The Webb data confirms the accuracy of 30 years of Hubble observations of Cepheids that were critical in establishing the bottom rung of the cosmic distance ladder for measuring the universe’s expansion rate. Webb’s sharper infrared vision allows for a Cepheid target to be more clearly isolated from surrounding stars, as seen in the right side of the diagram. Light contamination from surrounding stars may make the measurement of the brightness of a Cepheid less precise. These Cepheid variable stars are seen in crowded star fields. This diagram illustrates the combined power of the NASA’s Hubble and Webb space telescopes in nailing down precise distances to a special class of variable star that is used in calibrating the expansion rate of the universe. The brightnesses of certain stars in those galaxies tell us how far away they are and thus for how much time this light has been traveling to reach us, and the redshifts of the galaxies tell us how much the universe expanded over that time, hence telling us the expansion rate. Our sign is written into the stars in distant galaxies. “The sign cosmologists want to read is a cosmic speed limit sign that tells us how fast the universe is expanding - a number called the Hubble constant. “Did you ever struggle to see a sign that was at the edge of your vision? What does it say? What does it mean? Even with the most powerful telescopes, the ‘signs’ astronomers want to read appear so small that we struggle too. Nobel Laureate Adam Riess from the Johns Hopkins University and the Space Telescope Science Institute presents his and his colleagues’ recent work using Webb observations to improve the precision of local measurements of the Hubble constant. NASA’s James Webb Space Telescope provides new capabilities to scrutinize and refine some of the strongest observational evidence for this tension. Astronomers use Cepheid variables and Type Ia supernovae as reliable distance markers to measure the universe’s expansion rate.ĭownload the high-resolution file from the Resource Gallery.Ĭredit: NASA, ESA, CSA, and A. Among NGC 5584’s glowing stars are pulsating stars called Cepheid variables and Type Ia supernova, a special class of exploding stars. Combined observations from NASA’s NIRCam (Near-Infrared Camera) and Hubble’s WFC3 (Wide Field Camera 3) show spiral galaxy NGC 5584, which resides 72 million light-years away from Earth. However, a persistent difference called the “Hubble Tension” is seen between the value of the constant measured with a wide range of independent distance indicators and its value predicted from the big bang afterglow. The rate at which the universe is expanding, known as the Hubble constant, is one of the fundamental parameters for understanding the evolution and ultimate fate of the cosmos.
0 kommentar(er)
