Radiation or light is the primary source of information about the Universe and its constituents.
The Cartwheel Galaxy
The Cartwheel as seen by HST
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Updated December 20, 2022
The Cartwheel Galaxy (ESO 350-40) is a ring galaxy, located about 500 million light years away, in the constellation Sculptor in the southern hemisphere.
The cartwheel shape of this galaxy is the result of a violent galactic collision that occurred about 200 million years ago.
A small galaxy passed through the disk core of a large galaxy and produced this gigantic shock wave that spread surrounding gas and dust throughout the galaxy.
The Cartwheel Galaxy is now surrounded by a bluish ring 150,000 light years in diameter. This ring is composed of young and bright stars. The high-speed movement of the shock wave compressed the dust and gas, which encouraged the birth of the stars that now illuminate the periphery of the wave. In the image, star forming regions appear blue. The outer ring of the galaxy is 1.5 times the size of our Milky Way. We can see in this image that the galaxy is in the process of resuming the shape of a normal spiral galaxy, with galactic arms which are reforming from the central core.
This galaxy was an identical galaxy to the Milky Way before it suffered the head-on collision. This celestial object is one of the most remarkable examples of the class of ring galaxies.
Star formation in the rings of the Cartwheel Galaxy promotes the formation of very large, very bright stars. When these massive stars explode into a supernova, a neutron star or black hole remains in their cores. Some of these neutron stars and black holes attract material from nearby stars and become powerful sources of X-rays.
The Cartwheel contains an exceptionally high number of these X-ray source black holes (many massive stars have formed in the ring).
This image was produced with Hubble data and then reprocessed using the FITS Liberator 3 open source software developed at ST-ECF. The use of this tool allowed, from the original Hubble observations, to obtain even more details of the Cartwheel galaxy.
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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.
The Cartwheel as seen by JWST
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The James-Webb Space Telescope, placed at Lagrange Point L2, reveals new details about the Cartwheel Galaxy and its central black hole against the backdrop of many other galaxies.
The Galaxy Cartwheel sports two rings - a glowing inner ring and a surrounding colorful ring. Its cartwheel appearance is the result of an intense event - a high-speed collision between a large spiral galaxy and a smaller galaxy not visible in this image.
The outer ring, which has been expanding for about 440 million years, is dominated by numerous star formations, star clusters and supernovae.
James-Webb unveils new information about the nature of the wheel thanks to its ability to detect infrared light.
We also see two smaller galaxies (on the left), one blue and the other pink.
The NIRCam camera is the main imager of the James-Webb telescope. it looks at radiation near infrared (0.6 to 5 microns).
These crucial wavelengths of light can reveal even more stars than seen in visible light from the Hubble Telescope. Indeed, the stars are less obscured by the presence of dust when they are observed in infrared light.
In this James-Webb composite image, MIRI data is colored red. It reveals regions rich in hydrocarbons and other chemical compounds, as well as silicate dust, like that which exists on Earth.
Inside the wheel, we see spiral rays that will form the skeleton of the galaxy. These rays are also visible in previous Hubble observations, but they are much more distinct in this Webb image. The galaxy, which was presumably a normal spiral galaxy like the Milky Way before its collision, swept away by the gravitational force will return to its original shape.
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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.
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.