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Twinkle , Twinkle.
Dick Bain, USA
Astronomers use various types of standard candles or cosmic yardsticks to measure distances to stars and galaxies. One of these yardsticks is the class of stars known as the Cepheid variable stars. One of the apparent errors in The Urantia Book comes from using the distance to the Andromeda galaxy that astronomers held in the 1930's. This distance was determined using Cepheid variable stars in M31, also called the Andromeda galaxy.
Henrietta Leavitt, a Harvard astronomer, determined in 1917 that there is a direct relationship between the luminosity (brightness) of Cepheid variable stars and the length of their period. The longer between periods of peak brightness, the greater the absolute luminosity of these stars. Using this relationship, astronomers can determine the distance to other galaxies by noting the period and apparent luminosity of the Cepheid variable stars in these other galaxies.
In 1924, the well known astronomer Edwin Hubble presented a paper to the American Astronomical Society showing that M31, the great spiral galaxy in Andromeda, is about 750,000 light years from earth. This distance is now known to be about 2.2 million light years from earth. Hubble got the wrong distance to M31 because he was using Shapley's calibration of a period luminosity (P-L) relationship for Cepheid variable stars--which was in error because Shapley was unaware that there were actually two types of Cepheid variable stars (now known as Type 1 and Type 2 populations) having differing P-L relationships..
The authors of The Urantia Book tell us that it takes light from M31 a million years to reach the earth, which would make that galaxy one million light years distant from us. It is interesting that they extol the use of the Cepheid variable stars by astronomers to make this measurement: "In one group of variable stars the period of light fluctuation is directly dependent on luminosity, and knowledge of this fact enables astronomers to utilize such suns as universe lighthouses or accurate measuring points for the further exploration of distant star clusters. By this technique it is possible to measure stellar distances most precisely up to more than one million light-years." (456)
When astronomers first started using the Cepheid variables as standard candles, two million light years was about the limit of distances they could measure using this technique due to atmospheric distortion. Now, with improved terrestrial telescopes and the now repaired space-based Hubble telescope, that range has been pushed out to 60 million light years or more. Recently, this improvement in seeing has enabled astronomers to measure the distance to a galaxy in the Virgo cluster. The distance measured using Cepheid variable stars in the M100 galaxy was 56 million light years1. Being able to measure galaxies at this distance also allows the astronomers to determine a value for Hubble's constant, which is important in determining the age of the universe. Unfortunately for the current cosmology, the value of Hubble's constant they obtained indicated that the universe may be only 10 billion years old. This is rather embarrassing, because there are stars in globular clusters calculated to be as much as 16 billion years old. Will the cosmologists be able to apply another patch to keep the Big Bang theory limping along, or are their backs up against the wall? Stay tuned for the next exciting episode of "Cosmologists Meet Reality."
A Galaxy Too Far
Using the latest generation telescopes, astronomers continue to find ever more distant galaxies. The most recently discovered record-holder was reported to be between 12 and 15 billion light years from Earth, based on the red shift of light from this galaxy. This galaxy is apparently five times the size of M31, the giant spiral galaxy in Andromeda1. Astronomers feel that these most distant galaxies were formed close to the time of the Big Bang. But if so, there is a small problem.
The telescope is in effect a time machine. The further light travels from a distant galaxy, the earlier in the history of the universe we are seeing that galaxy. Since the newly discovered galaxy is perhaps 15 billion light years distant, we are seeing it as it was 15 billion years ago. The problem is that this galaxy is fairly well developed. It even appears to have either old stars or dust clouds from a past generation of stars1. If the Big Bang happened about 15 billion years ago, then this galaxy would had to have developed in a few hundred millions of years rather than in billions of years like later galaxies have. Now someone has to explain how the first galaxies could develop many times faster than later galaxies or another crack may appear in the Big Bang edifice. Tsk, tsk.
Reference
1. R. Cowen, "Keck Goes the Distance", Science News, January 14, 1995.
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