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Galaxies belong to galaxy clusters. Below is galaxy cluster Abell-426 in constellation of Perseus. Distance is 273 million light years, so the light started its journey to us when the dinosaurs began their era in Earth. When looking with telescope to the sky we see back in time. In picture below the distant galaxies look hazy compared to sharp edge star of our own galaxy. Because of expansion of the universe, this galaxy cluster is moving away from us at speed of 5300 kilometers per second. Picture taken with Helios Skyliner 200/1000 telescope 16.1.2020.

Quasars are the brightest objects in the Universe. They are massive black holes in the core of their galaxies. Matter and stars fall into black hole and while accelerating the mater shines a lot of energy. The farther away on object is the faster it recedes from us because of expansion of universe. The 'edge' of observable universe at distance of 13.7 billion light years recedes at speed of light.
Quasar 3C-273 imaged 4.3.2012. 3C-48 imaged 19.1.2020. Q1634+706 imaged 9.8.2012. CTA 102 imaged 15.12.2016.

When Albert Einstein made the theory of general relativity in 1920s, he found out that the universe cannot be in rest. It should either expand or contract. In 1920s general assumption was the universe is in rest, so Einstein added a correcting coefficient to his formula of space-time. Later he thought it was the biggest mistake of his life. He could have predicted the expansion of universe based on his theory before it was observed.

At same times Edwin Hubble started accurate observations of galaxies at Mount Wilson observatory in USA. He used the biggest telescope at that time. Diameter of mirror was 2.5 meters. He measured the movement of galaxies in relation to us (the shift of spectral lines of light from galaxies). To his surprise he found out that the further away a galaxy is from us, the faster it moves away from us.

Conclusion from this observation is that universe is expanding. And that universe has had a beginning, which we call Big Bang. From the speed of expansion it can be calculated that the Big Bang happened 13.7 billion years ago.

About 400 million year after Big Bang the stars and galaxies started to form from the hydrogen and helium gas which filled the Universe. Galaxies are in galaxy clusters in surfaces of bubbles, which resemble like soap bubbles. Inside bubbles there is no galaxies.

Current observations and theories state that largest part of matter in Universe is so called Dark Matter, which interacts with ordinary matter only by gravitational force. First indications of Dark Matter were observed back in 1930 when it was seen that galaxies are rotating too fast in order that gravity of ordinary matter would keep the galaxy together in one piece.

Below is the Virgo Galaxy cluster. Distance 54 million light years. There is about 1000-2000 galaxies in this cluster. In sky they are in area of several angular degrees. This is the closest cluster to us and actually our Milky Way galaxy and nearby galaxies belong to the Virgo super cluster. Picture was taken 20.1.2017 with 400mm teleobjective. Exposures were 5 x 60 seconds, ISO 3200 and stacked with DSS.

Below is Coma galaxy cluster Abell 1656 in the constellation of Coma Berenices. Distance 321 million light years. Picture was taken 6.3.2017 with Celestron 8 F6.3 focus. Exposures were 7 x 37 seconds and stacked with DSS.

Below is four distant galaxy clusters in constellation of Pegasus.
Abell 2634. Distance 405 million light years. Receding 9360 km/s. Picture taken 5.10.2016. C8 F6.3, 5x40s, ISO3200.
Abell 2666. Distance 344 million light years. Receding 7950 km/s. Picture taken 30.11.2016. 4x50s ISO6400 C8 F6.3.
Pegasus I. Distance 180 million light years. Picture taken 28.10.2018. 4x55s ISO3200 C8 F6.3.
Pegasus II. Distance 600 million light years. Picture taken 28.10.2018. 5x70s ISO3200 C8 F6.3.

Below is remarkable picture by Hubble Space Telescope. New born galaxies from time 350-600 million years after Big Bang. Distance about 13 billion light years. You can see that galaxies are there much closer to each other than today. Also there is no dust in the galaxies, since the first stars have just started to produce heavier elements. There is only hydrogen and helium in early universe. Also it may be that in this picture You see the cosmic dark age behind these galaxies. Time when there was no stars and galaxies. This Hubble Ultra Deep Field picture is taken from constellation of Fornax. Exposure time is tens of hours. Copyright for Hubble Ultra Deep Field picture: NASA, ESA, R.Ellis(Caltech) and UDF 2012 Team

Below is presentation of birth of Universe, its evolution and about the time period which Hubble reached in the Ultra Deep Field picture. Copyright for picture below: University of Arizona.

Copyright (c) for pictures, except two last ones, 2018 Harry Rabb. All rights reserved.

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