Hubble has taken another step to determine the rate of expansion of our Universe

Since the discovery of the expansion of the Universe, or almost, the question has plagued astrophysicists. How fast is this expansion going on today? Because observations and theory do not give the same answer. Now, the Hubble Space Telescope provides more accuracy.

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[EN VIDÉO] Interview: why is the universe expanding?
With the discovery of the expansion of the universe came other questions: how fast did this expansion occur? is there acceleration? or slowing down? Futura-Sciences interviewed Aurélien Barrau, astrophysicist who specializes in cosmology and author of the book Des univers multiples.

Amua universe expands. no doubt. What the debate is rapidly which continues today mobility. The current rate of expansion – translated by that the physicists baptized it, Hubble consistently. This is in honor of the American Edwin Hubble who discovered the phenomenon of the expansion of the universe and made its first measurements in 1920. And the tribute is further strengthened now as researchers reveal new new results more accurate than ever. Derived from data collected over 30 years of Hubble Space Telescope.

It should be remembered that measurement is really one of the main reasons for the existence of this instrument. Efforts made in the early 1970s were aimed at developing a tool capable of resolving Cepheids. Because the Cepheids, variable starshas long served as a cosmic marker, a kind of standard meter for measuring the distances of the Universe. Since 1912, exactly. They can be found in our Milky Way and inside galaxies away, thanks to the Hubble Space Telescope, up to about 80 millionlight years.

When Hubble was launched in the 1990s the first series of Cepheid observations were made. With the primary purpose of refinement measuring the distances of galaxies close to us. In the early 2000s, the efforts of astronomers reciprocated. They are thus able to deduce a value from Hubble always with an accuracy of 10%. The value is 72 plus or minus 8 kilometers per second per megaparsec (km/s/MPc).

What value is correct?

To refine this value, the researchers added new cameras to the space telescope. With the idea of ​​achieving an accuracy of 1%. An idea led specifically for collaboration Supernova, H0, for the Equation of State of Dark Energy (SH0ES).

The new results published today by the researchers are based on a sample of cosmic markers with more than double. They also include an updated analysis of past data. And in total, 42 supernovae-it is known that Hubble witnessed a supernova explosion per year, it is estimated that …-is also useful in determining the distances of the Universe. So astronomers estimate, given the size of their sample, only once in a million, the probability “from an unlucky draw”. And give a Hubble constant value of about 73 km/s/MPc. Very accurate 73.04 +/- 1.04 km/s/Mpc.

The problem is that from the measurements of Planck mission (European Space Agency, ESA) in our primitive universe and according to standard cosmological model, theorists predicted a value of the Hubble constant to be 67.5 plus or minus 0.5 km/s/MPc. So where does this difference come from? Astronomers still don’t know. But it is possible that they will find the answer somewhere in the new laws physically. A very recent study tests, for example, to explain the difference using a “world glass» invisible particles that interact only with our world by the gravity.

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