In September, Jupiter is the most prominent planet in the night sky. Look towards the South just after sunset, and Jupiter is low in the sky. On 9 of September, the Moon can be seen just below Jupiter, acting as a convenient guide.
At this time of year, the Earth is on the side of the Sun which allows us to look up at constellations such as Hercules, Cygnus and Lyra.
In Cygnus, the star that makes up the head of the swan is called Alberio, a colourful double star in a small telescope.
In Lyra, another nebulae is visible through a small telescope – the ring nebula. Looking like a ring of smoke, it lies 1500 light years away. At the centre is a very hot white dwarf star emitting intense ultraviolet radiation, causing the ring to glow.
Directly overhead in the evening is a triangle of bright stars – Vega, Altair & Deneb. They are known as the summer triangle. Even though the trio appear to be of similar brightness to each other, in reality Deneb is much brighter. It is one of the brightest stars we know of, 250,000 times brighter than the Sun. It only looks as bright as Vega & Altair because it is 100 times further away. If it was as close as either, it would be as bright as the Moon!
Visible towards the North-West this month is the great globular cluster in the constellation Hercules. Through even a small telescope the sight is stunning. This cluster contains several hundred thousand stars, and lives on the very outskirts of our own Milky-way galaxy.
Look towards the North, and you can find the pattern of stars called the Plough (the tail and body of the constellation of the Great Bear, Ursa Major). The handle of the Plough points towards Arcturus, which can be remembered by the ditty “Follow the arc to Arcturus!”. Arcturus is a bright red-giant star, 16 times wider than our own Sun, and over 100 times brighter.
On Monday, the NASA/ESA Cassini spaceprobe flew just 30 miles (50km) over the surface of Enceladus, and at a staggering 40,000mph! Cassini took numerous images of the grooves that run along the moon’s south pole, where jets of icy water vapour erupt hundreds of miles into space.
On Saturday the 16th of August, we get to enjoy a lunar eclipse! A lunar eclipse occurs when the Moon goes into the shadow of the Earth.
It is no coincidence that we have a solar eclipse (when the Moon casts a shadow onto the Earth) and a lunar eclipse (when the Earth casts a shadow onto the Moon) just a fortnight apart…
Because the orbit of the Moon is tilted, it travels from the South of our flat solar-system to the North, and back South again every month. During the eclipse on the 1st of August, the Moon was travelling from the North down to the South… and as it did so it happened to pass in front of the Sun. On the 16th of August, the Moon is heading North again, passing though the shadow of the Earth on its way.
It is also no coincidence that we are having a pair of eclipse’s six months after the last pair! This is because the nodal axis of the lunar orbit happens to be in line with the Sun at the moment, which happens every six months because the Earth orbits the sun every year (see the graphic to the left, and my earlier post from the February eclipse season for more details).
This lunar eclipse will be visible from everywhere with the exception of the continent of North and central America (see this map). The animation I have created below using the excellent (and free!) Celestia software explains why the eclipse is not visible from the top half of the America’s… our planet gets in the way!
But for us here in the UK, the Moon will be rising in eclipse, so we have some tremendous and unique photographic opportunities to look forward to!
And what will the eclipse look like? Well, the Moon will turn either a deep red, a pink colour or maybe grey… we really don’t know! Take a look and find out for yourself! It all depends on the atmospheric conditions of the Earth at the time of the eclipse, since some sun-light will bounce through our atmosphere and illuminate the Moon even when it is in the shadow of the Earth.
The Moon will first enter the outer shadow of the Earth at 18:25 GMT (19:25 British Summer Time) – although, you may not even notice. An hour later, at 19:36 GMT (20:36 BST) the Moon begins to go into the dark heart of the Earth shadow, and that’s when the eclipse really begins!
The Moon is in the middle of the Earth’s shadow by 21:10GMT (22:10BST), and has left the dark shadow by 22:44 GMT (23:44 BST). The entire eclipse ends at 23:55 GMT (00:55 BST).
And for those of you too impatient to wait, below is a time-lapse movie of a lunar eclipse I saw back in March 2007! (click for full details).