This allows astronomers to decode the light from these distant quasars and gather information about how much the universe has expanded during the time the light has been on its way to Earth. With HE0435-1223, PG1115+ 080, and RXJ1131-1231, the team carefully measured those time delays, which are inversely proportional to the value of the Hubble Constant. When a sufficiently massive galaxy closer to Earth gets in the way of light from a very distant quasar, the galaxy can act as a lens its gravitational field warps space itself, bending the background quasar's light into multiple images and making it look extra bright.Īt times, the brightness of the quasar flickers, and since each image corresponds to a slightly different path length from quasar to telescope, the flickers appear at slightly different times for each image-they don't all arrive on Earth at the same time. Though quasars are often extremely far way, astronomers are able to detect them through gravitational lensing, a phenomenon that acts as nature's magnifying glass. Quasars are extremely bright, active galaxies, often with massive jets powered by a supermassive black hole ravenously eating material surrounding it. Using Keck Observatory's AO system with the Near-Infrared Camera, second generation (NIRC2) instrument on the Keck II telescope, Chen and his team obtained local measurements of three well-known lensed quasar systems: PG1115+ 080, HE0435-1223, and RXJ1131-1231. This suggests that either there is a problem with the CMB measurements, which the team says is unlikely, or the standard model of cosmology needs to be changed in some way using new physics to correct the discrepancy. the late, more modern part of the universe (using local, nearby observations)." So, when we are comparing the Hubble Constants that come out of various techniques, we are comparing the early universe (using distant observations) vs. "While the Hubble Constant is constant everywhere in space at a given time, it is not constant in time. "Therein lies the crisis in cosmology," says Fassnacht. The team's results add to growing evidence that there is a problem with the standard model of cosmology, which shows the universe was expanding very fast early in its history, then the expansion slowed down due to the gravitational pull of dark matter, and now the expansion is speeding up again due to dark energy, a mysterious force. The unblinding revealed a value that is consistent with Hubble Constant measurements taken from observations of "local" objects close to Earth, such as nearby Type Ia supernovae or gravitationally-lensed systems Chen's team used the latter objects in their blind analysis. It's always a tense and exciting moment," says lead author Geoff Chen, a graduate student at the UC Davis Physics Department. "When we thought that we had taken care of all possible problems with the analysis, we unblind the answer with the rule that we have to publish whatever value that we find, even if it's crazy. This prevented them from making any adjustments to get to the "correct" value, avoiding confirmation bias. To rule out any bias, the team conducted a blind analysis during the processing, they kept the final answer hidden from even themselves until they were convinced that they had addressed as many possible sources of error as they could think of. The team's results are published in the latest online issue of the Monthly Notices of the Royal Astronomical Society. I have felt for many years that AO observations could contribute a lot to this effort." "In this project, we are using Keck Observatory's AO for the first time in the full analysis. "When I first started working on this problem more than 20 years ago, the available instrumentation limited the amount of useful data that you could get out of the observations," says co-author Chris Fassnacht, Professor of Physics at UC Davis. This is the first time ground-based AO technology has been used to obtain the Hubble Constant. Keck Observatory's Adaptive Optics (AO) system to observe three gravitationally-lensed systems. They used NASA's Hubble Space Telescope (HST) in combination with W. The team's new measurement of the Hubble Constant, or the expansion rate of the universe, involved a different method. The study comes on the heels of a hot debate over just how fast the universe is ballooning measurements thus far are in disagreement.
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