Episode 26: A Star is Born...


Two centuries ago William Herschel placed a thermometer below the red end of a spectrum of light from prism. He recorded a rise in temperature. He had discovered infrared or heat radiation. It is only in the past quarter-century, with telescopes on high mountain peaks and in space that infrared astronomy has come of age.

Infrared is able to peer inside dark clouds that mask regions of the galaxy such as the Orion Nebula from optical telescopes. Within these clouds we can now see the processes through which the gas clouds contract, heat up and ignite to give birth to a new generation of stars.

Episode 27: The Life and Death of Stars ...

Until the modern era of astrophysics, no one knew what made stars shine. Could they be burning coal? Or heating due to gravitational contraction? The answer arose from the nuclear age: the sun and stars are like giant hydrogen bombs -- controlled nuclear explosions.

In the 1950s, Fred Hoyle and his colleagues worked out the details and showed how new elements are created in stars as they burn hydrogen and helium. In the case of relatively small stars such as our Sun, the fuel eventually runs out, the bloated outer layers are lost into space and a slowly cooling white dwarf remains. But massive stars begin to collapse in on themselves when fuel runs out at the core, creating a massive explosion, a supernova.

Episode 28:A Plethora of Planets ....

Ever since the book of Genesis was written, people have been speculating on the origin of the Earth and other planets. As long ago as 1755 the philosopher Imanuel Kant suggested that our solar system may have been born from a rotating cloud or nebula of gas and dust. But it was not until an infrared telescope was sent into space in 1983 that astronomers began to gather images of such dusty discs around other young stars.

A forming planet must be a dangerous place. In 1955 Eugene Shoemaker showed that meteor crater in Arizona was blasted out by the impact of a large rock from space. He went on to show that most of craters on the Moon resulted from impacts too, early in the history of the solar system. The dawn of the space age is enabling us to begin to explore the rocks in our cosmic backyard and speculate about worlds beyond.

Episode 29: Worlds Beyond ...

In the 16th century, Giordano Bruno speculated that there must be other earthlike planets in the universe. He was burned at the stake for this and other heresies and no one could test his predictions.

Even today, with the best telescopes in the world, it's impossible to see planets around distant stars -- harder than spotting a firefly next to a searchlight. But in the last decade, astronomers have gathered indirect evidence for around 300 other planetary systems. They've been spotted by the way in which they make their parent stars wobble as they orbit around them. The easiest to detect and hence the first to be found were the most amazing: planets bigger than Jupiter orbiting so close to their star that they are almost touching. But now, evidence is emerging for solar systems more like our own, some with multiple planets, some with planets that may even be Earth-like.

Episode 30: Are We Alone?

In this series we have seen our place in the universe demoted from the central hub about which everything revolves to an insignificant lump of rock in orbit around a typical star in the outer suburbs of one galaxy among billions. The distances are unimaginable; the cosmic violence unforgiving. But are we alone in this cold, dark universe? Is Earth the only planet where life has a toehold and are we the only technological civilisation to send messages to the stars?

In this final episode, Heather Couper looks at the prospects for life elsewhere in our own solar system - could evidence of life have even been discovered already on Mars? And she tells the story of the search for extra-terrestrial intelligence as scientists scan the skies for messages from the stars.

Friday 4 July 9.00pm - Omnibus edition

Astronomer and writer Heather Couper presents an omnibus edition of the final episodes in her narrative history of astronomy and our place in the cosmos.

This series has followed the changing human perspective on the universe from the early days when the agricultural year was governed by the daily and seasonal cycles of the sun and moon, through past civilisations whose astrologers believed that the constellations mapped their lives in detail, to the present age when we can probe the furthest reaches of the physical universe.

At each stage, models of the universe have reflected the metaphors of the age. From the clockwork mechanisms and musical harmonies of the 18th century, through the thermodynamics of the steam age and the cosmic violence of the nuclear age to the more organic metaphors of today. In this final compilation we hear of the birth, life and death of stars, the formation of planets and the search for earth-like worlds beyond our own. Finally we ask if there could be other lifeforms, even intelligence, out there in the vastness of space.