Astrophysics Flashcards
what is meant by the terms Universe?
Universe is a large collection of billions of galaxies
What are the 4 things that gravity causes?
- causes moons to orbit planets
- causes the planets to orbit the sun
- causes artificial satellites to orbit the earth
- causes commits to orbit the sun
what are the differences between orbits of comets, moons, and planets?
- Comets have highly elliptical orbits, with the Sun at one focus. When they come in close to the Sun they speed up, due to the larger gravitational force on them.
- Moons have circular orbits and planets orbit in slightly squashed circles, called ellipses.
Describe the evolution of stars of similar mass:
- nebula
- star(main sequence)
- red giant
- white dwarf
Describe the evolution of stars with a mass larger than the sun:
detailed version
- After the stable period, a giant star expands into a red supergiant.
- When it finally runs out of nuclei to fuse it collapses due to the gravitational force and then explodes
- The explosion throws dust and gas back into space and so another nebula is formed.
- A dense core remains
- If its mass is large enough it can compress further to become a black hole.
simple version
after stable period -> giant star -> red super giant -> runs out of nuclei -> collapses (because of gravitational force) -> explodes -> throws dust and gas into space -> nebula -> dense core remains -> if mass large enough -> black hole
what is meant by the term galaxy?
A Galaxy is a large collection of billions of stars (our solar system is in the Milky Way galaxy)
what galaxy is our solar system in?
the milky way galaxy
what does an object’s gravitational field strength depend on?
depends on it’s mass
what does it mean when we say the moon has less mass than the earth? (aprox. 1/6 of the earth’s mass)
it means that the moon’s gravitational field is much weaker.
how strong will the gravitational field be on a planet with a large radius?why?
- the gravitational strength will be weaker.
- because the surface is further away from the centre of the planet
what is gravitational strength?
the gravitational force applied per unit mass.
what 2 stars with the exact same spectrum indicate?
- that they should be of similar brightness
- if one is dimmer it means it is further away (This can be used to estimate the distance of stars)
what does the spectrum of light indicate?
it indicates how bright the stars are
what is the colour of a star related to?
it is related to its temperature
how many groups can stars be classified to according to their colour?
what are they?
- 7 groups
- O, B, A, F, G, K, M
- O are hottest ((> 33 000 K)
- M are the coolest (2000 – 3700K)
