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November 2006

ASTRONOTES
Incorporating FRIENDS' NEWSLETTER Award-winning Armagh Story Moonbows in the sky Happy Birthday IAA! NISO launch Leonid Meteors

ARMAGHPLANETARIUM


2 Astronotes November 2006

Salt Lake City Success
A report on the Digistar Users' Group meeting in Salt Lake City, by Dr TR Mason, Director The Digistar Users Group (DUG) is an independent group of planetarium professionals who own and use one of the Digistar family of machines. This year, their annual conference was held at Evans & Sutherland's headquarters in Salt Lake City, Utah from September 27th ­ 29th. I attended the meeting accompanied by Julie Thompson, our Digital Theatre Manager, on behalf of Armagh Planetarium. Including the E&S staff, there were over eighty people attending the conference, the largest attendance its history. Bringing together many of the users of Digistar equipment from all over the world, the annual DUG event is an opportunity for Digistar users to share ideas and production techniques; meet new users; present their latest full-dome shows; and to provide feedback and suggestions to E&S about the Digistar systems and software. As the meeting was held at E&S, delegates were able to experience the latest in projection technology and show content from Evans & Sutherland. Kevin Scott of E&S deserves praise for organising the whole event and ensuring that it ran smoothly. As well as the DUG conference, E&S organised three days of technical meetings. Julie attended a workshop dealing with advanced programming techniques, while I learned how to set up, service, and repair Cathode Ray Tube (CRT) projectors. This proved to be a worthwhile addition to our skills, and will reduce our dependence on outside agencies for our adjustment and service needs. The greatest benefit of such meetings is the networking and contacts that are made during the meals and socialising. Over meal breaks we had the opportunity to talk with old friends and

"Mystery of the Christmas Star is ready to run in Armagh"
make some new ones from the facilities across the USA, as well as meeting with colleagues from Japan, Holland, Germany, India, Denmark and Canada. The first night of the DUG conference began with a reception at the Clark Planetarium, sponsored by Aaron McEuen's Starlight Productions, followed by a series of trailers for shows that Clark have produced for Digistar 3. They presented their latest full-dome show, `Black Holes'. E&S presented trailers for several of their new shows and Mirage 3D in Amsterdam premiered their latest show, `Origins of Life', a story of the beginning and development of life on Earth. Finally, E&S presented the world premiere of `Mystery of the Christmas Star'. This full-dome show is already installed on Armagh's D3 system, and is ready to run from December 1st.

Image Credit: Julie Thompson, Digital Theatre Manager

Outside E&S The DUG meeting is attended by the leading lights in the planetarium field.

The first full day began with the DUG Business Meeting where users discussed topics of interest to the membership. After lunch, sponsored by


November 2006 Astronotes 3 Bowen Technovation (the company responsible for the exquisite lighting system at Armagh), E&S was the venue for a choice of heavy-weight afternoon seminars. Before dinner on the first night, DUG members presented samples of their latest work for both Digistar II and Digistar 3 for this year's DUG. Digistar II submissions included entries from Longway Planetarium, Abrams Planetarium, the Boonshoft Museum of Discovery and the Universal Theatre and Planetarium. Digistar 3 content included submissions from Nehru Planetarium, the Sciencei Center of Iowa, Cranbrook Institute of Science, Northern Kentucky University, Boonshoft Museum of Discovery, Santa Barbara Community College, Don Harrington Discovery Center, Infovision and our very own Julie Thompson. Julie's submission was `The Armagh Story' which has been appreciated by audiences since we reopened in July. The evening ended with a screening of Secrets of the Sun, E&S' latest fulldome astronomy show. Friday's DUG events included the conclusion of the business agenda and another set of seminars at E&S. After dinner the presentation of the DUG Awards took place and I am delighted to tell you that Armagh Planetarium's Julie Thompson took first place in the Digistar 3 category. This is the second time that Julie has taken first prize in this contest for work produced at Armagh Planetarium, receiving this prize for her only previous entry in 2004. Well done for a very talented member of the Armagh team, helping us return to the forefront of planetarium innovation and show production. Julie's `Armagh Story' will continue to be shown as part of the Planetarium's regular programme of public astronomy shows.

