Stellar evolution Flashcards
What are the axis on a hertzsprung - russell diagram?
Absolute magnitude from -10 at highest to 15 at lowest, and spectral class on x-axis. Or temperature from 50,000 to 2500k.
What are the 3 principal groups in the HR diagram?
white dwarfs in bottom left, giants in top right and main sequence curving through the centre.
How can we determine relative size of a star from the HR diagram?
We use stephan’s law as luminosity is proportional to area, and we are also given the surface temperature of the star.
What class is our star currently and what is it’s absolute magnitude?
class G and magnitude 5, so it’s on the main sequence.
What are the stages our sun will go through before it dies?
Main sequence star —> red giant —–> planetary nebula —–> white dwarf ——> black dwarf.
What is a supernovae?
An object which exhibits a rapid and enormous increase in absolute magnitude.
Why can a type 1A supernovae be used as a standard candle?
It always reaches the same peak value of absolute magnitude -19.3. If its absolute magnitude is known, and its apparent magnitude can be measured, we can work out its distance.
Give the key points of the type 1A supernovae light curve.
Absolute magnitude on y axis and time in days on x axis. -12 to -18 on y axis and 0 - 300 days on x axis. Curve peaks at -19.3 after 20 days and then decreases to -12 magnitude at 300 days.
What is the advantage of using type 1A supernovae as a standard candle?
They are very bright and can be used to measure distances to the furthest galaxies.
When do neutron stars form?
When a core with a mass of twice the sun collapses.
What is a neutron star?
An extremely dense object composed entirely of neutrons. It has a strong gravitational field. They can behave as pulsars, which is a rotating neutron star with a very strong magnetic field
When do black holes form?
When cores of more than 3 solar masses collapse.
What is a black hole?
A region of space-time that has such a strong gravitational field that no particles or E.M radiation can escape from it. The escape velocity is greater than the speed of light within the event horizon.
What is the density of a black hole proportional to?
1/mass squared. Radius proportional to mass and volume porportional to radius cubed (therefore mass cubed)
What is a gamma ray burst?
Bursts originating from supernovae when supergiants collapse to form neutron stars or black holes. They come from distant galaxies and are very energetic. One gamma ray burst may release as much energy in one strong burst as the sun will in it’s entire lifetime. Potentially hazardous and one burst could destroy Earth.
