Re: We may not need McCoy's tape measure after all


"Kermit" <unrestrained_hand@xxxxxxxxxxx> wrote in message news:1154711782.887361.286560@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Astronomers have a simpler and more reliable way of measuring great
distances than using the Hubble constant. The universe may be bigger
and older than thought - by 15%.

http://www.sciencedaily.com/releases/2006/08/060803170712.htm

Details are forthcoming:
"Kris Stanek, associate professor of astronomy at Ohio State, and his
coauthors describe the method in a paper to appear in the Astrophysical
Journal (astro-ph/0606279)."

Ah! Press release science. You gotta love it.

Quoting from the release:

To calculate the distance to a faraway galaxy using
the Hubble constant, astronomers have to work through
several complex steps of related equations, and
incorporate distances to closer objects, such as the
Large Magellanic Cloud.

"In every step you accumulate errors," Stanek said.
"We wanted an independent measure of distance -- a
single step that will one day help with measuring
dark energy and other things."

...

They studied two of the brightest stars in M33,
which are part of a binary system, meaning that
the stars orbit each other. As seen from Earth,
one star eclipses the other every five days.

They measured the mass of the stars, which told
them how bright those stars would appear if they
were nearby. But the stars actually appear dimmer
because they are far away. The difference between
the intrinsic brightness and the apparent brightness
told them how far away the stars were -- in a single
calculation.

To their surprise, the distance was 15 percent
farther than they expected: about 3 million
light-years away, instead of 2.6 million light-years
as determined by the Hubble constant.

Hmmm. Correct me if I am wrong, but the Hubble constant
isn't used to determine the distance to M33. It is
one of those "closer objects, such as the Large
Magellanic Cloud" that get used in the chain of
inference leading to the Hubble constant.

This work may indeed lead to a revision of the constant,
but it is not going to be quite as direct and simple
as the press-release suggests.

.

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