Astronomers crunch numbers, universe gets bigger

[ordinary_guy]

From the OSU Research News, here's this tidbit to keep our theorists on their toes:<br /><blockquote><font class="small">In reply to:</font><hr /><p>Columbus , Ohio -- That intergalactic road trip to Triangulum is going to take a little longer than you had planned.<br /><br />An Ohio State University astronomer and his colleagues have determined that the Triangulum Galaxy, otherwise known as M33, is actually about 15 percent farther away from our galaxy than previously measured.<br /><br />This finding implies that the Hubble constant, a number that astronomers rely on to calculate a host of factors -- including the size and age of the universe -- could be significantly off the mark as well.<br /><br />That means that the universe could be 15 percent bigger and 15 percent older than any previous calculations suggested.<br /><br />The astronomers came to this conclusion after they invented a new method for calculating intergalactic distances, one that is more precise and much simpler than standard methods. 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).<br /><br />In 1929, Edwin Hubble formulated the cosmological distance law that determines the Hubble constant. Scientists have disagreed about the exact value of the constant over the years, but the current value has been accepted since the 1950s. Astronomers have discovered other cosmological parameters since then, but the Hubble constant and its associated methods for calculating distance haven't changed.<br /><br />"The Hubble constant used to be the one parameter that we knew pretty well, and now it's lagging behind. Now we know some things quite a bit better than we know the Hubble constant," Stanek said. "Ten years ago, we didn't even know that dark energy existed. Now we know how much dark energy there is -- better than we know the H</p></blockquote> <div class="Discussion_UserSignature"> <p style="font:normalnormalnormal12px/normalTimes;margin:0px"><strong>Mere precedent is a dangerous source of authority.</strong></p> <p style="font:normalnormalnormal12px/normalTimes;margin:0px">-Andrew Jackson (1767-1845)</p> </div>

 

[doubletruncation]

This is a very interesting result I think - it would be very interesting to see distances measured for other eclipsing binary systems in M33 and M31 as well.<br /><br />I don't know that this is so much a case of "astronomers crunch numbers" making the universe bigger which to me would imply a change in the theory - I think it's more a matter of actually determining a geometric distance to another galaxy beyond the magellanic clouds rather than relying on the Cepheid distance scale with zero-point established in the LMC (i.e. using the distance ladder).<br /><br />In the article it's mentioned that a new method for determining the distance has been invented, I think that is perhaps a bit misleading - measuring distances using eclipsing binaries is a very old technique, but it hasn't been applied before to M33 because until now technology has been limited in the ability to find, and then get precise light curves and radial velocity curves for stars that are so incredibly faint (18th-19th magnitude IIRC).<br /> <div class="Discussion_UserSignature"> </div>

 

[nexium]

Does that mean the Hubble constant may be 55 instead of 66? Neil

 

[qso1]

The religious folks wont be happy. A couple of years back, the Universe was getting smaller according to astronomical studies and I saw stories from religious people who were using that as evidence to support creation. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>

 

[doubletruncation]

<font color="yellow">Does that mean the Hubble constant may be 55 instead of 66?</font><br /><br />If their distance measurement is correct, then I think it might mean that (I haven't checked the numbers - but they sound about right). I would really want to see distances for a few more eclipsing binaries in perhaps other galaxies before making such a conclusion. There are some possible sources of systematic error I think in measuring these EB distances - one is determining the temperature for stars that are so hot, the other is figuring out the total extinction from dust (you can measure the selective extinction by determining how much redder the star appears than you expect, but to convert that to total extinction you have to assume a multiplying factor whose value is often debated). Even if their distance measurement is correct, it may not ultimately change the Hubble constant estimate since it could be that the Cepheids in M33 are peculiar so that using the period-luminosity relation gave an incorrect distance to M33 (there may be some metallicity dependence to the PL relation which is currently not considered).<br /><br />Currently the zero-point for the Cepheid distance scale is set in the large magellanic cloud. There are some inherent difficulties in measuring the distance to the LMC: There is an inherent 10% error in the distance for any individual source due to the depth of the galaxy - it may also have some funny structure which makes averaging distances somewhat suspect. But there have been many many different independent techniques used to measure the distance to the LMC, and the Cepheid zero-point is determined by some weighted average of those techniques (+ some distances to Cepheids in our own galaxy). I think M33 would definitely be preferable to the LMC, but we really need more direct distance measurements to many different galaxies as well in case M33 cepheids are peculiar in some way.<br /> <div class="Discussion_UserSignature"> </div>

 

[cmecu2]

Actually, religion, atleast from a christian point of view as far as i know, the Galaxy is Expanding , how ever it is also cooling down. From studies that I read in the past both have been stated by scientists, mans worldly view, and christian view.