 When we look at the scale of the universe we have to start looking at some big numbers. For example –  The age of the universe – seconds  Mass of the Sun – kg  Distance to the furthest galaxy – m 

 Given that the Universe is such a big place, there are lots of things in it.  We are only going to consider the bits that we can see and can prove that are there.... Dark matter is not on the list!

 A galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust.  Galaxies are categorised according to their apparent shape.

 A common form is the elliptical galaxy, which has an ellipse-shaped light profile.

 Spiral galaxies are disk-shaped with dusty, curving arms.

 Galaxies with irregular or unusual shapes are known as peculiar galaxies, and typically result from disruption by the gravitational pull of neighboring galaxies.

 The closest galaxy to our own is the Andromeda Galaxy at a distance of 2.5 million light years but the gap is closing at km/hour. Out of at least 100 million galaxies in the universe, this is the only one we have observed moving towards us.

Galaxies usually have a nucleus with a greater concentration of stellar matter and a central bulge. All of the star rotate around the nucleus and the further away they are, the longer the period of rotation. The Sun takes about 230 million years to complete one rotation.

 These emit EM radiation so are therefore the ‘blackbodies’ in the sky.  There are a few thousand that apparent to the naked eye but many more that are not.  Like galaxies, these can be broken down into many different classes.

 The definition of a planet is a relatively cold body orbiting a star.  Some of our closest planetary neighbours are visible to the naked eye.

 A moon is a satellite of a planet.  We only see moons because, like planets, they do not produce their own light but reflect light from the local star.

 These are clumps of dust and ice in highly elliptical orbits around the Sun.  Due to their highly elliptical orbit, they are seen infrequently, and those on a hyperbolic path are only seen once.  The tails of the comet are visible when close to the sun.  The tails are the melting ice and ionised particles.

 These are pieces of rock that are in the path of the Earths orbit.  As the rock enters the atmosphere, it heats up and burns.  Most burn up entirely but some make it through the atmosphere and impact on Earth.  Evidence of meteor collisions are very apparent on the Moon (there is no atmosphere to burn them up)

 Lyrids – April 22 nd  Aquarids – May 5 th – 6 th  Perseids – August 12 th – 13 th  Draconids – Ocober 7 th – 8 th

 A binary star system consists of 2 stars that rotate around each other.  The distance between them is not fixed (depends on the size of the system) neither is the period of orbit.

 Stars with an original mass greater than 8 solar masses become supergiants.  Just as the red giants collapse under their gravitational forces so do these supergiants but more spectacularly.  Due to their incredible mass, the outer shells accelerate to the iron core which collapses quickly, combining the protons and electrons present to form neutrons.

 The formed neutrons are very tightly packed and this combination takes less than a second.  This collapse is accompanied by a rapid rise in temperature and this intense radiation pressure causes the star to explode and eject the outer layers of the star.  This is what is known as a supernovae and may emit, for a few days, as much radiation as a whole galaxy.

 Part of the stars core, after a supernovae explosion may remain.  The core of a collapsing supergiant is compacted so much that the protons and electrons are pushed together to form neutrons.  The density of such a star would be a hundred million times greater than a white dwarf.  A teaspoon of material would have a mass of several million tonnes.

 Since these stars have such a small surface area, they emit insufficient radiation for visual or thermal observation.  As with other stars, these have a magnetic field but due to the density, this field is billions of times stronger.  If the magnetic field is at an angle with axis of rotation, the electrical field created would accelerate charged particles along the magnetic axis.  This causes a narrow beam of radiation to be emitted from around each magnetic pole.

 As the star rotates on its axis these beams sweep out a path in space.  If a detector happens to lie in its path it will receive a short burst of radiation – a pulse.  Hence rotating neutron stars are called PULSARS.

 A black hole is a region of space time in which gravity is so strong that not even light can escape.  This occurs if the neutron core is greater than about 2.5 solar masses.  Collapsing under its own gravity after its nuclear fuel is exhausted it becomes a cosmic vacuum cleaner!

 This theoretical collapse of a non- rotating mass to a singular point of zero volume and infinite density is called a singularity.  There are a number of observations that point towards the existence of a black hole.  Mass calculations of binary stars suggest that the invisible partner star is too massive to be any other end state. As material is accreted from the companion star it becomes hot and starts to emit x-rays. These strong x-ray signals from a single star system with the mass loss indicate the presence of a black hole.

 Very distant but VERY powerful  Possibly the formation of new galaxies with black holes at their centre.