Wonders of the Universe

by Professor Brian Cox

  The Omega Nebula (the Horseshoe, or Swan, Nebula) is a vast interstellar cloud that is over fifteen light years across and illuminated by hundreds of bright young stars. These stars, depending on their masses, will burn for hundreds of millions or billions of years, sending a constant stream of light across the Universe until their voracious hunger depletes the hydrogen in their cores and forces them to expand and transform into giants.

  As they near the end of their lives, the most massive stars are transformed into colossal giants – such as the red Mira, whose radius is 400 times that of our sun and only just clinging onto life. When the end finally comes for stars like these, the ensuing supernova explosion will leave only a faint trace of the star. For the largest stars, the supernova will leave a black hole behind – an object so dense that even light cannot escape its clutches. Slightly smaller stars will end their post-supernova days as neutron stars, which we detect by the lighthouse beam of radiowaves they emit as they spin every few seconds or less.

  Stars much smaller than Mira won’t go out with a bang. Such relatively cool stars are called red dwarfs and are the most common type of star in our galaxy. Perhaps the most famous of these we have studied is Gliese 581. Just over twenty light years away from Earth, this star has been the subject of intense observation in recent years due to the discovery of at least six exoplanets orbiting around it. Most excitingly, planet Gliese 581 g is thought to orbit within the habitable zone of the star and so is considered a prime location for the search for extraterrestrial life

  These fascinating ultraviolet images, taken by NASA’s Galaxy Evolution Explorer, show a star named Mira speeding across the sky and leaving behind it an enormous trail of debris. This material is in fact ‘seeds’ which will be recycled to create new stars, planets and possibly even life, as it travels through our galaxy.

  NASA

  Known as the Horseshoe, or Swan, Nebula, this molecular cloud is also often called the Omega Nebula, due to its similarity in shape to the Greek letter Omega. Ultraviolet light from a cluster of massive young stars buried within the nebula make the surrounding gas glow. This image was taken by the European Southern Observatory’s 3.6-metre (11.8-foot) telescope in La Silla, Chile.

  NASA

  Perhaps the most studied astronomical object, the Orion Nebula is also one of the most beautiful structures in the sky. On over 100 orbits of Earth between October 2004 and April 2005, NASA’s Hubble Space Telecope captured this nebula in one of the most detailed astronomical images ever produced. On a clear, dark night sky this impressive formation – which includes more than 3,000 stars of varying sizes – can be seen with the naked eye. This complex, constantly evolving formation has provided scientists with crucial insight into how stars are formed.

  The Venus transits of our sun are a rare occurrence, they only happen twice in eight years and won’t be repeated for another 100 years. The last transit happened in 2004, with another due in 2012. We will have to wait until 2116 for the next one.

  This is a composite image of Venus transiting the Sun on 8 June 2004. Venus can be seen from Earth as a small black disc moving across the face of the Sun.

  ECKHARD SLAWIK / SCIENCE PHOTO LIBRARY

  HOW TO FIND EXOPLANETS

  One of the most exciting areas of current astronomical research is the hunt for planets around other stars – known simply as exoplanets – which are potential homes for extraterrestrial life. Until recently such a search would have been impossible, as planets are too faint to see over interstellar distances, however, thanks to new modern instrumentation, we are now able to detect the telltale signals of exoplanets using two main techniques: the radial velocity method and the transit method. With these techniques, individual planets and even planetary systems have been discovered around hundreds of stars. Masses of these extrasolar planets range from a few times that of Earth, to the size of 25 Jupiters. Whether a planet could support life depends on its distance from the parent star. Around each star is a ‘habitable zone’, in which temperatures are suitable for water to exist as a liquid. The size of this zone depends on the energy output of the star; the faintest ones have the closest, narrowest zones. The red dwarf Gliese 581 is believed to have at least one planet within its habitable zone.

  Nathalie Lees © HarperCollins

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  As we observe all the cosmic structures around us in spectacular detail, each tells us something different about the life cycle of the stars. However, something much deeper can be learnt from understanding the existence of stars: they are the ultimate origin of all but the simplest of Leucippus’ and Democritus’ long-sought-after atoms, and as such are the building blocks of ourselves. To comprehend how the stars could play such a vital role in our existence, we must momentarily step back from the skies and come firmly back down to Earth.

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  The largest mountain range in the world, the Himalayas is also the youngest. This panorama, taken from the top of Kala Pattar in the Sagarmatha National Park, Nepal, shows only a fraction of its scale. Understanding the creation of these impressive mountains helps us to answer many questions about the structure of all living elements in the Universe.

  THE ORIGINS OF LIFE

  The first step in understanding how the lives of stars are precursors to our own lives is to discover exactly what we are made of. There is possibly no more beautiful, and perhaps no more instructive, place on Earth to begin this journey than in the shadow of the world’s tallest mountain range. With over 100 peaks exceeding 7,200 metres (23,620 feet), the Himalayan range is truly a land of giants; nine of the ten highest mountains on Earth are part of the Himalayas. The greater Himalaya is home to forty-five of the world’s top fifty highest peaks. Spectacularly beautiful, it is the sheer scale of these mountains that hides a fascinating and instructive first step on the road to understanding the building blocks of the Universe. Despite their majesty, just a few tens of millions of years ago these mountains were something very different.

