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Flashcards in Fourth-Fifth Test Deck (67)
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1

Harvard calculators

women who sat around in harvard and did math. famous: annie cannon and henrietta leavitt. both deaf math majors

2

Henry Draper

lived mid 19th century, interested in spectral lines but unsure what they were. had ability to make good spectra. on death wife gave money to harvard to study spectra, spectra discoveries there named after him.

3

star spectral types

Annie Cannon noticed similarities in different stars, designed an A-V sequence. When it was figured out what spectral lines are, cannon rearranged stars onto a scale from hot-cool, 30,000K to 3000K. O B A F G K M.

4

Draper Spectral Classification System

O B A F G K M. From hot to cool, 30,000K to 3000K. 0-9 subtypes. Oh, be a fine girl, kiss me!
division of temperature based on spectral lines.

5

HR Diagram

get apparent mag, get distance and temperature from spectral math filtering. get graph of line going top left to bottom right, hot left on X, bright high on Y. the line is the MAIN SEQUENCE. red giants in top right- low T high brightness, white dwarfs bottom left- opposite.

6

spectroscopic parallax

distance from star derived from spectrographs. astronomers call all distance spectrograph.

7

luminosity variance of stars

Henrietta Leavitt discovered that some stars vary in magnitude regularly, period measured in day. she checked if variation was related to anything useful- it was! luminosity... that is, the higher the period of of the star, the brighter it is.

8

cepheid star

UNCLEAR. a star that exhibits a certain kind of period-luminosity relationship. used as a standard candle to measure distances. including to distant galaxies, because 99% of the distance to a star is the distance to its galaxy.

9

two types of cepheid variables

Type I "classical", type 2 "w viginis" viginis lower and lefter on graph.

10

stellar nurseries

gas clouds such as orion. gas and dust ejected from supernova, gas collapses, protostars blow gas around, disks form etc.

11

Messier catalog

1781, by messier. Lots of items have messier number.

12

NGC catalog

new general catalog. 1886, more stars.

13

solar system formation

cloud->disk->star-> planets

14

what happens to materials of dying star

5-10% imploded. 90-95% sent out and recycled.

15

making mathematical model of stars

make star into series of concentric circles. assumptions: star is spherical, layers made by concentric circles are same all around. measure Temperature, density, pressure, composition (T1, Ro1, Comp1, P1) of outermost layer with spectral stuff. Use physics to calculate it for each layer going in. Calculus removes the layers and can make it a continuous calculation.

16

once mathematical model exists

star can be evolved in the fourth dimension!

17

first stage of stellar evolution

Very big, low density cloud, density increasing, hot gas rises, cold sinks... strong convection. Temperature stays same, cloud gets smaller, thus smaller brightness.

18

second stage of stellar evolution

density continues to increase, convection gets harder, almost stops, keeps collapsing. temp keeps going up, still getting smaller = dimmer. moves left on graph.

19

third stage

gets hot enough that star IGNITES: hydrogen burns into helium, starts temperature chain reaction. equilibrium between temperature and gravitational pressure. is a star with disk around it that forms into planet

20

collapse of cloud into star

cloud has some natural tendency to rotate. as gravity shrinks it, spins faster to conserve angular momentum. Horizontal force towards center, vertical force towards equator of spin: causes disk with packed middle. spirals up or down.

21

other STAR formation fact.s

clouds of gas often form more than one star, many points of light. can form binary, tertiary stars, star clusters

22

once mathematical model exists

star can be evolved in the fourth dimension!

23

first stage of stellar evolution

Very big, low density cloud, density increasing, hot gas rises, cold sinks... strong convection. Temperature stays same, cloud gets smaller, thus smaller brightness.

24

second stage of stellar evolution

density continues to increase, convection gets harder, almost stops, keeps collapsing. temp keeps going up, still getting smaller = dimmer. moves left on graph.

25

gestation times of different stars

100 solar mass stars born in 10k yrs, solar mass one million, 10^8 years for much smaller. they also die in related amounts of time.

26

collapse of cloud into star

cloud has some natural tendency to rotate. as gravity shrinks it, spins faster to conserve angular momentum. Horizontal force towards center, vertical force towards equator of spin: causes disk with packed middle. spirals up or down.

27

other STAR formation fact.s

clouds of gas often form more than one star, many points of light. can form binary, tertiary stars, star clusters

28

accretion theory

one idea of how planets form. in cloud orbiting protostar, molecules stick together chemically. those then start sticking together gravitationally. kepler's third say that each little orbiting body orbits at different velocities, tug and stick to each other

29

moon formation

maybe further accretion disks, maybe giant impact- he doesn't like this

30

minimum mass for H fusion

1/12th solar mass