Astro physics

Question 1

A galaxy is

Answer 1

a collection of stars, interstellar dust and gas

Question 2

A nebulae is

Answer 2

a gigantic cloud of dust and gas, often many hundreds of times larger than our solar system

Question 3

A planet is

Answer 3

an object in orbit around a star with three important characteristics:
it has a mass large enough for its own gravity to give it a round shape
It has no fusion reactions
It has cleared its orbit of most other objects

Question 4

A planetary satellite is

Answer 4

a body in orbit around a planet

Question 5

Examples of planetary satellites are

Answer 5

includes moons and man made satellite

Question 6

A comet is

Answer 6

a small irregular body made up of ice, dust and small pieces of rock

Question 7

An asteroid is

Answer 7

an object that is too small and uneven to be a planet

Question 8

A dwarf planet is

Answer 8

like a planet but it has not cleared the orbit of other objects

Question 9

What is the life cycle of stars with mass between 0.5-10 solar masses?

Answer 9

Main sequence - red giant - white dwarf

Question 10

What is the life cycle of a star with mass greater than 10 solar mass?

Answer 10

Main sequence - red supergiant - supernova - neutron star/black hole

Question 11

What is the electron degeneracy pressure?

Answer 11

A quantum mechanical pressure created by the electrons in the core of a collapsing star due to the Pauli exclusion principle

Question 12

What is the Chandrasekhar limit?

Answer 12

The mass of a star’s core beneath which the electron degeneracy pressure is sufficient to prevent gravitational collapse, 1.44 solar masses

Question 13

Describe a neutron star?

Answer 13

A star made up of almost entirely neutrons, can be very small-just 10km in diameter, they have a typical mass of 2 solar masses, and has a density similar to an atomic nucleus

Question 14

When does a star collapse into a black hole?

Answer 14

When the core has a mass greater than 3 solar masses

Question 15

Why are energy levels negative?

Answer 15

external energy is required to remove the electron from the atom

Question 16

What is the ground state?

Answer 16

The energy level with the most negative value possible for an electron within an atom - the most stable energy state for an electron

Question 17

What is an emission line spectrum?

Answer 17

each element produces a unique emission line spectrum because of its unique set of energy levels

Question 18

What is an absorption spectra?

Answer 18

this type of spectrum has a series of dark spectral lines against the background of a continuous spectrum. The dark lines have exactly the same wavelengths as the bright emission spectral lines for the same gas atoms

Question 19

What is a continuous spectrum?

Answer 19

All visible frequencies are present

Question 20

What is meant by quantised energy levels?

Answer 20

The energy levels can only exist in certain discrete values

Question 21

How is an absorption spectrum formed?

Answer 21

When light from a source that produces a continuous spectrum passes through a cooler gas

Question 22

What is a diffraction grating?

Answer 22

A glass or plastic slide on which as 1000 lines in a millimeter are ruled, at a spacing that diffracts visible wavelength of lights

Question 23

What is a black body?

Answer 23

An idealised object that absorbs all the em radiation incident on it and when in thermal equilibrium emits a characteristic distribution of wavelengths at a specific temperature

Question 24

What three things is the luminosity of a star proportional to?

Answer 24

Its radius squared
Surface area
its surface temperature to the fourth power