P8 definitions Flashcards
White Dwarf
When the fusion reactions in stars of a similar magnitude to the sun
come to an end, the star will contract under gravity and cool down to form a white
dwarf.
Supernova
The explosion of a massive star, that distributes the elements
created by the fusion reactions in the star, throughout the universe.
Sun
A star formed from a cloud of dust and gas being pulled together by
gravitational attraction. Fusion reactions occur in the sun.
Red-Shift
The observed increase in the wavelength of the light emitted by
distant galaxies. The more distant the galaxy, the faster it is moving and so the
bigger the observed increase in wavelength
Red Giant Star
When their hydrogen is used up and larger nuclei are produced
by fusion, stars of a similar magnitude to the Sun will expand to form a red giant.
Protostar
The first stage all stars go through after forming from a nebula. In this
stage the star becomes hot enough for hydrogen nuclei to fuse.
Nebula
A cloud of dust and gas.
Natural Satellites
: The moons that orbit planets.
Main Sequence Star
The stable state of all stars. The gravitational forces
pulling the star together, and the pressure pushing outwards, are balanced.
Dark Mass
A hypothesised type of mass that cannot be observed by current
methods. It is used to explain why some galaxies rotate faster than they should for
their observed mass.
Dark Energy
A hypothesised form of energy, believed to be responsible for the
universe’s ever increasing rate of expansion.
Circular Orbits
Planets and satellites travel in circular orbits. Gravity provides
the required force for these orbits.
Big Bang Theory
The currently accepted model for the origin of the universe. It
suggests that the universe has expanded from an initially very small, hot and
dense point.
Artificial Satellites
Man-made satellites that have been sent into space for
purposes such as satellite imaging and communications.