Bluffer's Guide to Meteors
Image Credit: P. Jenniskens (NASA/Ames, SETI Inst.) et al., APL, UVISI, MSX, BMDO

Recently I have been giving you just enough details about various celestial objects to let you show them off to your friends and family. By now they must be convinced that you are an expert astronomer, perhaps you'll soon have your very own monthly TV show. Inevitably someone will come and tell you something like "Last night, all of a sudden I saw this light streak across the sky...what was it?" What have they seen? Well, it wasn't a comet. Comets are lumps of stuff, mainly ice and rock, orbiting the Sun and are usually millions of kilometres from Earth. As the Sun's rays melt the surface ice, material can stream off a comet leaving a tail of gas and dust behind it. This tail can be millions of kilometres long and is clearly visible from Earth. Photographs of comets in the night sky can look as though they're depicting some white-hot fireball whizzing through the sky.

Meteor shower from above During the peak of the 1997 Leonid Meteor Shower, a satellite called MSX imaged 29 meteors over a 48 minute period entering the Earth's atmosphere


4 Astronotes November 2006 However that impression is not accurate; space is big, comets are far away, so they move across the sky in months rather than seconds. Rather than a comet, what the witness saw was most likely a meteor. Meteors are the bright trails left by fragments of natural space debris called meteoroids (usually chunks of rock and iron) falling through the Earth's atmosphere. A typical meteoroid hits our atmosphere at about 72 000 km/h (compare this to the 29 500 km/h speed of a Space Shuttle Orbiter returning to Earth). Traveling through the air at this speed warms it up until it's white hot, leaving a trail of equally hot vapour behind (the posh name for this vapour is `plasma'), so it appears as a bright streak in the sky. Most sources say that this warming is due to friction between the meteoroid and the Earth's atmosphere,

"Most meteoroids are smaller than a grain of rice"
and that is partially true. As the meteoroid zips through the atmosphere, air `piles up' in front of it, and very simple physics shows that when air is compressed into a small volume it heats up. This `ram-heating' is actually a larger contributor than friction and it's the main reason for objects such as satellites `burning up on reentry'. Most meteoroids are tiny, smaller than a grain of rice, and are quite common; if you watch the sky on a dark night you'll probably see several in an hour. Usually their arrival is completely random and unpredictable but some arrive in regular showers at particular times of the year. There is one coming up soon. Perhaps you could show it off? This is the Leonid meteor shower (call it the Leonids and you'll sound like a proper astronomer) and it peaks about 17-19 November. For more details see the article on page 10 in this issue. Where do meteors come from? They are essentially debris left over from the formation of the planets. Some are the little bits of stuff which didn't end up as part of a planet and have

Million Dollar Meteorite This 635 kg metorite is on display in Exploration Place, Kansas. Belonging to a rare class of meteorite called pallasites, it was discovered locally by Steve Arnold. US TV news shows claim it is worth $1 million. wandered around the Solar System for billions of years until one lucky day their path crosses Earth's and zip! ­that's the end of them. Others, including all those in the showers were once part of comets but escaped as the comets' icy surface was baked away by the Sun's rays. Most meteoroids completely burn up about 100 km above the ground but very occasionally the core of a larger one will reach the Earth's surface. These are called meteorites. There are three basic types of meteorite: stony meteorites are rocks, iron meteorites are largely composed of iron and stony-iron meteorites which unsurprisingly contain both iron and rocky material. Are they valuable? Well, there is actually a flourishing trade in meteorites for collectors and some change hands for large sums. However their greatest worth is in what they can tell us about our Solar System. So if you are ever lucky enough to find a fallen meteorite, please donate it to your local museum, university or planetarium. That's what a proper astronomer would do, rather than put it on e-Bay!

