This question has tormented astrophysicists since the discovery of the expansion of the universe, or almost. How fast is this expansion continuing today? Because observation and theory do not give the same answer. Today, the Hubble Space Telescope provides additional 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 is this expansion happening? Is there any acceleration? or slow? Futura-Sciences interviewed Aurelian Barau, an astrophysicist specializing in cosmology and author of the book Des Universe Multiples.
Our universe is expanding. There is no doubt about it. what is the debate pace which continues today motion, its current rate of expansion – which is translated by physicists Baptized it, the Hubble constant. It was in honor of the American Edwin Hubble He discovered the phenomenon of expansion of the universe and made the first measurements in the 1920s. And the tribute grows stronger today as researchers uncover new new results more accurate than ever. Obtained from data collected over 30 years by Hubble Space Telescope,
It should be remembered that measurement was one of the main reasons for the existence of this device. Efforts made in the early 1970s were aimed at developing tools capable of resolving Cepheids. Because Cepheids, changing starshave long served as cosmic markers, a kind of standard meter measure distances in the universe, From 1912, of course. they can be seen in both of us Galaxy in only galaxies away, thanks Hubble Space Telescopearound 80 million. untillight year,
It was when Hubble was launched in the 1990s that the first series of Cepheid observations were made. With the main objective of refining the measurement of the distances of galaxies near us. In the early 2000s, efforts of astronomers were rewarded. They were able to extract a value like this Hubble constant with an accuracy of 10%. A value of 72 plus or minus 8 kilometers per second per megaparsec (km/s/mpc).
Which value is correct?
To refine this value, the researchers then added new cameras to the space telescope. With a view to achieving accuracy of 1%. an idea led specifically to collaboration For the equation of state of supernova, H0, dark energy (SH0ES).
The new results, published today by the researchers, are thus based on a sample of cosmic markers that has more than doubled. They also include an updated analysis of past data. And in total, 42 supernovae — knowing that Hubble is seeing a supernova explosion per year, approx… – also useful for determining distances in the universe. Astronomers thus estimate, given their sample size, only one chance in a million, the probability “by an unfortunate draw”, and give the value of Hubble constant about 73 km/s/Mpc. Exactly 73.04 +/- 1.04 km/s/Mpc.
The problem is that by measuring planck mission (European Space Agency, ESA) On our early universe and according to the standard cosmological model, theorists predict a value of the Hubble constant to be 67.5 plus or minus 0.5 km/s/Mpc. So where does this discrepancy come from? Astronomers still don’t know. But it is possible that they will have to find the answer somewhere in the new laws. Body, a very recent study For example, a. Attempt to explain the discrepancy by using ” World Mirror, Invisible Particles That Will Only Interact With Our World Via Gravity.
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