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UH astronomers map distances to 56,000 galaxies, largest-ever catalog by Staff Writers Manoa HI (SPX) Sep 27, 2022
How old is our universe, and what is its size? A team of researchers led by University of Hawai?i at Manoa astronomers Brent Tully and Ehsan Kourkchi from the Institute for Astronomy have assembled the largest-ever compilation of high-precision galaxy distances, called Cosmicflows-4. Using eight different methods, they measured the distances to a whopping 56,000 galaxies. The study has been published in the Astrophysical Journal. Galaxies, such as the Milky Way, are the building blocks of the universe, each comprised of up to several hundred billion stars. Galaxies beyond our immediate neighborhood are rushing away, faster if they are more distant, which is a consequence of the expansion of the universe that began at the moment of the Big Bang. Measurements of the distances of galaxies, coupled with information about their velocities away from us, determine the scale of the universe and the time that has elapsed since its birth. "Since galaxies were identified as separate from the Milky Way a hundred years ago, astronomers have been trying to measure their distances," said Tully. "Now by combining our more accurate and abundant tools, we are able to measure distances of galaxies, and the related expansion rate of the universe and the time since the universe was born with a precision of a few percent." From the newly published measurements, the researchers derived the expansion rate of the universe, called the Hubble Constant, or H0. The team's study gives a value of H0=75 kilometers per second per megaparsec or Mpc (1 megaparsec = 3.26 million light years), with very small statistical uncertainty of about 1.5%. There are a number of ways to measure galaxy distances. Generally, individual researchers focus on an individual method. The Cosmicflows program spearheaded by Tully and Kourkchi includes their own original material from two methods, and additionally incorporates information from many previous studies. Because Cosmicflows-4 includes distances derived from a variety of independent, distinct distance estimators, intercomparisons should mitigate against a large systematic error.
Cosmic dilemma Physics of the evolution of the universe based on the standard model of cosmology predicts H0=67.5 km/s/Mpc, with an uncertainty of 1 km/s/Mpc. The difference between the measured and predicted values for the Hubble Constant is 7.5 km/s/Mpc-much more than can be expected given the statistical uncertainties. Either there is a fundamental problem with our understanding of the physics of the cosmos, or there is a hidden systematic error in the measurements of galaxy distances.
Additional studies The mysterious dark matter is the dominant component on larger scales. With knowledge of the motions of galaxies in response to the mass around them, we can recreate the orbits that galaxies have followed since they were formed, giving us a better understanding of how the universe's vast, dark-matter dominated structures have formed over the eons of time.
Instrument issue pauses NASA's James Webb Telescope observations Washington DC (UPI) Sep 21, 2021 Scientists have temporarily paused further observations with NASA's new James Webb telescope after a problem was detected with one of its instruments, the space agency confirmed. "The Webb team has paused in scheduling observations using this particular observing mode while they continue to analyze its behavior and are currently developing strategies to resume MRS observations as soon as possible," NASA said in a statement Tuesday. The deep space telescope has a problem with its Mid-Infr ... read more
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