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EDE71610 deep space:deep space poster AW 13/1/09 14:21 Page 1 a guide to DEEP SPACE 2009 SPACE ODYSSEY THE PILLARS OF CREATION In the constellation of Serpens lies the Eagle Nebula, (right) a giant cloud of interstellar gas and dust. Here new stars are being born, condensing out of the nebula. The radiation from these stellar infants is energizing the gas, causing it to glow. A closer look at the Eagle Nebula reveals intriguing structures including the famous Pillars of Creation. These dark structures are columns of cool gas, mainly hydrogen and dust, that serve as incubators for new stars. Astronomers have detected blobs of much denser gas inside the Pillars, these appear to be forming solar systems. Eventually the new star will become visible as their radiation blows away the surrounding material. Each Pillar is several light years long. The Pillars and the surrounding nebula are 7000 light years from Earth, so we see them as they were 7000 years ago. Possibly they no longer exist, the shockwave from a nearby exploding star may already have ripped through them and we will see this happening a few thousand years from now - or maybe tomorrow. THE HUBBLE SPACE TELESCOPE Probably the most famous astronomical satellite ever, the Hubble Space Telescope has given us amazing views of the wonders of the cosmos. Placed into orbit by a Space Shuttle mission in 1990, the HST initially suffered from a focussing problem. This meant that its images were blurred. A NASA investigation revealed that its main mirror had been manufactured incorrectly and the testing that should have disclosed this error had been cancelled as a money-saving measure. Happily astronauts were able to install a new component to correct this problem in 1993. Since then the HST has provided unparalleled views of deep space objects. Many of these are stunningly beautiful and have become familiar through their reproduction on posters, album covers and in science fiction movies. Visits by Space Shuttle crews to service the HST and replace worn-out components have extended its life but the end is in sight. The next servicing mission will be the final one, and all being well the HST will be replaced by the bigger still James Webb Space Telescope in 2013. TO THE ENDS OF THE UNIVERSE Since the invention of the telescope 400 years ago, astronomers have been striving to see further and further into the heavens. Every time you look up at the night sky, you are looking back in time. The light we can see left the stars and galaxies hundreds or even thousands of years ago. In fact, some of the stars we can see may not even be there any more. We live in a galaxy called the Milky Way, a vast flat spiral of hundreds of billions of stars. Our Sun and its family of planets, including the Earth, circle the Milky Way’s centre in a long slow orbit. The Milky Way’s size defies human comprehension: a beam of light would take 100 thousand years to travel from one side to the other. Until the 1920s many astronomers believed that our galaxy was essentially the entire Universe. Other galaxies were visible but were thought to be ‘spiral nebulae’, relatively small objects inside the Milky Way. Then Edwin Hubble, a flamboyant character of an astronomer, recognized a type of star called a Cepheid in the Andromeda Nebula, the largest of these spiral nebulae. Cepheids, stars which pulse at a rate governed by their brightness, are extremely useful ‘standard candles’ for astronomers, who can easily tell how far away a Cepheid is just by observing how long it takes to cycle from minimum to maximum brightness. Hubble did the calculations and discovered that the Andromeda Nebula was very distant indeed (2.2 million light years away is the accepted figure today), so far in fact that it could only be a galaxy in its own right. The Universe must be far larger than previously thought. At the time this was very controversial, but Hubble was about to create an even greater stir. However to understand what he did, we firstly will need to discuss light. HOW FAR ARE THE STARS? Light travels as a wave, and hence it has a wavelength. If you imagine waves in the ocean, their wavelength is the distance between each crest. Just for a moment think about the familiar colours of the rainbow (or spectrum). At one side we start with red which has a long wavelength, next orange with slightly shorter wavelength, moving through the colours to blue and violet the wavelengths get smaller and smaller. Light waves from moving sources are stretched or compressed by the motion. If an object is coming towards you its light is blueshifted meaning the light waves are squeezed together appearing more bluish, similarly if it is receding the light is redshifted. This is called the Doppler Effect and is very useful in many aspects of astronomy. For example, by studying the light from a star we can tell if it is coming in our