IB Physics HL option E: Astrophysics
Outline the general structure of the
solar system.
solar system.
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.
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.
Distinguish between a stellar cluster
and a constellation.
and a constellation.
…
Define the light year.
…
Compare the relative distances
between stars within a galaxy and
between galaxies, in terms of order of
magnitude.
between stars within a galaxy and
between galaxies, in terms of order of
magnitude.
…
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.
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.
…
State that fusion is the main energy
source of stars.
source of stars.
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.
in which hydrogen is converted into helium. They
do not need to know about the fusion of elements
with higher proton numbers.
Explain that, in a stable star (for
example, our Sun), there is an
equilibrium between radiation
pressure and gravitational pressure.
example, our Sun), there is an
equilibrium between radiation
pressure and gravitational pressure.
…
Define the luminosity of a star.
…
Define apparent brightness and state
how it is measured.
how it is measured.
…
Apply the Stefan-Boltzmann law to
compare the luminosities of different
stars.
compare the luminosities of different
stars.
…
State Wien’s (displacement) law and
apply it to explain the connection
between the colour and temperature
of stars.
apply it to explain the connection
between the colour and temperature
of stars.
…
Explain how atomic spectra may be
used to deduce chemical and physical
data for stars.
used to deduce chemical and physical
data for stars.
Students must have a qualitative appreciation of
the Doppler effect as applied to light, including the
terms red-shift and blue-shift.
the Doppler effect as applied to light, including the
terms red-shift and blue-shift.
Describe the overall classification
system of spectral classes.
system of spectral classes.
Students need to refer only to the principal spectral
classes (OBAFGKM).
classes (OBAFGKM).
Describe the different types of star.
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.
stars, Cepheids, red giants, red supergiants and
white dwarfs. Knowledge of different types of
Cepheids is not required.
Discuss the characteristics of
spectroscopic and eclipsing binary
stars.
spectroscopic and eclipsing binary
stars.
…
Identify the general regions of star
types on a Hertzsprung-Russell (HR)
diagram.
types on a Hertzsprung-Russell (HR)
diagram.
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.
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.
Define the parsec.
…
Describe the stellar parallax method
of determining the distance to a star.
of determining the distance to a star.
…
Explain why the method of stellar
parallax is limited to measuring stellar
distances less than several hundred
parsecs.
parallax is limited to measuring stellar
distances less than several hundred
parsecs.
…
Solve problems involving stellar
parallax.
parallax.
…
Describe the apparent magnitude
scale.
scale.
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.
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.
Define absolute magnitude.
The magnitude of a star viewed from a distance of 10 PC
Solve problems involving apparent
magnitude, absolute magnitude and
distance.
magnitude, absolute magnitude and
distance.
…
Solve problems involving apparent
brightness and apparent magnitude.
brightness and apparent magnitude.
…
State that the luminosity of a star may
be estimated from its spectrum.
be estimated from its spectrum.
…
Explain how stellar distance may
be determined using apparent
brightness and luminosity.
be determined using apparent
brightness and luminosity.
…
State that the method of
spectroscopic parallax is limited to
measuring stellar distances less than
about 10 Mpc.
spectroscopic parallax is limited to
measuring stellar distances less than
about 10 Mpc.
…
Solve problems involving stellar
distances, apparent brightness and
luminosity.
distances, apparent brightness and
luminosity.
…
Outline the nature of a Cepheid
variable.
variable.
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
star in which the outer layers undergo a periodic
expansion and contraction, which produces a
periodic variation in its luminosity
State the relationship between period
and absolute magnitude for Cepheid
variables.
and absolute magnitude for Cepheid
variables.
…
Explain how Cepheid variables may
be used as “standard candles”.
be used as “standard candles”.
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.
variable is located in a particular galaxy, then the
distance to the galaxy may be determined.
Determine the distance to a Cepheid
variable using the luminosity-period
relationship.
variable using the luminosity-period
relationship.
…
Describe Newton’s model of the
universe.
universe.
Students should know that Newton assumed an
infinite (in space and time), uniform and static
universe.
infinite (in space and time), uniform and static
universe.
Explain Olbers’ paradox.
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.
using the inverse square law of luminosity, that
Newton’s model of the universe leads to a sky that
should never be dark.