Over the course of the 20 years of Futura, it is interesting to point out some fascinating topics in astrophysics, which still raise many questions. The oldest being the dark matter that has haunted us for decades.
Laurent Sacco’s article Evaluates the recent hot debates about galaxies very prevalent, called UDG (Ultra-diffuse galaxies). They are big galaxies, but their massstars Who is this galaxies naines. Its surface density is very low, and theory predicts that it should be dominated by black matter. It is true that some, on the other hand, others interact with more massive galaxies, it is not.
Is it a problem of measurement or interpretation? Or are they still unbalanced, because they are upset with tidal forces ? These galaxies are also tests of alternative theories of dark matter.
Another area in which progress has been rapid in recent years is the field of fast radio blastsor FRB (fast radio blasts). Duncan Lorimer and colleagues published their discovery in 2007, and FRBs remained a mystery for several years because they did not repeat themselves; It was impossible to know which stars They were responsible for that. In the past decade, repeats have been discovered, and more and more FRBs, some in the Milky Way, have been traced back to neutron stars, especially things magnetic field intense, and magnetism.
Today, precursor toolsInterferometer SKA (square kilometer array) revealed hundreds of them as described Natalie Meyer in a his article. However, not all puzzles are solved…
Presentation by Professor Françoise Coombes for the 2016-2017 session: “Dark Energy and Models of the Universe”. © College of France
The mysterious and paradoxical accelerating expansion of the universe
tension over value Hubble constant It is a new source of discussion, and may lead to a new discovery physique (Editor’s note: An article on this discussion was also published today for 20 years by Futura).
The Hubble-Limeter constant He had a turbulent history. Edwin Hubble It was discovered in 1929 with measurements speeds From the Vesto Sliver galaxies, the distances obtained by the newly discovered law of the luminosity relationship period Cephedes, via Henrietta Levitt, in 1909. This first relationship between the distance and velocity of galaxies is the law of proportionality with a constant H0 It is equal to approximately 10 times the constant known today. Father Lemitri was the first to realize that it wasn’t really a question Doppler effect but who breadth Space saved by Equations Dr’Einstein from general relativity The year 1915. Going back in time, the primordial universe is baptized ascorn primitive that becomes the great explosion With Fred Hoyle in 1949.
This popular constant varied a lot during XXNS century, where the distances of galaxies are unknown. They range between 50 and 100 km/s/Mpc, which has a significant impact on the age of the universe: in addition to H0 Bigger, younger age of the universe.
So much so that some stars are getting older in the age of the universe!
Over time, and advances in telescopes, a new distance indicator, a new standard candle, appeared in the form of supernovae Type Ia: They make it possible to determine distances much further than Cepheids, because they are very bright. measuring the duration of the curve a light, it is possible to conclude brightness immanent, hence the distance between them. Surprise: These supernovae were much farther away than expected due to the spectral shift. This is how the acceleration of expansion was discovered in 1998 (Nobel Prize 2011), which makes the age of the universe consistent with the age of the stars.
For nearly 20 years, all the observations (cosmic background with WMAPAnd plankAnd Gravity lenses, SNIa, etc.), on creating a convergence model of the universe, with 30% matter, 70% ofdark energy, the constant H0 = 70 km / sec / MPC. However, in recent years, tension has arisen between the value of H.0 Measured locally (Cepheids and other standard candles) and inferred from cosmology LCDM, with the physics of the primordial universe: H.0= 73 on one side, 66 km/s/Mpc on the other side.
does it come from neutrino mass ? essence,dark energy ? Or other physics?
The area to be explored is still enormous…
For 13.7 billion years, the universe has not stopped evolving. Contrary to what our eyes tell us when we contemplate the sky, what it consists of is far from consistent. Physicists have observations of different eras of the universe and run simulations in which they reshape the universe and its evolution. Dark matter appears to have played a large role from the beginning of the universe until forming the large structures observed today. © CEA Research
This year, Futura Celebrating its twentieth anniversary. 20 years of discovery, exploration and promotion of science.
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Stay tuned to celebrate these two decades of success, we have many surprises Until the end of 2021!
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