Chapter 10 Quiz

Question 1

What basic characteristics/properties of stars are we trying to understand?

Answer 1

size, shape, distance, energy output, temperature, and mass

Question 2

Whats parallax and how do we use it to measure the distance to a nearby star?

Answer 2

stellar parallax- the apparent motion of nearby star among background of more distant stars. The smaller the parallax, the farther away. Parallax can only be used to measure distance of nearby stars

Question 3

How do we actually calculate the distance? What are the units of angle and distance that we use?

Answer 3

We use arc seconds for the angle and parsecs for the distance. d=1/p

Question 4

What is apparent magnitude? what does it measure? relative to what?

Answer 4

apparent magnitude (m) measures the brightness of stars seen from Earth. Brightness is measured regardless of distance

Question 5

How do we describe the brightness using the magnitude scale? what is the suns apparent mag’?

Answer 5

Reverse scale- larger positive is less bright, the lower the magnitude the brighter the star is. the suns apparent mag’ is (-26.7)

Question 6

What is absolute magnitude? what does it measure?

Answer 6

Brightness considering distance absolute magnitude (m) is the brightness each star would have at a distance of 10 pc (luminosity)

Question 7

What do we need to know for calculating the absolute magnitude (actual brightness) of a star? whats the absolute mag’ of the sun?

Answer 7

M= m-5log (d/10).
We need to know the absolute magnitude (M), the apparent magnitude (m) and the distance in parsecs (d).
the sun has a (+4.8) absolute magnitude

Question 8

What two ways do we have to measure the temp of a star? what temp is that?

Answer 8

Color- red (cool with long wavelenghts), orange, yellow, white, blue-white (hot with short wavelengths)
Blackbody curve

Question 9

How do we use the black body curve to measure the surface temp of a star?

Answer 9

Photometry- measuring the flux and intensity of the objects electromagnetic radiation. Telescope collects starlight. light passed through colored filters recorded on CCD. Atleast 3 different images added togehter and plotted to find blackbody curve

Question 10

How do we use spectral lines to measure the temperature of a star?

Answer 10

Different gases are present with certain temps and they give off different spectral lines

Question 11

What are spectral types in general? What are their various categories (the letters, the subtypes, the difference between the various types/subtypes)?

Answer 11

O stars are the hottest/bluest (30,000-50,000 K). M stars are the coolest/reddest (2,500-3,000 K). OBAFGKM sequence. Subtypes range from 0-9 (0 being the hottest and 9 being the coolest)

Question 12

Is color the same as temp?

Answer 12

color is representative of temp because you can tell the temp by loooking at the color

Question 13

what is the HR diagram? what do we measure on each axis, and what two alternate ways do we have for describing it? Roughly, what does the diagram look like?

Answer 13

The HR diagram identifies distinct groups of stars, graphs of the stellar luminosity or (M) against surface temp against spectral type. bright on top, dim at the bottom. hot on the left, cool on the right.

Question 14

What group of stars do we see on the HR diagram? Which of these groups do most stars belong to?

Answer 14

Ia, Ib are supergiants. II, III, IV are giants of various luminosities. V are main sequence (most stars belong to this class)

Question 15

How do stars’ properties (temp’, Energy-output, stellar size) change across the HR diagram?

Answer 15

Cooler to the right, hotter to the left, supergiants on top, giants in upper middle right. White dwarfs in lower left- still hot but also very small

Question 16

What is the Main Sequence?

Answer 16

its what we call the stage where stars spend most of their time, the more massive a star, the more luminous it is, the faster it leaves the main sequence

Question 17

Where are the Giants, Supergiants, White Dwarfs that we see on the HR diagram? How can we tell?

Answer 17

Supergiants and giants lie above and to the right of the main sequence on an HR diagram. The white dwarves are below and to the left or right depending mainly on surface temperature

Question 18

What type and class is the sun

Answer 18

G2v

Question 19

What ways do we have to measure masses of stars (What law do we use and what do we use it on)?

Answer 19

Keplers 3rd law: M1+ M2+ a^3/p^2 the sum of masses of both stars in a binary system is equal to the cube of semimajor axis over the spare of the period. The center of mass is the common point between which the elliptical orbits.

Question 20

What are the different kinds of Binaries?

Answer 20

Eclipsing binary- apparent magnitude dims when one star blocks out part of the other. Partial eclipse- creates a v-shaped trough.
Total eclipse- creates flat bottomed through visual binaries
Visual binary – pair of stars we can observe orbiting each other. To find the individual masses we need to know the distance from the center of mass. Radial velocity (star wobbling)

Question 21

As you move along the Main Sequence, how does the Luminosity change with higher or lower mass?

Answer 21

Mass-luminosity relation- the main sequence on the HR diagram is a progression in mass and luminosity and surface temp… the stars energy production is linked to its mass