Stars Flashcards
What are the characteristics of a planet?
It has a mass large enough to be given a round shape, it has no fusion reactions and it has cleared its orbit of most other objects.
What is the main difference between planets and dwarf planets?
Dwarf planets are generally smaller than planets and have not cleared their orbits of other objects such as asteroids.
What are asteroids?
Objects that are too small and uneven to be planets, without the ice present in comets.
What is a planetary satellite?
A body in orbit around a planet. (eg moons or man-made satellites)
What are comets?
Small irregular objects mostly made out of ice that orbit the Sun in highly elliptical orbits.
What is the solar system?
A collection of the Sun and everything that orbits it.
What is a galaxy?
A collection of stars and interstellar dust and gas. On average a galaxy will have about 100 billion stars.
What masses of stars will evolve into red giants?
Stars between 0.5 and 10 solar masses.
What causes stars to become red giants?
They begin to run out of hydrogen in their cores, reducing the outwards pressure so the core shrinks, increasing the pressure around the core which causes the fusion to restart in a ring around the core, making the outer layers of the star grow.
What causes a star to change from a red giant into a planetary nebula?
The outer layers of the star are shed off into space, leaving a planetary nebula with a hot white dwarf at the centre.
What is the Chandrasekhar limit?
When the mass of the core of a star is 1.44 times the solar mass.
What stars can fuse helium in their cores?
Stars with a mass greater than 10 solar masses as there is enough gravitational pressure in the core to fuse helium.
What is the last element that can be created by fusion in a star’s core?
Iron.
What are the 2 axes on the Hertzsprung-Russell diagram?
Decreasing temperature on the x-axis and luminosity on the y-axis.
What is luminosity?
The total radiant power output of the star.
What is an energy level of an electron?
The amount of energy required for the electron to leave its atom.
What is an emission line spectrum?
A spectrum where each energy level in an element produces a unique emission line.
What is a continuous spectrum?
A spectrum where all visible frequencies or wavelengths are present.
What is an absorption line spectrum?
A continuous spectrum where there are a series of dark spectral lines from where the light has passed through a gas.
What is a black body?
A theoretical object that completely absorbs all electromagnetic radiation and it emits a characteristic distribution of wavelength at a specific temperature.
What is Wien’s Displacement Law?
The peak wavelength from a black body is inversely proportional to its absolute temperature.
What is Stefan’s Law?
The total power radiated per unit area of a black body is directly proportional to the 4th power of its absolute temperature.
