05 life cycle of stars Flashcards

1
Q

Stars are formed from

A

nebulas

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2
Q

What are nebulas?

A

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

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3
Q

When the nebula reaches a certain density,

A

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

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4
Q

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

A

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

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5
Q

Where stars spend about 90% of their lives is…

A

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

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6
Q

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

A

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

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7
Q

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

A

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

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8
Q

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

A

Core collapses and
outer layer explodes as
supernova

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

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9
Q

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

A

Core collapses and
outer layer explodes as large
supernova

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

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10
Q

Life Cycle of the Sun

A

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

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11
Q

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?
A
  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
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