GCSE Physics P7 (OCR) - Mapping the Universe


GCSE Physics (P7) Flashcards on GCSE Physics P7 (OCR) - Mapping the Universe, created by Josh Price on 24/04/2015.
Josh Price
Flashcards by Josh Price, updated more than 1 year ago
Josh Price
Created by Josh Price over 8 years ago

Resource summary

Question Answer
What is parallax? The shifting of position against a fixed background. Therefore, it makes closer stars appear to shift more, relative to distant ones.
How do you define the parallax angle of a star? Half the angle moved against a background of very distant stars in six months.
The ________ the parallax angle, the __________ the star. Greater Closer
What is the definition of a parsec (pc)? The distance to a star with a parallax angle of one second of arc.
How much is one second of arc? 1/3600th of a degree.
How do you calculate distance in parsecs? 1 ---------------------------------------- Parallax angle (sec)
Typically, what is the distance between neighbouring stars? A few parsecs
What does the luminosity of a star depend upon? It's temperature and size
What do Cepheid variable stars do? Pulse in brightness, with a period related to their luminosity.
The _______ the period, the _______ the Cepheid. Longer Brighter
How do astronomers estimate the distance to Cepheid variables? - Find some nearby Cepheids whose distances have been measured accurately. - Measure their brightness and luminosity - Plot a graph of luminosity against period - Measure the observed brightness and period of a Cepheid of interest, and find the luminosity from the graph - Use luminosity and brightness to work out the distance.
What did telescopes reveal? That the Milky Way consists of millions of stars, and that the Sun was a star in the Milky Way galaxy.
What else did telescopes reveal? Fuzzy objects in the night sky, and these were originally called nebulae.
What was the main issue in the Curtis-Shapely debate? Where spiral nebulae objects within the Milky way or separate galaxies outside it?
What did Hubble's observations of Cepheid variables conclude? The Cepheid variables in one nebula indicated that it was much further away than any star in the Milky Way, so he concluded that this nebula was a separate galaxy.
What are intergalactic distances typically measured in? Megaparsecs (Mpc)
How do you calculate the speed of recession (km/s) of a distant galaxy? Hubble Constant (km/s per Mpc) ------------------------------------------------------- Distance (Mpc)
How do the motions of galaxies suggest that space itself is expanding? The further away they are, the faster they are moving. Everything appears to be moving away.
How do scientists believe the world began? With a 'Big Bang' about 14 million years ago.
Show full summary Hide full summary


GCSE Physics P7 (OCR) - Light, Telescopes, and Images
Josh Price
GCSE Physics P7 (OCR) - Astronomy
Josh Price
GCSE Physics P7 (OCR) - Sun, and Stars
Josh Price
GCSE Physics P7 (OCR) - Astronomy Community
Josh Price
Physics Revision
Tom Mitchell
OCR Physics P2 revision cards
Alex Howard
P2 Quiz
Leah Firmstone
Forces and their effects
OCR Physics P4 Revision
Dan Allibone
P1 - The Earth in the Universe