A Polish dish


IMAGE: The Torun RT4 radio telescope
The Universe can be observed throughout most of the electromagnetic spectrum. The atmosphere, luckily for life on Earth, blocks most of the EM spectrum only allowing us a few small windows to see through. Most people are familiar with one of these windows - the optical window - as that is how you see stars when you go outside at night. Optical telescopes (and your eyes of course) look at colours with wavelengths that are less than a millionth of a metre long. One of the other atmospheric windows exists in the radio part of the spectrum; where the lengths of the waves range from millimetres to around 10 metres. You could almost imagine measuring them with a ruler. This part of the spectrum also gets used for radio broadcasts, WIFI connections and mobile phones. One of the advantages of radio astronomy is that you can observe during the day and even through clouds. A good thing if you live where I do.

Radio astronomers use large antenna - affectionately known by some as 'bits of bent metal' - to collect the radio waves to a focus in the same way as optical astronomers do with lenses or mirrors. If you have a telescope you will know that the bigger the diameter of your light (or radio) bucket, the better your images both in quality and resolution. In this case size really does matter. A medium-sized radio telescope is about 30m (100ft) in diameter but big ones, such as the Lovell or Robert C. Byrd telescopes, tend to be three times bigger than that.

I'm currently at the Torun Centre for Astronomy in Poland where they have a 32-metre Cassegrain radio telescope which observes the sky at wavelengths from about 21cm down to 1cm (1.4 to 30 GHz). It is a nice dish that has improved quite a lot in the past couple of years as they have made the dish surface more accurate. It should improve even more in the next couple of years as it carrys out surveys of things in the radio sky.

I went up into the dish yesterday so I will post some pictures later. It is always a great experience to go up a radio telescope, especially on a nice sunny day, as the white surface looks really stunning against a blue sky. In fact, I could have done with some sunglasses as it was like being on top of a snow covered mountain. The picture shows the dish pointing upwards (it wasn't being used) with the secondary reflecting mirror sticking out at the top.

Posted in astro blog by Stuart on Wednesday 29th Jun 2005 (14:28 UTC) | Permalink

Planets on show

The weather almost thwarted my plans to see the triple planetary conjunction this week. Thursday was clear until the evening when some cloud decided to sit on the western horizon blocking the view. Friday was worse as it rained all day. I woke on Saturday morning to a cloud covered sky. The cloud hung around all day but in the late evening, thankfully, it started to clear. Not having a low western horizon nearby Megan and I rushed to the Physics building to get a better view. We found a vantage point on the top floor looking out across Manchester towards Salford Keys. I managed to take a few pictures with my camera, one of which is below.

Venus and Mercury

You can easily see Venus and, if you click on the image for the larger version, you should be able to see Mercury to the right of it as well. It was the first time that I've ever seen Mercury so it was quite exciting. You may be able to convince yourself that you can also see Saturn if you squint a bit, but it isn't obvious (it helps if you know where to expect it relative to Venus and Mercury). I think the sky was just a bit too bright and the murk a bit too thick to see the fantastic ringed planet. That wasn't the end of the show though, as Jupiter could also be seen below Arcturus in the WSW.

Mercury, Venus, Saturn (maybe), Jupiter and a shooting star (passing below Arcturus) all within the space of an hour. What a great night. If you haven't seen the conjunction yet, don't panic, there is still chance. Although the planets are now starting to move away from one another, they will be fairly close for a few more nights yet.

Posted in astro blog by Stuart on Sunday 26th Jun 2005 (01:21 UTC) | Permalink

NASA budget

So it seems that a Senate panel have approved President Bush's plan for exploring the Moon, Mars and beyond with humans. This plan has caused some concern among scientists as it squeezes budgets on important science programmes within NASA. However, things aren't as bleak as they may have appeared for astronomy and science as the Senate committee are concerned too:

While the Committee applauds those goals, it is concerned that the strong, balanced science program that has served the Nation so successfully for many years could be left behind instead of being nurtured and sustained. That science program has been based on a set of carefully crafted scientific strategies that are founded on scientific and technical merit, relevance to overall national needs, and broad consultation with the scientific community. NASA is encouraged to look for ways to maintain a balance with the productive science NASA is known for and currently has underway, while taking the steps to fulfill the exploration vision.



The committee go on to advise that the US segment of the ISS is turned into a national facility and shuttle capability is retained until a replacement is actually working. They even recommend an increase of USD250,000,000 to provide a servicing mission to Hubble. Fantastic!