Image Credit: Colin Johnston, Science Communicator


November 2006 Astronotes 5

Candles in the Dark
Image Credit: Wikipedia.org

By Colin Johnston, Science Communicator In the last issue of Astronotes I explained how astronomers have used the principle of parallax to measure the distance to other stars. However this technique gets harder to use for more distant stars and is in fact iuseless for measuring distances of more than about 1600 light years. How then can we tell, for example, that M31, the galaxy in Andromeda, is 2.2 million light years away? It would be straight-forward to tell how far away a star was if it was exactly the same brightness as our own Sun. We know how bright the Sun is and we know how the apparent brightness of a celestial body decreases with distance. It gets

Henrietta Swan Leavitt (1868-1921) She has a lunar crater and asteroid 5383 Leavitt named in her honour. Her death prevented her nomination for a Nobel Prize. ades. Not all stars are as constant as this, and astronomers know of thousands of variable stars which get brighter then dimmer, then brighter again. Some vary irregularly but many follow regular patterns, flickering in seconds or pulsing over years to a steady beat. Why this happens can be explained by the physics going on inside the star, but the details aren't important here. There is a type of giant yellow variable star called a Cepheid. Delta Cephi was the first to be identified, but the are many others, in fact familiar Polaris is a cepheid. In 1912 an American astronomer called Henrietta Leavitt realized something very special about cepheids. We had accurate distances to some cepheids, so we knew exactly how bright they were. We also knew how long it took the same cepheids to go though a cycle of getting dimmer then bright again. Leavitt's great discovery was to recognise that the brighter the cepheid, the longer it took to vary. Polaris, which varies in about four days, is about 2200 times as bright as the Sun, while a thirty-day cepheid is about 10 000 times as bright as the Sun. The variation is by a strict mathematical relationship, so how long it takes a cepheid of given brightness to fluctuate is completely predictable. It

"M31 and other nebulae were galaxies of many billions of stars"
dimmer according the Inverse Square Law, so we could use how much dimmer a star appears than the Sun to calculate how far away it is. In fact, the great William Herschel tried to use this idea to give a relative scale to the galaxy a couple of decades before parallax was successfully used in 1838 by Bessel. Rather than using the Sun as his standard star, Herschel used Sirius, but the idea was the same. Of course Herschel himself knew that it was unlikely that every star was exactly as bright as Sirius but it was the best anyone could do at the time. Now bear with me as I'm going to appear to change the subject but this is still part of the same story. Our Sun emits a steady stream of light and other radiation. In fact, and lucky for us, this stream is very steady; it has varied by only about 0.1% over the past couple of dec-


6 Astronotes November 2006 works the other way around too. If you found a cepheid anywhere in the Universe, you could watch how long it took its brightness to go up and down, and this would tell you how bright it was. Comparing this with how bright it looks would give you how far away it was. Suddenly we had a new way of measuring the size of the Universe! An early and important usage of this was when Edwin Hubble recognised a cepheid in what was then called the Andromeda Nebula (M31). Back in the 1920s, most astronomers believed that the Milky Way was the whole Universe, so M31 was presumably a relatively small and nearby object. Hubble calculated from the variation of his Andromeda Cepheid how far away it was and came up with the answer of more than 900 000 light years (better modern measurements give the accepted figure of 2.2 million light years). There was no possibility that M31 was inside the Milky Way. Not only that, but it also meant that M31 and other `spiral nebulae' were themselves galaxies of many billions of stars. In rather the same way as Bessel's discovery that 61 Cygni was 10 light years away had shocked astronomers a century before, astronomers abruptly had to accept that the scale of space was much, much bigger than they had previously thought. Cepheids are still used today as `standard candles' by astronomers. As they tend to be very bright, cepheid stars can be seen when they are very distant. The Hubble Space Telescope has been used to identify some cepheids in the Virgo cluster of galaxies showing them to be about 50-60 million light years away. However, some galaxies are much further away than this. We will examine how we measure the scale of the greater universe in the next Astronotes.

