Institute of Astronomy


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An exoplanet...?

Published on 28/02/2011 

What is an Exoplanet?

An exoplanet (short for extra-solar planet) refers to planets that are orbiting stars other than our Sun. So far more than 500 have been found, through a variety of different methods, but this number is always growing! (for an up to date count see

The first exoplanets were found in 1992, orbiting a pulsar, a star that has reached the end of its lifespan and collapsed to form a very dense object rotating much faster than our Sun. These exoplanets would not be a very good place to visit, due to the large amounts of radiation given off by the pulsar. The first planet discovered around a more Sunlike star, 51 Peg b, would also not be a nice place to visit - although its star is more like our Sun, this exoplanet is what we call a 'Hot Jupiter', as it's a large gaseous world (like the planet Jupiter in our Solar System) and orbits very close to its host star (and so is very hot) - in fact 51 Peg b completes one orbit of its host in only 4 (Earth)days!

Black holes

Published on 24/02/2011 

What is a Black Hole?

Black holes are some of the strangest object in space due to the effects they have on absolutely everything, even light!

A black hole is an area in space with extremely strong gravity. The gravity is so strong around black holes that once you get within a distance called the 'event horizon' of them, nothing can escape and everything is trapped within the black hole. This includes matter which makes up the world around us as well as light - and if light can't escape, as far as we know nothing can!


Published on 24/02/2011 

What is a star?

A star is a huge sphere of hot, glowing gas. The star produces its own heat and light through a process called nuclear fusion. This process forces lighter chemical elements to become heavier chemical elements. When this happens a large amount of energy is released and this energy is what causes the star to heat up and 'shine'.

Stars come in a range of sizes and colours. Our Sun is a fairly typical yellow or G type star. Stars which are hotter than our Sun tend to look bluer while those which are cooler look red. So the next time you look at the night sky, see if you can see stars of different colours!


Published on 23/02/2011 

Why is Pluto no longer classified as a planet?

In recent years, better observations have lead to the discovery of a number of small bodies of similar size to Pluto in the Solar System. These include Ceres, found in the Asteroid Belt between Mars and Jupiter, and Eris, found beyond Pluto.

In light of these discoveries, if Pluto were still to be classified a planet, then these other bodies should also be called planets, meaning there would be far more than the nine (or now eight) with which we are familiar. The International Astronomoical Union therefore decided to define the term 'planet' to include the eight in our solar system and to define Pluto and other similar sized objects 'dwarf planets.'