The Night Sky for June, 2010

Summer begins this month, and so the Sun is not setting until after 9pm, and darkness does not begin until 10pm. But there is plenty to see this month if you are willing to stay up a bit later.

As soon as it begins to get a bit dark, look towards the sunset, and by 10pm you will be able to see the planet Venus, very low in the sky. It looks a bit like an aircraft coming in to land… but if it is still there 10 minutes later, and hasn’t landed, then you have found Venus!

Look to the left of Venus, and slightly above it, and you will notice a red object – the planet Mars. During the month, Mars is close to the star Regulus, at equal brightness but not as red. On the 6th of June, Mars passes only 1 degree away from Regulus as it moves around the Sun and so moves around the sky.

Then look to the top left of Mars, and you have Saturn, which appears to be quite bright and slightly yellow in colour.

Venus is setting at about 11.30pm, with Mars following it an hour later, and then Saturn is setting an hour after that.

The positions of the planets can be seen in this movie below.

If you now look in the other direction towards the stars rising in the South-East (see graphic below, set at 22:30BST), you will see three bright stars – Deneb, Vega and Altair. Those three stars are known as the summer triangle of stars, and are fascinating in their own right. Vega has a dusty disk around it and maybe a planet; Altair rotates in just 7 hours, making it bulge around its equator; and Deneb is one of the brightest stars we know of. Deneb is over a 100 times further away than both Vega and Altair, but it looks equally bright because it is so big – at least 200 times the diameter of the Sun! If Deneb was as close as Altair, it would be almost as bright as the full Moon!

I will be writing more about what can be seen in this patch of sky over the coming months, as the Earth moves around the Sun to get a better look at this patch of the night sky.

Plenty of Planets!

Now is a great time to feel that you are part of the solar system. Venus, Mars, Saturn and the Moon are all visible in the evening sky. As you can see in the photograph I took a few nights ago (below), all the planets lie along a line called the ecliptic, which goes to show just how flat our solar system is. (Just hover your mouse over the image for labels)

Our solar system is like a big flat pancake! Imagine the Earth sitting on that pancake, along with the rest of the planets. The grid marks where that pancake (the flat plane of our solar system) goes out into space, and so where all the planets can be found. The constellations of Leo (top left) and Gemini (bottom right) are also shown.

The following animation shows just how it looks from the ground and from above the solar system.

Jupiter and Mercury, hiding behind the Sun!

If you are wondering where Jupiter and Mercury are at the moment... they are hiding behind the Sun!

Below is a movie using data from the Lasco C3 insrtument on the NASA/ESA SOHO observatory, during February 2010. SOHO points constantly at the Sun, and so it allows us the see Venus, Jupiter and Mercury following their orbits around the far-side of the Sun.

It begins with Venus leaving the scene towards the left (which is why we can see it now in the evening sky), and then Jupiter moving left to right, and finally Mercury appearing!

Note that Lasco C3 is sensitive to 540nm-640nm wavebands, which is mid-green through to mid-red... so I've changed the usual blue colour to grey-scale (I think true colour would be a yellowish-brown...?).

Note also the 'bleeding' of the bright planets - they are so bright, that electrons over-flow into neighbouring cells on the Lasco-C3 CCDs. Note the the Sun is hidden behind a disk, to ensure that its brightness does not damage the camera.