Since the beginning, it's been obvious to many forms of life - not just humans - that there is a very large, very hot object in the sky. However it's only humans who have the intellectual ability to ask questions about what the Sun actually is.
Quite rightly, the Sun has been revered in culture as a force that maintains life and literally holds the planets together. And almost all the energy that powers civilisation is directly or indirectly sourced from the Sun.
The nature of the Sun has been an elusive question, with many explanations; some good, some not so good. One of the better early examples was the Greek philosopher Anaxagoras, who reasoned that it's a giant flaming ball of metal that is larger than the area of Greece where he lived.
A more rigorous understanding of the Sun had to wait for the arrival of modern science with pioneers such as the astrophysicist Cecilia Payne-Gaposchkin (born 1900) .
It took a bold challenge by Payne to overturn the orthodox view that the Sun and Earth are of similar composition. In her 1925 doctoral thesis, she suggested that stars are in fact composed almost entirely of hydrogen and a smaller amount of helium.
Although the Sun does contain some silicon, carbon and other metals, they are about a million times less abundant.
Payne's discovery then led to the conclusion that hydrogen is the most common element in the universe (the so-called missing 'dark matter' is another story) .
To make her discovery, she primarily used the techniques of spectroscopy, which famously began when Isaac Newton used a prism to split light. Later scientists revealed that an element creates a unique fingerprint by selectively absorbing parts of the spectrum ('absorption lines').
As typically occurs in these stories, Payne's thesis was heavily criticised by people such as the astronomer Henry Russell which caused her to lose confidence in her work.
Russell subsequently wrote a paper which indicated he'd changed his mind. Although he briefly acknowledged Cecilia Payne, he is often given credit for the work.
Others persuaded Payne to move to a different field, but she later regretted it, writing, "I wasted much time on this account.... My change in field made the end of the decade a sad one."
However she did return to spectroscopy, using it to study stars called 'cepheids' that vary their brightness. That proved crucial to our understanding of the universe because it allows us to calculate the distance to other stars.
Cecilia Payne's work was hugely significant, and not just for advancing our understanding of the universe, but because she - and other women astronomers - pushed aside barriers in a male-dominated field.
She inspired women such as Joan Feynman who'd been discouraged from pursuing science by her mother and grandmother who said that women were not capable.
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