From The University of Hawai’i-Manoa Institute for Astronomy : “UH astronomers map distances to 56000 galaxies – largest-ever catalog University of Hawaiʻi at Mānoa”

From The University of Hawai’i-Manoa Institute for Astronomy

Roy Gal
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Full-sky map showing Cosmicflows-4’s 56,000 galaxies with distance measurements.

How old is our universe, and what is its size? A team of researchers led by University of Hawaiʻi at Mānoa 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 [below].

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.

Science paper:
The Astrophysical Journal

See the full article here .


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The The University of Hawai’i Institute for Astronomy is a research unit within the University of Hawai’i system. Institute for Astronomy’s main headquarters are located at 2680 Woodlawn Drive in Honolulu, Hawai’i, adjacent to the University of Hawai’i-Mānoa campus. Additional facilities are located at Pukalani, Maui and Hilo on Hawaiʻi island (the Big Island). Institute for Astronomy employs over 150 astronomers and support staff. Institute for Astronomy astronomers perform research into Solar System objects, stars, galaxies and cosmology.
The Institute for Astronomy was founded in 1967 to conduct research and to manage the observatory complexes at Haleakalā, Maui and the Mauna Kea Observatory on the summit of Mauna Kea. It has approximately 55 faculty and employs over 300 people.

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