NASA's Hubble Space Telescope, the Gaia Space Observatory of the European Space Agency, measures the rate of expansion of the Universe

July 16, 2018 |
<img data-attachment- id = "428956" data-permalink = "http: // www .clarksvilleonline.com / 2018/07/16 / nasas-hubble-space-telescope-european-space-agencys-gaia-space-observatory-measure-the- universe-rate-of-expansion / nasas-hubble-space-telescope-european -space-agencys-gaia-space-observatory-measure-the-universes-rate-expansion / "data-orig-file =" http: //www.clarksvilleonline.com/wp-content/uploads/2018/07/NASA&#39;s -Hubble-Space-Telescope-European-Space-Agency-Gaia-Space-Observatory-Measure-The-Universe Expansion-Rate.jpg "data-orig-size =" 1200,800 "data-comments-opened =" 1 "data-image-meta =" {"opening": "0", "credit": "", " camera ":" "," legend ":" "," created_timestamp ":" 0 "," copyright ":" "," focal_length ":" 0 "," iso ":" 0 "," shutter_speed ":" 0 "," title ":" "," orientat ion ":" 1 "}" data-image-title = "Using two of the world's most powerful space telescopes – Hu from NASA ESA and ESA's Gaia astronomers have made the most accurate measurements to date of the rate of expansion of the universe. This is calculated by measuring distances between nearby galaxies using special types of stars called cepheid variables as cosmic bounds. (NASA, ESA, and A. Feild (STScI)) "data-image-description ="

Using two of the world's most powerful space telescopes – NASA's Hubble and Gaia – ESA astronomers have made the most accurate measurements to date. the rate of expansion of the universe. This is calculated by measuring distances between nearby galaxies using special types of stars called cepheid variables as cosmic bounds. (NASA, ESA, and A. Feild (STScI))

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Using two of the most powerful space telescopes in the world – NASA's Hubble and ESA's G astronomers. Asia have made the most accurate measurements to date of the rate of expansion of the universe.This is calculated by measuring distances between nearby galaxies using special types of stars called Cepheid variables. as cosmic bounds. (NASA, ESA, and A. Feild (STScI))

Combining observations from NASA's Hubble Space Telescope and the Gaia Space Observatory of the European Space Agency (ESA) ), astronomers refined the previous value of the Hubble constant, but the measurements becoming more precise, the determination of the Hubble constant by the equation ipe has become increasingly inconsistent with the measurements of another space observatory, the Planck Mission of ESA. which is coming up with a different predicted value for the Hubble constant.

Planck mapped the primitive universe as it appeared only 360,000 years after the big bang. The whole sky is stamped with the signature of the Big Bang encoded in microwaves. Planck measured the sizes of the ripples in this cosmic microwave background (CMB) that were produced by slight irregularities in the big bang fireball. The fine details of these ripples encode how much dark matter and normal matter, the trajectory of the universe at that time, and other cosmological parameters.

These measurements, still under evaluation, allow scientists to predict how the primitive universe would likely have evolved to the rate of expansion that we can measure today. However, these predictions do not seem to correspond to the new measures of our near contemporary universe.

"With the addition of these new data from the Gaia and Hubble Space Telescope, we now have a serious voltage with the Cosmic Microwave Background data," said Planck team member and senior analyst George Efstathiou of the Kavli Institute of Cosmology in Cambridge, England, who was not involved in the new work.

"The tension seems to have become a full-fledged incompatibility between our views of the", said team leader and Nobel laureate Adam Riess of the Space Telescope Science Institute and Johns Hopkins University in Baltimore, Maryland. "At this point, it's clear that this is not just a gross mistake in a measure. It's as if you had predicted how much a child would grow up from a growth chart and then you discovered that the adult that he passed was well beyond the prediction. We are very perplexed. "

In 2005, Riess and members of the SHOES team (Supernova H0 for the State Equation) undertook to measure the rate of expansion of the universe In the following years, refining their techniques, this team reduced the uncertainty of measuring rates to unprecedented levels.Now, with the power of Hubble and Gaia combined, they have reduces this uncertainty to only 2.2%

Because the Hubble constant is needed to estimate the age of the universe, the answer sought is one of the most important numbers in It owes its name to astronomer Edwin Hubble, who discovered nearly a century ago that the universe was spreading uniformly in all directions – a discovery that gave birth to modern cosmology.

