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.

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.

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.

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.

XMM-Newton: 10 years old today!

The XMM-Newton space telescope is celebrating its 10th anniversary in space!

Although there is a huge amount of British involvement in XMM-Newton, it truly is an international mission. In brief...

• Two out of three X-ray camera's were built (and are maintained) in the UK (the EPIC-MOS camera's pictured above-left);
• The optical/UV telescope was built in the UK;
• One X-ray camera (the EPIC-PN) was built in Germany;
• Two spectrometers (the RGS) were built in the Netherlands and the USA;
• All three X-ray mirror modules were built in Italy;
• Data analysis software and data storage by the UK & USA;
• The spacecraft was assembled in the Netherlands;
• The radiation monitors were built in France;
• Continuous XMM-Newton support is based in Spain, with support from the UK, Germany, France, Italy, Netherlands, and the USA;

XMM-Newton has made some amazing discoveries about the high-energy Universe in that decade. Lots of images from those XMM-Newton discoveries can be found online at the XMM-Newton image gallery, and a slideshow is available on the BBC News online website, narrated by myself (Dr Darren Baskill) and my colleague Dr Kathy Romer here at the University of Sussex's Department of Physics & Astronomy.

The EPIC-MOS cameras were built in the UK by a team led by Martin Turner, who had helped plan and build XMM-Newton over more than 25 years, until his death 6 months ago. The last time I spoke to him, we were discussing how to celebrate XMM-Newton's 10th birthday. All our celebrations of the great success of XMM-Newton are done in the memory of Martin.

5 Years of Swift

Gamma Ray Bursts are know to be the biggest bangs since the big bang! And NASA's Swift space telescope celebrated 5 years of observing these bursts just a few days ago - it was launched on November the 20th, 2004.

And as with most space telescopes, British astronomers play a key role.

Scientists at the University of Leicester designed the X-ray telescope on-board, built the X-ray camera's, and continue to calibrate and monitor its health. Leicester also hosts the UK Swift Science Data Centre. The Mullard Space Science Laboratory, part of the University College London, helped build the Ultra-violet and optical telescope.

UK scientists at both Leicester and MSSL are also on call throughout the day and night for when a burst goes off, to assess whether to follow up the observation with larger ground-based telescopes. Such decisions need to be made within minutes. A full list of UK-based scientists involved in the Swift Space Telescope can be found here on Swift's UK website.

The key thing about Swift is that it is, well, swift! Swift can detect a burst of gamma-rays occurring in about a quarter of the entire sky, and then automatically and rapidly (within 30 seconds!) turn around to scrutinise the rapidly fading explosion with its other on-board telescopes (the X-ray and optical telescopes).

There are two types of gamma-ray bursts - short bursts that last on average about 0.3 seconds, and the long bursts that on-average last about 30 seconds.

Before Swift, scientists knew very little about the short bursts (for obvious reasons... they happened too quickly!), and Swift was the first telescope to discover where these quick explosions were coming from. While scientists are still unsure as to what causes them, the leading idea is that they originate from the mergers of binary neutron stars.

The longer bursts are usually seen to occur with a supernova, which unambiguously links long bursts to the deaths of massive stars... although, strangely, some relatively nearby long bursts appear to have no accompanying supernova. As is often the case in science, when one mystery is solved, another appears!

And because these burst of gamma-rays are the biggest explosions known to man, we can see very distant bursts. The most distant object known, pictured here, is a Gamma-ray burst seen by Swift (see this BBC News story).

X-treme Astronomy: Seeing the Universe through X-ray eyes

by Dr Darren Baskill of the University of Sussex

...is the next Institute of Physics South Central Branch (Brighton Area) lecture, and is to be held at the University of Sussex.

A beautiful clear night full of stars may look poetically peaceful, but it's the biggest illusion known to man. The Universe is violent almost beyond comprehension. Some stars you can see in the night sky are being consumed by their partners; others are violently collapsing in the biggest explosions known to man; and black holes are surrounded by disks of hot gas, the distorted remains of countless stars.
X-rays originate from wherever gas is heated up to millions of degrees in the most energetic phenomena we know of. During this talk you will see the universe as witnessed through the eyes of the latest generation of X-ray telescopes.

X-treme Astronomy - Seeing the Universe through X-ray Eyes
by Dr Darren Baskill of the University of Sussex
7pm, on Tuesday 13th October
Lecture Theatre 1A7
Pevensey 1 Building
University of Sussex


Admission is free and everyone is welcome. Details of how to get to the venue can be found here.

Image: XMM-Newton, Europe's X-ray Space Telescope

End of an observing run

Tonight is my sixth and final night using UKIRT.

During the night, I have been looking through the list of the various surveys we are working on, and each survey has its own priority (some require completion more urgently than others). The time-lapse movie below shows how the telescope has responded throughout the night to my and the telescope operators' instructions.

Not all the areas of sky we want to survey are visible above Hawaii at any one time, and so we are limited by what we can see that night. The Moon can also get in the way (it illuminates the entire sky, so the more sensitive surveys cannot be carried out when the Moon is up), as can high altitude clouds (star surveys can be done through thin cloud, but sensitive galaxy surveys cannot). And finally, it is always better to observe directly upwards, rather than at, say, half way up in the sky. Look up, and you are looking through about 30km of air and moisture; look towards the horizon, and you are looking through nearer 300km. The more air you look through, the more an image twinkles, resulting in blurred images - so to avoid this, we try to always look as directly upwards as possible.

As we go through the night, I am constantly considering all the limitations and all the possibilities of what we want to observe (which can change dramatically during the night, especially where the weather is concerned). As I do that, a telescope operator (Thor and Tim this week) controls the telescope, making sure it is guiding properly, fault fixing if needs be, and repeatedly making focus and other calibration observations throughout the night.

But after six long nights working at 4,200m, and getting at most just seven uncomfortable hours sleep during the day (due to the dryness of living on this volcano), I am more than ready to return home.

UKIDSS - the UKIRT infrared deep sky survey

I am currently at 4,200m, at the summit of Mauna Kea in Hawaii, using UKIRT - the United Kingdom's Infra-Red Telescope. We are using UKIRT to carry out the UKIDSS - the UKIRT Infra-red Deep Sky Survey.

Actually, UKIDSS is not one survey, but five similar surveys which will take 7 years to complete! The five surveys are:

• Large Area Survey (orange in the all-sky map below)
• Galactic Plane Survey (purple)
• Galactic Clusters Survey (green circles)
• Deep Extragalactic Survey (blue squares)
• Ultra Deep Survey (red dot within the blue square)

Both the Large Area Survey and the Ultra Deep Survey are looking for very distant galaxies (cities of stars). By "Ultra Deep", astronomers mean "ultra-sensitive", and so the Ultra Deep Survey will be able to detect very faint and very distant galaxies.

Running five surveys in parallel makes it a very efficient survey - if one of the surveys cannot be done on a particular night, another one can be done instead. For example, it may be slightly hazy as it is as I type this, which would mean that we cannot see the very faint galaxies that the Ultra-Deep Survey is looking for, but we can look at the star-filled galactic plane instead, which is easy to see through haze.

For the galactic plane survey, exposures are only 14 minutes long; for the ultra deep field, exposures are 75 minutes long!

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!