Galaxy

 Galaxy

Looking at the sky with the help of a telescope, it can be seen that somewhere in the space large groups of objects have been formed. Such groups of objects are called galaxies. Galaxies contain numerous stars, interstellar gas and dust, plasma, and large amounts of invisible matter. That is, a galaxy is a vast collection of numerous stars, interstellar gas and dust, plasma, and a large amount of invisible matter. Galaxies can range from a few thousand to hundreds of thousands of light years in diameter. A galaxy typically contains between ten million and one hundred billion stars. It depends on the size of the galaxy. Smaller galaxies are called dwarf galaxies and larger galaxies are called giant galaxies. Our solar system is also part of a galaxy. The name of this galaxy is Milky Way galaxy. In the dark night sky, the Milky Way galaxy appears as a white colored path running from one end of the sky to the other. In 1610, Galileo first observed this path with the help of a telescope and it was he who reported that this white path consists of numerous bright and dim stars. Galaxies can be of various shapes, such as elliptical, spiral and eccentric galaxies. 18 percent of galaxies appear to be elliptical. They are usually composed of red giant and white dwarf stars.

80 percent of all galaxies are twisted or spiral. Our Milky Way and Andromeda are such galaxies. They have a bright central mass region, where most of the galaxy's mass is concentrated. The flattened disk-shaped central region has several spiral arms. The entire structure rotates around a centripetal axis perpendicular to the disc plane. Our Solar System is located in a spiral arm 2.77 × 10^ light-years from the center of our galaxy.

Heterogeneous galaxies have no fixed size. 2 percent of galaxies are irregular in shape.

Radio waves can be seen radiating from some galaxies. Such galaxies are called radio galaxies. An ordinary radio galaxy has two lobes on either side (which look like two ears on either side of a human head (Fig. 11.8)) from which electromagnetic waves of frequency 10 MHz to 100 GHz are emitted. Radio galaxies differ from ordinary galaxies in that their radio The brightness (Radio luminosity) or radio power output (Radio power output) is about 10% W whereas the radio luminosity or radio power output of a typical luminous galaxy is 102 W.

The galaxy is called a radio galaxy. An ordinary radio galaxy has two lobes on either side (which look like two ears on either side of a human head (Fig. 11.8)) from which electromagnetic waves of frequency 10 MHz to 100 GHz are emitted. Radio galaxies differ from ordinary galaxies in that their radio The radio luminosity or radio power output is about 10% W whereas the radio luminosity or radio power output of a typical luminous galaxy is 102 W.

A quasar is a special type of radio galaxy. The word quasar comes from Quasi stellar radio source. This star is a source of electromagnetic energy whose light exhibits a very high redshift. Which means (according to Hubble's principle) - they are far away from us and they are moving away from us very fast (about 0.90 ). They are so far away that they are considered the boundary of the visible universe. Quasars are objects brighter than the Universe that appear as dots in telescopes. Their luminosity is greater than the combined luminosity of hundreds of average-sized galaxies. The first quasar was discovered in 1970. About 150 quasars have been discovered so far.