These astronomical sums of money - NASA's budget is over USD16,000,000,000 - make the UK's £175,000,000 space budget look quite pathetic really.

Posted in astro blog by Stuart on Saturday 25th Jun 2005 (00:14 UTC) | Permalink

MARSIS is go

MARSIS
IMAGE: Max Planck Society
It has taken a long time and likely caused a lot of people at ESA some headaches, but it looks as though the MARSIS instrument, on board Mars Express, is finally ready for action.

MARSIS consists of three radar booms that will be used to transmit radio waves towards the surface of Mars. These radio waves will be at frequencies in the medium wave (MW) band - 1.9, 2.8, 3.8 and 4.8 MHz - which means that they will be able to penetrate the surface. Some of the radio waves will be reflected back, by features under the surface, to the spacecraft. This will allow us, for the first time, to find out what Mars is like below the surface. However, MARSIS isn't a one-trick wonder; it will also look at the upper ionosphere of Mars and should produce some nice science.

The commissioning phase goes from 23rd June to 4th July during which it will be looking at interesting features such as the northern plains and the Tharsis region. Normal science operation should start from July 4th.

Posted in astro blog by Stuart on Wednesday 22nd Jun 2005 (22:12 UTC) | Permalink

Excitement Live

The Excitement of Science 2005 event is being webcast NOW. You can watch Tim and Ian talk about observations, taken over the last few weeks, with the 7m radio-telescope at Jodrell Bank. All the observations were done by school children using a web-based interface. They have mapped the hydrogen in our galaxy and hopefully the radio data will show the spiral arm structure.

Posted in astro blog by Stuart on Wednesday 22nd Jun 2005 (12:31 UTC) | Permalink

Solstice Moon

Solstice Moon

As I was about to go to bed, I looked out of my window and saw two lights rather than the usual solitary 'security' light. The second, more welcome light, was a pretty, orange-coloured full moon sitting just above the neighbours' houses. As I mentioned earlier, this is the lowest that the full moon will get during the year (at transit). I still don't have a telescope yet so this image was taken with my digital camera.

Posted in astro blog by Stuart on Tuesday 21st Jun 2005 (22:35 UTC) | Permalink

Summer Moon

Today is the 21st June which makes it the longest day of the year. This is known as the summer solstice - which actually occured at 06:36 UT (07:36 BST) this morning - and is the time when the Sun gets as far north as it will get during the course of the year.

Tomorrow sees full moon; the Moon will be on the opposite side of the sky to the Sun and therefore fully illuminated. With the Sun so high during the day, the full moon will be very low during the night. In fact, according to NASA's Exploring the Universe, it is the lowest full moon since June 1987. This gives you a good chance to see the famous 'Moon illusion' that makes the Moon look bigger when near the horizon.

Posted in astro blog by Stuart on Tuesday 21st Jun 2005 (10:33 UTC) | Permalink

Festival of Space

The second British Festival of Space will take place at Thinktank Museum of Science and Discovery, Birmingham, from Thursday 30th June - Sunday 3rd July. Thursday and Friday are aimed at 'space professionals' and school children, but the weekend events are for everyone. There will be rocketry workshops, comet making demonstrations and even live observing sessions using the Faulkes Telescope North which is based on Hawaii. It sounds like it should be fun.

Posted in astro blog by Stuart on Tuesday 21st Jun 2005 (09:30 UTC) | Permalink

When shall we three meet again?

Next Saturday would suit me fine, but I'd rather it wasn't in thunder, lightning or rain.

Mercury, Venus and Saturn in late June
IMAGE: Stellarium

As you can see from the image above, the three of the title are not the famous witches from Macbeth, but the planets Mercury, Venus and Saturn. The period from 23rd to 29th June will see the three planets appearing to get up close and personal as they get within 2.5 degrees of each other. Of course, in reality, they are all vastly different distances away from us, but their orbits happen to put them all in much the same direction at the end of the month.

The only trouble is that they will all appear fairly close to the Sun, making observing an evening event (just after sunset) and you will need a nice flat horizon to catch them before they disappear out of view. I reckon the best time will be shortly after 10pm (BST) but it is best to be outside with plenty of time to make sure you're looking in the right direction. Looking towards the west-north-west you should see a very bright Venus at magnitude -3.9. Then spot Mercury and Saturn nearby.

