P7

Stars, planets and the Moon appear to travel east-west across the sky

Sidereal day = time taken for the earth to rotate 360 degrees

Solar day = 24 hours

Lunar cycle = Moon's apperance during 28 day orbit of Earth

Solar eclipse = moon passes between earth and sun

Lunar eclipse = earth passes between sun and moon

Parallax = thought of as apparent motion of object against background

Parallax angle of star = half the angle moved against a background of distant stars in 6 months

Parsec = distance to a star with a parallax angle of one second of an arc

Intrinsic brightness = size and temperature

Observed brightness = intrinsic brightness and distance from earth

Cepheid variable star = pulses = varying brightness = used to work out distance

Stars have 3 main parts...

- Core = where fusion takes place

- Convection Zone = where energy is transported to surface

- Photosphere = where energy is radiated into space

Star's spectrum show the different elements it contains.

Beginning of life => gravity brings gas clouds together

=> pressure, temperature and gravity increase => protostar forms

=> hydrogen nuclei fuse into helium nuclei => stable star forms

End of life = core hydrogen begins to run out.... and either....

= small star become red giants = white dwarf

or

= larger stars become red supergiants = neutron star or black hole

Fuzzy objects in the sky called nebulae...

- curtis believed nebulae were distant galaxies

- shapley believed nebulae were gas clouds within our galaxy

Studying cepheid variables provided evidence that nebulae were distant galaxies

Speed of recession = hubble constant x distance

Gold foil bombarded with alpha particles = most particles passed straight through, some were deflected or bounced back

Conclusion = atoms have small, dense, positive core called nucleus. Electrons arranged around nucleus

Particles collide = force exerted = felt as pressure

Volume of fluid reduced = pressure increases

Fluid heated up = volume increases or pressure increases

Absolute temperature = measure of temperature starting at absolute zero

Kelvin converted into degrees celsius = subtract 273

Degrees celsius converted into kelvin = add 273

Power (dioptre) = 1/focal length (m)

Magnification = focal length of objective lens/focal length of eyepiece lens

Telescopes can be ground based or space based

International co-operation is beneficial developing space technology

Angular magnification = larger angle from distant magnified object = object appears bigger

Radio = long wavelength = easily diffracted = fuzzy image

Light = short wavelength = not diffracted easily = sharp image