05 life cycle of stars

Question 1

Stars are formed from

Answer 1

nebulas

Question 2

What are nebulas?

Answer 2

massive clouds of gases and dust (primarily Hydrogen and Helium)

Question 3

When the nebula reaches a certain density,

Answer 3

gravity pulls the gas and dust creating dense regions called a PROTOSTAR.

Question 4

The protostar keeps pulling in matter until it is so tightly packed that

Answer 4

nuclear fusion (hydrogen atoms fuse to form helium atoms) starts and it becomes a star.

Question 5

Where stars spend about 90% of their lives is…

Answer 5

the main sequence, where hydrogen atoms in the core are fusing into helium, releasing energy

Question 6

Once they have exhausted the hydrogen fuel in their cores, stars turn into…

Answer 6

red giants, which starts to burn helium and other heavier elements

Question 7

Small to medium star
(<5 solar masses)
Death and Remains

Answer 7

Core shrinks becomes hot, dense white dwarf star
White dwarf cools and fades forming a black dwarf

Question 8

Large star
(10-30 solar
masses)
Death and Remains

Answer 8

Core collapses and
outer layer explodes as
supernova

Core becomes
neutron star (very
dense star made of
tightly packed
neutrons)

Question 9

Extremely large
star
(>30 solar
masses)
Death and Remains

Answer 9

Core collapses and
outer layer explodes as large
supernova

Core becomes
black hole
(extremely dense
matter which no
light or matter can
escape)

Question 10

Life Cycle of the Sun

Answer 10

Sun was born from a nebula 4.6 billion years ago

The sun grew larger, eventually causing nuclear fusion

The sun is currently stable and about halfway through its life cycle

In ~3 billion years the sun will run out of hydrogen in its core, expand, and become a red giant

As the red giant burns out it will collapse into a planetary nebula and the core will contract into a white dwarf

Once all energy is exhausted it will theoretically become a black dwarf

Question 11

Given the following data:

Star A Star B
Apparent Magnitude:
-26.8 0.41
Absolute Magnitude:
4.83 -5.6

1. Which star ‘appears’ brighter from earth?
2. Which Star is actually brighter?
3. Which Star is closer to earth?

Answer 11

1. A because it has a lower apparent magnitude
2. B because it has a lower absolute magnitude
3. A because it appears brighter but isn’t