The document discusses several topics related to astronomy and space, including: - The formation of elements like hydrogen in the Big Bang and later fusion in stars that led to heavier elements like carbon. - How satellites orbit Earth due to centripetal force balancing gravitational attraction, with examples of low polar orbits and geostationary orbits. - How planets orbit the Sun due to centripetal force balancing gravitational attraction. - How the Sun will evolve over time from its current stable phase into a red giant and later a white dwarf or neutron star/black hole.

1. In the Big Bang, only hydrogen, in the form of protons, was created. Satellites are pulled by the
About 300 million years later, the very first protostar was born. The Earth’s gravitational force of
Weather and spy satellites orbit the Earth passing over
temperatures were hot enough to allow fusion to take place. Later the first gravity. This is the centripetal
its two poles as the Earth spins beneath – low polar orbits.
galaxies formed. force without which the
The International Space Station orbits about 300km
satellite would shoot off into
above us and takes about 90 minutes to orbit the Earth!
space.
Geostationary satellites are a long way out in Space (about
36 000km) and appear to remain above the same place
The carbon in our bodies was formed
because their orbital period is 24 hours.
by fusion in a first generation star.
The elements were spread into space
by the star exploding as a supernova.
About 9 billion years after the Big
Bang, the solar system was formed
The Stars and us
when dust and gas were pulled by Satellites
gravitational attraction. We are
stardust! Planets are pulled by the Sun’s gravitational
The Moon was formed by the collision force of gravity. This is the centripetal force
of the Earth with another planet. The without which they would shoot off into
less dense material became the Moon. space.
The orbits of the planets and comets are in
Space fact elliptical. Asteroids and near-Earth
objects can crash into the Earth.
The force of gravity increases as the distance
Our Sun has been stable for about 5
between the Sun and comet decreases – so
billion years because the gravitational
comets speed up as they approach the Sun.
forces balance the radiation pressure.
The Sun heats the comet and melts its ice to
The Sun sends out solar flares – high- Centripetal forces
speed charged particles that disrupt our When Time and form a tail.
and planets
satellites.
Our Sun will become a Red Giant, then a
Space began
white dwarf.
Much larger stars will explode as a
supernova to form either a very dense When an object goes round in a circle at constant speed, it is in
neutron star or, if it is really big, a black We know there was a beginning to fact accelerating because its velocity is changing. This requires an
hole, where the gravity is so strong not the Universe because the galaxies inward pulling force – a resultant force called the centripetal force.
even light can escape. appear to be rushing away from us. It can be friction for a car going round a roundabout, or tension in a
Cosmic ra Their light is red shifted by the string, or gravity for a planet or moon.
Doppler effect. Unmanned probes have explored the Solar System and its planets
Also the radiation from the Big Bang such as Voyager and the Mars Explorer robot – they can withstand
is still around us – the microwave the lethal environment of Space, such as cosmic rays.
background radiation, which we can
pick up with our TV aerial.