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.

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).

The Night Sky for March, 2010

March is one of the best times of the year for astronomy, simply because there is so much to see!

Orion and Taurus – along with all the amazing objects that surround that part of the sky, such as Orion's nebula, Betelgeuse, the Pleiades - are visible in the evening, and as they set by midnight, the summer highlights begin to rise in the east – Hercules, the Great Globular cluster, with Vega and the rest of the summer triangle on their way from the morning sky into the evening sky, signalling that summer is not far away.

We can see both Mars and Saturn throughout the night, with the latter rising at sunset. The Moon glides under Mars on the 25th March, and then passes under Saturn a few days later on the 29th. Both Mars and Saturn are quite bright, so they are easy to spot.

For more details, I recommend you use the free planetarium software Stellarium – you can download it for Macs, Windows or Linux.

The Night Sky for February, 2010

The highlight this month is the planet Mars. Easy to spot as a bright red object in the night sky, visible in the east at sunset, moving to the south at midnight, and heading further west in the morning hours. And, because both the Earth and Mars are on the same side of the solar system at the moment we are quite close to Mars, making Mars look brighter in the evening sky, and big when you look through a telescope.

This why there are some fantastic images of Mars being taken recently, including this one from local astro-photographer Pete Lawrence, showing a dust devil that has pasted across the martian south pole (more details at SpaceWeather.com).

By 10pm, the planet Saturn is also rising in the east. The rings of debris that surround this planet are visible through binoculars if you have good eyesight, or easily through a small telescope to the rest of us.

Orion (the hunter), Taurus (the bull) and Canis Major (the great dog) are the dominating constellations this month, with the bright star Sirius forming the nose (or sometimes the collar) of the dog. You should not miss out on looking at the Pleiades or the Orion Nebula through binoculars, and notice how Sirius twinkles due to our turbulent atmosphere.

To find these objects, I recommend that you use either Stellarium or SkyMaps.com.

The Night Sky for January 2010

We have two evening sky planets that we can see throughout January - Jupiter in the early evening, and Mars (right, as seen through a good telescope) in the late evening. You can see Jupiter setting in the South-West if you look before 7pm, and you can see Mars rising in the North-East if you look after 7pm. So, for a few minutes at around 7pm, you can see two very bright planets at opposite sides of the sky!

On the 17th, the Moon is just to the right of Jupiter, and on the 18th the Moon has moved just above Jupiter. By the 29th of January, the Moon will have travelled to the other side of the sky and will be next to Mars for the night. Saturn is also visible over night, now rising just before midnight in the south and visible until dawn. Unfortunately, we cannot see either Mercury or Venus this month, as they are both too close to the Sun.

The starry highlight of January is still the constellation of Orion, which I discussed in last months's blog.

December's Night Sky

This is the month to take advantage of, and enjoy, the long nights!

The earliest sunset here in Sussex occurs at 15:54 on the 12th of December, and the shortest day is on the 21^st this year. The Earth is tilted, and the shortest day occurs when that side of the Earth is tilted directly away from the Sun - and so the solstice actually occurs at a specific moment in time, at 17:46 on the 21^st December, 2009.

The increasingly inaccurately named summer-triangle is still visible, low in the west, but only until 7.30pm - ideal for after-school observing events! And the Andromeda galaxy is still well placed in the evening sky (see last months posting for full details about both of those).

Jupiter is still a wonderful sight until about 8pm throughout the month - just look for the brightest object you can find, low in the west, and that will be Jupiter! Look through binoculars or a small telescope to see four of the 60 moons that orbit this gas giant.

The 21^st of December is a great day for a photo' opportunity. That late afternoon and early evening, the planet Jupiter is visible just below the Moon. And just to the top-right of Jupiter, is the planet Neptune - although you will need a telescope to see Neptune, as it is 10,000 times fainter than Jupiter!

Rising at 8pm in the east is the constellation of Orion - a very familiar sight in the winter skies, thanks to the three stars that form a straight line, and which are known as Orion's belt (as in the photo to the left). Just below those three stars in a line, are another group of three stars in a line... only, the middle star is not a star at all, but a huge gas cloud where stars are in the process of forming. You can see it with your own eyes, but look through a telescope and you can see much more detail, and take a long exposure photo', and you can see even more detail! The movie below shows the difference between looking through a telescope yourself, and taking a 15 minute long exposure photograph.

You can get some very easy-to-use and clear star maps from either Skymaps.com, or by using the excellent (and free) Stellarium Planetarium software.

November's Night Sky

The sun is setting at around 5pm during November, so here is how to enjoy the long winter nights!

The highlight of the evening sky is the planet Jupiter, visible low in the south to south-west up until 10.30pm in the evening. Take a look at Jupiter with binoculars, or a small telescope, and see how many of Jupiter's Moons you can spot – just as Galileo did 400 years ago. You should be able to see up to four moons, and if you take another look just a few hours later, you may be able to notice that the moons have moved a bit in just that very short period of time.

The planets Uranus and Neptune are also visible in the evening sky, but they are just-too-faint to be seen with the unaided eye, which is why these two planets were not discovered until after the invention of the telescope.

Early in the evening, looking towards the west, you can still see the summer triangle of stars – Vega, Altair and Deneb – until about 9pm (see the chart to the right; click on it to see it full size). Within the triangle, you can see the remains of two dead stars using a telescope – the ring and dumbbell nebulae. There is also a beautiful double star called Albireo within the triangle.