  As well as being the largest mountain range on the planet, the Himalayas is also one of the youngest. Just seventy million years ago (a very short time in geological terms) the Himalayas didn’t exist. The relentless movement of Earth’s tectonic plates shaped these mountains in a geological heartbeat. As the Indo-Australian plate collided with the Eurasian plate at the rate of about 15 centimetres (6 inches) a year, the ocean floor in between began to crumple and rise up to form the mountain range. This means that much of the rock out of which these towering peaks are made was formed at the bottom of an ocean, only to be lifted up thousands of metres into the air over a few short millions of years.

  The evidence for this extraordinary journey is not difficult to find. If you look closely at any piece of Himalayan limestone you will see it has a chalky, granular structure. What you are looking at are the petrified remains of sea creatures – the bodies and shells of coral and polyps that died millions of years ago in a long-lost ocean. Given a relatively short timescale and a bit of pressure, these biological remains are quickly converted into solid rock. Limestone can also be formed by the direct precipitation of calcium carbonate from water, although the biological sedimentary form is more abundant. We know that the Himalayan limestone is predominantly biological because we have found fossils at the top of Mount Everest! There is perhaps no better example of the endless recycling of Earth’s resources that has been going on since its formation almost five billion years ago.

  We humans are also very much part of that system. As unsettling as it may sound, every atom in your body was once part of something else. It may have made up an ancient tree or a dinosaur, and you’ll be pleased to know it was certainly part of a rock. The reason this can happen – that the rocks of Earth can become living things and that living things will eventually die and become rocks again – is simple: everything in the Universe is composed of the same basic ingredients

  When you are presented with the sheer magnitude of the Himalayas and the towering peak of Mount Everest, it
is hard to believe that these huge mountains started off life at the bottom of an ocean.

  Natural recycling at its most impressive. The Himalayan limestone has been proved to be predominantly biological, due to the quantity of fossils of sea shells and creatures that have been found at the summit of Mount Everest.

  DIRK WIERSMA / SCIENCE PHOTO LIBRARY

  Periodictable.com © 2010 Theodore Gray

  THE PERIODIC TABLE

  For many people the Periodic Table will provide a strong echo of the school science laboratory. At its simplest, this chart is a list of the chemical elements, fundamental units of matter, which were considered to be the smallest building blocks of the world. However, this table is much more than just a list. Although elemental theories of matter were first postulated in Greece, it wasn’t until 6 March 1869 that the Russian chemist Dmitri Mendeleev finally tamed the ever-expanding list of the basic constituents of matter. Mendeleev’s genius was to arrange the list of the sixty-six then-known elements into a table according to their chemical properties. In the process, the table not only provided a neat way of grouping the elements according to their properties, but also predicted the existence of eight elements yet to be discovered. Over the next thirty years, all eight were discovered, including gallium and germanium, and were found to have the exact properties predicted by Mendeleev’s table. The number of elements continued to grow, and by 1955 the one-hundred-and-first element was discovered (named Mendelevium as a tribute to the father of the Periodic Table) by a group of scientists at the University of California, Berkeley. To date, 118 elements have been categorised, the latest of which, ununseptium, was successfully synthesized and detected by a Russian– US team in April 2010.

  Starting with hydrogen and ending with plutonium, the first ninety-four elements of the Table have been found occurring naturally on Earth. These elements are nature’s building blocks; the remaining twenty-four elements, can only be created artificially and live for very short periods of time. Using these ninety-four elements you can explain all of biology and chemistry without knowing about the underlying structure of protons and neutrons, electrons and quarks. This is because you need very high energies and temperatures to break apart the elements – a condition that only exists naturally deep inside the stars.

  The first step of our journey to explain where we come from is to understand the origin of these ninety-four elements. But first we must discover how we know that everything we see in the sky is made of the same stuff as us on the ground

  THE UNIVERSAL CHEMISTRY SET

  Surprising as it sounds, we know what every star, planet and moon in the observable Universe is made of, despite the fact that there is only one other place in the Universe that humans have actually visited in person.

  On 21 July 1969, Neil Armstrong and Buzz Aldrin became the first humans to set foot on another world. They spent 2 hours, 36 minutes and 40 seconds walking on the surface of the Moon, but it wasn’t until the last half hour that they carried out one of their most important scientific tasks. Using basic geological tools, Buzz Aldrin drove two core tubes into the lunar surface to collect the most famous rock samples taken in history. By the time they’d finished hammering and scooping up samples they had collected 22 kilogrammes (47 pounds) of lunar treasure. After using a pulley system to lift their scientifically priceless cargo on board, they closed the hatch and went to bed. As the two astronauts slept alongside the precious lunar rocks, the United States could justifiably claim to have won the greatest and arguably most glorious political victory in human history. For one rare moment, a political victory was also a triumph for all mankind.

