Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.armaghplanet.com/pdf/Astronotes/Astronotes2010/Astronotes%202010-08.pdf Дата изменения: Tue Sep 20 18:49:41 2011 Дата индексирования: Tue Oct 2 01:34:24 2012 Кодировка: Поисковые слова: annular solar eclipse

August 2010

ASTRONOTES
Incorporating FRIENDS' NEWSLETTER Life, but not as we know it! Going...going...totality! The sky this month Summer blast off! To the stars via hyperspace?

ARMAGHPLANETARIUM


2 Astronotes August 2010

Life, but not as we know it!
by Sinead McNicholl, Education Support Officer Recent press reports say scientists believe they may have found life on one of Saturn's moons called Titan. However, don't get too excited, we are not talking about little green men here or everyone's favourite extraterrestrial ET! Scientists merely speculate that there could be primitive life forms on Titan, which is still as exciting. The news came as a result of data taken from NASA's Cassini probe which analysed both Titan's surface and its dense atmosphere. The Cassini probe has been orbiting Saturn for the last six years sending back pictures of the planet and its moons. Titan is the largest moon of Saturn, discovered in 1655 by the Dutch astronomer Christiaan Huygens (1629-95). In fact,Titan is the second largest moon in our whole Solar System, the largest being Jupiter's moon Ganymede. It is home to mountains, streams, rivers and even glassy, inky-black hydrocarbon lakes, discovered as by the Huygens probe (which rode piggyback to Saturn on the much larger Cassini vehicle) in 2004. At the time this was quite a discovery as this is the only place that we know of, other than On the beach The first coloured view of the surface of Titan. The Huygen probe landed on a muddy beach strewn with fistsized stones. These boulders are, like much of Titan, composed of water ice. In this deep cold ice is a marblelike rock. Earth, to have liquid on its surface. Titan is often described as a `second Earth', or similar to the Earth four billion years ago. However is a very different place to the Earth today, being twice as big as our own moon, it has a thick atmosphere of orange smog made mostly of nitrogen.

"Titan is often described as a `second Earth'"
Life here on Earth is water-based, but life on Titan's surface (should it exist) is likely to be methane-based as it is too cold to support liquid water on its surface, with the average temperature being a very chilly -180°C. According to one theory, a long time ago, the impact of a meteorite might have provided enough heat to liquify water for perhaps a few hundred or thousand years which could have provided conditions sufficient for living creatures to thrive. However this moon was not thought to harbour life today, well that is until now! Clues have been found that hint that exotic lifeforms may be breathing in hydrogen from Titan's atmosphere, feeding on organic chemicals (such as acetylene) and exhaling methane on the surface. Scientists have said that there is a lack of hydrogen near the surface of Titan hinting that it could be being consumed by something. There is also a lack of acetylene on the surface which suggests that something is consuming it as food. Chris McKay, an astrobiologist at NASA Ames Research Center commented that hydrogen was "the obvious gas for life to consume on Titan, similar to the way we consume oxygen on Earth". If these primitive life forms did exist on Titan, what would they look like? This question in on the lips of many scientists who are researching what compounds they would be made up from,

Image Credit: NASA and ESA


August 2010 Astronotes 3 and, ultimately determine what they would look like. This is very speculative as instead of relying on water as a primary ingredient for life as we do here on Earth, life on Titan might have blood based on liquid methane. If these aliens do exist don't expect a visit anytime soon as such a creature couldn't survive on Earth as methane is a gas at our warmer temperatures. Any Titanian lifeform would rapidly melt and evaporate on the coldest Antarctic day! Also instead of using the element carbon which makes up life on Earth, these creatures' chemistry might be based on silicon. Scientists have also reached the conclusion that Saturn's moon has the chemistry required to produce even more advanced life (ie like ourselves). They have suggested that all that is needed is a little warmth to jump-start the process. They have even estimated that this may occur in around 4 billion years when the Sun swells up and becomes ever larger to form a red giant star. At that time, Titan will be a paradise to live on, though neither we nor our descendants will be around to experience it, because when the Sun gets to that size, it will end up swallowing the Earth!