Galaxies seem to move away from the Earth in proportion to their distances, which means that the further away they are, the faster they seem to move away. This is a consequence of the expansion of space, and not a value of true space velocity. By measuring the value of the Hubble constant over time, astronomers can construct an image of our cosmic evolution, derive the composition of the universe, and discover clues about its ultimate destiny.

The two main methods of measuring this number inconsistent results. One method is direct, building a cosmic "distance scale" from the measurements of the stars in our local universe. The other method uses the CMB to measure the trajectory of the universe shortly after the big bang and then uses physics to describe the universe and extrapolate at the current rate of expansion. Together, the measurements should provide an end-to-end test of our basic understanding of the so-called "standard model" of the universe. However, the pieces do not match.

Using Hubble and Gaia's new data, the Riess team measured the current rate of expansion at 73.5 kilometers (45.6 miles) per second per megaparsec. This means that for every 3.3 million more distant light years, a galaxy belongs to us, it seems to move faster by 73.5 kilometers per second. However, Planck's results predict that the universe is expected to be expanding today at just 67.0 kilometers (41.6 miles) per second per megaparsec. As teams' measurements have become increasingly precise, the gap between them has steadily widened and now represents about four times the size of their uncertainty.

Over the years, the Riess team has refined Hubble 's constant value by rationalizing and reinforcing the cosmic distance scale, used to measure precise distances to near and far galaxies. They compared these distances to the expansion of space, as measured by the light stretching of neighboring galaxies. Using apparent velocity at each distance, they then calculated the Hubble constant.

To measure distances between nearby galaxies, his team used a special type of star as a cosmic landmark or milestone marker. These pulsating stars, called Cephied variables, illuminate and darken at frequencies corresponding to their intrinsic luminosity. By comparing their intrinsic luminosity with their apparent luminosity as seen from Earth, scientists can calculate their distances.

Gaia refined this measure by geometrically measuring the distance to 50 Cepheid variables of the Milky Way. These measurements were combined with precise measurements of their Hubble luminosity. This allowed astronomers to more precisely calibrate Cepheids and then use those seen outside the Milky Way as markers of milestones.

"When using Cepheids, you need distance and brightness. Hubble provided information on brightness, and Gaia provided the parallax information needed to accurately determine distances. The parallax is the apparent change in the position of an object due to a change in the observer's point of view. The ancient Greeks first used this technique to measure the distance between the Earth and the Moon.

"Hubble is really amazing as a general purpose observatory, but Gaia is the new benchmark in distance calibration.It is specially designed to measure parallax, it's what it was designed for, "added Stefano Casertano of the Institute of Space Telescope Sciences and member of the SHOES team." Gaia brings a new ability to recalibrate all past distance measurements, and this seems to confirm our previous work. We get the same answer for the Hubble constant if we replace all the previous calibrations of the distance scale by Gaia parallaxes. It is a cross between two very powerful and precise observatories. "

The goal of the Riess team is to work with Gaia to cross the threshold of refining the Hubble constant to only 1% in the early 2020s. Meanwhile, astrophysicists will continue Probably to explore their ideas on the physics of the early universe.

The latest findings of the Riess team are published in the Astrophysical Journal July 12.

The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency) NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope.The Institute of Space Telescope Sciences (STScI ) in Baltimore, Maryland, conducts Hubble's scientific operations STScI is operated for NASA by the Association of Universities for Research in Astronomy, Washington, DC

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Themes [19659028] Baltiamore MD, Cepheid s, Dark Energy, Dark Matter, ESA, European Space Agency, Gaia Space Observatory, Greenbelt MD, Johns Hopkins University, Milky Way, NASA, NASA's Goddard Space Flight Center, NASA's Hubble Space Telescope, National Administration of 39, Aeronautics and Space, Space, Space Telescope Science Institute, Stars, Universe