Fixing the Lower Rungs of the Cosmological
Distance Ladder
Carroll & Ostlie p.541-556 (stellar pulsation)
Also have a look at the
DIRECT project website
1) Find the periods of these stars (if periodic);
2) Classify these variables;
3) Knowing that the distance to M33 is about 800 kpc, what are
the absolute magnitudes of these stars? Compare to the Sun.
Here are the light curves, columns are: (1)-epoch (in days), (2)-V mag:
| var1.dat | var2.dat |
var3.dat |
If you cannot access the above, try these:
| var1.html | var2.html |
var3.html |
SUMMARY: Despite decades of effort, the basis of the cosmological
distance ladder remains unsteady. I will review several major local
distance indicators (Cepheids, RR Lyrae, red clump stars and detached
eclipsing binaries), highlighting their advantages and disadvantages.
I will also discuss some of the major problems of the local distance
scale: the distance to the LMC, the metallicity dependence for
Cepheids and the blending of Cepheids in distant galaxies, and how
these problems can be addressed. Finally, I will concentrate of the
ongoing, long-term project DIRECT to measure direct distances to Local
Group galaxies M31 and M33.
READ THE FOLLOWING IN PREPARATION FOR OUR MEETING:
Carroll & Ostlie p.201-218 (binary stars)Problem Set:
Below I include light curves of three variable stars found
by the DIRECT project in the M33 galaxy.
Questions or Comments?
Send me an e-mail to kstanek@cfa.harvard.edu.
This page was last updated on Tue Oct 19 14:16:26 EDT 2004