Moon Phases, Nov 2006
Sun 5 Nov Sun 12 Nov Mon 20 Nov Tues 28 Nov FULL MOON Last Quarter NEW MOON First Quarter

Space on show in Kansas
by Colin Johnston, Science Communicator The Smithsonian's National Air and Space Museum in Washington DC possesses the largest collection of historic American space artefacts. But where can you find the world's second largest collection of lovingly-preserved NASA craft, spacesuits and so on? The obvious answers would be at the Kennedy Space Centre in Florida, or perhaps the Johnson Space Centre in Houston. However this treasure-trove of astronautical history is actually on display on a leafy residential street in the small town of Hutchinson in the state of Kansas. The collection is housed in an excellent site called the Kansas Cosmosphere and recently I was lucky enough to pay it a visit. The centre was originally founded on the State Fair Grounds as the Hutchinson Planetarium
Image Credit: Colin Johnston, Science Communicator

Man of Bronze A life-sized sculpture of an Apollo astronaut greets visitors to the Kansas Cosmosphere


November 2006 Astronotes 7 in 1962. Proving very popular, the planetarium moved to its current location in 1966 and added a museum section which has expanded in size every decade since. Currently it is housed in a magnificent building guarded by full-scale replicas of Mercury-Redstone and Gemini Titan rockets. Inside the foyer there is a retired but still futuristic SR-71 aircraft hanging from the ceiling and a full-scale mockup of a Shuttle Orbiter. On its lower level the museum houses a staggering array of objects from both the US and Russian space programmes. The Cosmosphere has a skilled staff who have restored many of these items to their original condition after, in some cases, years of neglect. There are far too many exhibits to list, but among the most noteworthy are the US and Russian spacesuits, Nazi V-1 and V-2 missiles, `Odyssey', the Apollo 13 Command visit I attended a show on the Hubble Space Telescope and a live presentation on the night sky, both were interesting and informative. The presenter enriched the shows by injecting a lot of his own personality into the narration. Beside the planetarium, there is a facility called `Dr Goddard's Lab' where the presenter gives a family-friendly talk on the principles of rocketry and performs some very spectacular demonstrations. I haven't seen anything as elaborate enacted `live' before, and it is well worth seeing. There is also an IMAX theatre where I saw a spectacular show called `Roving Mars' which showcases NASA's Spirit and Opportunity rovers. The Cosmosphere offers a great experience to visitors interested in space and astronomy. I would set aside a full day for your visit to see it at its best. Full details are available from www. cosmo.org. If you are staying in Kansas, you should also take a trip to Exploration Place in Wichita. This is a fine modern science museum which houses the Cyberdome, a combined IMAX theatre and planetarium. The Cyberdome's foyer features screens running ViewSpace- just like we do in our Kepler Room in Armagh and a display of very large and impressive pallasite meteorites which had fallen locally. In the theatre, a Digistar 3 projection system just like ours is used to present the shows. When I visited I saw two excellent bought-in presentations; `Black Holes' and `Cosmic Collisions', the latter being augmented with additional content made in-house. The Cyberdome is another great facility and I'd highly recommend a visit if you're in the area. Full details are available from www.exploration.org .

