Physical Properties of Stars Flashcards
Explain the difference between Optical Double stars and True Binary Stars.
-True Binary stars are linked together Gravitationally and orbit a common centre of mass. e.g. Castor in Gemini. e.g. Algol in Perseus. -Optical Double stars merely appear nearby but may be light years apart.
How many times brighter is a star with a magnitude of 5 compared with a star with a magnitude of 1?
100 times
What is Pogson’s ratio?
The difference in magnitudes is the 5th route of 100 which equals 2.51
Give 4 factors that affect the apparent magnitude of a star.
-Energy radiated by star ○ Size ○ Temperature -Interstellar gas and dust. -Amount of light absorbed by Earth’s atmosphere. -Distance from Earth
What is the magnitude of the brightest star in the sky?
1.5 Sirius (α Cma)
What is the Absolute Magnitude?
A measure of Apparent magnitude if observed from a distance of 10pc
Name two types of variable star.
-Cepheid Variables -True Binaries
What is a True Binary?
Two Stars orbiting around their common centre of mass.
What is a Cepheid Variable?
A giant yellow star that regularly expands and contracts in size.
What is an eclipsing binary?
If two binary stars orbit each other in a plane along our line of sight, two stars will eclipse each other. e.g. Algol (β Per)
What is the Primary Star?
The brighter star in a binary system
In what way is the variability of light intensity of Cepheid Variables different to that of eclipsing binaries?
-One is due to the star pulsating (Cepheid) -The other is due to stars eclipsing each other (eclipsing binaries)
Draw the light curve of a Cepheid Variable.
Draw the light curve of a Eclipsing Binary.
What is Parallax?
The apparent motion of near and more distant objects in respect to each other, caused by the motion of an observer.
