IB Physics Option D Astrophysics

Small rocky body that drifts around the solar system

Asteroid on a collision course with another planet

Mixtures of rocks and ice in very elliptical orbits around the Sun

Cloud of gas and dust where stars begin to form

Two or more stars orbiting around their common centre of mass

Can be distinguished using a telescope

As one star approaches Earth, the other recedes

A large number of stars held together in a group by gravitational attraction

Stars formed around the same time in the same the region probably from the same nebula

Up to several 100 stars, younger than 10 billion years

Group of stars that form a recognisable pattern that are not gravitationally bound together

Distance light travels in one year

Mean distance between the Earth and the Sun

Total power emitted by the star

Incident power per unit area received at the surface of the earth

Line of length 1 astronomical unit subtends an angle of 1 arcsecond at this distance

Extremely luminous stars that undergo regular and predictable changes in luminosity

Produce energy from fusion of hydrogen, helium and carbon, among other nuclei (~ 90% of stars)

Cooler than main sequence stars and emit less energy per square metre but are more luminous, with a greater surface area and diameter

White dwarves cannot have a mass greater than 1.4 * the mass of the Sun

For neutron stars between 1.5 and 3 solar masses, the neutron degeneracy pressure can resist the collapse into a black hole

Optical (absorption) spectra moved towards the red end of the EM spectrum

A body moving away from an observer

Due to the stretching of space itself leading to stretched wavelengths

Magnitude of the (gravitational) potential energy of the gas must be greater than the kinetic energy of the gas (depends on the temperature and particle density in the gas cloud)

Production of different nuclides by the fusion of nuclei

Slow neutron capture (producing nuclides up to Bi-209) – small neutron flux, in massive stars

Rapid neutron capture (producing nuclides heavier than Bi-209) – strong neutron flux, in supernovae

No hydrogen line, evolved from old, low-mass stars

Hydrogen line present, evolved from young, massive stars.
(Consist of single massive stars in the final stages of their evolution)

Result from accretion of matter between two stars in a binary star
Standard candles – all have same peak luminosity as they are formed when mass reaches Chandrasekar limit. Measure apparent brightness and calculate distance

Universe is homogeneous and isotropic

Density of universe greater than critical density

Density of universe less than critical density

Density of universe equal to critical density

Massive compact halo objects: high density stars, hidden as they are far away from any luminous object – black holes, neutron stars, black dwarfs

Weakly interacting massive particles; non-baryonic subatomic particles, weakly interacting with baryonic matter; need huge quantities to make up dark matter

Minute temperature fluctuations in the CMB

Objects of known luminosity

A measure of cosmological redshift

the redshift of a wavelength

the wavelength measured at rest on Earth

Original size of the universe

Current size of the universe