Module 5 part 3 astrophysics

Question 1

planet def and 3 characteristics

Answer 1

A body that orbits around a star, in our case, the Sun.

1. mass large enough for its grav to give round shape
2. no fusion reactions
3. cleared its orbit of most objects

Question 2

comet

Answer 2

Concentrated clusters of ice and dust that orbit star in elliptical orbit

Question 3

planetary satellite

Answer 3

Bodies that orbit a planet. The gravitational force of the
planet’s mass provides the centripetal force of rotation.

Question 4

solar system

Answer 4

A collection of planets that orbit a common star.

Question 5

galaxy

Answer 5

Collections of billions of stars, planets, gases and dust, held together by
gravitational attraction

Question 6

universe

Answer 6

The name given to all space and matter

Question 7

difference between comet and astroid

Answer 7

1. comets have ice while astroids do not
2. not all comets orbit star

Question 8

atroid

Answer 8

objects which are too small and uneven in shape to be planets, with a near circular orbit around the sun/star

Question 9

Dwarf planets

Answer 9

planets where the orbit has not been cleared of other objects

Question 10

formation of star

Answer 10

1. gravitational attraction pulls gas and dust particles, forming clouds
2. gravitational collapse accelerates, regions become denser
3. gravitational energy converted to thermal
4. protostar forms in cloud, very hot very dense sphere
5. high temp and pressure allow hydrogen nuclei to overcome elctrostatic repulsion between nuclei and undergo nuclear fusion
6. helium nuclei produced and star created

Question 11

nebulae

Answer 11

A cloud of dust and gas in space, often hundreds of times larger then our solar system

Question 12

star life and equilibrium

Answer 12

star remains in stable equilibrium with constant size.
radiation pressure (from photons emitted in fusion) and gas pressure (from nuclei in core) balance gravitational force compressing star. This is known as a main sequence

Question 13

evolution of low mass star

Answer 13

1. low - 0.5M☉ to 10M☉ core mass
2. hydrogen supply decreases
3. gravitational force overcomes gas and radiation pressure
4. star collapses inward, becomes red giant
5. helium fusion stops in core continues in outer shell
6. helium low, evolves into white dwarf
7. outer shell drifts off becomes planetary nebula

ADD MODE

Question 14

low and high mass star core mass

Answer 14

low - 0.5M☉ to 10M☉
high - above 10M☉

smaller remain in main sequence longer

Question 15

characteristics of white dwarf

Answer 15

1. very dense
2. temp of around 3000K
3. no fusion, will eventually die

Question 16

how does fusion in core of star prevent gravitaitonal collapse

Answer 16

photons emitted from fusion create outward radiation pressure. gas pressure from nuclei also causes outward force, balancing the forces

Question 17

what is electron degeneracy pressure and found where

Answer 17

when electrons are squeezed together, but cannot exist in same energy state. results in pressure. Found in white dwarf

Question 18

chandrasekhar limit

Answer 18

if white dwarf core mass below 1.44M☉, white dwarf is stable. If above, degeneration of electrons cannot balance gravitational force, it will collapse

Question 19

evolution of massive starM☉

Answer 19

1. high - above 10M☉
2. temp high enough for helium fusion to heavier elements
3. red supergiant forms with layers of increasing heavy elements, with iron core (cannot fuse further)
4. iron core unstable, type 2 supernova occurs (implosion)
5. if remaining core above 1.44M☉, electrons and protons combine, forming neutron star
6. if core greater than 3M☉, gravitational force so strong escape velocity of core greater than speed of light, black hole is formed

Question 20

characteristics of neutron star

Answer 20

1. almost entirely made of neutrons
2. just 10km in diameter
3. around 2M☉

Question 21

characteristics of black hole

Answer 21

1. No light can escape gravitational field
2. mass greater than 3M☉
3. greatest density in the universe

Question 22

solar mass def

Answer 22

1.99 x 10^30kg, mass of the sun

Question 23

why are energy level of electrons neg

Answer 23

external energy is required to remove electron from atom. Neg values indiciate electron trapped within pos nuclei

Question 24

what is most neg energy level known as

Answer 24

ground state

Question 25

what happens when electron moves energy level

Answer 25

high to lower - energy conserved, electron makes transition with photon emitted (de excitation)

lower to higher - external energy required (e.g. electric field) results in excitation

Question 26

how are emission line spectra formed

Answer 26

1. elements in gas cloud with energy levels, electron de excited, releases photon (specific wavelength)
2. wavelengths of light produced for each element different (Different energy levels)
3. white light from star placed in diffraction grating, wavelengths seperate, producing emission line spectra

Question 27

how is absorption line spectra formed

Answer 27

1. light from source producing continuous spectrum passes through cooler gas
2. photons absorbed by gas, raising electron energy level exciting the atom
3. photons with energy equal to difference in energy between levels absorbed
4. goes through diffraction grating, creates dark lines on spectrum