W9 L1 - Life cycle of stars

Question 1

Up to what size are low mass stars

Answer 1

Equal to or less than 8 solar masses

Question 2

Protostars evolve into what type of stars on the HR diagram?

Answer 2

Main sequence stars

Question 3

What does the position of a star on the HR diagram depend on?

Answer 3

Its initial mass

Question 4

Roughly how long does it take for a star the size of the sun to condense and enter the main sequence?

Answer 4

30 million years

Question 5

Do stars of higher mass form faster or slower than the sun?

Answer 5

Faster

Question 6

Do low mass stars form faster or slower than the sun?

Answer 6

Slower

Question 7

What are the three categories of stars?

Answer 7

High mass, solar mass or sun-like, and low mass

Question 8

What proportion of their life do stars spend on the main sequence?

Answer 8

90%

Question 9

Which zone dominates in high mass and low mass stars respectively?

Answer 9

High mass = conduction, low mass = convection

Question 10

What part of their mass do high mass stars have access to for fuel?

Answer 10

Only the part at their core

Question 11

What is the rough equation for lifetime of a star?

Answer 11

Lifetime = mass / luminosity

Question 12

How long can the lifetime of an M-type star be?

Answer 12

10^11 years

Question 13

What proportion of the gas in a nebula might usually be converted to stars?

Answer 13

About 30%

Question 14

Which stars form most commonly from a nebula?

Answer 14

Small stars

Question 15

What are the two types of star clusters?

Answer 15

Open and globular

Question 16

Which are older: open clusters or globular clusters?

Answer 16

Globular clusters

Question 17

what type of star cluster did our sun form within?

Answer 17

Open cluster

Question 18

What is an isochrone diagram used for?

Answer 18

Dating a cluster by working out the position of the stars on the HR diagram

Question 19

Where are most of the stars on the HR diagram for the Matariki cluster?

Answer 19

On the main sequence

Question 20

What age is the Matariki open cluster?

Answer 20

Roughly 100 million years

Question 21

What are the 3 steps for a low mass star when it leaves the main sequence?

Answer 21

Red giant, planetary nebula, white dwarf

Question 22

What are the 3 potential steps in the fork of the life of a high mass star when it leaves the main sequence?

Answer 22

Supergiant, supernova, then either neutron star or black hole

Question 23

What is the upper limit on how big stars can get?

Answer 23

Roughly 150 solar masses

Question 24

Roughly how long will the sun spend in the main sequence?

Answer 24

10 billion years

Question 25

Roughly how long will our sun spend as a red giant?

Answer 25

1 billion years

Question 26

How long will the sun spend as a planetary nebula?

Answer 26

A few thousand years

Question 27

What happens to the core of our sun at “core exhaustion” as it transforms to a red giant?

Answer 27

1) core H runs out, 2) inert helium core contracts from gravity, 3) H shell around core contracts, 4) H fusion occurs faster

Question 28

What is the Helium flash?

Answer 28

Core gets hot enough to fuse helium to carbon

Question 29

Will the Sun fuse beyond carbon and oxygen?

Answer 29

No

Question 30

Roughly what size will the sun be as a white dwarf?

Answer 30

The size of the earth

Question 31

At roughly what size do Type 1A Supernovae occur?

Answer 31

About 1.4 x the mass of the Sun

Question 32

Where do most of the fused elements accrete?

Answer 32

At the core