Titan laid bare This IR view of Titan removes its obscuring clouds to uncover new territory not previously seen . conditions on the moon. So far, only one such model has been used to estimate hydrogen flow on Titan. Once others are used and more Cassini data comes in, scientists will have a better idea about whether hydrogen really is being depleted at the surface. If it is, experiments that simulate Titan conditions on Earth could show whether catalysts that help hydrogen and acetylene react with one another might work on Titan. But we may have to wait quite a while before we have definitive proof that there is life in another place other than Earth. Several missions to Titan's surface would be essential to find unambiguous evidence for life. One of the first steps may be to send a robotic probe equipped with a mass spectrometer, which could look for complex organic molecules. Mass spectrometry is an analytical technique used for the determination of the elemental composition of a sample or molecule. Currently a team of researchers are asking NASA to fund one such spacecraft, the Titan Mare Explorer, and if this is accepted, it will launch in 2017. A larger Titan mission that would include a balloon and Lander was deferred by NASA in 2009 in favour of developing two probes to explore Jupiter and its moons instead. These probes are scheduled to lift off in 2020. But we hope that NASA will be able to fund the mission to Titan as it would be fascinating and exciting to find proof of other living organisms out there: we may not be alone after all!

"Titan has the chemistry required to produce even more advanced life"
The suggestion that there may be life is still in the preliminary stages. Scientists are quick to point out that non-biological chemical reactions could also be behind the observations. Mark Allen, a principal investigator with the NASA Astrobiology Institute Titan team, explained there is "a lot of work to do to rule out possible non-biological explanations. It is more likely that a chemical process, without biology, can explain these results". Allen points out that sunlight or cosmic rays could be transforming the acetylene in icy aerosols in the atmosphere into complex molecules that fall to the surface with no acetylene traces. Another explanation could be that the mathematical model used to estimate the flow of hydrogen in Titan's atmosphere from the Cassini measurements did not accurately simulate

Image Credit: NASA


4 Astronotes August 2010

Going...going...totality!
The moments of eclipse Author's Illustration of a total solar eclipse in stages. by Martina Redpath, Education Support Officer Last month citizens in the South Pacific were witness to one of the most extraordinary events Mother Nature has to offer. On 11 July thousands of visitors flocked to Easter Island and the southern parts of Argentina and Chile not to watch the World Cup Final but to see a total solar eclipse. So what exactly causes this phenomenon? Solar eclipses occur when the Moon passes in between the Sun and the Earth. The Moon has no light of its own; instead when we see moonlight we are seeing sunlight reflecting off the surface of the Moon. The Moon goes around or orbits the Earth once roughly every 29Ѕ days. In orbit, as the Moon moves with respect to the Sun, it causes us on Earth to see it in various shapes or phases. The first phase in the monthly cycle is a New Moon, and it is only when the Moon is in this phase that we see a total solar eclipse. Although we have a new Moon every month we do not have a solar eclipse every month because the Moon revolves around the Earth in an orbit inclined at an angle, and for a total eclipse to happen the Moon, Earth and Sun need to be in a straight line. This only occurs a couple of times a year. Although the Moon is 400 times smaller than the Sun, the fact that it is 400 times closer allows both objects to appear the same size in the sky.
Image Credit: Martina Redpath

"Two ancient Chinese astrologers were killed for failing to predict a solar eclipse"
If you have never witnessed a total solar eclipse, allow me to set the scene a little. Imagine the sky darkening gradually. A black disc is moving in front of the Sun until the sunlight vanishes. The birds return to their nests and day becomes dusk. All that remains visible is a small halo-like disc, the solar corona. This is known as Totality. The total eclipse rarely lasts longer than several minutes, so scientists studying the solar corona welcome this spectacular but brief opportunity as the corona is only visible during a total eclipse. There are different kinds of solar eclipses in which the Sun is not fully concealed by the Moon. A partial eclipse occurs when the Moon passes in front of the Sun but does not cover it completely. An annular eclipse occurs when the Moon is further away from Earth than normal so the Sun appears with a dark centre. The Moon's orbit around the Earth is not perfectly circular so it can be at varying distances away from the

Image Credit: The Exploratorium

The Sun in Totality during a total solar eclipse in 2008, the halo like corona is clearly visible.


