Tthe universe is huge. By the time you finish reading this sentence, it will be even bigger.
That’s because the universe is expanding—but not everything is expanding at the same rate. The further away things are, the faster they get away from us. For every megaparsec (about 3.3 million light years) of distance from our vantage point, this rate of expansion increases by about 45 miles per second. This rate is known as “Hubble’s Constant,” named after astronomer Edwin Hubble of space telescope fame, who discovered it in 1929.
Now, astronomers from the University of Tokyo have developed a new method called “time-delay cosmography” to obtain a more precise measurement of the Hubble Constant, and they publish their findings in Astronomy and Astrophysics.
Traditionally, the Hubble Constant has been recorded using “distance ladders”. Astronomers choose a relatively close and familiar cosmic entity—a supernova or a star—and observe it, then choose a more distant one and observe that, and so on, to measure the rate at which they are traveling away from us.
COSMIC DISTORTION: Eight artificially colored time-delayed gravitational lensing systems. Each representation has a huge galaxy at the center, and the surrounding bright dots are images of quasars lensed around the galaxy. Images from TDCOSMO Collaboration et al.
Meanwhile, time-lapse cosmography relies on the gravitational lensing of massive objects in space to determine the Hubble Constant. In this method, scientists use a huge galaxy to act as a lens. Super bright objects beyond this galaxy called quasars appear curved because gravity bends their light. Changes in these distorted images allowed the researchers to measure the difference in the time light from the objects took to reach them.
Using this clever methodology, the authors arrived at a value for the expansion rate consistent with the Hubble Constant. This could help resolve a major cosmic kerfuffle.
When astronomers measure this expansion rate using space telescopes (like the one named for Edwin Hubble), they get a single number—about 45 miles/second/megaparsec; when they use another method, which measures the cosmic background radiation generated during the early universe, they get a different, smaller number—about 42 miles/second/megaparsec. This discrepancy is called the “Hubble Tension,” and it has attracted much debate as to whether it was due to experimental error, or the actual physics of the universe.
Read more: “How Much More Can We Learn About the Universe?“
“Our measurement of the Hubble constant is more consistent with other current-day observations and less consistent with measurements of the early universe,” study co-author and University of Tokyo astronomer Kenneth Wong said in a statement. “This is evidence that the Hubble strain may indeed arise from real physics and not just some unknown source of error in the various methods.”
Still, the team stressed that they will need to further refine their time-lapse cosmography method to get more accurate results. Its current accuracy is about 4.5 percent, but it needs to reach an accuracy of about 1 to 2 percent “to really close the Hubble constant to a level that definitively confirms the Hubble strain,” study co-author Eric Paic, also at the University of Tokyo, said in the statement.
The only real constant in astrophysics? More research is needed.
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Lead image: ESA/Hubble & NASA, C. Murray, J. Maíz Apellániz
This story was originally featured on Nautilus.