Types-of-star

Types of star 

 A star begins to shine when nuclear reactions in its core convert hydrogen into helium and release energy. It is then called a main sequence star. Not all main sequence stars are the same they differ in size, temperature,colour, brightness,and the amount of matter they contain. When stars begin to run out of fuel and near the end of their lives, they stop being main sequence stars and many swell up and turn inton read giants or shrunk to become white dwarfs 

The scale of space 

The universe is so vast that we cannot appreciate its size without making leaps of scale. In this series of pictures, each nstage represents a microscopic speck of the image to its right. When dealing with the vast distances in space, kilometres aren’t big enough. Instead, astronomers use the speed of light as a yardstick. Light is so fast it can travel around Earth 7.5times in a second. One light year is the distance lighttravels in a year: nearly 10 trillion km (6 trillion miles).

Earth and Moon

Earth is 12,756km(7,926 miles) wide our nearest neighbour in space –the moon –orbites Earth at a distance of 384,400km (238,855 miles) .If Earth were the size of a football,the moon would be the size of a melon about 21 metres (69ft) away. 

Solar System 

The sun’s family of eight planets occupy a region of space 9 billion km (5.6 billion miles )wide. If Erath were a football,it would take five days to walk across this part of the Solar system. The nearest star would be a 58-year walk away. 

Stellar neighbourhood 

The nearest star to the sun is proxima centauri,wich is just over four light years away. There around 2,000 stars within 50 light years of the sun. These make up our stellar neighbourhood, which is a tiny fraction of the milky way galaxy. 

Milky way galaxy 

The Milky Way is a vast cloud of 200 billion stars. Its ahape resembles a pair of fried eggs held back to back, It measures 100,000 light years across the disk and 2,000 light years deep through the bulge.




Local Group of galaxies 

The Milky Way is just one of perhaps seven trillion galaxies in the obserable Universe.Galaxies exist in groups called clusters, held together by gravity. The Milky Way is part of a cluster known as the Local Group, wich is about 10 million ligt years wide.



Supercluster

Clusters of galaxies exist in even larger groupings called superclusters.We live in the Virgo supercluster in the known Universe.Between these are immense empty areas called cosmic voids.

Universe

Superclusters are thought to form a vast web of filaments riddled with enormous voids containing no galaxies. The true size of the Universe is a mystery, and only a fraction of it is visible to us. The Universe may even be infinite in size