Karteikarten
GCSE Physics P7 (OCR) - Mapping the Universe
Karten in diesem Stapel (19)
- 1What is parallax?The shifting of position against a fixed background. Therefore, it makes closer stars appear to shift more, relative to distant ones.
- 2How do you define the parallax angle of a star?Half the angle moved against a background of very distant stars in six months.
- 3The ________ the parallax angle, the __________ the star.Greater
Closer - 4What is the definition of a parsec (pc)?The distance to a star with a parallax angle of one second of arc.
- 5How much is one second of arc?1/3600th of a degree.
- 6How do you calculate distance in parsecs?1
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Parallax angle (sec) - 7Typically, what is the distance between neighbouring stars?A few parsecs
- 8What does the luminosity of a star depend upon?It's temperature and size
- 9What do Cepheid variable stars do?Pulse in brightness, with a period related to their luminosity.
- 10The _______ the period, the _______ the Cepheid.Longer
Brighter - 11How 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. - 12What did telescopes reveal?That the Milky Way consists of millions of stars, and that the Sun was a star in the Milky Way galaxy.
- 13What else did telescopes reveal?Fuzzy objects in the night sky, and these were originally called nebulae.
- 14What was the main issue in the Curtis-Shapely debate?Where spiral nebulae objects within the Milky way or separate galaxies outside it?
- 15What 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.
- 16What are intergalactic distances typically measured in?Megaparsecs (Mpc)
- 17How do you calculate the speed of recession (km/s) of a distant galaxy?Hubble Constant (km/s per Mpc)
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Distance (Mpc) - 18How 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.
- 19How do scientists believe the world began?With a 'Big Bang' about 14 million years ago.
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- GCSE Physics (P7) Karteikarten am GCSE Physics P7 (OCR) - Mapping the Universe, erstellt von Josh Price am 24/04/2015.
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- Josh Price
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