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Astronomers who measure the expansion of the cosmos as a result of the Big Bang are still faced with a puzzling conflict between the value observed today and the value derived from the observations of the Universe extremely early. Taking into account dark energy and the acceleration of cosmic expansion, it would appear that the modern Universe is flying faster than expected based on how quickly it was moving soon after the Big Bang.
Using the Hubble Space Telescope and the Gaia Observatory of the European Space Agency, the researchers calculated a value for the Hubble constant, a measure of the rate of expansion of the Universe, 73.5 kilometers (45.6 miles) per second per million of badyzes. This means that for every 3.3 million light years – 1 million parsecs – further than a galaxy could be, it moves away from us 73.5 kilometers per second faster.
The measurement is remarkably accurate with an uncertainty of only 2.2%.
But the results of ESA's Planck probe, based on observations of microwave background radiation, the residual heat after the Big Bang, place the value of the Hubble constant at 67 km / sec by megaparsec.
seems to be generally in good agreement for such esoteric measures, the gap between Hubble-Gaia data and Planck's measure is about four times the size of their combined uncertainty. This indicates "a total incompatibility between our visions of the universe of the beginning and the end," said in a statement Adam Riess, Nobel laureate at the Institute of Space Telescope Sciences, who contributed to discover black energy. Exchange with Astronomy Now, Riess says it's supposed "The Universe is growing at the same pace at one point on the entire Universe."
"In this case, the Universe is now growing faster, even after accounting for dark energy, as our understanding tells us that it should be based on how it fits. developed shortly after the Big Bang, "he said. "We should perhaps rejoice that we are only 9%, but as the margin of error is only 2.2%, 9% is a lot." We are missing something. "
The value derived from Planck's Hubble constant is based on the precise observations of the cosmic background radiation spacecraft dating back to a few hundred thousand years ago. years of the Big Bang. These observations, plugged into the "standard model" of physics, allowed researchers to extrapolate the current rate of expansion.
Hubble-Gaia's findings were based on a different technique, direct observation of the galactic cepheid variable stars. Cepheids pulsate in a predictable way that indicates their true brightness. By observing the apparent luminosity of a Cepheid in a distant galaxy, astronomers can calculate how far the star should be.
Gaia provided the most accurate data on 50 Cepheids in the Milky Way. This allowed Hubble astronomers to carefully calibrate their observations of extra-galactic Céphéides.
By comparing the positions of these stars and galaxies with the expansion of space as indicated by the light shift of neighboring galaxies, the Riess team was able to derive a speed toward the Outside at different points and from that, the Hubble constant.
"Gaia is the new standard for distance calibration," said Stefano Casertano of the Space Telescope Science Institute. "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 previous calibrations from the distance scale by the parallax of Gaia.This is a cross between two very powerful and accurate observatories. "
The Riess team hopes to reduce the uncertainty of its value for the Hubble constant to less than 1% in the early 2020s. Explaining the gap with Planck's data is another matter.
"It's the fifth independent verification of the measure," Riess said in the e-mail exchange, "so that does not sound like a mistake."
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