Chapter 17/18/19: Measuring Properties of Stars Flashcards
What is a Parallax?
uses the change in the object’s apparent position, compared to the background.
What is a Stellar Parallax?
the parallax of the star is equal to teh angular radius of the Earth’s orbit as seen from the star. (closer = greater angle)
What is a parsec?
the parallax angle of that star in arcseconds.
1pc
3.26 ly
If p = 1 arcsecond
d = 1 parsec
What is Luminosity/Intrinsic Brightness?
measure of the total energy radiated by a star (energy/second)
What is Apparent Brightness?
how bright a star appears when viewed from Earth (depends on luminosity and distance)
What is brightness?
the amount of light arriving at a particular place.
What is the inverse square law of radiation?
Brightness decreases as the distance from the light source increases. Light spreads out over a greater area.
What is Wein’s law?
Red stars are cooler, blue stars are hotter
What are the spectral classes? (hottest to coolest)
O, B, A, F, G, K, M
What is the absorption line spectra?
it is what the atmosphere of stars produces depending on different elements.
What determines what we see in the star’s spectrum?
The star’s surface temperature.
What is a Brown Dwarf?
Objects with masses less then 7.5% of our Sun, not hot enough for hydrogen fusion to take place. (LYT)
What do Brown Dwarfs burn at their core?
Deuterium.
What are binary stars?
Stars that orbit each other (can help measure their masses)
What theory do binary stars use?
Newton’s theory of gravity
What law can be applied to any 2 orbiting objects?
Kepler’s Third Law of Planetary Motion
What kinds of binary stars are there?
Visual binaries, Spectroscopic binaries, Eclipsing binaries, Astrometric binaries
What is a Visual Binary?
They can be measured directly and both are observed through a telescope.
What is a Spectroscopic Binary?
Can be measured using their Doppler shifts. (spectral lines move back and forth as stars move towards and away as they orbit)
What is an Eclipsing Binary?
Can be used to measure star size by observing how long the eclipse takes by using their distance from each other.
What is an Astrometric Binary?
Stars wobble in their proper motion periodically due to gravitational influence
What is the HR diagram (Hertzsprung-Russell)?
Plot of stellar luminosity vs surface temp (OBAFGKM).
What is the Sun on the HR diagram?
Kind of in the middle (G-K and just above 1)
What are the main regions?
Red Giants, Blue Giants, Red Dwarfs, White Dwarfs
What is the main sequence?
Where most stars are.
What is a Red Giant?
Cooler but still very luminous stars.
What is a Blue Giant?
Hotter and very luminous stars.
What is a Red Dwarf?
least massive main sequence stars and most common (cool and dim (under red giants)).
What is a White Dwarf?
Stars that are hit and not luminous (under Blue giants (dim and hot)).
What is the Mass-Luminosity Relation?
the greater the mass of the main sequence star the greater the luminosity.
What is a stellar lifetime dependent on?
Mass
The higher the mass…
The less the lifetime.
What stars last the longest?
small red dwarfs.
