# Unit 5 Astrophysics

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• Created by: megan
• Created on: 24-03-13 17:14
• Astrophysics and Cosmology
• The attraction of the stars
• Every particle with mass attracts every other particle with mass.
• The big bang spread tiny particles across space, the particles move towards each other and clump together
• This effect is more pronounced for particles nearer to each other.
• a particle that has a mass will feel a force when it is in a gravitational field
• The force that a body will feel is the strength of the gravitational field multiplied by the amount of mass
• f=mg=ma.
• a massie particle will generate a radial gravitational field around itself
• Gravity is always attractive
• The gravitational force between two masses which are separated by a distance is F= Gm1m2/r^2
• G Is the gravitational constant = 6.67x10^-11
• Gravitation field strength
• The strength of the field decreases with increasing distance from the mass causing it.
• The field strength is independent of the object being acted upon.
• g= -GM/r^2
• Electric and gravitational fields
• They are similar because they are both types of field that are radial from a point.
• They differ because gravitational field is always attractive and an electric field is not. Electric fields are also stronger than gravitational fields
• Stella Properties
• The only information we receive from the stars is the electromagnetic radiation from them
• This tells us their temperature, chemical composition, speed of movement, age and size.
• The stefan botlzmann law
• Luminosity is the precise measure used to classify the brightness of stars.
• Is is the rate at which energy of all types is radiated by an object in all directions
• Luminosity depends on size and temperature.
• A perfect radiator is a black body and will give off energy across the entire electromagnetic spectrum
• The stefan boltzmann law tells us that the power output from a black body is proportional to its surface area and the forth power of its temperature.
• L= oT^4 4Pi r^2
• o= 5.67x10^-8
• Wiens law
• To calculate luminosity we need to know the temperature of the star.
• As the temperature increases, a star emits more energy.
• The wavelength of the peak wavelength gets shorted as temperature rises
• Max Wavelength x Temperature = 2.89x 10^-3