Posted in astro blog by Stuart on Saturday 18th Jun 2005 (00:05 UTC) | Permalink

Vela Remnant

Here is a rather nice image of the north-eastern edge of the Vela supernova remnant probably near knot A. The Vela supernova exploded about 815 light years away (or 1500, or 2000 light years), about 11,000 years ago and is one of the closest supernova remnants to the Solar System. This image is created by combining radio observations made using ATCA and Parkes at a radio wavelength of 21cm (1420 MHz). Usually I would say that light colours corresponded to brighter parts of the image but I reckon the colour scale is reversed here, so dark means bright and light means dim. In case you were wondering, the centre of the supernova is below the bottom left of the image.

ATCA Parkes 21cm continuum image of the edge of the Vela SNR
IMAGE: N. McClure-Griffiths, J. Dickey, B. Gaensler and A. Green.

Posted in astro blog by Stuart on Friday 17th Jun 2005 (17:28 UTC) | Permalink

Buzz Live

For those that are interested, there will be an interview, with astronaut Buzz Aldrin, on the BBC Five Live's weekend breakfast show (you can listen online) on Saturday at 08.45 GMT. You can even send in questions for him, from their website.

I hope that no ill-informed people, with little knowledge of the facts, will try to claim that the Apollo 11 landing was faked. That has happened before, and understandably he got rather annoyed at them. Remembering that incident reminds me of a late night radio show I once heard that was going to feature an interview with the astronomer Patrick Moore. Just before the interview, one of the presenters read out some astrological horoscopes. Sir Patrick stormed out of the studio leaving some very sheepish DJs with five or ten minutes of airtime to fill.

Posted in astro blog by Stuart on Thursday 16th Jun 2005 (21:04 UTC) | Permalink

The UK in space?

The Royal Astronomical Society (RAS) has set up a commission to investigate whether the UK should break with tradition by funding human spaceflight and they are asking readers of BBC News Online what they think. This does not mean that the UK will have its own space programme again; mission control won't be in Grimsby and there won't be a launch pad on the Isle of Wight. The debate is actually about the possibility of the UK contributing to ESA's Aurora programme which aims to send people to Mars.

As usual, the comments sent into the BBC cover all the normal ranting positions about how much money should or should not be spent. The BBC website states that the UK 'space budget' is currently £175 million per year (that is about 320 million USD) which has annoyed the people that don't like money to be spent on anything other than health or education. I reckon that this £175 million covers both astronomy and space science, as the annual budget of the Particle Physics and Astronomy Research Council (PPARC) is £300 million and a large amount goes to CERN. Most of this actually gets spent on people (I for one am a beneficiary of a very small portion which I got as a student grant) and UK built hardware; it doesn't get put in a box and sent to the Moon as some people seem to think. It all goes back into our economy and generates knowledge.

Personally, I would prefer to see money spent on robotic missions which can go to more extreme places and do better science for a fraction of the cost of manned flight. Also, a few huge telescopes (at all wavelengths) would be great, but then I am biased. There is an argument for the inspiration that comes from human exploration, but I think the cost is just too huge. One thing I do know is that manned space-flight will not solve over-population problems, as we will not be able to ferry significant - we're talking millions - of people off the planet any time soon.

Posted in astro blog by Stuart on Thursday 16th Jun 2005 (20:49 UTC) | Permalink

The Pole Dance

The pole I am referring to is the North magnetic pole. Unlike the rotational North pole, the magnetic poles don't stay in one place. The magnetic poles are generated in a complex way, by the rotating molten iron core of the Earth, and have a tendency to move around a bit.

The magnetic North pole has been in Canada for some years but it seems that it has now finally moved out into international waters, heading in the direction of Siberia. Far from being upset about the departure of the magnetic pole from Canada, Larry Newitt, head of the Natural Resources Canada geomagnetic laboratory in Ottawa takes solace in the fact that "we're still the closest country to it." This sentiment was echoed by Carolyn Relf, a geologist with Indian and Northern Affairs. "As long as Santa's still in the North, I don't care about the pole," she said.

Still, the pole dance is difficult to predict so one day it will probably be back on Canadian soil.

Posted in astro blog by Stuart on Tuesday 14th Jun 2005 (11:27 UTC) | Permalink

Aurora Alert: 12 June

The UK Sub-Auroral Magnetometer Network, operated by Lancaster University, has issued an amber alert for a possible sudden storm commencement. The auroral oval (data the NOAA POES satellite) may just reach far enough south to give the northern parts of the UK (Scotland, Northern Ireland and the north of England) some good shows. Now if only the rain would stop.

