Astro 110 Test 2

Front 1

absolute magnitude

Back 1

a star's true energy output, its luminosity; the absolute magnitude of a star equals the apparent magnitude of a star at a distance of 10 parsecs

Front 2

apparent brightness

Back 2

brightness, amount of energy that passes each second through a square meter of the sphere's surface

Front 3

apparent magnitude

Back 3

how bright an object appears to an Earth-based observer, directly related to apparent brightness; scale goes backwards

Front 4

hertzsprung-russell diagram

Back 4

a diagram where the luminosities (absolute magnitudes) of stars are plotted against their spectral types (or surface temperatures)

Front 5

parallax

Back 5

apparent displacement of an object because of a change in the viewer's point of view

Front 6

parsec

Back 6

the distance at which a star has a parallax of one second; the word is a contraction of the phrase "the distance at which a star has a PARallax of one arcSECond" ; star with a parallax angle of 1 arcsec (second of arc) is at a distance of 1 parsec

Front 7

radial velocity

Back 7

the component of a star's motion parallel to our line of sight; either towards us or away from us

Front 8

tangential velocity

Back 8

the component of space velocity perpendicular to our line of sight; across the plane of the sky

Front 9

spectroscopic parallax

Back 9

the luminosity of a star if found using spectroscopy

Front 10

spectral types

Back 10

the added integer of 0 - 9 to the original letter from OBAFGAKM

Front 11

photometry

Back 11

measuring a star's apparent brightness

Front 12

spectral classes

Back 12

a star could be assigned a letter from A to O according to the strength or weakness of the hydrogen Balmer lines in the star's spectrum

Front 13

hydrogen fusion

Back 13

the process of converting hydrogen into helium, also called hydrogen burning

Front 14

thermonuclear fusion

Back 14

the fusing together of hydrogen nuclei, only takes place at extremely high temperatures because all nuclei are positively charged and repel each other, but at high temperatures, they are moving so fast that they overcome electric repulsion and touch one another, leading to thermonuclear fusion

Front 15

proton-proton chain

Back 15

a sequence of several separate reactions during which two of four protons (hydrogen nuclei) are turned into neutrons and eventually combine with the other protons to produce a helium nucleus

Front 16

hydrostatic equilibrium

Back 16

a balance between the weight of a layer in a star and the pressure that supports it

Front 17

thermal equilibrium

Back 17

the principle that the temperature in a star is different at different depths, but the temperature at each depth remains constant

Front 18

radiative diffusion

Back 18

protons created in the thermonuclear inferno at a star's center diffuse outward toward the star's surface; result: migration from hot core to cooler surface where they escape into space

Front 19

neutrino (solar neutrino)

Back 19

particles that have no electric charge, a solar neutrino is a neutrino from the sun

Front 20

photosphere

Back 20

a thin layer of gas from which all of the sun's visible light emanates

Front 21

stellar evolution

Back 21

how stars are born, live their lives, and finally die. Examples:
1) contracting clouds give birth to a clump called a protostar that becomes a main-sequence star
2) Protostar contracts and increases in surface temperature over time, not hot enough for thermonuclear fusion, glows b/c of heat form contraction
3)Accretion disks - starts adding mass to selves because accretion disk in nebula with protostar at center spins and particles in disk collide with each other and spiral in to the protostar
4) Cocoon nebulae - luminous starts emit UV radiation which makes dark nebula evaporate and leave pillars with a cocoon nebula containing a star at tip

Front 22

interstellar medium

Back 22

the combination of gas and dust between stars in space

Front 23

nebula

Back 23

an interstellar cloud

Front 24

accretion

Back 24

a process when particles orbiting the protostar within the disk collide with each other, causing them to lose energy, spiral inward onto the protostar, and then add to the protostar's mass

Front 25

protostar

Back 25

a star in its earliest stages of formation

Front 26

main-sequence lifetime

Back 26

the total time that a star will spend as a main-sequence star

Front 27

helium fusion

Back 27

the thermonuclear fusion of helium nuclei to form carbon and oxygen, releases energy

Front 28

Pauli exclusion principle

Back 28

a principle first stated in 1925 that states that two electrons cannot simultaneously occupy the same quantum state

Front 29

degeneracy

Back 29

a phenomenon where closely packed particles resist compression as a consequence of the Pauli exclusion principle

Front 30

star colors

Back 30

red stars - cold; blue stars - hot

Front 31

brown dwarf

Back 31

a substar too small of thermonuclear fusion, glows by heat

Front 32

white dwarf

Back 32

a small, but hot star with a low luminosity; frequently stars become white dwarfs after their time on the main sequence

Front 33

optical double stars

Back 33

two stars that are in the same line of sight but at different distances

Front 34

binaries

Back 34

a pair of stars that orbit each other

Front 35

dark nebulae

Back 35

nebulae that block all light because they have a dense concentration of dust; many stars form here

Front 36

reflection nebulae

Back 36

nebulae with a lower concentration of dust than dark nebulae, the dust scatters short wavelength blue light better than longer wavelength red light giving the nebulae a blue color

Front 37

interstellar extinction

Back 37

intensity of light is reduced as it passes through material in interstellar space

Front 38

interstellar reddening

Back 38

an effect where the light from remote stars appears redder because as it passes through the interstellar medium, blue light is scattered and abosrbed, while long wavelength red light passes through

Front 39

best formation places for stars

Back 39

1) stars will most easily form in places where the interstellar material is relatively dense because gravity must overcome the internal pressure pushing particles apart to form a star.
2) the pressure of the interstellar medium should be low
3) temperature should be as low as possible, pressure goes down as gas temperature decreases
All of this equals - Dark Nebulae

Front 40

Earth's 3 main energy sources

Back 40

solar energy, tidal forces from sun and moon power ocean, internal heat creates geologic activity

Front 41

plate tectonics

Back 41

movement of the plates, driven by convection within the asthenosphere

Front 42

Earth's 3 main energy sources

Back 42

solar energy, tidal forces from sun and moon power ocean, internal heat creates geologic activity

Front 43

plate tectonics

Back 43

movement of the plates, driven by convection within the asthenosphere

Front 44

Earth's 3 main energy sources

Back 44

solar energy, tidal forces from sun and moon power ocean, internal heat creates geologic activity

Front 45

plate tectonics

Back 45

movement of the plates, driven by convection within the asthenosphere

Front 46

Theories of the moon's origin
1) Fission Theory
2) Capture Theory
3) Co-Creation Theory
4) Collisional Ejection Theory

Back 46

1) Early Earth was spinning so fast that a chunk of its mass tore away and became the Moon.
2) the Moon was formed elsewhere in the solar system but but was drawn to the earth by gravitational forces
3) Earth and Moon were formed at the same time, but separately.
4) Proto-Earth was struck off-center by a Mars-sized object and this collision ejected debris from which the moon was formed. CORRECT ONE!