Definitions Astrophysics

Moa Lindström
Flashcards by Moa Lindström, updated more than 1 year ago
Moa Lindström
Created by Moa Lindström over 7 years ago
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physics HL, chapter 10 Don't know if any of these are redundant though

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Question Answer
Time for Earth to do one full revolution 23 hours 56 minutes
Precession turning effect, pulling the axis of rotation slightly out of line
Time for Moon to orbit Earth 27,3 days
Official defiition of a planet, International Astronomical Union (IAU) A 'planet' is a celestial body that (a) is in orbit around the sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit
Mercury Orbit radius (m): 5.79 x 10^10 Mass (kg): 3.3 x 10^23 Radius (m): 2.44 x 10^6 Period: 88.0 days
Venus Orbit radius (m): 1.08 x 10^11 Mass (kg): 4.87 x 10^24 Radius (m): 6.05 x 10^6 Period: 224.7 days
Earth Orbit radius (m): 1.50 x 10^11 Mass (kg): 5.98 x 10^24 Radius (m): 6.38 x 10^6 Period: 365.3 days
Mars Orbit radius (m): 2.28 x 10^11 Mass (kg): 6.42 x 10^23 Radius (m): 3.40 x 10^6 Period: 687.0 days
Jupiter Orbit radius (m): 7.78 x 10^11 Mass (kg): 1.90 x 10^27 Radius (m): 6.91 x 10^7 Period: 11.86 years
Saturn Orbit radius (m): 1.43 x 10^12 Mass (kg): 5.69 x 10^26 Radius (m): 6.03 x 10^7 Period: 29.42 years
Uranus Orbit radius (m): 2.88 x 10^12 Mass (kg): 8.66 x 10^25 Radius (m): 2.56 x 10^7 Period: 83.75 years
Neptune Orbit radius (m): 4.50 x 10^12 Mass (kg): 1.03 x 10^26 Radius (m): 2.48 x 10^7 Period: 163.7 years
Asteroids smaller orbiting bodies
Comets small orbiting body, unlike asteroids it's made up of loose particles of ice and rock, forming a tail
Stars all shapes, sizes and colours massive balls of plasma
Constellations 'join the dots' the stars are not related by anything physical except maybe that they are all bright
Stellar cluster group of stars that are physically close together rather than looking as if they are formed by the collapse of a gas cloud
Astronomical Unit (AU) 1.5 x 10^11 m distance between Sun and Earth
Light year (ly) 9.46 x 10^15 m distance travelled by light in one year
Parsec (pc) 3.26 ly defined in terms of the angle subtended at the star defined by making a triangle between Earth, Sun and distant object. if the angle at the distant object is 1 arcsec then it is 1 parsec away
Galaxy large collection of stars held together by gravity, between 10^3 and 10^5 ly across
Stable star isn't getting bigger or smaller
Luminosity (L) the total amount of energy emitted by the star per second
Apparent brightness (b) the amount of energy per second receiver per unit area b=L/4(pi)d^2 unit: W m^-2
Stefan-Boltzmann law power per unit area =(S-B constant)T^4
If a star has surface area A, temperature T, then the total power emitted (L) is given by... L= (S-B constant)AT^4
O B A F G K M Temperature, colour 30 000- 60 000, blue 10 000- 30 000, blue-white 7 500 -10 000, white 6 000- 7 500, yellow-white 5 000- 6 000, yellow 3 500- 5 000, orange 2 000- 3 500, red
Red (doppler) shift longer wavelength moving away
Blue (doppler) shift shorter wavelength moving closer
90% of stars on H-R diagram main sequence stars
Giants cool star that gives out lots of energy
Supergiants very big cool star
White dwarfs small hot stars
Variable stars has a changing luminosity, position on H-R diagram is not constant this is due to a change in size of the star, this variation is sometimes cyclid as in a Cepheid variable
Binary stars pairs of stars that orbit eachother
Visual binaries can be seen to rotate around eachother some binaries are too far away or too small to resolve the individual stars; we only know they are binaries due to fluctuations in the light we receive
Eclipsing binaries binary stars which orbits causes them to periodically pass between the Earth and each other, causes a reduction in the stars apparent brightness
Spectroscopic binary binary stars which, in their orbit, are sometimes moving towards the Earth and sometimes away, this will cause a varying Doppler shift in the light received on Earth
Stellar parallax ...?
Spectroscopic parallax ...?
Second one degree can be split up into 60 arc minutes and each arc minute into 60 arc seconds, so there are 3 600 arc seconds in one degree in radians, 1 arc second is therefore (1/3600) x (2(pi)/360)
Standard candle (Cepheid variables) knowing the luminosity of a candle you can use it to measure distance. the further away, the dimmer. since the luminosity of Cepheid variables is known they can be used in the same way
Cepheid variable unstable star that undergoes periodic expansions and contractions, leading to a periodic change in the apparent brightness
Apparent magnitude (m) a+1 was 100 times brighter than a+6 starting from the dimmest each step in magnitude is therefore 2.512 times brighter than the previous
Absolute magnitude measure of luminosity the magnitude of a star viewed from a distance of 10 pc
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