August 2010 Astronotes 5 Earth. An annular eclipse is still very bright so the Sun's corona is not visible during this type of eclipse. Another type of solar eclipse is the hybrid eclipse, so as the name suggests this would be a mixture of events. A hybrid eclipse appears as a total eclipse in some parts of the world but appears as an annular eclipse in other parts. This is caused by the curvature of the Earth moving different areas into the shadow of the Moon. The next hybrid eclipse will be in November 2013.

"The word eclipse comes from a Greek word meaning abandonment"
As well as solar eclipses we also have lunar eclipses. This is when the Earth comes between the Sun and the Moon. A lunar eclipse can only occur when we have a Full Moon, and we see the Earth's shadow on the Moon. Lunar eclipses may also be partial or total. A lunar eclipse is only visible on the night side of the Earth. During a lunar eclipse the Moon appears a reddish colour. This is because sunlight is passing through the Earth's atmosphere. Red light has much longer wavelengths compared to blue light. Shorter wavelengths are more likely to be scattered on passing through the atmosphere therefore longer red wavelengths are more visible, leaving the Moon a reddish colour.

The Moon's shadow on the Earth A solar eclipse as viewed from the international Space Station in 2006. The shadow of the moon has fallen over Turkey and the Mediterranean Sea. Chinese astrologers were killed for failing to predict a solar eclipse. Also in ancient China, some people believed that a celestial dragon was devouring the Sun during a solar eclipse and the Moon during a lunar eclipse. In was therefore a tradition to bang drums and pots and make a lot of noise to frighten the dragon away. Even as late as the nineteenth century, the Chinese navy fired cannons during a lunar eclipse to frighten off the dragon. The word eclipse comes from a Greek word meaning abandonment, viewed as the Sun abandoning the Earth. When doing some research here are some other myths that I came across. You may have heard of some of them. It is harmful to eat or drink during an eclipse. If you are pregnant you should remain indoors as it could be harmful to you and child. Also believed is that during an eclipse it is more likely for there to be famine, floods, war, unrest, death, disease, violence, turmoil.... perhaps recession? Anyhow these are all myths. The only harm that can come from watching a solar eclipse is staring directly at the sun without taking correct precautions to protect your eyes. An eclipse of any kind is a wonderful sight. So here are some total eclipses for you to pencil into your diaries. Total Lunar Eclipse 21 December 2010, visible Australia, Pacific, Europe and Americas and a Total Solar Eclipse November 13 2012, visible in Australia and South Pacific.

"The Moon is 400 times smaller than the Sun, the fact that it is 400 times closer allows both objects to appear the same size in the sky"
Today a total solar eclipse is an interesting sight, tourists flock to different areas to view the spectacular event. It's very exciting! Solar eclipses have been observed throughout history; however, different cultures have held varying opinions on eclipses of the Sun. In ancient China, the ability to predict a solar or lunar eclipse was of high importance as they were believed to foretell the future of the Emperor. Two ancient

