The universe is expanding faster and faster. This accelerated expansion has been measured in different ways, but there is a big problem. Depending on whether you are looking at the very distant universe or not, you will get two different numbers for the rate of expansion of the universe.
This cosmological crisis has plagued astrophysicists for several years now. A new study measured the rate of expansion of the universe using a different method and found that the difference in the number is definitely there.
In an article accepted in The Astrophysical Journal, the team described how they measured the infrared properties of 63 elliptical galaxies within 330 million light-years (100 million parsecs) of the Earth. The astronomers used the surface brightness fluctuation (SBF) technique, which works for elliptical galaxies because they are old and have a constant population of old stars.
The researchers measured the Hubble constant – also known as H –0 (H-zero or H-zero) – find a value for it of about 73 kilometers per second per megaparsec. This means that if two galaxies are 1 million parsecs apart, they appear to be moving away from each other at a speed of 73 kilometers per second,
This is similar to other methods that looked at the rate of expansion in the local universe, but it is greater than what was measured in the early universe. Observation of the cosmic microwave background set H0 about 68 kilometers per second per Megaparsec.
“Measuring distances to galaxies up to 100 megaparsecs is a fantastic method,” co-author Professor Chung-Pei Ma of the University of California, Berkeley, said in a statement. “This is the first paper to compile a large, homogeneous set of data across 63 galaxies, with the aim of studying H-nothing with the SBF method.”
The fact that several independent methods find different values is really a challenge. There may be something we have not taken into account in our theories – or perhaps the uncertainty about the measurements is too optimistic.
“The jury is out,” Professor Ma said. ‘I think it’s really in the error bars. But if we assume that everyone’s error bars are not underestimated, the tension becomes uncomfortable. ”
Whatever the cause, this tension is here to stay. Cosmology stands at an important crossroads. Mankind’s understanding of the universe is the best it has ever been, and yet limited. New observatories, both on the ground and in space, will hopefully offer new ways of looking at the universe and solving this mystery.