Hubble Constant maybe wrong

[Guest_Jim*]

The Hubble Constant is the rate of expansion for the universe and according to a new study maybe off by as much as 15%. This may not seem that big of a deal but it is since this is needed to estimate the size and age of the universe. Here's a link to a podcast about it that has links to more information.

http://hubblesite.org/explore_astronomy/skywatch/#66

[Martin]

If I understand your news article, it is talking about a study that came out in June 2006.

 

I remember discussing it with people at several science boards----including, I seem to recall, here.

Yes, that's right, here is a discussion we had in August, here at SFN

http://www.scienceforums.net/showthread.php?p=294428#post294428

 

one of the lead scientists of that team was Bonanos, another on the team was Stanek. they based the finding on just one eclipsing binary pair of stars.

here is the article they published about it in Astrophysical Journal

 

http://arxiv.org/abs/astro-ph/0606279

The First DIRECT Distance Determination to a Detached Eclipsing Binary in M33

A. Z. Bonanos, K. Z. Stanek, R. P. Kudritzki, L.M. Macri, D. D. Sasselov, J. Kaluzny, P. B. Stetson, D. Bersier, F. Bresolin, T. Matheson, B.J. Mochejska, N. Przybilla, A.H. Szentgyorgyi, J. Tonry, G. Torres

36 pages, 12 figures, accepted for publication in ApJ

Astrophys.J. 652 (2006) 313

 

"We present the first direct distance determination to a detached eclipsing binary in M33, which was found by the DIRECT Project. Located in the OB 66 association at coordinates (alpha, delta)=(01:33:46.17,+30:44:39.9) for J2000.0, it was one of the most suitable detached eclipsing binaries found by DIRECT for distance determination, given its apparent magnitude and orbital period. We obtained follow-up BV time series photometry, JHKs photometry and optical spectroscopy from which we determined the parameters of the system. It contains two O7 main sequence stars with masses of 33.4+/-3.5 Mo and 30.0+/-3.3 Mo and radii of 12.3+/-0.4 Ro and 8.8+/-0.3 Ro, respectively. We derive temperatures of 37000+/-1500 K and 35600+/-1500 K. Using BVRJHKs photometry for the flux calibration, we obtain a distance modulus of 24.92+/-0.12 mag (964+/-54 kpc), which is ~0.3 mag longer than the Key Project distance to M33. We discuss the implications of our result and the importance of establishing M33 as an independent rung on the cosmological distance ladder."

 

I don't have the expertise to give you anything like an independent evaluation but what I remember as a general reaction, from back then, was that it is too early to say much. It was just one observation----one pair of stars.

 

You may quite possibly be on to a big story! The Hubble parameter may be going to be revised. But right now it is still iffy. they might do other pairs of stars and get different answers. Stay tuned:-)