618502
Description
Flashcards by Moa Lindström, updated more than 1 year ago
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Created by Moa Lindström
almost 11 years ago
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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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