How we measure space

Measuring distance in space is pretty complicated. Over the years scientists have come up with a few different ways of measuring - or calculating the distance - between astronomical objects.

The most widely known unit of measure is the "light year". One light year is the distance light can travel in one year - approximately 9.5 trillion kilometres. It is mainly used to calculate distances on a galactic scale and is mainly used by popular science publications for the general public.

A more commonly used scientific measure is an "astronomical unit". The astronomical unit is the average distance between our planet Earth and the Sun. It is a fixed number equal to 149,597,870,700 metres - almost 150 million kilometres. Astronomical units are mainly used to measure things within our own Solar System. An astronomical unit is represented by the symbol "au" and the Earth is therefore described as being "1au from the Sun". By comparison Jupiter is aproximately 5.2au from the Sun.

The unit of measure most commonly used by scientists is the "parsec". A parsec is equal to 3.2615638 light years or 206,264.81 astronomical units. It is the measure used most often to describe distances between our Solar System and distant galaxies.

So...

1 parsec ≈ 206264.81astronomical units ≈ 3.2615638 light years

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