UNIT 6 Space Physics

Question 1

Light year [=9.5x10^15]

• time taken for light to travel from Sun to Earth?

Answer 1

📌 a distance travelled by light in 1 year - show that: speed of light in vacuum x no. of sec in yr = 3x10^8 x 3.15x10^6 = 9.5x10^15

• 8 minutes/500 s
• distance from sun to Earth = 1.5x10^11

Question 2

using motions of celestial bodies, define

-year
-month
-day

Answer 2

-year: the Earth to orbit the Sun

• month: the Moon to orbit Earth

-day: the Earth to rotate on its axis

Question 3

name of force causes the comet to orbit the sun
+
=> speed increases as comet gets closer to sun; explain in terms of energy transfer why

Answer 3

gravitational force
+ sun contains most of mass of solar system

=> as comet moves closer to Sun, gravitational potential energy decreases and kinetic energy increases.

Question 4

CIRCULAR ORBIT, change to speed & velocity from 2 points on circular path, near Sun? [4]

Answer 4

speed: remains constant as distance from sun is constant

velocity: velocity is changing as direction of motion of comet is always changing

Question 5

show direction of force acting on comet

Answer 5

Single straight arrow pointing towards Sun

Question 6

two ways how orbits of earth and mars are similar

• different?

Answer 6

Orbit shapes both approximately circular/[same direction of orbit]

both planets orbit the Sun

• Different orbital radii

Question 7

SIMILAR orbital period but larger orbital speed

explain how possible

Answer 7

Orbital radii of the two moons are different

Orbit radius of Enceladus is bigger
[despite smaller orbital period & larger speed]

Question 8

jupiter largest gravitational field strength

+ why Sun appears to move across sky each day

Answer 8

has the largest mass

• earth rotates on its axis once every 24 hours

Question 9

‘smaller the planet the shorter its period of orbit’

Answer 9

• Period as time of orbit

Period depends on distance from the Sun

Statement is not correct

Question 10

different stages in life cycle of small star.

Answer 10

a cloud containing hydrogen collapses due to gravitational attraction =>

=> hydrogen undergoes nuclear fusion to produce helium =>

=> a red giant produced =>

=> a white dwarf is produced

Question 11

evidence for big bang theory
+

• 1 measurement taken when determining speed at which galaxy is moving away from Earth

Answer 11

increase in observed wavelength of radiation emitted by distant galaxies = redshift.
+ “all galaxies and earth were together 13-14 billion years ago”

• change of wavelength

Question 12

state 2 diff btwn asteroid & comet

Answer 12

• a comet comes from far outside solar system and is highly elliptical; asteroids are between mars and jupiter [& orbit Sun]
• comet is a ball of ice and dust; asteroids are made of rock

Question 13

why Earth takes long to orbit Sun than Mercury.

Answer 13

• circumference of orbit/orbital radii of Earth around sun is larger
• Earth has a smaller orbital speed; moves slower

Question 14

suggest how astronomer uses change in brightness of star to measure orbital period of planet around star

Answer 14

-measuring time from t1 to next time when brightness starts to reduce is orbital period

Question 15

📌 DEFINITIONS: red end of spectrum meaning
galaxy meaning

-redshift of light meaning

Answer 15

📌 -longest wavelength/lowest frequency
📌 - a collection of billions of stars

📌 - increase in observed wavelength of the electromagnetic radiation emitted from receding stars and galaxies

Question 16

what can be deduced from redshift of light from glowing hydrogen in distant galaxy

Answer 16

• the distant galaxy is moving away from Earth
• and its velocity can be calculated by comparing the wavelengths

Question 17

one method of estimating distance of distant galaxy from Earth

Answer 17

by measuring brightness of a supernova in that galaxy

Question 18

desc process that produces energy in sun from nuclei of hydrogen

• why high temp needed to occur

Answer 18

Hydrogen nuclei fuses together to form helium and releases energy.

• nuclei will repel each other so high speed and energy to fuse hydrogen nuclei required

Question 19

Desc life cycle of star after it’s passed through stage of protostar [4 MARKS]

Answer 19

-it becomes a main sequence star then expands to become a red super giant. it turns to a supernova and throws its outer layer. the core becomes a neutron star or if mass is massive, core shrinks to become a black hole.

Question 20

explain why moon is visible from Earth

+ what phases of moon indicate about motion of moon

Answer 20

-the light from the sun is reflected from the moon’s surface

-The Moon orbits the Earth & duration of Moon’s orbit is approximately 29 days

Question 21

explain how according to big bang theory 1/H0 represents age of universe

Answer 21

📌 according to big bang theory all matter in universe was present at a single point

📌 if distance travelled is d, velocity of recession is v, then time it has been moving away is d/v

📌 d/v = 1/H0, eqn represents age of universe/time from when universe began