Image Credit: NASA


6 Astronotes August 2010

The August night sky
By Mary Bulman, Education Support Officer Few beautiful things in life are free. August provides us with one such rarity, an amazing celestial show that is free for all. Go now and put a circle around 12 August on your calendar or put a reminder on your mobile phone. August provides us with one of the most dependable and wonderful meteor showers of the year, the Perseids. August is also a good month to observe the planets as four of Earth's siblings are on view. On the evening sky stage three planets are visible above the western skyline this month as Venus at magnitude ­4.3, Saturn at 1.1 and Mars at 1.5 perform a type of celestial slow dance. As the month progresses the trio get lower and lower in the evening sky so an unobstructed horizon will be a prerequisite to spotting them. As these three planets set in the west you'll find Jupiter appearing above the eastern skyline. At magnitude ­2.8 the planet dominates the constellation of Pisces. At the beginning of the month it rises at 10pm but by the month's end it is clearly visible by 9pm. Of course planets, stars and the Moon are not the only players in the night sky. There are other interesting phenomena to view in the heavens. "Shooting stars," whisper the lovers in the dark. We have all heard of shooting stars and may even have made a wish on seeing one. Sorry to disappoint but a shooting star is not a star at all. It is a meteor burning up in the sky. Before proceeding let's get some clarity on the terminology. Bits of space debris, ranging in size from enormous rocks to tiny grains of sand, floating about the Solar System, are called meteoroids. When they enter the Earth's atmosphere and form streaks of light they become meteors (commonly called shooting stars). A very bright meteor is called a fireball or bolide. If a meteoroid survives the journey through the atmosphere and falls on Earth it is known as a meteorite. Meteors are small particles of debris from space that enter our atmosphere at speeds of around 70 kilometres per second. As they reach the dense inner layers friction rapidly heats them causing them to glow. But it is not the glowing dust grains that we see. The celestial fireworks that we enjoy are actually glowing gas. As the meteor ploughs through the thick atmosphere it

Can you `catch a falling star and put it in your pocket'? Astronomer John Chumack captured this image of a Perseid meteor (just visible at right) taken over Yellow Springs, U.S.A. in 2007. Also note the Pleiades star cluster at the top left side of picture.

Image Credit: John Chumack, www.galacticimages.com


August 2010 Astronotes 7 reaches approximately 1500°C. At this temperature it ionises the air around it making it glow like a fluorescent tube and this is what we witness as shooting stars. They become visible at an altitude of about 100 kilometres. Most particles will vaporise from the effects of heat well before reaching the surface of the Earth. There are two broad groups of meteors. Those that arrive from random locations in the sky are termed sporadic, while others that appear to originate from a particular region of sky, and are large in number are known as meteor showers. in 1992. With a 133-year orbit, the celestial body is expected to appear again in 2125. American astronomers Lewis Swift and Horace Parnell Tuttle discovered the comet independently in 1862. The Italian astronomer Giovanni Schiaparelli (1835 ­ 1910) made the connection between Comet Swift-Tuttle and the Perseid meteor shower. Schiaparelli's connection established comets as the originators of meteor showers. The Perseid meteor shower is not a one night wonder. Perseids start streaking across the sky as early as July and continue through late August. But the meteors usually peak in midAugust, with average rates of 70 to 80 shooting stars an hour. They reach their maximum on the night of 12/13 August. On that night, given good conditions, anyone taking a midnight stroll cannot fail to notice an amazing spectacle in the sky. This year the New Moon on 10 August is perfectly timed to provide us with dark skies for observing.

Image Credit: William Larkin Webb via Wikipedia.org

Mars Canal Man Giovanni Schiaparelli (18351910) is best remembered for his observations of Mars but he also made the link between comets and meteor showers. Meteor showers are named after the constellation in the part of the sky, called the radiant, which the stars appear to be falling from. So we have the Leonids, the Orionids and the Geminids to name a few well-known showers. The Perseids of August are one of the most impressive and popular meteor showers of the year, so called as the falling stars all appear to come from the constellation of Perseus. A meteor shower looks like a shower of stars falling from the sky. As Perseus is a northern constellation this spectacular annual shower can only be seen in the northern hemisphere. The Perseid meteor shower has been observed for about 2000 years. Meteor showers happen when the earth in its orbit around the sun travels through a trail of debris left by a comet. The Perseids are the result of debris left behind by comet Swift-Tuttle, which last passed by Earth

