(Chapter 6.1) Describing the Universe

Question 1

Define star

Answer 1

A giant luminous ball of plasma, mainly consisting of hydrogen and helium, held together by its own gravity

Question 2

Recall what feature of plasma makes it the fourth fundamental state of matter

Answer 2

A significant portion of plasma consists of charged particles – ions and/or electrons. The presence of these charged particles is what primarily sets plasma apart from the other fundamental states of matter

Question 3

Define nuclear fusion

Answer 3

A reaction in which at least 2 atomic nuclei are combined to form one or more different atomic nuclei and subatomic particles

Question 4

Identify where nuclear fusion takes place in a star

Answer 4

Nuclear fusion takes place in the core of the star

Question 5

Explain why stars emit light

Answer 5

Nuclear fusion converts mass into energy and electromagnetic radiation, such as visible light

Question 6

Define apparent magnitude

Answer 6

Apparent magnitude (m) is a measure of the brightness of a star or other astronomical object observed from Earth

Question 7

Identify the factors that impact the apparent magnitude

Answer 7

An object’s apparent magnitude depends on its intrinsic luminosity (energy output/distance), its distance from Earth, and any extinction of the object’s light caused by interstellar dust along the line of sight to the observer

Question 8

Define absolute magnitude

Answer 8

The apparent magnitude an object would have if it were located at a distance of 10 parsecs

Question 9

Recall the lifecycle of a star

Answer 9

1. Birth from clouds of gas and dust
2. Steady state - The star fuses hydrogen into helium to survive
3. Old age - The star runs out of hydrogen fuel, expands and cools
4. Death - The star implodes and the particles is blown away

Question 10

Identify what property changes the colour of a star

Answer 10

The temperature of a star affects its colour

Question 11

Identify the colour of a star in descending order of temperature

Answer 11

Blue, white, yellow, and red

Question 12

Identify what property changes the brightness of a star

Answer 12

The size

Question 13

True or False: “The size of a star is inversely proportional to the brightness”

Answer 13

False. The size of a star is proportional to the brightness

Question 14

Define galaxy

Answer 14

A gravitationally bound system of stars, stellar remnants, interstellar gas, dust, and dark matter

Question 15

Define solar system

Answer 15

The gravitationally bound system of a central star (the Sun) and the objects that orbit it

Question 16

Define nebula

Answer 16

A cloud of gas, predominately hydrogen, and dust in space and is the ‘birthplace’ of stars

Question 17

Define planet

Answer 17

According to the IAU (International Astronomical Union), a planet is a celestial body that:
* is in orbit around the Sun;
* has sufficient mass for its self-gravity to overcome rigid body forces so it assumes hydrostatic equilibrium (a nearly round shape), and;
* Has “cleared the neighbourhood” around its orbit

Question 18

Define planetary nebula

Answer 18

A type of emission nebula consisting of an expanding and glowing shell of ionised gas ejected from red giant stars late in their lives

Question 19

True or False: “Planetary nebulae are related to planets”

Answer 19

False. Planetary are misnamed as when they were discovered, they were misclassified as planets

Question 20

Identify another term for planetary nebula

Answer 20

Stellar nebula is another term for planetary nebula

Question 21

Define asteroid

Answer 21

A small rock body that orbits the Sun

Question 22

Define comet

Answer 22

A celestial object consisting of a nucleus of ice and dust and when it approaches the Sun, a ‘tail’ of gas and dust particles appears

Question 23

Define meteoroid

Answer 23

A small rocky or metallic body that orbits the Sun

Question 24

Define meteor

Answer 24

A small rocky or metallic body of matter from outer space that enters the Earth’s atmosphere, becoming incandescent as a result of friction and appearing as a streak of light

Question 25

Define meteorite

Answer 25

A piece of rock or metal that has fallen to the Earth’s surface and previously was a meteor

Question 26

Identify the most common minerals of meteors

Answer 26

The most common minerals are rock, iron, and nickel

Question 27

Identify another term for apparent magnitude

Answer 27

Another term is stellar magnitude

Question 28

Identify what property changes the lifespan of a star

Answer 28

The mass of a star affects the lifespan

Question 29

Define accretion

Answer 29

The accumulation of particles into a massive object by gravitationally attracting more matter, typically gaseous matter, in an accretion disk

Question 30

Define accretion disk

Answer 30

A structure formed by diffuse material in orbital motion around a massive central body, typically a star

Question 31

Define binary star

Answer 31

A system of 2 stars that are gravitationally bound to and in orbit around each other

Question 32

Define parsec

Answer 32

The radius of Earth’s orbit subtends an angle of one second of arc

Question 33

Identify the elongated term for parsec

Answer 33

Parallax second is the elongated term for parsec

Question 34

Explain what the stellar parallax is

Answer 34

The stellar parallax describes the effect of observing a star from different positions, which then the star’s position relative to other stars appears to be different

Question 35

Explain why parsec is used to measure distances closer than 100 light-years

Answer 35

The parsec is used as it is an appropriate unit in terms of the number it produces

Question 36

Define proper motion

Answer 36

The astrometric measure of the observed changes in the apparent places of stars or other celestial objects in the sky

Question 37

Recall the formula to calculate the distance of a star

Answer 37

d = 1/p
where:
d = distance (pc)
p = parallax angle (arc seconds) (1/3600)

Question 38

Recall the conversion between parsec and light-years

Answer 38

1 pc = 3.26 light-years

Question 39

Recall the speed of light

Answer 39

3 * 10^8 m/s

Question 40

Contrast a solar system with a galaxy

Answer 40

A solar system is all the celestial bodies that orbit a cental star. On the other hand, a galaxy is the collection of stars, spanning a number of solar systems