Unit 8 - Astrophysics

Question 1

describe the difference between a planets and a comets orbit

Answer 1

comet orbit is very elliptical
planets orbit is slightly elliptical

Question 2

define absolute magntidue

Answer 2

brightness of star at a standard distance

Question 3

give 2 evidences of Big Ban THeory

Answer 3

• Red shift of the galaxies
• CMBR (cosmic microwave background radiation)

Question 4

how does red shift support the big bang theory

Answer 4

• the further the galaxy from us , the greater the red shift
• the greater the red shift , the greater the speed of the galaxy
• speed of the galaxies increases with its distance from earth
• the relationship between speed and distance implies an explosion at a single point

Question 5

D

Answer 5

The power of the energy emitted by a star, in all directions and across all wavelengths of electromagnetic radiation.
This is measured in watts (W).

Question 6

define nebula

Answer 6

A cloud of dust and gas in space which slowly
collapses into itself because of gravity

Question 7

define protostar

Answer 7

A ball of gas which contracts due to gravity and heats up due to pressure

Question 8

define main sequence star

Answer 8

A stable gas sphere which has ongoing nuclear fusion, releasing energy as electromagnetic radiation in all directions

Question 9

define red giant

Answer 9

A star that is fusing helium to make heavier elements up to oxygen

Question 10

define white dwarf

Answer 10

A star that is shrinking and is no longer stable as nuclear fusion is stopping

Question 11

define black dwarf

Answer 11

A star that has completely stopped fusing atoms and is no longer emitting heat or light

Question 12

define red super giant

Answer 12

A star that is fusing helium and other nuclei to make atoms as large as iron

Question 13

define supernova

Answer 13

An explosion that sends out the outer layers of a red super giant, leaving behind a dense core

Question 14

define neutron star

Answer 14

A dense core left behind after a supernova, made up of neutrons

Question 15

define black hole

Answer 15

A collapsed mass left behind after the largest stars explode in a supernova, with such a strong gravity even light cannot escape

Question 16

what is a red shift

Answer 16

An increase of wavelength of a detected electromagnetic wave compared to the source, caused as it moves away
from the observer

Question 17

how does CMBR support the big bang theory

Answer 17

1. The universe was much hotter long ago
2. Wavelength of the radiation increased because the universe expanded
3. CMBR appears to be the same in all directions
4. That means that all parts of the universe were in contact long ago

Question 18

what do all stars star off as

Answer 18

huge cloud of gas and dust

Question 19

which force is responsible for forming a protostar from a nebula

Answer 19

gravity

Question 20

what kind of reaction causes the expansion of a star

Answer 20

nucleur fussion

Question 21

how does a main sequence star remain stable

Answer 21

fusion reactions produce outwards forces which balance the gravitation forces pulling it iinwards

Question 22

what determine the life cycle of a star

Answer 22

mass

Question 23

what is the life cycle of a star with much more mass than the sun

Answer 23

protostar -> main sequence star -> red supergiant -> supernova -> neutron star or blackhole

Question 24

how are naturally occurring elements formed

Answer 24

from nuclear fusion during the life cycle of stars

Question 25

to change the speed of an object in a stable orbit which factor must change

Answer 25

radius of the orbit