Download Herzsprung-Russell Diagram

PHYS
206
Stars in General
Only 6 of the 20 brightest stars in the sky are closer to us than 10pc 
14 of the 20 brightest stars in the sky must have absolute magnitude of at
least 1.5 (20 times brighter than the Sun)
Out of the 6000 stars visible, only 50 are dimmer than the Sun in absolute
magnitude.
Question: Is the Sun below average????
Answer: NO!!!!!!!!!!!!!
Because, bright stars are very rare,
however, when they are bright,
they are very bright.
Majority of the stars are dim stars,
even the closest star to us, Proxima
Centauri (+16) is not visible to the
naked eye.
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Nearest Stars
Only 3 of the 43 nearest stars is among the 20 brightest stars: Sirius,
Alpha Centauri, Procyon.
13 out of 44 nearest stars are binaries  total of 59 stars.
43 out of these 59 stars have less than 0.01 Ls.
Only 3 are as bright as our Sun.
If we go to a distance of 10 pc  456 stars.
12 out of these 456 are > 2 Ls.
1:20 as bright as the Sun
1:38 as bright as 2 Ls.
So, the Sun is an average star.
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206
Near vs. Bright
PHYS
206
Temperature vs. Luminosity
PHYS
206
Hertzsprung-Russell diagram
PHYS
206
Different Stars
Main Sequence Stars
Giants:
Subgiants
Giants
Supergiants
Dwarfs
Neutron stars
Black holes
PHYS
206
Spectroscopic Parallax
The correlation between luminosity and spectral type also gives us
further means to measure the distance to far away stars in our galaxy
(Spectroscopic parallax)  RUNG 4
Procedure:
•Determine the star’s spectral type from spectroscopy and measure
the star’s apparent brightness.
•Use the main sequence to get the star’s luminosity.
•Use the Inverse Square Law for Brightness to get the distance to the
star from the apparent luminosity and the absolute luminosity.
PHYS
206
Homework
Draw a Hertzsprung-Russell diagram.
1.
There are 88 constellations listed
in the Appendix 19 of MorrisonWolff-Fraknoi.
2.
Pick two constellations each.
3.
Every person should have at least
10 stars in the picked
constellations.
4.
Using the Internet, find the
Color Indices and the
Luminosities of these stars.
5.
Draw the HR diagram.
6.
Groups of 5 should draw all of
their data on one paper as well.