Riess calls this latest Hubble effort a "magnum opus" given that it draws upon practically the telescope's entire history, 32 years of space work, to deliver an answer.
Hubble's data nailed down its observed expansion rate under a program called SHOES (Supernova, H0, for the Equation of State of Dark Energy.) The dataset doubles a previous sample of measurements and also includes more than 1,000 Hubble orbits, NASA stated.Because they are seen exploding at a rate of about one per year, Hubble has, for all practical purposes, logged as many supernovae as possible for measuring the universe's expansion." (Again, Hubble has been in space for about 32 years, having launched on April 24, 1990; a mirror flaw that hindered early work was addressed by astronauts in December 1993.).
Riess said it is best to see the expansion rate not for its exact value at its time, but its implications.— The Hubble Space Telescope and 30 years that transformed our view of the universe.Webb, NASA said, will look at Cepheids and Type 1a supernovas "at greater distances or sharper resolution than what Hubble can see." That may in turn refine Hubble's observed rate.