The Night Sky for June, 2010

Summer begins this month, and because the Sun is not setting until after 9pm, 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.

The Night Sky for May, 2010

This month is a great month for planets! If you go out on a dark night you can see and feel for yourself how we are part of the solar system.

Look low in the west, half an hour after sunset, you can see Venus - the brightest object in the sky after the Sun and Moon. Now wave your arms around in an arc going from Venus low in the west, over the south and then towards the south-east, and you will bump into two more planets in the night sky – the red planet Mars, and Saturn which is yellowish in colour.

Ancient people knew of the planets Mercury, Venus, Mars, Jupiter and Saturn because they are all so easy to see with your own eyes - they are all bright objects that can even be seen through our light polluted skies. However, Mercury cannot be seen at the moment since it is too close to the Sun (Mercury passed between us and the Sun on the 28th of April), and Jupiter is above the morning side of the Earth, and so we can only see Jupiter very early in the morning.

But do take a look for Venus, Mars and Saturn, the bright planets in this months evening sky. They are forming a beautiful arc across the night sky, which really highlights that we live close to the centre of the very flat solar system.

Goodbye Mercury... until next time!

It is now impossible to see the planet Mercury in the evening... Until it orbits around the Sun again. But I did manage to take the following photograph last Thursday, of a beautiful alignment of the Moon, Mercury and Venus.

Mercury disappearing into twilight

Mercury orbits the Sun in just 88 days, and over the next week, you can see how quickly it moves in relation to Venus.

I took the photograph to the left on Monday the 12th April, at about 9pm, and you can see Mercury and Venus side by side (Venus is the bright object; Mercury the fainter object to the right of the image just slightly lower then Venus in the evening sky). But over the next week, as Mercury orbits around the Sun, it will rapidly move away from Venus to be in line with the Sun on the 28th of April.

So, if you want to see Mercury for yourself, the next few days would be a good time to look...

Mercury & Venus in the evening sky

The next few weeks are an ideal time to see Mercury & Venus together in the evening sky.

Mercury is always a difficult planet to find. It is the closest planet to the Sun, and so it always remains close to the Sun in the sky, usually totally hidden in the Sun's glare. But at the beginning of April (as the simulation below shows), Mercury gets to its Greatest Eastern Elongation, meaning that it is as far away eastwards of the Sun as it is ever going to get, and so it is the best time to see Mercury in the evening sky.

So wait for the Sun to set, and then go out and see if you can see Mercury for yourself! The best days to look are the 15th and 16th of April, when the Moon acts as a useful guide. This will be your best chance to see the elusive Mercury!

Each frame in the simulation above is a view looking west when the Sun is 6 degrees below the horizon (about 40 minutes after sunset) - that's dark enough to see Venus and Mercury, but not so late that they are hidden behind trees. The simulation was done using Stellarium.

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.

Venus is back!

In January, Venus was on the far side of the Sun and totally hidden in the glare of the Sun.

But now it is back! Take a look in the evening sky for a glimpse of the brightest planet...

Venus will be a prominent member of the night sky throughout the summer until the end of August. If you have a zoom lens on your camera you may be able to just make out the crescent of this planet, which is very obvious with even a small telescope. Our view of Venus' crescent will change over the next few months, as it orbits the Sun. The animation below shows this in more detail.

Venus began 2010 on the opposite side of the solar system to the Earth, which is why we could not see it. By March 2010 (when the Earth is at the 11 O'clock position in this animation), Venus became visible in the evening sky.

By 20 August 2010, Venus will reach its maximum Eastern position from the Sun (when the Earth is at the 5 O'clock position on this animation). And then Venus rapidly "catches up" with the Earth, being between the Earth and the Sun on the 29th October, 2010.

The animation then returns to the beginning of the year to watch how the phase of Venus (what fraction of Venus is illuminated) changes during 2010.

But by October, when Venus is between us and the Sun, we will only be able to see the night-time side of Venus. (Venus will also appear to get larger in size during the course of the year).