky, its form is marked by two first-magnitude stars, Rigel and Betelgeuse, on either side of Alnitak, Alnilam and Mintaka, the three stars that make up Orion’s belt.

Betelgeuse and Rigel themselves are a study in contrasts. Betelgeuse or Betelgeux — the name is a corrupted form of its Arabic name — has a distinct red tone, even to the naked eye. Rigel, by contrast, is a brilliant white-hot supergiant star, one of the most luminous objects in the Milky Way. Such stars burn through their fuel rapidly, and so Rigel must be young, one of many youthful stars scattered through the Orion region. The reason for this abundance of youthful stars is that Orion contains the nearest large stellar nursery, a reservoir of gas and dust in the process of collapsing to form stars. In the infrared this whole region of sky glows, but our eyes, restricted to visible light, see only the regions where gas is lit up by the light of the stars born from it. The brightest of these, the great Orion nebula, M42, is marked on our chart.

To find it, take directions from Tennyson who, in Merlin and Vivien told us to look for “the second in a line of stars, that seem a sword beneath a belt of three”. Even from light-polluted skies, this will appear to the naked eye not as a single point of light but as a fuzzy, misty patch. Through a small telescope, it is an unforgettable sight, described by William Herschel as “an unformed fiery mist, the chaotic material of future suns”.

Returning to today’s stars, the belt of Orion points the way up to Aldebaran in the zodical constellation of Taurus, the bull, and down to Sirius, the brightest star in the sky. The line made by Rigel and Betelguex points up toward the twins of Gemini, Castor and Pollux, while directly above Orion is the bright star of Capella, in the constellation of Auriga. With the Milky Way running through it, this is one of the richest regions of the sky, and the long nights of January should give us ample opportunity to drink it in.