Measuring the rate of expansion of the universe was one of the main missions of the Hubble Space Telescope when it was launched in 1990.
Over the past 30 years, the space observatory has helped scientists reveal and refine this pace of acceleration — as well as discovering a mysterious warp that only new physics could solve.
Hubble has observed more than 40 galaxies that include pulsating stars, as well as exploding stars called supernovae, to measure long cosmic distances. Both phenomena helped astronomers mark gigantic distances and calculate the rate of expansion.
On a mission to understand how fast our universe is expanding, astronomers already made an unexpected discovery in 1998: “dark energy”. This phenomenon acts as a mysterious repulsive force that accelerates the pace of expansion.
And there’s one more detail: an unexplained difference between the expansion rate of the local universe versus that of the distant universe just after the Big Bang.
Scientists don’t understand the discrepancy, but they recognize that it’s strange and needs new physics.
“We are seeing the most accurate measurements of the universe’s expansion pace through the highest standard of telescopes and cosmic distance meters,” said Adam Riess, distinguished professor at Johns Hopkins University and Nobel laureate member of the Space Telescope Science Institute, in note.
“That’s what the Hubble Space Telescope was built to do, using the best technologies we know to do it. This is probably the magnum opus (Latin for “masterpiece”) of Hubble, because it would take another 30 years of the device’s life to at least double the size of the samples.”
decades of observation
The telescope is named after Edwin Hubble, who discovered in the 1920s that clouds far away in space were actually galaxies. He died in 1953, more than thirty years before the release of his namesake.
Hubble relied on the work of astronomer Henrietta Swan Leavitt and her discoveries made in 1912, which highlighted periods of light in pulsating stars called Cepheids. Cepheids act as cosmic distance markers, as they periodically light and dim between our galaxy and others.
Hubble’s work led to the revelation that our galaxy is one of many, ever-changing our perspective and place in the universe. The astronomer continued his work and found that distant galaxies appear to be moving rapidly, suggesting that we live in an expanding universe that began with the Big Bang.
Detecting the rhythm of the universe’s expansion helped lead to the 2011 Nobel Prize in Physics, awarded to Saul Perlmutter, Brian P. Schmidt and Riess “for discovering the accelerated expansion of the universe through observation of distant supernovae.”
Riess continues to lead SHOES, acronym for Supernova H0 for the Dark Energy Equation of State, a scientific collaboration investigating the pace of expansion. His team is publishing a paper in The Astrophysical Journal that will bring the latest updates on the Hubble constant, as the step is known.
unresolved discrepancy
Measuring distant objects has created a “cosmic distance ladder” that can help scientists better estimate the age of the universe and understand its basis.
Several teams of astronomers using the Hubble telescope have arrived at a value for the Hubble constant equal to 73 plus or minus one kilometer per second per megaparsec. One megaparsec is equal to one million parsecs, or 3.26 million light years.
“The Hubble constant is a very special number. It can be used to thread the needle between the past and the present for an integral test of our understanding of the universe. This has generated a phenomenal amount of detailed work,” Licia Verde, a cosmologist at the Catalan Institute for Research and Advanced Studies and the Institute of Cosmic Science at the University of Barcelona, said in a statement.
But the true prediction of the expansion rate of the universe is slower than that observed by the telescope, according to astronomers using the standard cosmological model of the universe (a theory suggesting the components of the Big Bang) and measurements taken by the Space Agency’s Planck mission. European Union between 2009 and 2013.
Planck, another space observatory, was used to measure the cosmic microwave background, or leftover radiation from the Big Bang 13.8 billion years ago.
Scientists from the Planck mission arrived at 67.5 plus or minus 0.5 kilometers per second per megaparsec.
The James Webb Space Telescope, launched in December, will be able to observe Hubble’s distance markers at a higher resolution and at greater distances, which could contribute to understanding the discrepancy between the two numbers.
It’s an exciting new challenge for cosmologists, who are determined to measure the Hubble constant — and now find themselves questioning what physics is needed to help them unlock a new mystery about the universe.
“Actually, I don’t care what the exact value of the expansion is, but I’d like to use it to learn more about the universe,” Riess said.
Source: CNN Brasil
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