  However, it is not widely known that as the Apollo 11 lunar module rested on the Moon, a Soviet spacecraft was also in lunar orbit. The unmanned Luna 15 was the Soviets’ third attempt to land on the Moon and collect lunar rock samples. Launched three days before Apollo 11, Luna 15 was a last-ditch attempt to win the scientific race to return rock samples from another world. Unfortunately, although Luna 15 successfully began its descent to the Moon’s surface, it crashed into it shortly afterwards. Only Apollo 11 returned with moon rocks, which continue to be analysed to this day in the high-security labs of the lunar sample building in Houston, Texas.

  Despite forty years of study, one thing has been clear pretty much from the start: these priceless examples of alien geology are remarkably similar to rocks found on Earth. In the main, they are composed of the common rock-forming elements oxygen, silicon, magnesium, iron, calcium and aluminium, but there is absolutely nothing on the Moon’s surface that couldn’t be found here on Earth.

  Since Apollo 11’s success, we have landed on Mars and Venus, parachuted into Jupiter’s atmosphere, touched down on Saturn’s moon Titan, and visited asteroids Eros and Itokawa and the comet Tempel 1. Each time the story is the same; the Solar System is made of the same stuff as we are. To date, eight landings on our nearest neighbour, Mars, have allowed us to explore the planet’s geology in intimate detail. We now know Mars is rich in iron, which has oxidised to form its familiar rusty red colour, and that Martian soil is slightly alkaline and contains elements such as magnesium, sodium, potassium and also chloride. We also know that Venus’ thick atmosphere is full of sulphur, and the planet Mercury is a large metal ball of iron with a thin crust comprised mostly of silicon. Even at the very edge of the Solar System, billions of miles away from Earth, we have discovered that Neptune is rich in organic molecules such as methane, a substance we find in abundance on our planet. Again and again we find there is much to discover in our solar system, but there are never new elements to unearth. From a scientific perspective this is unsurprising, because long ago Mendeleev’s table revealed there isn’t any room for other light elements in nature – we have discovered the full set. It would take a change in the laws of physics to discover something on the surface of another world that doesn’t fit into Mendeleev’s scheme, but from the explorer’s perspective, seeing is believing!

  On 21 July 1969, Neil Armstrong and Buzz Aldrin became the first humans to set foot on the Moon. This successful landing also opened up infinite possibilities for scientists to understand the formation of the lunar landscape. This photo shows Aldrin collecting some of the lunar rock samples that they took back to Earth for analysis.

  NASA

  The Apollo 11 lunar mission was launched from the Kennedy Space Center, Florida, on 16 July 1969 and safely returned to Earth on 24 July 1969, complete with its priceless cargo of samples from the Moon’s surface. The first container was transferred to Ellington Air Force Base and was taken directly to the Lunar Receiving Laboratory at the Manned Spacecraft Center (MSC) in Houston, Texas.

  Once safely returned to Earth, the treasures from the Moon, including rock samples, were painstakingly analysed at a high-security laboratory, and are still being used for analysis today.

  NASA

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  Again and again we find there is much to discover in our solar system, but there are never new elements to unearth.

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  This false-colour photograph of Neptune was taken by Voyager 2. This image has enabled scientists to discover that the planet is rich in organic molecules such as methane.

  So what about the rest of the Universe? How universal are these elements across the far reaches of the cosmos? Could it be that there are places in the distant Universe where the laws of physics are different? This is a legitimate question – we shouldn’t simply assume that everything at the edge of the visible Universe, billions of light years away, operates exactly as it does here, no matter how persuasive the arguments from theoretical physics. Experiment and observation are the ultimate reality check. It may seem impossible to presume that we could ever answer this question directly and discover what the stars are made of, because they are so far away (they may indeed remain untouchable forever), but in fact we knew what the stars were made of long before we got our hands on that first piece of lunar rock

  WHAT ARE STARS MADE OF?
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br />   Over a simple campfire I recreated the experiments of Gustav Kirchhoff and Robert Bunsen that made such a major impact in the development of quantum theory. Just as they discovered 150 years ago, when I threw the copper into the fire it burned with a spectacular blue flame.

  The Sun, the burning star at the heart of our solar system, is 150 million kilometres (93 million miles) away from Earth. Beyond that, the nearest known star, the red dwarf Proxima Centauri, requires a journey of over four light years or forty thousand billion kilometres (twenty-five thousand billion miles). We have learnt a lot about Proxima Centauri since it was discovered by Robert Innes at the Cape Observatory, in South Africa, in 1915. It is thought that Proxima Centauri is part of a triple star system with its neighbouring binary star system, Alpha Centauri A and B, and although it cannot be seen with the naked eye, we have been able to measure its mass and diameter and chart its brightness across the last 100 years. Despite the fact that our only contact with these neighbouring stars, and with any star other than our Sun, is the light that has crossed the Universe to reach us, we have been able to go much further than simply cataloguing their vital statistics. We can measure the precise constituents of any and every visible star in the sky, because encoded in the light that rains down on Earth is the key to understanding what they are made of. It is all made possible by a particularly beautiful property of the elements.