Orion is now in prime position in everyone’s evening sky. Lying across the celestial equator, with his main stars slotting neatly between 10° N and 10° S of the celestial equator, the Hunter’s figure is visible from all parts of the Earth bar the central regions of the Arctic and Antarctic. I accept, of course, that most of the latter currently enjoys 24-hour daylight and is hardly the place to go for visual star-watching in January.
Last month, our chart displayed Orion’s stellar neighbours as they filled Britain’s S sky soon after midnight. That chart is just as applicable at 22:00 GMT tonight and by 21:00 at the month’s end. This time, though, our focus is on Orion itself.
Very few constellations resemble the figure or object they represent – Triangulum the Triangle and Crux the Southern Cross are exceptions that spring to mind. Another is Orion, with a belt of three stars at his waist, prominent stars to mark his shoulders and knees and a knot of stars for a head. He even carries a shield, the arc of stars to his NW (upper-right) and is brandishing a club of faint stars above his head.
As I mentioned last time, though, his most fascinating feature, the hazy gas and dust of the Orion Nebula, lies in the sword that hangs below (at least, for us N hemisphere observers) the middle star of his belt.
Six of Orion’s seven main stars are young blue-hot giant or supergiant stars, including the brightest, Rigel. The exception and second brightest, Betelgeuse, is a bloated and relative cool red supergiant, large enough to engulf the entire orbit of the Earth if it were to replace the Sun. It pulsates slowly and semi-regularly in size and brightness and may die as a supernova within the next million years.
Another fainter star worth checking is Cursa, near Rigel but next door in Eridanus the River. Perhaps because of an unusually violent flare, this apparently brightened to surpass Rigel for a brief 2-hour spell back in 1985.
Orion will grace our evening sky for weeks to come, edging relentlessly westward so that it stands due S at nightfall by mid-March.
A brief look at the planetary year ahead has Mars keeping company with the brilliant Venus in our W evening sky until Venus dives around the Sun’s near side on 25 March and becomes a morning star. We lose Mars in May and it, too becomes a morning object from August.
Jupiter is resplendent above Spica in Virgo in the S before dawn and close to the Moon on the 19th. It is visible all night at opposition on 7 April and slips into the Sun’s glare by September. Saturn, low in our SE morning twilight at present, reaches opposition in S Ophiuchus on 15 June and remains in view until November with the N face of its rings wide open for telescopic study. Mercury, below and left of Saturn at present, has its best evening visibility in March-April and before dawn again in September.
For many, though, the year’s astro-highlight will be the total solar eclipse visible from coast to coast across the USA on 21 August.
