Astro physics Flashcards
A galaxy is
a collection of stars, interstellar dust and gas
A nebulae is
a gigantic cloud of dust and gas, often many hundreds of times larger than our solar system
A planet is
an object in orbit around a star with three important characteristics:
it has a mass large enough for its own gravity to give it a round shape
It has no fusion reactions
It has cleared its orbit of most other objects
A planetary satellite is
a body in orbit around a planet
Examples of planetary satellites are
includes moons and man made satellite
A comet is
a small irregular body made up of ice, dust and small pieces of rock
An asteroid is
an object that is too small and uneven to be a planet
A dwarf planet is
like a planet but it has not cleared the orbit of other objects
What is the life cycle of stars with mass between 0.5-10 solar masses?
Main sequence - red giant - white dwarf
What is the life cycle of a star with mass greater than 10 solar mass?
Main sequence - red supergiant - supernova - neutron star/black hole
What is the electron degeneracy pressure?
A quantum mechanical pressure created by the electrons in the core of a collapsing star due to the Pauli exclusion principle
What is the Chandrasekhar limit?
The mass of a star’s core beneath which the electron degeneracy pressure is sufficient to prevent gravitational collapse, 1.44 solar masses
Describe a neutron star?
A star made up of almost entirely neutrons, can be very small-just 10km in diameter, they have a typical mass of 2 solar masses, and has a density similar to an atomic nucleus
When does a star collapse into a black hole?
When the core has a mass greater than 3 solar masses
Why are energy levels negative?
external energy is required to remove the electron from the atom
What is the ground state?
The energy level with the most negative value possible for an electron within an atom - the most stable energy state for an electron
What is an emission line spectrum?
each element produces a unique emission line spectrum because of its unique set of energy levels
What is an absorption spectra?
this type of spectrum has a series of dark spectral lines against the background of a continuous spectrum. The dark lines have exactly the same wavelengths as the bright emission spectral lines for the same gas atoms
What is a continuous spectrum?
All visible frequencies are present
What is meant by quantised energy levels?
The energy levels can only exist in certain discrete values
How is an absorption spectrum formed?
When light from a source that produces a continuous spectrum passes through a cooler gas
What is a diffraction grating?
A glass or plastic slide on which as 1000 lines in a millimeter are ruled, at a spacing that diffracts visible wavelength of lights
What is a black body?
An idealised object that absorbs all the em radiation incident on it and when in thermal equilibrium emits a characteristic distribution of wavelengths at a specific temperature
What three things is the luminosity of a star proportional to?
Its radius squared
Surface area
its surface temperature to the fourth power