"The Perseids of August are one of the most impressive and popular meteor showers of the year"
To really get the most out of this annual celestial show here are a few tips. Find a good, dark but safe place to settle down for a few hours. Look away from any lights in your area so your eyes stay as dark-adapted as possible. All you need is the naked eye, a reclining chair and a nice warm wrap or blanket for comfort. Easy company and some light refreshments will make the experience all the more enjoyable. Any time after midnight to the early morning hours is the best time to view. And of course you need to look in the general direction of northeast. Instead of looking directly at Perseus keep an eye on the area just below the W of Cassiopeia. If 12/13 August is a clear night you could see up to 100 meteors per hour. Meteors like stars have their own mythology and legends. For some Christians they are "the tears of St. Lawrence". The festival of St. Lawrence, a martyr burned by the Romans, is on 10 August and in the mid 19th century the Perseid shower


8 Astronotes August 2010 was seen on the night/morning of the 9/10 August. The peak of a meteor shower occurs about three days later each century. Making a wish when seeing a shooting star goes back to a time when people believed that the gods would occasionally open the dome of heaven to have a look at what we humans were up to on Earth. This released a star, and if one made a wish while there was still light, and before the dome slammed shut, the gods might hear and grant the wish. May all your wishes be granted as you view the Perseids around mid August.

Moon Phases August 2010
Tuesday Tuesday Monday Tuesday 3 August 10 August 16 August 24 August Last Quarter NEW MOON First Quarter FULL MOON

Summer Blast off!
By Tracy McConnell, Education Support Officer Summer kicked off with a blast here at Armagh Planetarium on 3 and 4 July as we entertained families from all over Ireland in our Family Fun Weekend. From the moment we opened the doors on this free event, little ones were all around us. Some came to see our brand new preschool show the "Little Yellow Star", after which they got their very own balloon astronaut made for them to decorate. Face painters from Friendly Faces were on site both days and as a result there was a barrage of dogs, vampires, lions and princesses enjoying the festivities too. A big hit, as always, was our traditional water rockets workshop, where budding engineers got to build their own rocket, then launch them into the sky to test its effectiveness. For any promising astronauts, we also offered the opportunity to create their own space mission patch badge. All attendees were asked to keep a look out for the eggs left behind throughout the Planetarium by escaped aliens, and I'm pleased to report that all such infants were rounded up and secured with their parents before the weekend was over. All of our Digital Theatre shows on both days were full to capacity. This is why it's important to remember to book show tickets in advance when coming to the Planetarium. The weekend also opened another new show, "Violent Universe, Catastrophes of the Cosmos". This stellar show looks at all the potential treats to the Earth that may come from space and is narrated by the legendary actor Sir Patrick Stewart.
Image Credit: Danielle Fields

Supertroopers The Staff at the Armagh Planetarium, along with our loyal Mascot, Angus the Irish Astronaut, and friends from Knights of the Empire, Emerald Garrison. I decided to give the Knights a run for their costuming money and dressed as a NASA astronaut for the day too. As always, some of the greatest entertainment of the weekend came in the many forms of our friends from Knights of the Empire, Emerald Garrison, in full Star Wars costumes. They security checked visitors entering the shows, terrorised passersby into submitting for a visit, and posed for photos with loyal subjects of the Empire. For those who missed this spectacular experience, fear not! Another opportunity will present itself on the 28 and 29 August as we have another Family Fun Weekend, as a final farewell to the summer school holidays. Keep your eyes on local publications and our website for details. This forthcoming event will offer discounts off the usual prices. Hope to see you all there. It's sure to be a Blast!


