Cepheid + Parallax Measurements

A buddy of mine once pointed out that if we could get a parallax
measurement on a Cepheid variable star, we could calibrate our interstellar
distances much better than they are now.

How far are we from being able to do that? How far are the nearest
Cepheids and how close are the farthest parallax stars? Has Hubble ever
tried any parallax measurements? What are the current limitations on our
ability to do them?

On Sat, 24 Jan 2004 17:29:19 +0000, John Schutkeker wrote:


A buddy of mine once pointed out that if we could get a parallax
measurement on a Cepheid variable star, we could calibrate our
interstellar distances much better than they are now.

How far are we from being able to do that? How far are the nearest
Cepheids and how close are the farthest parallax stars? Has Hubble ever
tried any parallax measurements? What are the current limitations on
our ability to do them?

Yes, it was done by Hipparcos. See :

Anonymous, Hipparcos sizes up the Universe, Sky & Telescope (May) 1997; 93
(5): 12-13

In essence Hipparcos found that the Galactic Cepheids are 10% further
away than previously thought.

--

Gautam Majumdar

Please send e-mails to

Gautam Majumdar wrote in
newsan.2004.01.24.20.30.31.364708.3283@XSPAMfree uk.com:

it was done by Hipparcos

It's wonderful to be alive in the 21st century!

"Gautam Majumdar" wrote in message
newsan.2004.01.24.20.30.31.364708.3283@XSPAMfree uk.com...
On Sat, 24 Jan 2004 17:29:19 +0000, John Schutkeker wrote:

In essence Hipparcos found that the Galactic Cepheids are 10%
further
away than previously thought.


Wait wait...

As it seems Hipparcos had a systematic error and previous estimates
were right.

At 5:29 PM +0000 on 1/24/04, John Schutkeker wrote:
A buddy of mine once pointed out that if we could get a parallax
measurement on a Cepheid variable star, we could calibrate our interstellar
distances much better than they are now.

How far are we from being able to do that? How far are the nearest
Cepheids and how close are the farthest parallax stars? Has Hubble ever
tried any parallax measurements? What are the current limitations on our
ability to do them?

In addition to the HIPPARCOS measurement, there is an HST measurement:

G. F. Benedict, B.E. McArthur, L.W. Fredrick, T.E. Harrison, C.L. Slesnick,
J. Rhee, R.J. Patterson, M.F. Skrutskie, O.G. Franz, L.H. Wasserman, W.H.
Jefferys, E. Nelan, W. van Altena, P.J. Shelus, P.D. Hemenway, R.L.
Duncombe, D. Story, A.L. Whipple and A.J. Bradley, ³Astrometry with Hubble
Space Telescope: A Parallax of the Fundamental Distance Calibrator d Cephei,
Astron. J 124, 1695-1705 (2002).

Bill

--
Bill Jefferys/Department of Astronomy/University of Texas/Austin, TX 78712
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