Leavitt's
Discovery:
- While working at Harvard College
Observatory, as a human computer, Leavitt was
tasked with documenting the variable stars of
the Magellanic Clouds. She documented over
2400 variable stars while at Harvard; 1777 in
the Magellanic Clouds alone.
- "Leavitt noticed that the distribution
of variable stars was nonuniform across the
sky, being greatest in the directions of ...
[the] "Milky Way Clouds"" (1908, Harvard
Circular; cited in Byers).
At that time scientists assumed the Magellanic
Clouds were part of the Milky Way.
- Because of Leavitt's discovery, it was
later shown that the stars of the Magellanic
Clouds are two distinct galaxies of their own
residing outside of the Milky Way.
- Leavitt discovered the
period-luminosity relationship for Cepheid
variable stars. She was able to plot the
apparent magnitude of the stars she observed
vs. their period. This relationship connected
the luminosity of each star to time and
allowed the data to be graphically represent.
By plotting the brightness of a star over time
Leavitt was able to calculate the period of
time required to go from dim to bright.
- The distance to a star can then be
calculated by comparing the true luminosity in
Watts to the observed brightness through a
telescope form earth. The observed brightness
through the telescope yields the flux in Watts
per meter squared. The observed brightness in
this case falls off as the square of the
distance. (Byers)
http://www.capphysics.ca/PhysLab/Phys107/Variable%20Stars/images/light_curves.jpg
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