Talk - Lewes Astonomers

A phone call to Matthew Hepburn, who is this week giving a talk for the Lewes Astronomers on ‘Stars: how they form and what they do’, leaves me realising how little I know about the subject. I didn’t for example; know that there are around 100 billion stars in our galaxy, and that there are around 100 billion galaxies. Or that each galaxy produces about 10 new stars a year - our galaxy has produced its 100 billion in about 14 billion years. I didn’t know that the sun is about four and a half billion years old. “We know this with quite startling accuracy,” he says. “The figure people normally give is 4.567 billion years, which is quite an easy number to remember.”

His talk is about how our ideas about star formation and their function in the universe have changed quite dramatically in the last 50 years. “We have discovered,” he says, “that it’s essential that cool molecular clouds are in existence before a star can form,” he says. By ‘cool’ he means very, very cold: “about 15-20 absolute degrees”. He will also be talking about the fact that, rather than burning all their matter up, as we previously believed, stars actually emit matter. “They are engines for changing matter and returning it to the inter-stellar medium.” This is where common elements, like carbon, hydrogen, oxygen and nitrogen come from, as well as less common elements such as iron, silicon and calcium. The conversation leaves me with more questions than answers, which is a good thing. Does this mean I am composed of stellar emissions? I feel I need to find out.