direction (blueshift) or moving away (redshift), or we can use the Doppler Effect to measure its speed. Between 1912 and 1917, astronomer Vesto Slipher was using the Doppler Effect to measure the speed of ‘nebulae’, at the time still believed to be nearby objects inside our own galaxy. To his surprise, of twenty five nebulae, four were blueshifted (and therefore coming towards us) and the rest were redshifted and hence moving away from us. By the late 1920s Hubble was using the 100 inch Mount Wilson telescope, the largest in the world at the time, to look at distant galaxies. By 1929 he had catalogued 46 galaxies by their distance and speed (measured by the Doppler Effect). The conclusions were unmistakeable and confirmed Slipher’s results. Firstly most galaxies are receding from our galaxy, Secondly, the degree of redshift (and therefore the galaxy’s velocity) is directly proportional to its distance away. In other words, if a galaxy was twice as far away as another, it would appear to be travelling twice as fast. This is now called Hubble’s Law, and it made his name. Hubble’s Law opened up a new way of determining intergalactic distances. If we measure the redshift of a galaxy, we will know its velocity, and by Hubble’s Law, we will automatically know its distance away. Page 2 THE BIG BANG THEORY Edwin Hubble’s observations showed that the Universe is expanding. This implies that in the past the Universe was much smaller than it is now. Then the galaxies would have been closer together, going further back in time there would have been a time when they were squeezed closer together still and ultimately there would have been a time when everything was at a single point. In the 1930s, Belgian physicist and priest Georges Lemaître suggested that if the Edwin Hubble evident expansion of the universe was reversed until it could contract no further, all the mass of the Universe would be squeezed into what he called the ‘primeval atom’ or ‘cosmic egg’. This had exploded, expanding outwards to create the Universe we see today. In 1948 two physicists Ralph Alpher and George Gamow calculated that most of the chemical elements could have been created in this massive explosion. Their work implied that heat from this explosion should be spread throughout space, appearing as a faint radio (or microwave) emission. Alpher and Gamow did not believe it would possible to detect this background radiation. THE SEARCH FOR E.T. Searching for life elsewhere in the Universe is a fascinating endeavor. Astronomers in the 1800s used telescopes to search for signs of life and even civilization elsewhere in the Solar System. Some even believed they saw signs of intelligent life on Mars in the form of a grid of canals across the Red Planet’s surface. Illustrations and maps of Mars published by NASA as late as the early 1960s still showed these. Disappointingly, visits to Mars by spaceprobes from the mid-60s onwards revealed it to be more barren and inhospitable than previously thought. There is still a possibility that life arose on Mars billions of years ago when conditions on the planet were milder, and perhaps some bacteria-like organisms cling on to life under the surface. We probably will not know if this is true or not until people travel to Mars to explore. Elsewhere in the Solar System, there is evidence for oceans of water under the icy surfaces of Jupiter’s moon Europa and Saturn’s moons Enceladus and Titan. These may be the best prospects for life-bearing sites in the Solar System. Could bizarre aquatic life swim in the inky depths of these alien seas? Given the difficulties of sending a mission to drill through the crusts of these distant moons, we will probably not know the answer for centuries. DARK MATTER 96% of the Universe is invisible to us! Astronomers reached this unsettling conclusion by studying galaxies. Observations showed that the spin rates of galaxies are faster than they should be, in fact high enough to pull them to pieces, so some unseen force must be holding the galaxies together. This could not be the gravity of the stars we see in the galaxies as there are not enough of them. The only reasonable conclusion is that some mysterious form of undetectable matter dominates each galaxy. This has been called Dark Matter ( because it does not give out any light). Some of it may be tiny black holes or brown dwarf stars drifting between the stars but most of it seems to be composed of sub-nuclear particles which have yet to be studied in the laboratory. The unexpected discovery of dark matter shows that there is still so much for us to learn about the Universe. RADIO ASTRONOMY In 1930 Karl Jansky was investigating radio interference which was disturbing transmissions on a trans-Atlantic radio link. Using a giant radio antenna which could be pointed in any direction he discovered that some of this radio noise came from the sky and particular the constellation of Sagittarius. Jansky