Chapter 3: Properties Of Stars

Question 1

Photons

Answer 1

• photons provide energy to electrons which allow them to escape
• more energetic (blue) photons are needed to excite an electron to higher orbits from the ground state. Less energy (red) needed for smaller jumps

Question 2

Emission spectrum

Answer 2

Is unique for each element which has a unique configuration of electrons

Question 3

Lyman series

Answer 3

Lowest energy level n=1
Seen in the ultraviolet
Alpha: change n = 1
Beta: change n= 2
Gamma: change in n =3

Question 4

Balmer series

Answer 4

Second energy level n=2

Seen in the optical

Question 5

Paschen series

Answer 5

Third energy level n=3

Seen in the infrared

Question 6

Black body radiation

Answer 6

• a continuous spectrum emitted by an ideal non-reflecting surface and has a very distinctive shape
• hotter a star the more blue it is due to its lamda max being in the blue, red are cooler
• the hotter a star the more bright it is

Question 7

Continuum spectrum

Answer 7

Has a bar with not lines through it

Question 8

Emission line spectrum

Answer 8

Caused from hot gas

Has bars through it

Question 9

Absorption line spectrum

Answer 9

Caused from cold gas in front of a continuum source
Has many bars (Fraunhofer lines)
-typical stellar spectrum

Question 10

Spectroscopy

Answer 10

-provides an accurate thermometer of surface temp based on what lines are seen
-refer to the different spectral types
OBAFGKM
-lines of each molecules or atoms are strongest at a certain temp

Question 11

Absorption lines

Answer 11

Tell us about abundance’s

-Cecelia Payne Gapishikin found the composition of the sun

Question 12

More things the spectrum can tell us

Answer 12

Besides it’s temp and chemical composition of it can also tell us radial velocity

Question 13

Doppler shifts

Answer 13

Towards you (blue) away (red)

Question 14

Blueshift

Answer 14

Results in spectral lines having shorter observed wave lengths

Question 15

Redshift

Answer 15

Results in having longer observed wavelengths

Question 16

Proper motion

Answer 16

3D motions show up as proper motions

• parallax : apparent motion
• proper motion: real motion

-true space motion is a combination of transverse (proper) and radial velocities

Question 17

Parallax

Answer 17

Nearby stars are measured by parallax

- angle is half the angle the star appears to move in 6 months

Question 18

Parsec

Answer 18

Distance to an object who’s parallax is 1 arcsec

1AU/P(parsec)

• can only be used from Earth
• 206265 AU or 3.26 light years or 3.09 times 10 to 13

Question 19

Distances used for what?

Answer 19

• Use AU within the solar system
• Pc and Kpc distances within galaxies
• Kpc and Mpc distances between galaxies

Question 20

Absolute magnitude

Answer 20

• The apparent magnitude a star would have if it were 10pc away
• knowing the distance to an orbit is critical for determining absolute mag (or luminosity)

Question 21

Bolometric (app or absolute)

Answer 21

Add up all the light in all the spectrums (always brighter)

• suns absolute mag in Vband Mv =4.83
• absolute bolometric mag is 4.74
• sun has a small bolometric correct
• most of the suns light comes out in Vband

Question 22

Stellar sizes

Answer 22

• Stefan-Boltzmann law
• higher surface area = brighter star
• luminosity increases with T
• stellar sizes vary greatly

Question 23

Stellar masses

Answer 23

• need to have a binary star system to calculate this
• binary stars orbit around a common centre of mass
• closer to the higher mass

Question 24

Distance modulus

Answer 24

m-M

Apparent mag - absolute mag