Decades worth of data from the Hubble Space Telescope has produced a new, more accurate measurement of the expansion rate of the universe†
The new examination of data from the 32-year-old Hubble Space Telescope attempts to identify how quickly the universe expands, and how much that expansion is accelerating through a number called the Hubble Constant (named after astronomers Edwin P. Hubble and Georges Lemaître who first attempted to measure it in 1929).
Different confusing results
The number is a notoriously tough one to pin down because different observatories looking at different areas of the universe have produced different results. Now a new study of Hubble’s most recent effort may have just found the right answer, according to a press release by NASA published Thursday.
“You are getting the most precise measure of the expansion rate for the universe from the gold standard of telescopes and cosmic mile markers,” said Nobel Laureate Adam Riess of the Space Telescope Science Institute (STScI) and the Johns Hopkins University in Baltimore, Maryland .
Riess leads a scientific collaboration investigating the universe’s expansion rate called SHOES, which stands for Supernova, H0, for the Equation of State of Dark Energy. “This is what the Hubble Space Telescope was built to do, using the best techniques we know to do it. This is likely Hubble’s magnum opus, because it would take another 30 years of Hubble’s life to even double this sample size,” Riess said .
Riess is leading the biggest and likely last major update on the Hubble constant with new results more than doubling the prior samples of cosmic distance markers. His team also reviewed all of the prior data that takes into account about 1,000 Hubble orbits.
“The Hubble constant is a very special number. It can be used to thread a needle from the past to the present for an end-to-end test of our understanding of the universe. This took a phenomenal amount of detailed work,” said dr. Licia Verde, a cosmologist at ICREA and the ICC-University of Barcelona, speaking about the SHOES team’s work.
The team analyzed 42 of the supernova milepost markers with Hubble that are seen exploding at a rate of about one per year. Riess said, “We have a complete sample of all the supernovae accessible to the Hubble telescope seen in the last 40 years.” Like the lyrics from the song “Kansas City,” from the Broadway musical OklahomaHubble has “gone about as far as it can go!”
What did the team finally conclude?
The SHOES team produced a Hubble Constant estimate of 73. This turned out to be higher than previous research that combined the Standard Cosmological Model of the Universe and measurements by the European Space Agency’s Planck mission to predict a value for the Constant or 67.5 plus or minus 0.5 kilometers per second per megaparsec.
Who’s right? It turns out it doesn’t matter so much. This confusion is exciting for astronomers like Riess. “Actually, I don’t care what the expansion value is specifically, but I like to use it to learn about the universe,” Riess concluded.