Universe - Overall Study Flashcards
What are all stars born out of?
Stellar nebula; molecular cloud
State the life cycle of a massive star
Stellar nebula –> massive star –> red supergiant –> supernova –> black hole or neutron star
State the life cycle of an average star
Stellar nebula –> average star –> red giant –> planetary nebula –> white dwarf
Define luminosity in terms of a star’s energy.
The rate at which a star produces energy
Which spectrum shows the true colour of a star?
Emission spectrum
TRUE or FALSE
The lower the number in the B-V colour index, the bluer the star.
True
What is the blue and green filters used to find the colour of stars called?
B-V Colour Index
What is the colour of a star dependent on?
Temperature
When two hydrogen atoms fuse, what element is created?
Helium
What process does a star produce its energy from?
Nuclear fusion
Who proposed the heliocentric model?
Nicolaus Copernicus
Who proposed the geocentric model?
Claudius Ptolemy
How does a geocentric and heliocentric model differ?
Geocentric: Earth at the centre
Heliocentric: Sun at the centre
Where is the best place for an optical telescope to be placed?
At a high altitude with low light pollution.
TRUE or FALSE
The further away a star, the more it appears to move due to parallax.
False
It appears to move less.
What is the formula for calculating distance to a star in parsecs?
Distance to star (in pc) = 1
———————–
parallax angle in arcseconds
How do we know the universe is moving away from us?
Because when astronomers look at the spectra from distant galaxies, they find the emission lines are commonly shifted towards the red part of the spectrum
How are galaxies classified?
Their shape according to the Hubble galaxy classification scheme.
How do we know about other planets outside the Milky Way?
Because planets don’t emit light, they only reflect it from stars, they create miniature eclipses when passing in front of their stars
What is the limit (of distance) that parallax is used?
Around 100 light years
How fast does light travel?
300 million metres per second (3*10^8m/s)
Define Hubble’s Law.
The further away a galaxy is, the faster it is moving away from Earth.
Define recessional velocity.
The relative rate at which a star is moving away from Earth
Define dark energy
A theoretical force responsible for accelerating the expansion of the universe