P7 Ultimate Test

The [blank_start]observed brightness[blank_end] of a star depends on it's [blank_start]luminosity[blank_end] and how [blank_start]faraway[blank_end] it is from Earth, the [blank_start]luminosity[blank_end] of a star being the [blank_start]energy[blank_end] it gives out in the form of [blank_start]radiation[blank_end]. The luminosity of a star depends on the [blank_start]size[blank_end] and [blank_start]temperature[blank_end] of the star - the [blank_start]bigger[blank_end]/[blank_start]hotter[blank_end] it is, the the [blank_start]greater[blank_end] it's luminosity. If a star is further away, it will appear dimmer.

Cepheid Variables are [blank_start]groups of stars[blank_end] which [blank_start]pulse in brightness[blank_end]. They get [blank_start]brighter[blank_end] and [blank_start]dimmer[blank_end] over the course of [blank_start]several days[blank_end].

Tick the correct statements about Cepheid Variables:

Astronomers can work out the [blank_start]distance[blank_end] to a star by comparing it's [blank_start]luminosity[blank_end] with it's [blank_start]observed brightness[blank_end].

Curtis believed that: • The [blank_start]Universe[blank_end] was made-up of [blank_start]multiple galaxies[blank_end] • The [blank_start]Sun[blank_end] was at the [blank_start]centre[blank_end] of our galaxy • Our galaxy was [blank_start]10,000pc across[blank_end] • [blank_start]Spiral Nebulae[blank_end] were [blank_start]distant[blank_end] galaxies, [blank_start]not a part of[blank_end] the Milky Way

Shapley believed that: • The Universe was [blank_start]one big galaxy[blank_end], [blank_start]100,000pc[blank_end] across • He also believed that the [blank_start]Sun[blank_end] and the [blank_start]Solar System[blank_end] were [blank_start]faraway[blank_end] from the centre of the Universe. • He believed that nebulae were [blank_start]huge clouds of dust and gas[blank_end] and that these clouds were [blank_start]nearby[blank_end] and [blank_start]a part[blank_end] of the Milky Way.

With cepheid variables, the greater the luminosity, the longer the time between pulses.

Scientists can work out the [blank_start]distance[blank_end] to a star by comparing [blank_start]luminosity[blank_end] and [blank_start]observed brightness[blank_end]. Luminosity is worked out using the [blank_start]time between pulses[blank_end].