Catching the waves

Traditionally, astronomers have observed the Universe by catching photons of electromagnetic radiation (that's light, radio waves, infrared, UV, X-rays and gamma rays) in telescopes and detectors. These methods have (and continue) to help us work out a tremedous amount about the physics and chemistry of what is out there, but it is always good to have even more ways to look at things.

A promising, and totally new way to observe the Universe would be to measure wrinkles in the very fabric of space-time; gravitational waves. These may sound like something from Back to the Future, but they are a prediction of Einstein's Theory of General Relativity. It is thought that they are created by large moving masses such as two orbiting black holes or in supernovae explosions. For several years physicists have been building instruments in an attempt to detect these ripples. So far they have been unsuccessful because the ripples are so excruciatingly tiny that the detectors have not been sensitive enough; even the strongest ripples are expected to produce an effect in the detector much smaller than the size of an atom. That is pretty tiny. The push for more and more sensitive detectors has been progressing over the last few years and it is thought that we aren't far off the sensitivity required.

There are already detectors operating in the US and Japan, but now a joint German-British team have an 18 month observation run with the GEO600 instrument. This is great news because it means that if any of the instruments makes a detection of a gravitational wave, the others should detect it too. This double and triple checking, by separate teams, will be vital to show that the first ever detection of a gravitational wave is indeed that rather than due to siesmic activity or someone knocking over a wardrobe several miles away.

The only gloomy news at the moment is that with NASA's budget cuts, the space-based gravitational wave detector Lisa may not be going ahead.

Posted in astro blog by Stuart on Wednesday 28th Jun 2006 (11:32 CEST) | Permalink

By Jove!

I'm working in Italy for the summer (no, seriously) and at the weekend I visited Venezia (Venice) the city famous for being built in the middle of a lagoon. While walking through Piazza San Marco (St. Mark's Square) on Saturday night, I spotted Jupiter shining brightly in the southern sky. I managed to get an image of Jupiter appearing next to one of the columns where St Mark's Square meets the Grand Canal. It somehow seemed appropriate to observe Jupiter in the city where Galileo first used a telescope to discover its Moons.

Jupiter seen next to one of the columns at the edge of Piazza San Marco CREDIT: Stuart

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Posted in astro blog by Stuart on Monday 26th Jun 2006 (11:08 CEST) | Permalink

Names for moons

According to ScienceNOW (via the Bad Astronomer), the second and third moons of Pluto are about to be officially assigned names by the International Astronomical Union. So far they have been known as S/2005 P1 and S/2005 P2, but will now go by the names Nix (a mis-spelling of Nyx) and Hydra. The announcement is earlier than I expected as I thought it might occur at the IAU General Assembly in August.

Pluto and candidate moons
An image of Pluto, Charon and the candidate moons created by the Hubble Space Telescope in 2005 CREDIT: NASA/ESA/H. Weaver/A. Stern

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Posted in astro blog by Stuart on Thursday 22nd Jun 2006 (12:39 CEST) | Permalink

Longest/shortest day

Doesn't the year fly-by quickly? It doesn't seem like that long ago that it was January and now we have reached the longest day of the year - the time when the Sun reaches its maximum declination. Of course whilst it is the longest day in the northern hemisphere, it is the shortest day in the southern hemisphere. For those of us in the north this means that the number of daylight hours will start to get less from now on.

APoD has a nice image of the Sun rising over Stonehenge taken this time last year.

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Posted in astro blog by Stuart on Wednesday 21st Jun 2006 (11:28 CEST) | Permalink

Raymond Davis Jr. (1914-2006)

Although astronomy covers the very big, sometimes you have to examine the very small to find out more about our universe. These days this cross-over between disciplines is called astroparticle physics and is a very exciting field. One of the pioneers was Raymond Davis Jr. who started off as a physical chemist and found his way into the study of neutrinos in around 1948. He died on 31st May 2006 at the age of 91.