August 2010 Astronotes 9

Beyond the impossible!
inthis kind of timescale is difficult (try to write a fast-paced thriller novel in a world where it takes a decade to go between London and Paris, and a century to go from Europe and America and you'll get the idea). To their credit some authors, notably Poul Anderson, Stephen Baxter and Joe Haldeman have managed this, but it is easier to assume journey times between the stars measured in weeks (basically as fast as travel around the world in the age of sail). How could this be done? At the Atomic Rockets website (http://tinyurl. com/38qyhcp, a truly wonderful resource, I'm sure it is exactly what Al Gore had in mind when he was inventing the internet) there is a pretty exhaustive list of FTL techniques. I am not going to go through them all (are those sighs of relief I hear?) but let us examine some of the most common.
Image Credit: Warner Brothers

Hyperspace Heroes 1 Travel in TV's Babylon 5 universe was via hyperspace and was nicely depicted. By Colin Johnston, Science Communicator (This article follows article "Impossible, am lazy, throughout avoid typing "faster "science fiction") on directly from last month's that's all!" Once again, as I this article I will use "FTL" to than light" and "SF" to mean

Last time I went on and on about how Einstein anticipated odd things happening on a spaceship travelling at close to lightspeed and impossible things happening at the speed of light. These predictions are enough to convince much smarter people than me that reaching the crucial speed is impossible. But what if we could exceed the speed of light somehow? Follow me on a voyage beyond the impossible. Most vaguely plausible speculation about breaking Einstein's speed limit has come from either bored physicists going for a walk on the wild side or authors of science fiction trying to make their stories more plausible, so I make no apologies for concentrating on their works. Even in the first half of the previous century astronomy was starting to suggest that the Solar System wasn't exactly going to be brimming over with settings for rattling good yarns with craggy heroes and their sultry lady friends, ray gun fights and exotic wildlife. The solution was to go interstellar, but if you want to be sort of realistic (and some SF aims to be) you ran into the problem of journey times between your locations of decades or more. Imagining societies which operate over

"Tachyons would live backwards"
Some theoretical physicists, driven no doubt by the fact that their subject isn't as cool as astronomy, have speculated on the possibility of particles which always travel faster than light, avoiding the complications. They even gave them a name, tachyons (from the Greek takhus, meaning "fast", and the English "-on"meaning "elementary particle" (yes, really)). There is a history of particle physics predicting the existence of particles needed to fill gaps in our knowledge which are later discovered, neutrons being the classic example. Could this happen with tachyons? Tachyons would be really, really bizarre things, for example their mass would be imaginary. "Imaginary" is used in its mathematical sense, meaning a multiple of the square root of -1, whatever that may mean. Not only that, adding kinetic energy to a tachyon would make it slow down, but it would take infinite energy to drop its


10 Astronotes August 2010 wrong!) Little has been written about them recently but they show up all the time in TV shows (Hollywood SF, or sci-fi, cares little for science). The term "hyperspace" actually goes back to the nineteenth century. It was originally a term from pure mathematics to describe a mathematical space with more than the normal three dimensions (note that this was purely an abstract mental plaything; no one was suggesting such a place actually existed). Sometime in the early twentieth century an enterprising SF author, possibly John W. Campbell Jr, was the first to suggest accessing a hyperspace to evade the cosmic speed limit. By the 1950s this was a common plot device (used for example, in many of Asimov's tales) and hyperspace is still seen today, although the names may vary; jumpspace, foldspace, FTLspace, phasespace, the Warp and so on all refer to the same concept. How is this supposed to work?

Hyperspatial heroes 2 FTL travel in the Star Wars universe utilises hyperspace. velocity down to the speed of light! Finally, they would live backwards, being destroyed before flying around space until they were created (I'm afraid just thinking about that is enough to make one's headmeat go all explody). A few physicists played around with the concept of tachyons in the late 1960s through to the mid70s, but a few (admittedly half-hearted) experiments to detect tachyons in cosmic ray showers failed to find any. Nevertheless tachyons rapidly (how else?) spread to the pages of SF. Beams of tachyons wer