W9 L1 - Life cycle of stars Flashcards
Up to what size are low mass stars
Equal to or less than 8 solar masses
Protostars evolve into what type of stars on the HR diagram?
Main sequence stars
What does the position of a star on the HR diagram depend on?
Its initial mass
Roughly how long does it take for a star the size of the sun to condense and enter the main sequence?
30 million years
Do stars of higher mass form faster or slower than the sun?
Faster
Do low mass stars form faster or slower than the sun?
Slower
What are the three categories of stars?
High mass, solar mass or sun-like, and low mass
What proportion of their life do stars spend on the main sequence?
90%
Which zone dominates in high mass and low mass stars respectively?
High mass = conduction, low mass = convection
What part of their mass do high mass stars have access to for fuel?
Only the part at their core
What is the rough equation for lifetime of a star?
Lifetime = mass / luminosity
How long can the lifetime of an M-type star be?
10^11 years
What proportion of the gas in a nebula might usually be converted to stars?
About 30%
Which stars form most commonly from a nebula?
Small stars
What are the two types of star clusters?
Open and globular
Which are older: open clusters or globular clusters?
Globular clusters
what type of star cluster did our sun form within?
Open cluster
What is an isochrone diagram used for?
Dating a cluster by working out the position of the stars on the HR diagram
Where are most of the stars on the HR diagram for the Matariki cluster?
On the main sequence
What age is the Matariki open cluster?
Roughly 100 million years
What are the 3 steps for a low mass star when it leaves the main sequence?
Red giant, planetary nebula, white dwarf
What are the 3 potential steps in the fork of the life of a high mass star when it leaves the main sequence?
Supergiant, supernova, then either neutron star or black hole
What is the upper limit on how big stars can get?
Roughly 150 solar masses
Roughly how long will the sun spend in the main sequence?
10 billion years
Roughly how long will our sun spend as a red giant?
1 billion years
How long will the sun spend as a planetary nebula?
A few thousand years
What happens to the core of our sun at “core exhaustion” as it transforms to a red giant?
1) core H runs out, 2) inert helium core contracts from gravity, 3) H shell around core contracts, 4) H fusion occurs faster
What is the Helium flash?
Core gets hot enough to fuse helium to carbon
Will the Sun fuse beyond carbon and oxygen?
No
Roughly what size will the sun be as a white dwarf?
The size of the earth
At roughly what size do Type 1A Supernovae occur?
About 1.4 x the mass of the Sun
Where do most of the fused elements accrete?
At the core
