Far Depths of the Universe

Chapter 1.

Introduction to astronomy

Within the observable part of the Universe there are several tens of billions of large galaxies of various shapes.

Gas and dust are collected in gas and dust clouds, which are observed as diffuse luminous nebulae and reflection nebulae near stars.

Open and globular star clusters are observed.

The average density of matter in the Universe in the form of stars, gas, dust and galaxies is only about 1.2 × 10 -26 kg/m 3 .

The densest objects are neutron stars.

The remnants of supernova explosions are observed, in which matter scatters at a speed of thousands of kilometers per second, resulting in the formation of relativistic particles.

At the center of the Milky Way is a supermassive black hole.

To study the most distant celestial bodies, astronomers build giant telescopes to distinguish as small details as possible of celestial bodies.

To get rid of the influence of the atmosphere and to study the radiation of celestial bodies in X-ray, γ- and infrared rays, space telescopes are launched.

Structure and scale of the Universe

The science of celestial bodies is called astronomy (from the ancient Greek words astron – star and nomos – law). She studies their visible and actual movements and the laws that determine these movements; shapes, sizes, masses and surface topography; nature and physical condition of celestial bodies; interaction between them, their evolution – probable past history and future development. The object of research by astronomers is the entire universe as a whole.

Within the observable part of the universe there are several tens of billions of galaxies. Each galaxy contains tens and hundreds of billions of stars. The total number of stars in the observable part of the Universe is about 1022.

When photographing the sky with the most powerful telescopes, it is possible to capture up to 10 billion stars. Almost all of them belong to our Galaxy, which in ancient times was given the name Milky Way .

Astronomers have measured the distances to many stars. The distance to our nearest star, Proxima Centauri, is 4.2 sv. d. The value “several light years” characterizes the average distance between stars in the Milky Way.

Along with stars and planets, the universe contains gas and dust. The mass of gas and dust in galaxies is almost a hundred times less than the mass enclosed in stars

The rarefied regions of the Universe are the space between galaxies, and the densest regions are the cores of stars. If the average density of the Sun is about 1400 kg/m3, almost like the density of water, then in the center of the Sun it is already about 150,000 kg/m3.

Astronomers have been able to measure and calculate the temperatures of various celestial bodies and regions of space. So, the coldest were dense clouds of gas and dust, distant at great distances from the stars – in them the temperature is only a few Kelvins. It is in these regions that new stars are formed.

On the surface of the Sun, the temperature is about 6000 K, and in its center – about 15,000,000 K. In some stars, the temperature in the center reaches billions of Kelvin. Due to high temperatures, thermonuclear reactions proceed in them and everything is formed, including heavy chemical elements.

Recent observations have shown that the universe is expanding at an accelerating rate. According to observations of the accelerated removal of galaxies, a new force of the Universal Repulsion was recently discovered. The nature of this force is not yet clear. In addition, it was found that the main part of the Universe is occupied by dark matter and dark energy , and ordinary matter makes up only a few percent.

Far Depths of the Universe

Modern astronomy is aimed at studying the most distant regions of the universe and the detailed structure of celestial bodies. In recent decades, several observatories with giant telescopes have been built.

Of note is the Southern International Astronomical Observatory in Chile at an altitude of about 5,000 meters. Very Large Telescope, consisting of four telescopes with diameters of 8.2 m each. With the help of computer technology, they can work together like a giant interferometer, with an angular resolution of a few milliseconds of arc.

The good astronomical climate in the observatory and sensitive infrared light receivers made it possible to penetrate into the center of the Milky Way through clouds of gas and dust that are opaque to visible light, study the movement of individual stars in the center and detect a supermassive black hole in it.

To exclude the influence of the atmosphere on the results of observations, astronomers launch telescopes outside the earth’s atmosphere.

Using long exposures, images of protogalaxies, the first clumps of matter that formed less than a billion years after the Big Bang, were captured for the first time.

The Russian space observatory “Radioastron” is currently operating in outer space. The telescope moves in a very elongated orbit with an apogee of up to 360,000 km. Radioastron makes it possible to obtain information about the structure of galactic and extragalactic radio sources on angular scales up to 8 microseconds of arc (8 × 106″).

The Fermi Gamma Telescope is currently orbiting the Earth in outer space. Since gamma radiation is produced during high-energy processes, the birth and annihilation of particles and antiparticles, during nuclear reactions, the telescope allows you to study these processes in celestial bodies. Many astronomers tend to think that gamma rays exhibit unusual properties of dark matter.

Neutrino astronomy has received great development. With her methods, she managed to look inside the Sun and into the cores of exploding supernovae. A completely new direction is represented by gravitational-wave astronomy. Her first successes are associated with the direct observation of gravitational radiation, which, apparently, was formed during the merger of two black holes.

Summing up

ISSUES FOR DISCUSSION:

An object with what minimum linear size can we distinguish in the Andromeda Nebula galaxy, the distance to which is 2.5 million sv. years, with the help of RadioAstron?

The speed of the fibers in the Crab Nebula is 1500 km/s. The distance to it is 6500 St. years. In how many years will we be able to notice this movement in a telescope with a diameter of 86 m with a spatial resolution of 0.004 ′′?

How is research in astronomy different from research in physics and biology?

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