Neutinos are pretty strange, almost massless, particles that are created in various nuclear reactions. Neutrinos don't really interact with other matter - i.e. the stuff that makes us up - and there are trillions of them passing through our bodies every second. The Sun is our largest, local source of neutrinos producing a few hundred trillion trillion trillion of them per second. As normal matter is pretty transparent to them, they quickly escape and get a head start on the particles of light (photons) which have a very long random walk to the surface of the Sun.

Detecting these solar neutrinos was the focus of one of Ray's early experiments at the Homestake Gold Mine in South Dakota. There, almost a mile underground, he helped construct a 100,000 gallon tank of cleaning fluid with which to attempt to detect the ghostly neutrinos. Over the years, with many improvements in the methods, the experiment was found to detect only one third the number of neutrinos that were expected. This lack of neutrinos became known as the solar neutrino problem and was a pretty huge question in physics. It has only been in the last few years that other experiments such as SuperKamiokande and the Sudbury Neutrino Observatory (SNO) have been able to show that the problem is caused by neutrinos changing into one of the three different types of neutrinos; those early detectors could only detect one of the types (the electron-neutrinos). Nowadays neutrino detectors are becoming astronomical observatories, not only detecting neutrinos from the Sun but those emitted from stars in the last moments before they explode as supernovae. For more on neutrinos listen to the Planetary Society's programme about the SNO.

In 2002, Ray Davis was presented with the Nobel Prize for Physics for "pioneering contributions to astrophysics, in particular for the detection of cosmic neutrinos". As well as studying neutrinos, he had an interest in other things astronomical. He found ages for meteorites from the decay of Chlorine into Argon and he also analysed the composition of lunar rocks brought back by the Apollo astronauts.

My belated condolences and sympathy go to his family.

Posted in astro blog by Stuart on Tuesday 20th Jun 2006 (10:20 CEST) | Permalink

Occultation animation

Rob over at Dirty Skies has a fantastic animation that he made from raw images from the Cassini probe. It shows Saturn's moon Enceladus occulting, by his deduction, Tethys. Not only do we see one of Saturn's moons occult another, but the image seems to show the day side of one and the night side of another, seemingly defying logic.

After a bit of thought, Rob managed to work out that the images actually show Tethys illuminated by Saturn-shine; sunlight reflected from Saturn. The positioning of the three bodies is tricky to understand and I needed to draw a diagram on paper to help me to get my head around it. The reason Enceladus isn't also illuminated (especially considering that it is more reflective than Tethys) is because it was in a part of its orbit that meant it couldn't see as much of the daylight side of Saturn. However, the plumes of material from the cryo-volcanism on Enceladus are nicely back-illuminated by the direct sunlight.

Cassini keeps providing wonderful and mind-bending images.

Posted in astro blog by Stuart on Friday 09th Jun 2006 (19:52 CEST) | Permalink

Diamond dust

The European Southern Observatory's Very Large Telescope (VLT) has released a great image of the central part of a globular cluster of stars named 47 Tucanae (47 Tuc to its friends) which can actually be seen by eye from the Southern hemisphere. It looks about the same diameter of the Moon (around half a degree) on the sky but in reality is about 120 light years across. Globular clusters look fantastic when seen through a small telescope (in any hemisphere) and I was lucky enough to see some when I visited Ian back in March. Globular clusters contains tens of thousands of stars and Ian put it brilliantly (MP3) when he said they looked like "diamond dust" through the telescope.

47 Tucanae
A 7 arc minute wide image of the central part of 47 Tucanae taken in 2001 with FORS1 on Kueyen, UT2 of the Very Large Telescope CREDIT: Kotak/Boffin/FORS/VLT
Each cluster is thought to have formed from an individual cloud of gas which is interesting because it means that all the stars in it formed at roughly the same time. As the stars are similar ages, this lets you directly compare the development of stars of different masses at one point in their lives. I guess this is sort of like looking in a high school year book; you get a single snapshot of the different kids lives with which you might guess that the kids that did well at maths and science may go on to get jobs in finance, engineering or research. The analogy shouldn't be taken too far because the future lives of stars are more predictable than the lives of the kids in the year book!

