IB Physics HL option E: Astrophysics – Flashcards
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Outline the general structure of the solar system.
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Students should know that the planets orbit the Sun in ellipses and moons orbit planets. (Details of Kepler's laws are not required.) Students should also know the names of the planets, their approximate comparative sizes and comparative distances from the Sun, the nature of comets, and the nature and position of the asteroid belt.
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Distinguish between a stellar cluster and a constellation.
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Define the light year.
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Compare the relative distances between stars within a galaxy and between galaxies, in terms of order of magnitude.
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Describe the apparent motion of the stars/constellations over a period of a night and over a period of a year, and explain these observations in terms of the rotation and revolution of the Earth.
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State that fusion is the main energy source of stars.
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Students should know that the basic process is one in which hydrogen is converted into helium. They do not need to know about the fusion of elements with higher proton numbers.
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Explain that, in a stable star (for example, our Sun), there is an equilibrium between radiation pressure and gravitational pressure.
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Define the luminosity of a star.
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Define apparent brightness and state how it is measured.
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Apply the Stefan-Boltzmann law to compare the luminosities of different stars.
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State Wien's (displacement) law and apply it to explain the connection between the colour and temperature of stars.
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Explain how atomic spectra may be used to deduce chemical and physical data for stars.
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Students must have a qualitative appreciation of the Doppler effect as applied to light, including the terms red-shift and blue-shift.
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Describe the overall classification system of spectral classes.
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Students need to refer only to the principal spectral classes (OBAFGKM).
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Describe the different types of star.
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Students need to refer only to single and binary stars, Cepheids, red giants, red supergiants and white dwarfs. Knowledge of different types of Cepheids is not required.
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Discuss the characteristics of spectroscopic and eclipsing binary stars.
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Identify the general regions of star types on a Hertzsprung-Russell (HR) diagram.
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Main sequence, red giant, red supergiant, white dwarf and Cepheid stars should be shown, with scales of luminosity and/or absolute magnitude, spectral class and/or surface temperature indicated. Students should be aware that the scale is not linear. Students should know that the mass of main sequence stars is dependent on position on the HR diagram.
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Define the parsec.
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Describe the stellar parallax method of determining the distance to a star.
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Explain why the method of stellar parallax is limited to measuring stellar distances less than several hundred parsecs.
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Solve problems involving stellar parallax.
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Describe the apparent magnitude scale.
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Students should know that apparent magnitude depends on luminosity and the distance to a star. They should also know that a magnitude 1 star is 100 times brighter than a magnitude 6 star.
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Define absolute magnitude.
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The magnitude of a star viewed from a distance of 10 PC
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Solve problems involving apparent magnitude, absolute magnitude and distance.
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Solve problems involving apparent brightness and apparent magnitude.
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State that the luminosity of a star may be estimated from its spectrum.
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Explain how stellar distance may be determined using apparent brightness and luminosity.
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State that the method of spectroscopic parallax is limited to measuring stellar distances less than about 10 Mpc.
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Solve problems involving stellar distances, apparent brightness and luminosity.
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Outline the nature of a Cepheid variable.
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Students should know that a Cepheid variable is a star in which the outer layers undergo a periodic expansion and contraction, which produces a periodic variation in its luminosity
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State the relationship between period and absolute magnitude for Cepheid variables.
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Explain how Cepheid variables may be used as "standard candles".
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It is sufficient for students to know that, if a Cepheid variable is located in a particular galaxy, then the distance to the galaxy may be determined.
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Determine the distance to a Cepheid variable using the luminosity-period relationship.
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Describe Newton's model of the universe.
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Students should know that Newton assumed an infinite (in space and time), uniform and static universe.
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Explain Olbers' paradox.
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Students should be able to show quantitatively, using the inverse square law of luminosity, that Newton's model of the universe leads to a sky that should never be dark.
