BRAINCAKESpace
Revision notes for Space in Edexcel Physics (9PH0). Read the start of any lesson here, then sign in free for the whole lesson, the R.E.C.I.P.E. recall steps and the quiz.
- Black-Body RadiationA black body is an idealised object that absorbs all the electromagnetic radiation that falls on it, at every wavelength.
- Stefan-Boltzmann LawThe luminosity L of a star is the total power it emits as electromagnetic radiation, in watts.
- Wien's LawThe wavelength at which a black body emits the greatest intensity is called the peak wavelength, λmax.
- Luminosity and IntensityTwo different quantities describe how bright a star is, and it is important not to mix them up.
- The Inverse Square Law for IntensityA star radiates its power equally in all directions.
- Estimating Stellar Radius and TemperatureWe cannot measure the size of a distant star directly, but combining the laws from the previous lessons lets us calculate it.
- The Hertzsprung-Russell DiagramThe Hertzsprung-Russell (H-R) diagram is a graph of stars' luminosity against their surface temperature.
- Formation of a StarStars form inside a nebula, a huge cloud of dust and gas that is mostly hydrogen.
- Life Cycle of a StarWhat happens to a star after the main sequence depends mainly on its mass.
- White Dwarfs, Neutron Stars and Black HolesWhen fusion stops, what is left of a star's core is a compact remnant.
- Trigonometric ParallaxTrigonometric parallax is used to measure the distance to nearby stars.
- Standard CandlesParallax only works for relatively nearby stars.
- The Doppler Effect and Red ShiftWhen a source of waves moves relative to an observer, the observed wavelength and frequency change: the Doppler effect.
- Hubble's LawIn the 1920s, Hubble measured the red shifts of galaxies, giving their recession velocities, and their distances, using standard candles such as…
- The Age of the UniverseHubble's law can be used to estimate the age of the universe.
- The Expanding UniverseAlmost every galaxy shows a red shift, and the red shift increases with distance (Hubble's law).
- Dark MatterDark matter is matter that does not emit or absorb electromagnetic radiation, so it cannot be seen.
- The Fate of the UniverseThe universe is expanding, but gravity between all the matter in it acts to slow that expansion down.