"the museum houses objects from the US and Russian space programmes"
Module, a full-scale Lunar module replica and Gus Grissom's capsule `Liberty Bell 7' which was salvaged after lying on the sea bed of the Atlantic for three decades and restored. This is a fascinating collection and you can spend many hours looking over it and marvelling at the human ingenuity on display. The planetarium is on the upper level and presents a programme of both pre-recorded and live shows. The dome houses a traditional `dumbell' projector with slide projectors and a Barco video system for special effects. On my

Moonbows in the sky
by Wendy McCorry, Science Communicator Few meteorological sights are more pleasing to the eye than a rainbow, usually seen during or just after rainfall, when emerging sunlight hits the droplets of moisture still present in the air. When it hits the roughly spherical raindrop, sunlight is refracted and dispersed into its constituent colours: red, orange, yellow, green, blue, indigo and violet. But did you know that rainbows also appear at night time? The same process occurs due to rainfall at night, but this time the light which is being refracted comes from the Moon instead of the Sun. The resulting phenomenon is not called a rainbow,


8 Astronotes November 2006 but a moonbow! Moonbows are much rarer than their daytime counterparts, because the light from the Moon is much less intense than that from the Sun. For a moonbow to occur, several factors must be in place at the same time: 1. The Moon must be bright; 2. It must be raining in the area opposite the Moon; 3. The sky must be very dark; 4. The Moon must be less than 42 degrees high. Moonbows are quite often perceived as being white, a fact which has historically given them the name `white rainbow'. This is simply because at low light intensities, the cone colour receptors in our eyes are not activated, so we are unable to distinguish between the different colours of the spectrum. Sometimes, moonbows appear to encircle the Moon itself. This is due to moonlight reflecting off ice crystals high in the atmosphere. Folklore tells us that a halo around the Moon means that bad weather is coming. There is actually some truth in this, as the ice crystals indicate the presence of high-altitude cirrus

A colourful moonbow over Venus in the night sky It's not surprising that this beautiful scene won a prize in an on-line competition for weather photographs in 2004. clouds, which typically precede a warm front by one or two days. A warm front is often associated with a low pressure system ­ commonly referred to as a storm.

Anousheh's Orbital Holiday
by Sharon Carroll, Science Communicator On Monday September 18th 2006 a little girl's dream became reality when Anousheh Ansari boarded a Russian Soyuz spacecraft. IranianAmerican Anousheh Ansari blasted off from the Baikonur Cosmodrome in Kazakhstan accompanied by a fresh crew for the International Space Station (her crewmates were Russian cosmonaut Mikhail Tyurin and US astronaut Michael LopezAlegria). Next to Dennis Tito, Mark Shuttleworth and Greg Olsen, Anousheh Ansari has earned a place in history by becoming the fourth (and first female) space tourist. The first woman explorer was not able to disclose the amount she paid to reach for the stars, but previous space tourists have paid in excess of US$20 million. Lift-off took place at 1010 local time (0410 GMT), with the Soyuz TMA-9 successfully entering orbit soon after. After a difficult and cramped journey for the crew, the space craft docked with the International Space Station (ISS) on Wednesday 20 September 2006. During her eight-day stay onboard the ISS,

Image Credit: Weatherwise.org


November 2006 Astronotes 9 young people all over the world that there is no limit to what they can accomplish." A living example of the American dream, Anousheh emmigrated to the United States as a teenager unable to speak English. At 35, Anousheh Ansari was one of only two women to be featured in a list of America's 40 most successful business figures under the age of 40. She was described as "the boldest newcomer". In 1993, Anousheh Ansari set up a telecommunications company with her husband Hamid which eventually sold for hundreds of millions of dollars. Part of this fortune went into funding Anousheh Ansari's interest in space. Anousheh and her brother Amir have donated much of the prize money for the X-Prize to promote development of space tourism vehicles, won by Burt Rutan's SpaceShipOne in 2004. Unlike her Soyuz crew members, who are starting a six-month stint in the ISS, Anousheh Ansari returned to Earth after a journey of a lifetime on 29th September 2006. She returned with the outgoing U.S- Russian crew (astronaut Jeff Williams and cosmonaut Pavel Vinogradov). Back down to Earth, Anousheh was greeted with a bunch of red roses from an unidentified official and a surprise kiss from her husband, Hamid.