Posted in astro blog by Stuart on Sunday 12th Jun 2005 (19:06 UTC) | Permalink

Pulsar symphony

At the end of its life, if a star is massive enough - say 15 times the mass of the Sun - it will go supernova. This violent explosion throws much of the star outwards into interstellar space leaving beautiful expanding remnants. However, the inner parts of the star collapse inwards, becoming so dense that the electrons and protons are squeezed together to form neutrons and ghostly particles called neutrinos. The neutrinos don't interact much so head out merrily into space leaving the neutrons behind. As most of the matter making up the star now consists of neutrons, it gets called a neutron star.

The original star would likely have been spinning like big balls of stuff tend to do while sat in space. When the supernova explosion occurred, and the core collapsed inwards, it spun up in the same way that an ice-skater spins up as they bring their arms inwards. In fact, they can spin up so fast that they can rotate several hundred times per second. They also have strong magnetic fields and charged particles on the surface get funnelled out along the magnetic poles, emitting radio waves as they accelerate. This results in two beams of radio waves, one from each magnetic pole, giving the radio equivalent of a cosmic lighthouse. These pulsating neutron stars, or pulsars, were first discovered by Jocelyn Bell in 1967. After nearly forty years of research, over 1500 pulsars have been found.

Now you can't look through a radio telescope, so usually they are connected to a chart recorder or a computer to record the brightness of the signal. An alternative is to connect the output to a speaker and listen. Astronomers at Jodrell Bank did exactly that, with measurements of pulsars, so that you could 'hear them'. There is a nice page of pulsar sounds that includes the Crab pulsar rotating 30 times per second and the fastest known pulsar - PSR B1937 21 - rotating 642 times per second. Actually, its period is very accurately known - it is 0.00155780644887275 seconds! Dr Michael Kramer also put together the sounds of pulsars in the globular star cluster, 47 Tucane which makes for interesting listening. You can also see a movie which flys-through the cluster, although I should warn you that it is 40 MB so you will probably need a fast connection.

Posted in astro blog by Stuart on Sunday 12th Jun 2005 (12:24 UTC) | Permalink

Caught on camera

Years ago, astronomers would use their eyes to look through telescopes. Then came the development of photographic film and suddenly a much more reliable way to measure light from stars and galaxies was available. With the development of electronics, charged coupled devices (CCDs) emerged as an even better way to measure light; they recorded a greater percentage of the photons than film did.

These technological developments, together with larger telescopes (light buckets), have massively improved the amount of light that is recorded. This has lead to fantastically better images. The only trouble, as you will know if you are lucky enough to have your own astronomical CCD, is that it takes time to get an image of a faint object and there is dead time between exposures while the CCD gets read by the computer. This isn't a huge problem but it means that you miss out on events that happen very quickly. That includes eclipses, transits and occultations, not to mention anything that flickers, flares, pulsates, oscillates, outbursts or explodes.

To catch these quick changes in brightness, astronomers from the University of Sheffield, the University of Warwick and the UK Astronomy Technology Centre developed a special CCD camera called ULTRACAM that could be attached to big telescopes. This instrument is actually made up of three separate 1024 by 1024 pixels CCD cameras which are much more sensitive than those you would find in a digital camera. The light from the telescope gets split into three colours - blue (u), green (g) and red (r, i or z) - and each one goes to a different detector. Depending on how they use the instrument, they can get exposure times as short as a millisecond with essentially zero dead-time between exposures. This results in a continuous stream of over 3 MB of data per second. That is as much as 130 GB of data each night!

Since May 2002, ULTRACAM has been used on the 4.2-m William Herschel Telescope (WHT), on La Palma, as well as other telescopes around the world. Two years ago they began preparing it for use on the ESO's Very Large Telescope (VLT) in Chile. First light on the VLT was on 4th May this year and they had 17 consecutive nights of observing.

ULTRACAM on VLT
IMAGE: European Southern Observatory.

During that time, they observed a black hole binary system named GU Muscae. This consists of a black hole and star orbiting each other every 10 hours. What the ULTRACAM team noticed though, was that there was a sudden brightening roughly every 7 minutes. This stable repeating signal is thought to be associated with some stable structure in the disk of matter that surrounds the black hole but nobody is really too sure.

The ULTRACAM team have also observed extrasolar planets, originally discovered by the OGLE project, but now using short exposure times at the three different colours. When these planets pass in front of their parent star, they cause the star to dim as they block out some of its light. This gives a direct indication of the size of the planet as bigger planets block out more light than smaller ones in the same way that someone with a huge hat can block your view of the stage at a concert. Comparing the size of the planet, in the different colours bands, should hopefully say something about the composition of the exoplanets' atmosphere.

