What is Astronomy ?

Astronomy is the scientific study of celestial objects.

Celestial objects are objects such as stars, planets, moons, asteroids, and galaxies.

Stars

A star is a sphere of gas that is hot and dense enough for nuclear fusion to happen in its core.

Planets

A planet is a large spherical object that orbits (travels around) a star.

Moons

A moon is a large object that orbits (travels around) a planet .

Asteroids & Comets

Asteroids & comets are chunks of rock and metals (Asteroids) or dust and water-ice (Comets) left-over from the creation of the solar system.

Galaxies

Galaxies are huge collections of billions of stars, dust and gas that are held together by gravity.

Distances In Space

Light travels at 300,000,000 ms^-1 or 3x10⁸ ms^-1.

In most cases, this is so fast that can we assume that Light moves instantaneously.

Scientific Notation

The x10^number is ‘how many places to the left (positive) or right (negative) have you moved the decimal point ?’.

For Example -

4500 m = 4.5x10³ m (d.p. 3 to left)

660,000 m = 6.6x10⁵ m (d.p. 5 to left)

0.002 m = 2x10^-3 m (d.p. 3 to right)

0.000007 m = 7x10^-6m (d.p. 6 to right)

Scientific Notation on a calculator

All scientific calculators will have either a button labelled ‘x10^x’ or ‘exp’.

Distances in Space

Space is so huge, however, that even Light takes a large amount of time to travel these distances.

This means that when we look into Space, we are actually looking back through time!

In our Solar System, measurements are usually made in Astronomical Units (A.U.).

1 A.U. = Distance from the Earth to the Sun (1.5x10¹¹ m)

In our galaxy, measurements are usually made in Light-Years.

1 ly = Distance travelled by Light in one year ( 9.5x10¹⁵ m )

To distant galaxies, measurements are usually made in Megaparsecs.

1 Mpc = 3.26x10⁶ Light-Years ( 3.1x10²² m )

Below shows some example conversions:-

As an Astronomer or Astrophysisist, you would observe and study huge stars and planets or tiny particles in space to help us understand more about how the universe works.

You'd take part in big research projects to look at objects and events in space. You'd collect data from the research and work out what it tells us about the origin and structure of the universe.

You'd use computers, optical and radio telescopes, spectroscopes, satellites, spacecraft and space probes to collect and analyse information.

You might specialise in observational and theoretical astronomy or focus on a particular topic, like planetary science or the formation of galaxies.

As well as working in laboratories and observatories, you could also work in a museum or planetarium, or teach and carry out research at a university.

You'd normally study for a postgraduate qualification such as a PhD when you are working as a professional astronomer. You'd go to conferences and keep up to date with new ideas and evidence.