Astrophysics

Question 1

What is the Hubble constant?

Answer 1

𝐻 = 65 km s–1 Mpc–1

Question 2

What is the formula for the magnification (M) in telescopes?

Answer 2

𝑀 = angle subtended by image at eye / angle subtended by object at unaided eye

Question 3

What is the Rayleigh criterion?

Answer 3

𝜃 ≈ 𝜆 / 𝐷

Question 4

What is the magnitude equation?

Answer 4

𝑚 – 𝑀 = 5 log(𝑑) / 10

Question 5

What does Wien’s law state?

Answer 5

𝜆max 𝑇 = 2.9 × 10−3 m K

Question 6

What is Stefan’s law?

Answer 6

𝑃 = 𝜎A𝑇^4

Question 7

What is the Schwarzschild radius?

Answer 7

𝑅s ≈ 2GM/c^2

Question 8

What is the Doppler shift formula for v &laquo_space;c?

Answer 8

Δ𝑓/𝑓 = – Δ𝜆/𝜆 = 𝑣/c

Question 9

What is the formula for red shift (z)?

Answer 9

𝑧 = − 𝑣/𝑐

Question 10

What is Hubble’s law?

Answer 10

𝑣 = 𝐻d

Question 11

Absolute Magnitude (M)

Answer 11

The apparent magnitude that an object would have if it were
placed at a distance of 10 parsecs away from Earth

Question 12

Apparent Magnitude (m)

Answer 12

How bright an object appears in the sky. This depends on the
object’s brightness and its distance from Earth.

Question 13

Arcsecond

Answer 13

A unit used to measure small angles. An arcsecond is equal to 1/3600th of a
degree

Question 14

Astronomical Unit (AU)

Answer 14

The average distance between the centre of the Earth and the
centre of the Sun.

Question 15

Chromatic Aberration

Answer 15

An effect caused by the different focal lengths of different
wavelengths of light that leads to different colours being focused at different points. This can
cause a white object to appear as if it has coloured edges.

Question 16

Doppler Effect

Answer 16

The apparent change in the wavelength of a wave as the source moves
relative to an observer. For a source moving away the wavelength increases (red shift), for a
source moving towards the observer the wavelength decreases (blue shift).

Question 17

Event Horizon

Answer 17

The boundary of a black hole, along which the escape velocity is equal to
the speed of light

Question 18

Hipparcos Scale

Answer 18

A way of classifying astronomical objects by their apparent magnitude.
The brightest stars have an apparent magnitude of 1 and the faintest visible stars have an
apparent magnitude of 6. The intensity of a magnitude 1 star is 100 times greater than a
magnitude 6 star so the scale is logarithmic.

Question 19

Hubble’s Law

Answer 19

The speed of a galaxy moving away from ours is proportional to its distance
away from us. The constant of proportionality is Hubble’s constant.

Question 20

Hydrogen Balmer Spectrum

Answer 20

A spectrum formed from the excitation of hydrogen atoms
from the n=2 level. The prominence of the Balmer lines from a star can give an indication of
the star’s temperature and state of the hydrogen within it.

Question 21

Magnifying Power/Angular Magnification (M)

Answer 21

The ratio of the angle made by the image
from the eyepiece to the angle made by the object with the unaided eye.

Question 22

Main Sequence Star

Answer 22

The equilibrium stage of a star’s life cycle, where the inward
gravitational forces balance the outward forces caused by fusion. In this stage, hydrogen
nuclei fuse to form helium.

Question 23

Neutron Star

Answer 23

An incredibly dense star that is formed when the core of a large star
collapses. Protons and electrons are forced together under gravity to form neutrons

Question 24

Protostar

Answer 24

A young star formed when clouds of gas and dust are pulled together under
gravity. Protostars are surrounded by a circumstellar disc, and when the centre becomes hot
enough, the star will begin to fuse elements.

Question 25

Quasar

Answer 25

Active galactic nuclei – supermassive black holes surrounded by a disc of matter, which, as it falls into the black hole, causes jets of radiation to be emitted from the poles. Quasars display very large red shift, indicating they are very far away. The power output of a quasar is around that of an entire galaxy.

Question 26

Red Giant

Answer 26

A stage in the life cycle of a star less than 3 solar masses, in which the hydrogen has run out and the temperature of the star increases. Helium nuclei fuse to form heavier elements

Question 27

Spherical Aberration

Answer 27

An effect caused by the curvature of a lens or mirror that can lead to light rays at the edges to be focused in different places to those from the centre. This can cause an image to be blurry or distorted.

Question 28

Stefan’s Law definition

Answer 28

A law stating that the power output (luminosity) of a star is directly proportional to its surface area and its absolute temperature to the 4th power.

Question 29

Type Ia Supernova

Answer 29

A consequence of a white dwarf star exploding. They can be used as a standard candle since they always reach the same maximum absolute magnitude (-19.3).

Question 30

White Dwarf

Answer 30

A stage in the life cycle of a small star (less than 1.4 solar masses) that occurs when all the fuel has been used up. The star contracts since there is no longer an outwards force caused by fusion.

Question 31

Wien’s Displacement Law

Answer 31

A law stating that the peak wavelength of emitted radiation is inversely proportional to its absolute temperature