herbie@watdcsu.UUCP (Herb Chong, Computing Services) (11/12/84)
What's the current best value for the Hubble constant?
Herb Chong...
I'm user-friendly -- I don't byte, I nybble....
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N2L 3G1 (519)886-4733 x3524ethan@utastro.UUCP (Ethan Vishniac) (11/15/84)
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[Herb Chong]
>What's the current best value for the Hubble constant?
The canonical range of 50-100 km/sec/Mpc has not been
significantly narrowed in recent years. Part of the problem
is that each of the extreme values has a small group of
ardent partisans who continue to get their favorite value
(with small error bars) each time they try a new method.
One of the best efforts in recent years by an unprejudiced
group of observers found that their best estimate could be
varied from 65 to 90 by changing the local calibration of
the Cepheid luminosity. (These are variable stars with a
period - luminosity correlation.) The distances to the local
Cepheids are known through a variety of indirect distance estimators.
This particular uncertainty may only disappear when accurate
parallax measurements become possible on these stars. There
are many other sources of uncertainty.
I take the arithmetic mean myself.
"I can't help it if my Ethan Vishniac
knee jerks" {charm,ut-sally,ut-ngp,noao}!utastro!ethan
Department of Astronomy
University of Texas
Austin, Texas 78712