Astronomy

All the energy in a star is made in its centre (its core), by a process called nuclear fusion. The star releases the energy as heat and light. This is what makes a star shine. The outward force generated by the fusion process is balanced by the inward pull of the star's gravity. It is the balance between the two which stops the star from collapsing or expanding.

How do we measure distance? 

Knowing the distance to objects in space is important. However, measuring it is also very hard—you can't just use a ruler! Astronomers have created a range of ways to measure the distance to objects in space. 

(1) Luminosity 

This is a more physical measurement. It measures the energy output of the object. This is done by looking at how much light is given out by the object over time. 

The units of luminosity are more standard, given in Watts - much like a light bulb! A typical LED light bulb in a house might be 20 Watts - the Sun is 20 million billion billion (2 x 1025) times brighter! 

So that means there are 1,296,000 arcseconds in a circle (360 degrees × 60 arcminutes × 60 arcseconds).

Stars

What we know about stars has changed over thousands of years. Early astronomers recorded the positions and numbers of stars. They did not think that stars could change. The first catalogue of stars was made by Chinese astronomers Gan De and Shi Shenfu around 400 BCE. Astronomers soon realised that 'new stars' could appear in the sky. We know these now as supernovae. The final explosion of a massive star's life.

In 1781, William Herschel became the first person in thousands of years to discover a planet. He used a telescope he had built himself and found the 7th planet, Uranus. A few years' later in 1845, Neptune was found by both British and French astronomers. Both groups had watched the orbit of Uranus and used their data to predict there was an 8th planet. They worked out where it would be and when they looked, there it was!

Early Life

William was born in Germany but moved to England when he was 19. In England, he worked as a music teacher and spent a lot of his spare time doing astronomy. William rented a small telescope to look at the stars and planets. He dreamed of having his one of his own, so learned how to build a large telescope. He ground and polished the mirrors himself and finished building his first telescope when he was 36 years old.

Early Life

Tycho was born in Knudstrup, Denmark. His family were very wealthy and one of Denmark’s noble families. He lived with his uncle when he was young and his uncle paid for him to study Law at the University of Copenhagen. Tycho had become interested in astronomy after seeing a solar eclipse when he was 14. He preferred to learn about science and did not spend much time studying the law. When he was 20, Tycho was in a fight and lost part of his nose.

Early Life

Isaac was born in Woolsthorpe, England. For most of this childhood he was raised by his grandmother and went to a grammar school. At school, he learned Latin, Ancient Greek, and some maths. His mother wanted him to be a farmer, but Isaac hated farming. At the age of 18, Isaac went to the University of Cambridge. His uncle had previously studied there and recommended him to the university. 

Early Life

Patrick was born in Pinner, UK. He had health problems when he was young and was educated at home. As a child, Patrick was interested in astronomy. When he was 11, he joined the British Astronomical Association. At the age of 14, he was asked to run a small local observatory. Patrick trained as a pilot during World War II. After the war, he studied at the University of Cambridge.