Astrophysics - Stellar Classification Flashcards

(37 cards)

1
Q

Define apparent magnitude

A

Perceived brightness of a star seen from Earth

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2
Q

How many times brighter is a magnitude 1 star compared to a magnitude 6 star

A

100 times brighter
For every star for example between 1 and 2, brightness decreases by 100^1/5

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3
Q

Define luminosity

A

Luminosity = total power radiated by all wavelengths [W]
Intensity = power per unit area [Wm^-2]

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4
Q

Difference between luminosity and brightness and why they’re useful

A

Luminosity = total power radiated but brightness is the power as measured on earth
Helpful for measuring how far it is away from Earth

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5
Q

How do you calculate Intensity using area and luminosity

A

For any given star luminosity is constant

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6
Q

Define AU

A

Mean distance from centre of earth to the centre of sun

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7
Q

Define light year and how do you calculate it

A

Distance travelled by light in one year
You can calculate distance by distance = speed x time
Where speed is the speed of light and time is 1 year in seconds

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8
Q

Define parsec and state everything you need to know about it

A
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9
Q

Define absolute magnitude

A

Apparent magnitude if it was observed 10 parsecs away from the Earth

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10
Q

For all spectral classes, state temperature range, absorption lines and intrinsic colour

A
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11
Q

For each spectral class, explain their respective prominence of the balmer lines

A
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12
Q

Draw the Hertzsprung-russel diagram

A
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13
Q

Draw and describe evolutionary path of a solar mass star

A

(from A to B) : protostar to main sequence
(from B to C) : Main sequence to red giant
(From C to D) : red giant to white dwarf

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14
Q

The black body temperature of each star is approximately 9200 K.
Explain why a Hydrogen Balmer line was chosen for the analysis of wavelength variation.

A

Temperature indicates spectral class is A
Hydrogen Balmer lines are strongest in A class stars and therefore would be more easily measured.

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15
Q

In m-M = 5logd/10 which is the absolute and apparent magnitude

A

m is apparent
M is absolute magnitude

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16
Q

Which of these three stars appears the brightest

A

Lowest value of apparent magnitude indicates brightest star
Vega has lowest apparent magnitude so is brightest

17
Q

Which of these three stars is the largest

A

Deneb is largest
It has approximately same temperature but has a much greater absolute magnitude and therefore greater power output
P = OAT^4
To have a much greater power output for a similiar temperature, it must have a greater area

18
Q

Draw a black-body radiation curve

A

You only need to draw one curve, do not need three temperatures and the colours

19
Q

Draw hertzsprung Russell diagram but it’s absolutele magnitude against temperature

A

You must remember that absolute magnitude is 15 to -10 and temperature is 50,000 to 3,500

20
Q

Matar has an absolute magnitude of -2.1. Sun has an absolute magnitude of 5. They have similiar temperatures, which is the largrer star

A

Matar since the more negative the absolute magnitude, the brighter the star. As increase in absolute magnitude means larger power output, Matar must be larger

22
Q

Which of the two starts is closer to earth
B) why does spectrum of Betelgeuse not contain prominent hydrogen balmer lines

A

B) temperature too low to have hydrogen in n=2 state

23
Q

A) State which star is likely to appear orange
B) appears brightest from Earth

A

A) shedir as it is spectral class K which is towards red end
B) shedir as it has smallest apparent magnitude value

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Theta = s/r what doee this mean
Theta = diameter / distance
27
Remember hotter stars will appear less red / more blue or white
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Where is Sun on Hertzsprung Russell diagram
At 5000 Kelvin and absolute magnitude 5
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Absolute magnitude of Quasar is -26.6 and absolute magnitude of the galaxy is -22.8
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Binary is when they're basically at the same distance
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