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Study > Astrophysics Terminology SL > Flashcards

Astrophysics Terminology SL Flashcards

1
Q

solar system

A

collection of planets, moons, asteroids, comets, and other rocky objects in elliptical orbit around the sun

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2
Q

asteroids

A

rocky objects orbiting the sun

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3
Q

comets

A

irregular objects of ice, rock, and dust orbiting the sun

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4
Q

nebula

A

enormous cloud of dust and gas where stars often form

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5
Q

binary stars

A

two stars that rotate about a common center of mass

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6
Q

stellar cluster

A

group of stars close enough to be held together by gravity

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7
Q

open cluster

A

several hundred stars younger than ten billion years that still contain gas and dust

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8
Q

global cluster

A

stars older than 11 billion years containing little gas and dust

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9
Q

constellation

A

pattern formed from stars, not held together by gravity

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10
Q

galaxy

A

stars, gas, and dust held together by gravity containing billions of stars

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11
Q

spiral galaxies

A

disc shape with spiral arms spreading out from a central galactic bulge that contains the greatest density of stars

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12
Q

spiral arms

A

many young blue stars, gas, and dust

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13
Q

irregular galaxies

A

shapeless and can be stretched in the presence of other bigger galaxies

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14
Q

light year

A

distance traveled by light in one year ( 1ly = 9.46 x 10^15 m )

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15
Q

astronomical unit

A

average distance between the sun and earth (au) 1au =1.50 x 10^11m – approximately 8mins

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16
Q

parsec

A

(pc) most commonly used distance in astrophysics 1pc = 3.26 ly = 3.09 x 10^16m

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17
Q

stellar parallax

A

the star’s apparent shift of position of any nearby star against the background of distant stars – which can be used to measure the distance of stars from us

18
Q

luminosity

A

the energy emitted by the star per second in watts – amount of light emitted from the stars surface

19
Q

brightness

A

watts per square meter (Wm^-2) – how bright the star appears to be from earth

20
Q

black bodies

A

theoretical objects that absorb all radiation incident upon them. perfect emitters for radiation, emitting the maximum radiation possible at their temperature

21
Q

black body radiation

A

all objects with temperatures above absolute zero emits this

22
Q

cepheid variables

A

highly luminous stars with regular and predictable changes in luminosity due to its cycle

23
Q

What is the cycle of a cepheid star?

A
  1. Layer loses hydrostatic equilibrium and compresses inwards
  2. The star becomes less transparent
  3. The star heats up and internal pressure increases
  4. The layer of the star is pushed outwards, therefore, the star expands
  5. The layer cools and becomes less dense
  6. The radiation escapes and the pressure inside the star decreases. – The cycle then repeats
24
Q

Hertzsprung-Russell diagram

A

depicts the relationship between the luminosities and temperatures of the stars (memorize the groups of stars on that diagram)

25
Q

red giant stars

A

Cooler stars that emit less energy. They have higher luminosities and a larger surface area/diameter compared to the sun

26
Q

Supergiant stars

A

Gigantic, bright stars that emit more energy with a larger surface area/diameter compared to the sun

27
Q

White dwarfs

A

Remnants of old stars that are hot and dense. They have low luminosity and a small surface area

28
Q

Main sequence star

A

Any star that fuses hydrogen in its core and has a stable balance of outward pressure due to nuclear fusion. Gravitational forces push inwards. – hotter and bigger stars w/ a finite life time

29
Q

hydrostatic equilibrium

A

pressure due to gravitational attraction of inner shells is equal to the thermal and radiation pressure acting outwards

30
Q

electron degeneracy pressure

A

resistance a densely patched gas of electrons exerts against further compression – this prevents the collapse of celestial objects

31
Q

supernova

A

when a star collapses and the neutrons come close to each other. the outer layers of the star rush toward the core but then explode. the remnants are the neutron stars

32
Q

neutron degeneracy pressure

A

pressure of a neutron star that resists further gravitational collapse into a black hole

33
Q

Oppenheimer-volkoff limit

A

the upper value of a neutron star where neutron degeneracy resists further collapse of a black hole

34
Q

black hole

A

a region of space having a gravitational field so intense that no matter or radiation can escape

35
Q

local redshift

A

occurs within galaxies or clusters, when movement causes the wavelengths emitted to be longer

36
Q

blue shift

A

when movement causes the wavelengths emitted to be shorter

37
Q

cosmological redshift

A

the larger scale of local redshift that is associated with the expansion of the universe. Light travels through the expanding space thus its wavelength is stretched

38
Q

solar mass

A

standard unit of mass in astronomy – the approximate mass of the sun ( 2 x 10^30 kg )

39
Q

What is the period-luminosity law for the Cepheid stars?

A

It’s the relationship between the pulsation period of a cepheid star and its luminosity. The brighter the star, the slower it pulses.

40
Q

Chandrasekhar mass limit

A

Approximately 1.4 times the mass of the sun – determines whether a star will form a white dwarf or a neutron star
If the mass of the remnant core after the red giant phase is < mass limit, it will become a white dwarf
If the mass of the remnant core > mass limit, it will become a neutron star or black hole

41
Q

hubble’s law

A

the velocity that galaxies are moving away from us is directly proportional to their distance from us – the further away the galaxy is, the faster it is moving away

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