This is also a great time of year to see the Andromeda galaxy – the most distant object that you can see with your own eyes! It may be 2.25 million light-years away, but it is quite easy to find. Just go somewhere dark, away from the light pollution and inefficient lighting of our towns and cities, and look for the square of Pegasus. The square can be found by looking towards the South, about half way up the sky. It’s quite a big square – just bigger than your hand at arms length. Look towards the star that makes the top-left corner of the square, then follow two bright-ish stars up towards the top left, and then follow two more slightly fainter stars towards the top right (as in the map, right), and just there is the Andromeda galaxy! The W-shaped constellation of Cassiopeia also usefully “points” towards the galaxy.

And it is huge! It is actually six times the diameter of the full Moon, but it appears faint because it is so far away, and so with our own eyes we can only see the bright centre of this massive city-of-stars. For the best view, take a look through binoculars (telescopes usually have too high a magnification for you to see this galaxy clearly).

Now look to the left of the square of Pegasus, about 4 times its size, and you will see a bright red giant star called Aldebaran. Just to the top-right of Aldebaran, you’ll be able to see the Pleiades star cluster, also know as the seven sisters because you can see up to seven stars with your own eyes (pictured left as a wide-angle view, and right as a close-up photograph). This cluster is a beautiful sight through binoculars, where you can see up to 50 stars. Again, don’t use a telescope, since you will only be able to see one or two stars at a time – low magnification is what you need for a cluster that appears bigger than the Moon in the night sky.

You can get some very easy-to-use and clear star maps from either skymaps.com, or by using the excellent (and free) Stellarium Planetarium software.

October's Night Sky

October is traditionally the month when you notice that the Earth is moving through space, as this is the time of year when the nights are rapidly drawing in. As the month begins, the Sun is rising at 7am and setting at 18:30. By the end of the month, the Sun is rising an hour later and setting an hour earlier. Plus, we change the clocks back to normal on the 25th to give us some daylight in the morning, and so the sunset occurs another hour earlier. By the month's end, the Sun will be setting over Sussex at 16:30!

This is all because the Earth is tilted as it orbits the Sun. In summer, our side of the Earth is tilted towards the Sun; in winter, it is tilted away – and there is a difference of 47° between the two.

All this tilting also means that the summer triangle of stars is still visible at this time of year. Look directly upwards as soon as it goes dark and the brightest three stars you can see, covering quite a large patch of sky, are the summer triangle stars.

There are some amazing sights that can be seen in the summer triangle when using even a small telescope, such as the ring and dumbbell nebulae – the glowing remains of exploded stars. The star close to the centre of the triangle is a beautiful double star called Albireo – but you will need a telescope to be able to see this star as a pair, since they are so close together in the night sky.

At this time of the year the Milky-way, the city of stars within which we live, can be clearly seen for the first-half of the night from anywhere away from light pollution. The photograph to the left was taken from the outskirts of Brighton. The lower you look at the milky-way, the closer you are looking at the bright centre of our galaxy.

During October, Jupiter (as also seen in the photograph to the left) is rising in the south-east at sunset, and setting in the west at 2am when Mars is rising. Jupiter is the brightest object in the night sky at the moment (after the Sun and Moon, of course!), and if you go somewhere that is beautifully dark, away from any light pollution, you will be able to see your own shadow cast by the light reflected from Jupiter. As a guide, the Moon will be to the top right of Jupiter on the 26th of October, and to the top left on the 27th.

Take a look through a small telescope or binoculars, and you will be able to see up to four dots in a line around Jupiter. Those four dots are the four biggest and so brightest Moons of Jupiter, so bright that there were easily seen by Galileo 400 years ago with one of the first (and so very primitive) telescopes. Sometimes, one of those moons are hidden behind or in front of Jupiter – so just take a look an hour or two later to see if another moon has reappeared into view.

The darkest nights of the month will be from the 15th to the 25th of the month, when the Moon is close to new (the new Moon, when the Moon is in line with the Sun, occurs on the 18th of October). Full moon occurs on the 4th of October, and the 2nd of November, and so the sky is awash with moon light at the start and end of the month.

We hope you enjoy October’s beautiful night-skies! And if you want to see the night sky as it will be at any time on your own computer, I recommend that you download the excellent and free Stellarium software.

Perseid Meteor Shower

It is the time of year again when the Earth passes through the debris left behind by Comet Swift Tuttle.

For the last 10 days, the number of meteors (shooting stars) have been greater that usual, and I myself saw a bright meteor through partial cloud a few nights ago. But over the next few nights and mornings (the 11th and 12th), the Earth will be going through the heart of the debris stream. The plot below, from British amateur radio astronomer Dave Swan (see the radio meteor observers website for other contributors), shows the number of meteors, tiny bits of rock less than a millimeter in size, currently burning up over the UK.

As you can see from Dave's data, we see more meteors after midnight than before. But why is this?

Our Earth is orbiting around the Sun at 70,000 mph. In the evening, we are looking backwards, at where the Earth has been. But in the morning, we are looking forward in the direction of Earth's travel around the Sun. If you've ever driven through falling snow in a car, you will realise that it is more exciting looking forwards than looking backwards, and so you see more meteors burning up in the Earth's atmosphere looking into space after midnight than before.

It is also best to go somewhere dark, well away from the light pollution of the cities. The darker your location, the more meteors you will see - and you may see a sight that you will always remember!