As a result, the light takes different paths around the galaxy, and the object appears to observers as multiple images. When in line with a distant object, such as a supernova, a massive foreground galaxy or galaxy cluster bends the object’s light via strong gravitational lensing. Time-delay cosmography was pioneered in the 1960s by the namesake for the newly analyzed supernova, Norwegian astrophysicist Sjur Refsdal. “Measuring the Hubble constant using many different techniques is the way we’re going to ultimately convince ourselves that an accurate measurement has been made,” says Wendy Freedman, an observational cosmologist at the University of Chicago who was not involved in the research. Measurements of H 0 made using the cosmic microwave background (CMB) radiation from the early universe, on the other hand, yield a rate of about 67 km/s/Mpc.Īlthough the new time-delay measurement is closer to the CMB value, there is still enough wiggle room for an agreement with standard candle measurements. That compares with values of 70–74 km/s/Mpc attained through measurements of standard candles-objects such as type Ia supernovae and pulsing red giant stars called Cepheids that have known luminosities, which allow astronomers to determine their distance from Earth by measuring how bright the objects appear. Using a method called time-delay cosmography with a burst named Supernova Refsdal, a team of astronomers has reported in Science an H 0 value of 66.6 + 4.1 – 3.3 km/s/Mpc. Over the decades, different methods of measuring the universe’s expansion rate, also known as the Hubble constant or H 0, have produced different values.Ī novel analysis of a supernova provides an important new result for H 0. What continues to be up for debate is how fast the expansion is happening. Postman (STScI) and the CLASH team and Z. Lotz (STScI) and the Frontier Fields team M. Kelly (UC Berkeley), and the GLASS team J. Another image of the burst appeared the following year, enabling a novel measurement of the Hubble constant. A test of the General Theory of Relativity.” A&A, 2020: arXiv_2009.In this 2014 Hubble Space Telescope portrait, four images of Supernova Refsdal appear surrounding the yellow galaxy above the bright blue star. “The solar gravitational redshift from HARPS-LFC Moon spectra. Rafael Rebolo, a researcher and the Director of the IAC, said, “New measurements with the laser frequency comb attached to the ESPRESSO spectrograph, on the 8.2 m VLT telescopes, would allow us to improve these measurements.” Journal Reference: This has enabled us to verify one of the predictions of Einstein’s Theory of General Relativity, the gravitational redshift, to a precision of just a few meters per second.” Jonay González Hernández, a Ramón y Cajal researcher at the IAC and first author of the article, said, “Combining the precision of the HARPS instrument with the laser frequency comb, we have been able to measure with high accuracy the position of the iron lines in the solar spectrum. The observations were obtained with the HARPS (High Accuracy Radial velocity Planet Searcher) instrument using the laser frequency comb technology. To gauge it, the scientists have utilized observations of the solar spectrum reflected from the Moon. Now, an international team of researchers led by the Instituto de Astrofísica de Canarias (IAC) has measured the gravitational redshift of the Sun with unprecedented accuracy. For the Sun, its existence is difficult to judge because the effect is so small. Whether this effect exists is an open question, and astronomers are currently working hard to resolve it.
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