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 Automatic translation  Automatic translation Category: galaxies
Updated December 20, 2022
  galaxie cartwheel as seen by HST

Composite HST image: A small galaxy passed through the disk of a large galaxy, and produced this gigantic shock wave, which formed this wheel of gas and dust. The reprocessed image of this cosmic event shows the Cartwheel Galaxy or Cartwheel Galaxy (ESO 350-40). Image taken by the NASA/ESA Space Hubble Telescope.
Very high resolution Hubble images.

    
  cartwheel galaxy as seen by JWST

Composite JWST image: The large, wheel-shaped pink Cartwheel Galaxy taken by the James Webb Telescope. You can see in this image much more detail than in the image taken by the Hubble telescope in 2010. Credits: NASA, ESA, ASC, STScI.

Radiation or light is the primary source of information about the Universe and its constituents.
Light spans the entire spectrum of electromagnetic waves from high-energy gamma and X-rays, to low-energy microwaves and radio waves, to visible light, picked up by our eyes.
Radiation is carried by a particle called a photon. In physics theories, the propagation of light is described both in terms of waves and photons.
In general at low energy, the number of photons received by a telescope is very high (several hundreds of thousands per second) and we prefer to describe the phenomena in terms of waves.
At high energy photons are rarer from a few photons per second in X-rays to a few photons per day in very high energy gamma waves, and we prefer to describe the phenomena in terms of photons.
The main advantage of light is that it makes it possible to observe very distant sources. The two main sources of light are fossil radiation linked to the first stages of the evolution of the Universe, and the sum of the radiation emitted by stars, galaxies and clusters of galaxies.
The gravitational force was discovered in 1687 by Newton, this attractive force acts on all masses. Gravitation is the weakest of the four forces of nature, but also the one with the greatest range, it acts on the whole universe, it is the glue of the cosmos.
The intensity of this force depends on the mass of the object and concerns the entire universe.
Masses: Earth (6x1027g), Sun (1033g), Galaxy (1044g), clusters of galaxies (1047 g).
Newton expressed his theory in the form of a mathematical equation (FA/B = FB/A = G (MAMB/d2).
A and B are two massive bodies, MAand MB (mass in kg), the gravitational constant G=6.67384 x 10-11 N.m2.kg-2.
           
           
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