astro

Question 1

what is one light year

Answer 1

the distance that light travels in one year in a vacuum
9.46x10^15 m

Question 2

what is parallax

Answer 2

apparent shift in relative position of two objects due to the changing position of the observer

Question 3

what is the astronomical unit (AU)

Answer 3

the mean distance between the Earth and the sun
is 1.50 x 10^11 m

Question 4

what is the parsec

Answer 4

A unit of distance that gives a parallax angle of 1 second of an arc (of a degree), using the radius of the Earth’s orbit (1 AU) as the baseline of a right–angled triangle

Question 5

what is the hipparcos scale

Answer 5

scale which tells you the brightness of a star

Question 6

what magnitudes are the brightest and dimmest stars

Answer 6

brightest are magnitude 1
dimmest are magnitude 6

Question 7

what magnitude is used in hipparcos scale

Answer 7

apparent magnitude

Question 8

what is apparent magnitude

Answer 8

how bright a star appears from earth

Question 9

why was the apparent magnitude system formalised

Answer 9

our eyes have logarithmic response to light

Question 10

how many times brighter is magnitude 1 than magnitude 6

Answer 10

100 x

Question 11

how many times brighter is a magnitude brighter than the previous

Answer 11

100^1/5
2.51

Question 12

are we able to observe magnitudes lower than 6 and negative magnitudes

Answer 12

yes

Question 13

what is luminosity

Answer 13

the total power output of a star
measure is watts

Question 14

what is apparent magnitude

Answer 14

apparent magnitude being measured from a distance of 10 pc

Question 15

distance modulus equation

Answer 15

m - M = 5 log (d/10)

Question 16

what is a blackbody

Answer 16

an idealised emitter and absorber of radiation (object that absorbs all radiation and emits radiation over a continuous range of wavelengths)

Question 17

what is the area under a black body curve

Answer 17

total energy radiated per unit of time per unit of surface area by the object at that temperature

Question 18

what do you have to remember when drawing black Body curve diagrams

Answer 18

The left hand side must be drawn steeper than the right hand side
The intensity must decrease towards (but not reach) zero as the wavelength increases.
The line must not cross the intensity axis (y-axis)

Question 19

what is peak wavelength determined by for a black body

Answer 19

temperature

Question 20

what is weins displacement law

Answer 20

λmaxT=2.9×10−3m⋅K

Question 21

what is weins law used for

Answer 21

to find the surface temperature of the star

Question 22

stefan boltzman law describes

Answer 22

The temperature of a blackbody and the amount of energy it radiates

Question 23

what is stefan Boltzmann law

Answer 23

P=σAT^4
σ = 5.67×10−8Wm−2K−4
A = 4πr^2

Question 24

what does energy flux or surface flux show

Answer 24

shows energy leaving the star

Question 25

what is the energy flux or surface flux of the star

Answer 25

P=σT^4

Question 26

what happens when photons are absorbed by electrons in a cool gas

Answer 26

a dark line is created in an continuous spectrum

Question 27

what is the order of the hydrogen Balmer lines

Answer 27

O B A F G K M

Question 28

what is the temperature range for O

Answer 28

25,000 - 50,000

Question 29

what is the temperature range an the strongest absorption lines for B

Answer 29

11,000 - 25,000 He H

Question 30

what is the temperature range an the strongest absorption lines for A

Answer 30

7,500 - 11,000 H

Question 31

what is the temperature range an the strongest absorption lines for F

Answer 31

6,000-7,500 ionised metals

Question 32

what is the temperature range an the strongest absorption lines for G

Answer 32

5000 - 6000 ionised and neutral metals

Question 33

what is the temperature range an the strongest absorption lines for K

Answer 33

3,500 - 5,000 neutral metals

Question 34

what is the temperature range an the strongest absorption lines for M

Answer 34

less than 3,500 neutral atoms, TiO

Question 35

what is on the axis of HR diagram

Answer 35

spectral class or temp on the x axis and absolute magnitude or luminosity on the y axis

Question 36

where is the main sequence on the HR graph

Answer 36

absolute magnitude from -10 to 15 spectral classes O to M shape squiggly line from left to right

Question 37

where is super giants on the HR graph

Answer 37

absolute magnitude from -5 to -10 spectral classes A to end of M shape oval

Question 38

where is giants on the HR graphs

Answer 38

absolute magnitude of zero spectral classes start of g to end of M shape oval

Question 39

where is white dwarfs on HR graph

Answer 39

absolute magnitude between 10 15 spectre class between B shape oval

Question 40

length of axis on HR diagram

Answer 40

-10 to 15 y axis O to M

Question 41

how are stars born

Answer 41

out of nebulae. the gravitational forces pull at the gas compressing it forming protostar. GPE Turns into thermal energy so interior becomes hotter and hotter. there's fusion of hydrogen to form helium, fusion reactions cause the outer layers of protostar to become hot and a light emitting layer and protostar becomes star

Question 42

what is a nebula

Answer 42

interstellar cloud of gas

Question 43

what is a protostar

Answer 43

making of a star

Question 44

what happens once new star is formed

Answer 44

star reaches internal equilibrium as inward gravitation attraction is balanced by outward radiation pressure, star becomes stable with constant luminosity.and joins the main sequence according to its mass

Question 45

where does a star spend most of its time

Answer 45

main sequence

Question 46

when does a star become a supergiant or a giant

Answer 46

when most of the hydrogen has been converted to helium so core collapses on itself and so outer layers of star expand and cool so star swells out and becomes super giant or giant

Question 47

when does red giant become white dwarf

Answer 47

when nuclear fusion in the core of star stops the star cols off and the core contracts causing the outer layers to be thrown off. outer layers thrown off as shells of hot gas forming a planetary nebula

Question 48

why is supernova called a supernova

Answer 48

because the event is brighter than a nova (new star) in the same galaxy

Question 49

what is a neutron star

Answer 49

core of a supernova after all surrounding matter has been thrown off into space

Question 50

what is a black hole

Answer 50

object so dense that not even light can escape it

Question 51

why is a black hole so dense

Answer 51

because escape velocity is above the speed of light

Question 52

what is the event horizon

Answer 52

sphere surrounding the black hole from which nothing can emerge

Question 53

what is the Schwarzschild radius

Answer 53

radius of the event horizon

Question 54

equation for Schwarzschild radius

Answer 54

R(s) = 2GM/c^2