High Flyer Preparations for Anousheh's flight were slightly marred by an unseemly row over whether her spacesuit could display both the US and Iranian flags to reflect her heritage. In the end she wore only the Stars and Stripes. Anousheh Ansari performed a series of experiments on behalf of the European Space Agency and reported back on her experiences to Earth. Anousheh's main objective for this mission was to become a Space Ambassador and help to bring the space travel experience to others. Interviewed shortly after arrival, Anousheh Ansari said, "By reaching this dream I've had since childhood, I hope to tangibly demonstrate to

Happy Birthday IAA!
On 13 October we were delighted to host a very special event for our friends in the Irish Astronomical Association. The IAA is celebrating its 60th Anniversary this year and Armagh Planetarium opened its doors for a special evening opening as part of the festivities. After an introduction by Director Tom Mason, Digital Theatre Manager Julie Thompson gave our guests an exclusive `behind the scenes' look at the process of creating a Digistar 3 show and a sneak preview of upcoming shows. A celebratory dinner with a special presentation to Mr David Beesley, the IAA's longest-serving member, completed a very enjoyable evening.

Image Credit: NASA

IAA Logo For more details about the Association see www.meteorlogni.com/iaa/


10 Astronotes November 2006 Originally the Belfast branch of the Irish Astronomical Society, the IAA has provided a forum for local amateur astronomers since 1946. There are currently about 200 members, ranging from beginners to experienced observers from all over Ireland and beyond. The IAA publishes a glossy colour magazine, Stardust, for its members, and presents an annual lecture programme from September until May in the Teacher Training College, Stranmillis Road, Belfast as well as special observing events. All of us here at Armagh wish the IAA many happy returns!

Here come the Leonids
The Leonids are one of the many annual meteor showers. The name comes from how they appear to emerge from the constellation Leo- the term for their apparent point of origin is the Radiant. The Leonids tend to be brighter than average meteors and they are also very fast by meteor standards. They enter Earth's atmosphere traveling at speeds of over 253 000 km/h (158 000 mph). In contrast the Stardust capsule, the fastest vehicle ever to re-enter the Earth's atmosphere, returned at a snail-like 46 440 km/h. The Leonids we will see in our skies began their one-way trip to Earth in a dim comet called Tempel-Tuttle (named for its discoverers- Ernst Tempel was an especially prominent comet hunter). The comet was discovered 140 years ago and returns every 33 years. Comets have been traditionally described as `dirty snowballs' as they have surfaces rich in frozen water and dusty grit- though results from NASA's Deep Impact probe's visit to Comet Tempel 1 (another found by Ernst Tempel) suggest the proportions of the ingredients are different from those expected. Perhaps we will have to start to call them `snowy dirtballs' instead. Whatever the exact details, the Sun's heat releases the dust and grit from the comet's surface which ends up spread along the comet's orbit. The orbits of the comet and the Earth intersect and every so often, at regular intervals, the Earth ploughs into the oncoming dust, resulting in a shower of meteors. Every 17-19 November Earth crosses TempelImage Credit: Colin Johnston, Science Communicator

Leo The Leonid Meteors have their radiant in this constellation. Image created with Starry Night software Tuttle's orbit and the Leonids become visible. With clear, dark skies observers may see 10 to 15 Leonid meteors every hour on those mornings. The rate of meteors observed is called the Zenith Hourly Rate, so this is a ZHR of 10-15. You should start watching sometime after about 11:30 pm (1130 UT). Leo will be in the eastern sky. The density of the material of the trail is not uniform, and tends to be replenished after the comet has been through one of its periodic solar warmings. Occasionally the Earth passes through a thicker than average patch. Then we are treated to an even more spectacular display, a meteor storm. This has happened recently; displays of 250-300 per hour were observed in 1998, an astonishing


November 2006 Astronotes 11 3700 per hour occurred in 1999, and 480 per hour occurred in 2000. Predictions of meteor shower activities based on modeling the dust trails along the comet's orbit are getting more and more accurate. David Asher of Armagh Observatory has predicted a heavy shower this year. He has calculated that a short and sharp outburst will occur at about 0445 on 19 November (with an uncertainty of about 10 minutes to either side). The ZHR may reach as high as 120 during the outburst. To see this spectacle you will need to be watching from a dark site with minimal light pollution, if you are fortunate enough to know of such a place, why not have a go at observing? You may be in for a stunning natural fireworks display!

