Wonders of the Universe - Brian Cox [37]
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,