concluded that the radio noise originated in the centre of the Milky Way. This was the start of radio astronomy, radio astronomy has enabled us to observe a new depth to the Universe. Astronomers use the natural radio emissions of clouds of hydrogen to map the galaxy including regions obscured to our sight. We have been able to explore and chart the core of the Milky Way in great detail and determine that a vast black hole must dominate its centre. Pulsars, fast-spinning remains of exploded stars were discovered through radio observations by Portadown-born Jocelyn Bell Burnell. Radio astronomy shows that there is more to the Universe than meets the eye! 2009 SPACE ODYSSEY Astronomers accept that, rather than being two separate entities, space and time are one, sometimes called spacetime. Rather than simply saying where something is located, it would be more correct to say how long it is there for too. This is based mainly on the work of Albert Einstein, specifically his theory of General Relativity. Einstein’s theories had other important implications, one of which is that an object’s gravity distorts spacetime. Rather than saying a planet exerts a Albert Einstein gravitational pull towards it, it is truer to say its gravity bends the space around it. The path of a beam of light passing a star would be curved as it passes through the warped space around the star. This has been observed and astronomers are now well aware of the phenomena of ‘gravitational lensing’ when the image of a distant galaxy is distorted by the gravity of other galaxies between it and the Earth. Stranger still as space and time are one, gravity distorts time too. Time runs slower near a massive object such as a star than it in empty space. This is not just some obscure prediction about the distant Universe, experiments with very accurate atomic clocks have verified that time moves faster on the Earth’s surface than it does on high mountain peaks. This difference is so tiny as to be imperceptible to human senses but would be obvious near a black hole. If an astronaut could leave her spacecraft to somehow safely approach a black hole, her crewmates would see her appear to slow down until she became almost frozen in place. British scientist Fred Hoyle championed a rival explanation called the Steady State theory and fiercely disagreed with this explosion theory which he sarcastically called ‘the Big Bang Theory’. This name stuck and has been used ever since. The Steady State theory is no longer accepted. In the early 1960s, two engineers Arno Penzias and Robert Wilson, were employed by the Bell corporation to find a source of radio interference picked up in a satellite communications antenna. The interference was a faint but steady radio noise coming from every direction the antenna was pointed. It appeared to come from all over the sky. Penzias and Wilson consulted other scientists and realised that they had accidentally discovered the Cosmic Microwave Background predicted by Gamow and Alpher. Today’s free poster SPACE AND TIME DEEP SPACE 14:22 Don't miss tomorrow's Star Chart poster 13/1/09 www.belfasttelegraph.co.uk EDE71610 deep space:deep space poster AW Jodrell Bank radio telescope 2009 SPACE ODYSSEY Today’s free poster DEEP SPACE Since 1995 astronomers have discovered 300 or so planets orbiting other stars. The vast majority so far discovered are huge gas giant planets like Jupiter or Saturn but as technology improves we ought to find worlds more like Earth. To find life out there all we can do at present is try to listen for radio signals from alien beings. This is the Search for Extra-terrestrial Intelligence (SETI) and is conducted mainly as a spare-time project by some astronomers. At present no government funds SETI research, but private groups such as the Planetary Society have paid to scan the sky for artificial signals. Grandest of these efforts is the Allen Telescope Array, 42 linked 6 metre radio telescopes funded by Microsoft billionaire Paul Allen. We humans have sent our own messages into space. Plaques and discs of data were been bolted to the Voyager and Pioneer deepspace probes should any space travelling ETs find them. Many astronomers would say that alien life is a possibility, but one astronomer, Frank Drake, has tried to work out the number of extraterrestrial civilizations active in the galaxy. The Drake Equation uses estimates of how common planets are around other stars, how many are suitable for life, on how many actually develop life and so on to give ‘N’ the number of alien civilizations. Unfortunately, most of these values are little more than guesses at the moment, so values of N vary from hundreds of thousands to just one (ourselves!). Perhaps the Cosmos is full of life or perhaps we are alone. Either possibility is awe-inspiring. Don't miss tomorrow's Star Chart poster Content & Images supplied courtesy of: www.belfasttelegraph.co.uk Poster design by Jonathan Simms