Even though the summer has long gone, we can still see the summer triangle!
The Sun is now setting so early that we are still able to see the constellations of Cygnus, Lyra & Aquila in the evening sky (see chart; click for a larger version) - and it is the brightest star in each of these constellations that make up the summer triangle. Although these constellations were directly overhead in the summer, they are now low down in the west, ducking beneath the western horizon at around 9pm. But they are still ideal for late afternoon or early evening observing.
The star that forms the head of Cygnus the swan is called Albireo, a blue and golden double star that is a beautiful sight through a small telescope. Notice how Cygnus is flying directly downwards, head-first into the western horizon! Just to the right of Albireo is the Ring Nebula in Lyra, the left over remains of a star that puffed out its outer layers to form the nebula some 1,500 years ago. And to the left of Albireo is the Dumbbell Nebula, another treat for small telescope owners.
Almost directly overhead, high in the east, is the easily recognisable W-shape of the constellation Cassiopeia (see chart, right; click for a larger version). Below Cassiopeia is Perseus, which contains the star Mirphak.
If you want to see a comet, look toward Mirphak. While all the stars are pin sharp, you will be able to see a fuzzy object just next to Mirphak - that is the incredible Comet Holmes! For more details about Holmes, see my previous posts. This is a rare opportunity to see a comet with the unaided eye, so do not miss out!
To the right of the W-shape, is the Andromeda Galaxy. It is the most distant object that can be seen with the unaided eye, a staggering 2.25 million light-years away! The hundred thousand million stars that make up the Andromeda galaxy are what allow us to see it over such a vast distance.
Looking to the east, you can see Orion rising from 9pm, meaning that winter is here!
In the chart to the left (click it for a larger map), Mirphak (with Comet Holmes passing by) is visible at the top-right, in the constellation of Perseus. In the constellation of Auriga to the bottom left is the bright star Capella. Below Perseus is Taurus, with the beautiful desert-island cluster of stars called the Pleiades. Also known as the seven sisters (because seven stars are just about visible to the unaided eye), the Pleiades are about the same size in the sky as the full Moon. In fact, the Moon is not too far away from the Pleiades on 23rd and 24th of November.
The planet Mars, the only planet that is sociable this month, can be seen to the left of Taurus, in the group of stars that form the constellation of Gemini.
And finally, we have the beautiful Orion. The red supergiant star to the top left is Betelgeuse, and to the bottom right is the white hot star Rigel. In the middle of both is Orion's belt of three bright stars. Hanging down from the belt is a dagger of three fainter stars, at the centre of which is Orion's nebulae – a cloud of gas and dust where new stars are forming.
The Orion nebula is easily visible to the unaided eye, and is a splendid sight to see even in a small telescope throughout the winter.
The Camera Obscura will be closed from 21 May until 25 May. The rest of the Royal Observatory and Meridian Line remain open.