Unit 8: Characterizing Stars Flashcards
Why do stars appear in different colors?
because of their temperature
What is an Astronomical Unit
The average distance between the earth and sun
What is a Light Year
The distance that light travels in a vacuum in one year
What is a Parsec
1 pc= 3.26
What is the most convenient measurement for measuring interstellar and inter galaxies distance
- Light year and Parsec
What are the properties of interest of Stars
Distance Visible brightness luminosity surface temperature size age mass
What is the Parallax Method used for?
This is a measurement of the distances to nearby stars
- This method only works for closer and nearby stars
- not more than 1000 pc away from the earth
The Parallax Method is the only method allowing what?
Only method allowing to express distances to stars in terms of diameter of Earth’s orbit.
When was the first parallax measurement made? By who?
1838 by Friderich Wilhem Bessel
What is Apparent Magnitude?
The brightness of stars without regard to their distances
(m)
the brightness of stars as seen from Earth
Objects which are brighter than first-magnitude stars have apparent magnitudes ______ than 1, even _______ ones.
- Less
2. Negative
What is the apparent magnitude of Sirius
This is the brightest star in the night sky, has a negative apparent magnitude: m= -1.44
What is the apparent magnitude of Venus
m= -4.4
What are the Moon and Sun’s apparent magnitudes
Moon (-12.6)
Sun (-26.7)
What is the contemporary measurement of an apparent magnitude based on?
Electronic devices directly measuring an intensity of light
What us the naked eye limit of apparent magnitude
+6.0
What is a star’s absolute magnitude
M
The stars apparent magnitude the star would have if it were 10 pc from the Earth
What is the range of absolute magnitude
Absolute magnitude range from roughly M= -10 for the brightest stars to M= +17 for the dimmest
What is Luminosity
the total amount of energy radiating from the star’s surface each second
The absolute magnitude of a star and its luminosity are _____ _________.
directly proportional
What is the Harvard Classification Scheme and who created it?
The first serious attempt to organize and classify stars based on their temperatures
- Edward Charles Pickering and Annie Jump Cannon
What are the Stellar Classes
O, B, A, F, G, K, M,
0= coldest (blue violet)
M= hottest (red-orange)
What does the Hertzsprung-Russell Diagram show
that stars luminosity and surface temperature are correlated
What percent of stars belong to the main sequence band
over 90%
