Chapter 19 - Stars (UNFINISHED)

Question 1

What are the requirements for something to be described as a planet?

Answer 1

-Orbits a star.
-Large enough mass to give it a round shape.
-No fusion reactions.
-Orbit cleared of most other objects.

Question 2

Define planetary satellite.

Answer 2

A body in orbit around a planet.

Question 3

Define comet.

Answer 3

A small irregular body made up of ice, dust & small pieces of rock, with an eccentric elliptical orbit.

Question 4

Define solar system.

Answer 4

A system made of a star and the satellites that orbit it.

Question 5

Define galaxy.

Answer 5

A collection of stars and interstellar dust & gas.

Question 6

Define universe.

Answer 6

Everything that exists within space and time.

Question 7

Outline the formation of a star.

Answer 7

-Dust & gas particles gravitate together into a protostar.
-Gravity becomes strong enough for nuclear fusion.
-Main sequence star, where gravity = radiation pressure.

Question 8

How does a low-mass main sequence star form a red giant?

Answer 8

-Hydrogen in core runs low.
-Star begins to collapse as gravity > radiation pressure.
-Pressure becomes high enough for fusion in the shell around the core, causing expansion.
-Electron degeneracy pressure stops the core getting any smaller.

Question 9

How does a red giant form into a white dwarf?

Answer 9

-The outer layers drift into space, forming a planetary nebula.
-The core is left behind.

Question 10

What is electron degeneracy pressure?

Answer 10

A pressure created by the electrons in the core of a collapsing star.

Question 11

What is the Chandrasekhar limit?

Answer 11

The maximum mass a star can have at which electron degeneracy pressure prevents it from collapsing.

Question 12

Define planetary nebula.

Answer 12

The outer layers of a red giant that have drifted off into space.

Question 13

What are the characteristics of a white dwarf?

Answer 13

-No fusion occurs.
-Leaks photons made earlier in its lifecycle.
-Hot & dense.

Question 14

How does a high-mass main sequence star form a red supergiant?

Answer 14

-Hydrogen is used up quicker.
-Helium in the core fuses into heavier elements, causing expansion.

Question 15

How does a red supergiant go supernova?

Answer 15

-When fuel runs out, the core contracts.
-Outer layers fall in and rebound, causing a supernova.
-Either a neutron star or a black hole is left.

Question 16

What are the characteristics of a neutron star?

Answer 16

-Made up of neutrons & neutrinos.
-Very dense, small & fast-rotating.
-Emits radio waves in 2 beams as it rotates.

Question 17

What are the characteristics of a black hole?

Answer 17

-Core has collapsed into an infinitely dense point (singularity)
-Gravity is so strong that past the event horizon, nothing can escape its pull.

Question 18

Why do all energy levels have negative values?

Answer 18

‘Zero energy’ is defined as the amount of energy required to free an electron from the atom.

Question 19

Why do hot gases only emit certain wavelengths of light?

Answer 19

Electrons can only emit certain wavelengths, as this releases enough energy to drop down to their unique energy levels.

Question 20

Why do different atoms have different sets of spectral lines?

Answer 20

Different elements have their own unique sets of energy levels that require different amounts of energy from the absorption/emission of different wavelengths.

Question 21

Describe continuous spectra.

Answer 21

All visible wavelengths are present. A heated solid metal will release this type of spectrum.

Question 22

Describe emission line spectra.

Answer 22

A spectra showing only the wavelengths that are emitted by the element.

Question 23

Describe absorption line spectra.

Answer 23

A series of dark lines across the background of a continuous spectrum.