This montage shows the five lensed quasars and the foreground galaxies studied by the H0LICOW collaboration. Using these objects astronomers were able to make an independent measurement of the Hubble constant. They calculated that the Universe is actually expanding faster than expected on the basis of our cosmological model.
Galactic Lenses Lead to New Data About the Universe’s Expansion
published during a waxing crescent moon.

A new study indicates that astronomers were likely wrong about the rate of the Universe’s Expansion (but no one knows why).

Here’s something you probably know: the universe has been expanding ever since the Big Bang.

Here’s something you may not know: the rate of the universe’s expansion is increasing. It’s getting bigger faster.

Here’s something you probably didn’t know: the universe is expanding even faster than we thought.

One might think gravity would slow down the growth of the cosmos, but it hasn’t (and no one is quite sure why). Edwin Hubble proved this trend back in 1929, and he determined the Hubble Constant, the rate of the universe’s expansion. Since then, astronomers have confirmed and supplemented these findings—until now.

HE0435-1223, located in the center of this wide-field image, is among the five best lensed quasars discovered to date. The foreground galaxy creates four almost evenly distributed images of the distant quasar around it. Credit: NASA, ESA, Suyu (Max Planck Institute for Astrophysics), Auger (University of Cambridge)

A recent study of information harvested by ground telescopes in Mauna Kea, Hawaii and the Hubble and Spitzer space telescopes indicates a departure from previous Hubble constant values. Satellites, such as the ESA Planck, have determined the Hubble constant by using the cosmic microwave background, the Big Bang’s residual radiation. But the new measurements were observed differently, focusing on faraway galaxies backlight by luminous quasars. When observed, the light from a quasars bend around the galaxies, producing something called gravitational lensing. Thus, the light doesn’t arrive into view at the same time, and causes the appearance of multiple images of the same quasar. The differences in the time it takes for the light to travel into view have provided new, complicated insights on the Hubble constant, and the “discrepancies may possibly point towards new physics beyond our current knowledge of the Universe,” says lead astronomer Sherry Suyu.

Four images of a supernova split by cosmic lensing. Credits: NASA/ESA/STScI/UCLA

The new data has enabled researchers to determine the most precise measurement of the Hubble constant yet—3.8%. This number is higher than expected, which means that even though astronomers continue to piece together and refine their understanding of the universe, what comprises it, and how quickly it’s expanding, there’s still much we don’t know or understand. Maybe Einstein’s theory of relativity doesn’t hold up after all. Maybe the answer hinges on dark energy, dark matter, and/or dark radiation. Maybe it’s something else entirely. Regardless, one thing is for certain: trying to figure out the answer will be a fascinating journey.