1.9 What are we made of? 9 November, 2013. Key words Nuclear fusion Life cycles.

1.9 What are we made of?April 10, 2023

Key words

• Nuclear fusion

• Life cycles

Stars and Earth stuff

• Scientist can now spread light into spectra and study the colour present

• If light is shone through different elements then each produces its own unique finger print

• Dark lines show areas where light is absorbed• Analytical scientists use this information to

determine what chemical are present in a sample

The sun

• The sun is a light source. Its light tells us how hot it is, and what it is made of

• When astronomers first looked at the spectrum of sunlight, they were amazed to find similar patterns to those seen in the laboratory

• They looked at other stars – the same 92 elements everywhere

Nuclear fusion

• Scientists once struggle to understand the Sun

• It could not be a ball of gas on fire as it would have burned up long ago

• It was found that atoms have central cores called nuclei, joining these together releases a lot of energy and new elements are created

2mcE

bombs Hiroshima 1000About

109

1031

103

1

16

218

18

2

JE

mskgE

msc

kgm

mcE

A star is born• Gravity pulls a star together from hydrogen

gas• The hydrogen gas collapses, faster and

faster• Some of the nuclei collide fast enough to

overcome repulsion• Fusion begins• Fusion releases heat to keep the

temperature high, the nuclei fast and gravity balanced

Heavy elements

• The most common element in the Universe is hydrogen

• In stars, fusion continues to make heavier and heavier elements up to iron

• When a star explodes in a supernova all the heavier elements are formed

• This is what you and I are made of – star dust!

Questions

• How can scientists find out about (a) temperature and (b) chemical elements in the outer layers of a star

• How do you know that the Sun is not a ball of gas on fire

• Scientists believe that hydrogen, helium and a little lithium were the only elements in the Universe before they were stars. There are 92 natural elements on Earth. Where did they come from?