astrophysics

Question 1

the evolution of stars of similar mass to the Sun

Answer 1

• cloud of dust and gas forms called a nebula
• the attraction of gravity pulls the dust and gas together, forming a protostar
• temp of the star rises as more particles collide with each other
• when the temp gets high enough the nuclear fusion of hydrogen nuclei to form helium nuclei occurs which produces a lot of energy, keeping the core of the star hot
• star enters a long and stable period where the outward pressure (thermal expansion) is equal to the inward pressure (force of gravity). in this period it’s called a main sequence star
• eventually the supply of hydrogen runs out which means that the inward pressure (force of gravity) is stronger than the outward pressure (thermal expansion/nuclear fusion)
• the star is compressed until it is dense and hot enough that the energy makes the outer layers of the star expand, forming a red giant
• the red giant then becomes unstable and ejects its outer layer of dust and gas which leaves behind a solid, dense core known as a white dwarf

Question 2

the evolution of stars with a mass larger than the Sun

Answer 2

• cloud of dust and gas forms called a nebula
• the attraction of gravity pulls the dust and gas together, forming a protostar
• temp of the star rises as more particles collide with each other
• when the temp gets high enough the nuclear fusion of hydrogen nuclei to form helium nuclei occurs which produces a lot of energy, keeping the core of the star hot
• star enters a long and stable period where the outward pressure (thermal expansion) is equal to the inward pressure (force of gravity). in this period it’s called a main sequence star
• eventually the supply of hydrogen runs out which means that the inward pressure (force of gravity) is stronger than the outward pressure (thermal expansion/nuclear fusion)
• the star is compressed until it is dense and hot enough that the energy makes the outer layers of the star expand, forming a red supergiant
• these stars undergo more fusion to make heavier elements, expanding and contracting several times. eventually they explode in a supernova
• the exploding supernova ejects the outer layers of dust and gas, leaving a very dense core called a neutron star
• if the star is massive enough, it will collapse and become a black hole

Question 3

classification of stars

Answer 3

red, orange, yellow, white, blue
lowest FQ highest FQ
coolest hottest

stars of similar colour have similar surface temperatures

Question 4

universe

Answer 4

a large collection of billions of galaxies

Question 5

galaxy

Answer 5

large collection of billions of stars

Question 6

our solar system

Answer 6

the milky way

Question 7

why gravitational field strength varies

Answer 7

• depends on the mass of the body creating the field, larger mass=stronger g
• varies with distance, closer you are the stronger g is

Question 8

gravitational force causes

Answer 8

• moons to orbit planets
• planets to orbit the sun
• artificial satellites to orbit the earth
• comets to orbit the sun

Question 9

orbit of comets

Answer 9

• highly elliptical
• sun at one focus
• orbital period longer than the earth’s
• travels faster when it’s nearer to the sun because the pull of gravity is stronger

Question 10

orbit of moons and planets

Answer 10

• slightly elliptical

Question 11

orbital speed formula

Answer 11

orbital speed= 2 x pi x orbital radius/time period

v= 2 x pi x r/ T