I have a particular fondness for 47 Tuc because I remember spending hours making measurements on photographic plates to work out the radius of the cluster. The radius for something with no distinct edge, such as a cluster, is something of a fuzzy concept so I was actually working out the tidal radius and the core radius. In this case, the tidal radius is the distance from the centre of the cluster where the gravitational effect of our galaxy dominates the gravity of the cluster. Any star further than this distance from the cluster will be pulled away towards the galaxy. The core radius is the distance at which the brightness of the cluster is half of the brightness at the centre. My measurements basically involved counting stars within millimetre squares at a whole range of distances from the cluster centre. Although this doesn't take much thought to do, it is very frustrating when you keep losing count, especially when you have counted 60 stars in a particular square and have to start again.

Posted in astro blog by Stuart on Friday 09th Jun 2006 (13:23 CEST) | Permalink


A great thing about the sky is that it is brilliant for naviagation. This probably conjours up images of Elizabethan sailors in your mind but I have found myself, on more than one occasion, finding my way around using the Sun, Moon, planets and stars. The other day for instance I arrived in an unfamiliar city at a railway station that I had no directions from to my destination (the train went to the wrong station). The information offices were shut (it was late on a Sunday evening) and I had no map to hand either.

Even though the Sun had already set, I was able to find north, south, east and west well enough to head confidently in the right direction. Having common points of reference on the sky made me feel much more relaxed in a potentially worrying situation. Of course, all this only works when it isn't cloudy!

Posted in astro blog by Stuart on Tuesday 06th Jun 2006 (20:59 CEST) | Permalink

Going down the pan

Students, astronomers and staff of science museums in Japan have come up with a truely novel way to disseminate astronomical discoveries - through the medium of toilet paper. Yes, you read that correctly, they are printing on the soft, squares of paper that sit by your toilet. So, not only will you now have something to read while you are... waiting... but you will learn some astronomy too.

The first edition of the astronomical toilet paper (ATP) is themed around the life-cycle of stars going from molecular clouds, the formation of a star, the growth of a red giant and finally a planetary nebula. The image quality isn't too great but then I guess the maximum dpi for toilet paper is quite limited. The second edition of ATP will feature astronomical objects in the direction of different zodiac constellations.

The down side for the international market is that these are only printed in Japanese, although English versions can be read on the website. The website also features images of the ATP on location!

Astronomical toilet paper
Astronomical toilet paper at Mauna Kea, Hawaii CREDIT: The TENPLA project.

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Posted in astro blog by Stuart on Saturday 03rd Jun 2006 (10:34 UTC) | Permalink

Podding along

The latest edition of the Jodcast (June) is now out. It features an interesting interview with Vatican Astronomer, Brother Guy Consolmagno that Dave managed to organise. Brother Guy explains his views on the status of 2003 UB313 as well as the possibility of finding life out there in the universe. There is also an interview with Dr Don Pollacco of Queens University Belfast about the wide-angle search for planets (WASP). Apparently they got some of their lenses from eBay! Oh and the intro/outro are in the style of The Matrix in case you were wondering.

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Posted in astro blog by Stuart on Friday 02nd Jun 2006 (17:13 UTC) | Permalink

Comet 73P meteors

I've been looking out for meteors from Comet 73P tonight, but the cloud has now got the better of me. It was almost the first clear night I've had in ages. Anyway, you don't always need to look with your eyes to be aware of meteors. Some people have been detecting them via the use of radio. Thanks to Ian for the pointer.

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Posted in astro blog by Stuart on Thursday 01st Jun 2006 (00:29 UTC) | Permalink
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