Bath Astronomers

January Night Sky

Our early evening skies this month  are dominated by Venus shining a brilliant white in the south west, setting at around 9pm. It is an impressive sight with the naked eye, but  a disappointing one in a telescope. The wall to wall toxic cloud cover of our near twin planet presents a uniformly white appearance over the illuminated part of the disc, which for most of this month resembles a half-moon. And that is all you will see. It is so bright that any variation in the tone of the cloud cover will be impossible to detect. If you want to observe Venus through a telescope it is better to do so in daytime. That same brightness makes it reasonably easy to find when, as now, it is near its maximum elongation from the sun. (The usual precautions apply if you are sweeping with your telescope for it. The safest and most effective way is to place your telescope in the shade (from the sun) of a nearby building, yet with a view of the right part of the sky.)

By about 9pm the evening sky to the south offers a splendid view of Orion, my favourite constellation. (The map below shows its main features.) Orion  is topped and tailed by two very different supergiant stars – orange/red Betelgeuse to the north, and blue/white Rigel to the south. It straddles the celestial equator, which runs just above the distinctive 3 stars of Orion’s belt, so at least part of the constellation can be seen on a clear night at this time of year from anywhere on the planet. And in M42, the Orion Nebula, it offers the finest deep sky object in the night sky. It can be seen with the naked eye as a fuzziness in the distinctive “sword” hanging from Orion’s belt. Binoculars will show a bright patch of nebulosity. Telescopes will offer much detail, especially with the aid of an OIII filter which helps the energetic Oxygen in this huge star forming region stand out. Large telescope aperture helps, of course! And in the centre of it all you can see the 4 hot young stars of the Trapezium, whose radiation powers much of what you can see.

Modern wide field images of Orion show that this cloud of dust and gas spans much of the constellation, of which the Orion nebula is just the brightest part. But this area alone is a magnificent sight.

Orion in January 2017