NISO takes off!
By Robert Hill, NISO As part of UK World Space Week, Armagh Planetarium launched its latest initiative, the Northern Ireland Space Office (NISO) The Space Office is being jointly funded by Space Connections (a member of the Yorkshire Forward Regional Development Agency) and the Council for Curriculum, Examinations and Assessment (CCEA) in Northern Ireland. NISO aims to build on the interest and enthusiasm of teachers already involved in space science projects by developing resources to support all teachers in aligning the potential offered by developing technologies to the requirements of the revised Northern Ireland Curriculum. The resulting resources and support materials will use the context of space to relate science, technology and mathematics to real life. The Space Office is a fantastic opportunity here in Northern Ireland to create a learning environment that encourages school children to recognise the importance of Science, Engineering and Technology in modern industry and society. There are already many astronomy and space-related resources available to teachers and pupils throughout Europe, and the Northern Ireland Space Office will align these resources and learning journeys to the new Northern Ireland curriculum. There is a real problem facing Europe with not enough students tackling the disciplines in school that they perceive as difficult, and this
Image Credit: Robert Hill, Business Development Manager

NISO logo The Office will promote space science across the Province. new initiative will inspire a new generation of scientists and engineers. Northern Ireland has a fabulous educational reputation and it is important that our next generation gain the necessary knowledge to compete in a European knowledge-based society. NISO will also engage with ESA and its partners to realise an educational resource centre for local teachers, pupils and parents based at the Planetarium. For further information on the Northern Ireland Space Office contact: Robert Hill rob@armaghplanet.com or phone: +44 (0)7929278501


12 Astronotes November 2006

Image of the Month
Image Credit: CICLOPS, JPL, ESA, NASA

Recently the Cassini probe was eclipsed by Saturn for twelve hours or so and this lovely image was created. A mosaic of 165 separate images pieced together, it gives us an amazing new perspective on the planet, its moons and the rings, and perhaps life on Earth too. We can see some of the fainter rings, these are difficult to observe in the usual views of the daylight side. In fact, two new rings, too dim to be detected in previous observations, were discovered in this image. Since the particles composing the rings reflect and scatter light differently depending on their size, seeing the rings from various angles gives more data on their structure. Viewing them in a range of wavelengths, such as ultraviolet and infrared, as well as visible light helps us understand exactly what the rings are made of. The latest research suggests that the rings are not the eternally unchanging structures they have always been thought to be. Instead the rings, which are identifed with letters, are dynamic

and continuously evolving. As recently as 1984 an intruding comet or asteroid apparently collided with the faint innermost ring, the D ring, leaving it crumpled. The E ring is created and maintained by the newly discovered geysers on the moon Enceladus. Meanwhile meteoroid collisions with Saturn's smaller moons bash debris off their surfaces, forming short-lived diffuse rings. If these were not dramatic enough, some rings, such as the G ring, may be the shattered remains of moons broken up in collisions. On the left of the original image, just above the bright main rings is a pale blue point. Sadly it is too small to see here in print, but this tiny speck is the planet Earth. All of the drama of the evolution of life, all of human history and the lives of everyone you have ever heard of happened there, but from Saturn our world is just one more star in the immense darkness of space.

www.armaghplanet.com
Astronotes, Incorporating Friends' Newsletter is published monthly by Armagh Planetarium, College Hill, Armagh, Co. Armagh BT61 9DB Tel: 02837 523689 Email: cj@armaghplanet.com Editor: Colin Johnston ©2006 Armagh Planetarium All rights reserved