Universe Getting Bigger, Faster
L O N D O N, Sept. 22 -- The celestial yardstick most commonly used for measuring the universe may have to be recalibrated.
That’s the upshot of an analysis by a team of astronomers, who worked with new, more precise measurements of the distance to a far-off galaxy.
If their analysis is correct, the universe may be expanding faster and could be somewhat younger than currently thought, the researchers reported in Thursday’s issue of the journal Nature.
Ever since Edwin Hubble discovered the universe was expanding in 1929, astronomers have sought to determine the rate of that expansion, called the Hubble constant, and whether the universe will continue expanding or eventually collapse in on itself. Over the past five years, astronomers have come up increasingly more accurate measurements, and some believe their estimates are within 10 percent of the actual rate.
NGC4528 vs. LMCTo reach these estimates, astronomers measure and compare distances to certain flickering stars called Cepheid variables. Astronomers use the brightness of Cepheids observed in far-off galaxies and compare them with Cepheids in a galaxy known as the Large Magellanic Cloud.
For example, if a Cepheid variable in a galaxy of unknown distance is one fourth as bright as a Cepheid in the LMC, that galaxy is twice as far away as the LMC. The drop in brightness is always the inverse of the square of the distance—a Cepheid in a galaxy three times as far away will be one ninth as bright.
The problem, however, has been determining the distance to the LMC, which has been measured only to within 10 percent accuracy.
NASA researcher Eyal Maoz and his colleagues tried to get around the problem by using new, more precise measurements to another galaxy altogether, known as NGC4258. These measurements are believed to be accurate to within 4 percent.
Shaking the Boat
These new findings indicate “something is probably wrong with the Cepheid calibration,” said Maoz, who is at NASA’s Ames Research Center at Moffett Field, Calif. “If it is correct, it has significant implications for our understanding of the universe.”
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