Variable Stars
High School

The following are a number of examples in which astronomy relates to the High School curriculum.


Spectral Lines: Spectral lines reflect the temperature in the 7 different classes of stars- The coolest stars show spectral lines of molecules and neutral metals while the hottest, bluest stars’ spectral lines are from ionized helium atoms; the hotter the gas, the faster the molecules or atoms move, the more likely electrons will be disturbed (excited) or disrupted (removed); emission and absorption lines thus depend on electron orbital structure of atoms.

Star Equilibrium: Main-sequence star equilibrium is determined by star's mass and chemical compositions. Nuclear reactions result in change of equilibrium, leading the stellar evolution. Hydrogen-burning lifetime = (mass/luminosity in solar units) x 9 billion years, since larger stars have higher interior temperatures, faster use of nuclear fuel and faster evolution.

Nuclear Reactions: Main-sequence stars convert hydrogen to helium. More evolved stars convert helium to carbon, oxygen, etc. This is how most of the elements are formed.


Doppler Effect: Blue-shifts or red-shifts in stars; by measuring wavelengths and shifts in wavelengths, velocities of stars moving towards or away can be studied; shift in wavelength divided by the wavelength at rest equals approach or recession speed divided by the velocity of light; can determine the following basic properties of stars- rotation, atmospheric motions, circumstellar material and motion; evidence for the expansion of universe.

Measuring tangential velocity: This is the motion of the star perpendicular to the line of sight, determined from measurements of the distance to the star, and the rate of angular motion across the sky.

Stellar Forces: Gravity pulls inward on stellar particles, while gas pressure, radiation pressure and magnetic support push outwards. The balance between pressure and gravity is called hydrostatic equilibrium.

Wien’s Law: W= 0.00290/T, where W is the wavelength at which the maximum amount of radiation comes from a body of temperature T. The law has implications for the prediction of infrared stars or star-nebula complexes, and is a way to measure the 'surface' temperature of stars.


Inverse Square Law: This is the relation describing any entity, like radiation or gravity, that varies as 1/r^2, where r is the distance of the entity from source.

Parallax determination: Parallax, the apparent shift in the position of an object caused by a shift in the observer’s position, gives the distance to the object using trigonometry.

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Site created by JoAnne Hosick and Vince Velocci, and extended by Akos Bakos and Artur Chudolinski. Last updated July 19, 2004.