Tom Marsh of the University of Warwick hopes that "...ULTRACAM will now become a regular visitor at the VLT, giving European astronomers access to a unique new tool with which to study the Universe".

Posted in astro blog by Stuart on Saturday 11th Jun 2005 (13:51 UTC) | Permalink

Star Shapes

What shape is a star? Although small children think stars have several sharp points, we normally assume that they are spherical; a bit like the Sun. This is mainly because stars are so far away that we can't actually see the shape of them with a telescope. Well, we couldn't, until the development of optical interferometers such as the Very Large Telescope (VLT). In 2003, a group of ESO astronomers were able to get a detailed view of the star Achernar (Alpha Eridani) and got a shock. It turned out that this star was certainly not spherical but more like a spinning top; its radius at the equator was 50% bigger than at the pole. How squashed the star looks is given a number called the oblateness, with a spherical star having a value near 1. Achernar has an oblateness of around 1.6.

It is important to find stars with rather large waist sizes as they help test theories about their structure. However, even with optical interferometers, star shapes can only be measured for relatively nearby stars. For instance, Achernar is only 127 light years away. Now, astronomers in the MOA collaboration (named after the extinct NZ bird) have used a completely new technique to find a star's shape - gravitational microlensing.

Einstein's theory of general relativity tells us that light gets bent slightly (its direction changed) when it passes a large mass. The mass has to be pretty big, say the size of a star and this was first confirmed by Arthur Eddington during the total solar eclipse of 1919. Now, although we don't notice it due to the huge distances involved, all the stars are moving about. Occasionally, a particular star will happen to pass directly in front of another star that is further away. The nearer star will then act as a lens to magnify the light from the more distant star and this is known as gravitational microlensing. The reason it is called microlensing is that this effect was first seen, in 1979, on the scale of clusters of galaxies. These galaxy scale effects became known as gravitational lenses so star-sized versions had to have a different name to avoid confusion.

By looking at the exact way in which the star appears to brighten and dim, during the microlensing event, it is possible to work out what shape the more distant star is. For the particular event observed by the MOA team (MOA-33) they worked out the shape of the background star to be very close to circular (oblateness of 1.02). Although that seems like a very boring answer, it is amazing when you realise that this star is over 16,000 light years away.

Posted in astro blog by Stuart on Wednesday 08th Jun 2005 (14:06 UTC) | Permalink

The Shocking Sun

This month's Sky At Night was broadcast last Sunday night. The programme was all about the Sun and the observations that amateurs and professionals make of it. There are some clips of the solar observations made at Patrick Moore's recent star party as well as a chat, with the Astronomer Royal for Scotland, about SOHO and TRACE observations.

As usual, the BBC messed about with the time, so my recording missed the last five minutes of it. Luckily, it gets repeated on Saturday, on BBC 2, so I might catch the end then. For those who do not live in range of a BBC transmitter, you will probably be able to watch it later in the month from the Sky At Night website where they also have previous programmes that you can watch online.

Posted in astro blog by Stuart on Tuesday 07th Jun 2005 (20:31 UTC) | Permalink

Martian Cepheids

Last March, the Spirit rover took an interesting picture showing a streak of light across the Martian sky.

Martian Meteor
IMAGE: NASA/JPL/Cornell/Texas A&M

At the time it was theorised that it could be a meteor or an out of commission spacecraft orbiting the red planet. Now, some French researchers not only think that it was a meteor, but think they know which comet it came from. The comet is named Wiseman-Skiff and was originally discovered in 1987 by Dr Jennifer Wiseman and Brian Skiff.

Assuming that it did originate from comet Wiseman-Skiff, the meteor shower would appear to come from the direction of the constellation of Cepheus if you were stood on the surface of Mars. That makes the meteor a Cepheid and the first meteor seen from the surface of another planet.

Posted in astro blog by Stuart on Thursday 02nd Jun 2005 (16:47 UTC) | Permalink

Supersized

The AAS meeting is throwing up some interesting astronomy stories this week. ABC.net.au have an article about the Andromeda galaxy (M31) which is the furthest things you can see with the un-aided eye. It is about 2.9 million light years away from our galaxy, the Milky Way.

According to the article, recent observations using the W.M. Keck telescope, show that the galaxy is actually about 220,000 light years in diameter, making it up to three times larger than previously thought. I would say it was less than two times big as I was under the impression that the Andromeda galaxy was a bit larger than the Milky Way which is 100,000 light years in diameter.

Posted in astro blog by Stuart on Wednesday 01st Jun 2005 (10:29 UTC) | Permalink
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