The Earth can see only the 5 largest satellites of Uranus: Miranda, Ariel, Umbriel, Titania and Oberon.

The Earth can see only the 5 largest satellites of Uranus: Miranda, Ariel, Umbriel, Titania and Oberon.

This distinguishes Uranus from other planets, where the poles are always colder.

How many rings does Uranus have?

Astronomers used to believe that the rings are only in Saturn. However, in 1977 they discovered that Uranus also has 11 rings consisting of stone fragments up to 1 m in size. The fragments are kept in the ring by the attraction of small companions of shepherds. Uranus rings are difficult to observe because they are very narrow (most up to 10 km wide). In addition, their substance is the darkest in the solar system.

What is the structure of Uranus?

The dense atmosphere of Uranus consists of hydrogen, helium and methane; mantle – of water, ammonia and methane ice. In the center is an iron-stone core.

What do Uranus satellites look like?

Only the 5 largest satellites of Uranus are visible from Earth: Miranda, Ariel, Umbriel, Titania and Oberon. Voyager 2 has discovered 10 more small satellites. Large satellites are huge balls of stone and ice, dotted with craters and long cracks. Titania’s largest satellite has a diameter of about 1,600 km.

What are the features of Miranda?

Miranda is the smallest satellite that can still be seen from Earth: its diameter is only 500 km. Close-ups show that this is the most interesting satellite of all discovered. Its surface is a set of different types of landscape: craters, gorges, steep cliffs and valleys.

Astronomers speculate that Miranda once crashed to pieces after colliding with another body. Eventually, these pieces reunited to create the existing landscape.

11/14/2011

Galaxies as a subject of cosmogonic research. Abstract

Galaxies have been the subject of cosmogonic research since the 1920s, when their true nature was reliably established and it turned out that it writes lab reports for you was not nebulae, ie not clouds of gas and dust near us, but huge stellar worlds lying behind us. at very great distances from us

At the heart of all modern cosmology is one fundamental idea – ascending to Newton’s idea of ​​gravitational instability. Matter cannot remain uniformly scattered in space, because the mutual attraction of all particles of matter tend to create in it a thickening of various scales and masses.

In the early universe, gravitational instability initially exacerbated very weak irregularities in the distribution and motion of matter and in a certain era led to strong inhomogeneities: "pancakes" – protoclusters. The boundaries of these layers of compaction were shock waves, on the fronts of which the primary non-rotating, irreversible motion of matter became vortical. The disintegration of the layers into individual thickenings also occurred, apparently due to gravitational instability, and this gave rise to protogalaxies. Many of them turned out to be rotating rapidly due to the vortex state of the substance from which they were formed.

The fragmentation of protogalactic clouds as a result of their gravitational instability led to the appearance of the first stars, and the clouds turned into stellar systems – galaxies. Those of them that had a fast rotation acquired a two-component structure because of it – they formed a halo of more or less spherical shape and a disk in which spiral arms appeared, where the birth of Protogalactic stars still continues, in which rotation was slower or absent. turned into elliptical or irregular galaxies. In parallel with this process there was the formation of a large-scale structure of the universe – there were superclusters of galaxies, which, connecting their edges, formed the likeness of cells or honeycombs; they have been recognized in recent years.

In the 20′s and 30′s of the XX century, Hubble developed the basics of the structural classification of galaxies – giant stellar systems, according to which there are three classes of galaxies:

I. Spiral galaxies are characterized by two relatively bright branches arranged in a spiral. The branches come either from a bright nucleus (such galaxies are denoted by S) or from the ends of a light jumper that crosses the nucleus (denoted by SB).

II. Elliptical galaxies (denoted by E) – have the shape of ellipsoids.

Representative – a circular nebula in the constellation Lyra is located at a distance of 2100 light years from us and consists of a glowing gas surrounding the central star. This shell was formed when an aging star dropped its gas veils and they headed into space. The star shrank and turned into a white dwarf, comparable in mass to our sun, and in size to Earth.

III. Irregular (irregular) galaxies (denoted by I) – having irregular shapes.

According to the degree of ragged branches of spiral galaxies are divided into subtypes a, b, c. In the first of them the branches are amorphous, in the second they are somewhat ragged, in the third they are very ragged, and the nucleus is always dim and small.

The density of the distribution of stars in space increases with the approach to the equatorial plane of spiral galaxies. This plane is the plane of symmetry of the system, and most stars, when they rotate around the center of the galaxy, remain near it; circulation periods are 107 – 109 years. In this case, the inner parts rotate as a solid, and on the periphery of the angular and linear velocities decrease with distance from the center. However, in some cases, what is inside the nucleus is even smaller nucleus ("core") rotates most likely. Irregular galaxies, which are also flat star systems, rotate similarly.

Elliptical galaxies consist of stars of the second type of population. Rotation is found only in the most concise of them. Cosmic dust in them is usually no different than they are from irregular and especially spiral galaxies, in which light-absorbing dust is present in large quantities.

In spiral galaxies, there is more light-absorbing dust. It is from a few thousandths to a hundredth of their total mass. Due to the concentration of dust to the equatorial plane, it forms a dark band in galaxies turned to us by the edge and have the form of a spindle.

Subsequent observations have shown that the described classification is insufficient to systematize all the variety of shapes and properties of galaxies. Thus, galaxies have been found that occupy in some sense an intermediate position between spiral and elliptical galaxies (denoted by Co). These galaxies have a huge central condensation and a surrounding flat disk, but spiral branches are absent.

In the 60s of the twentieth century, numerous finger-shaped and disk-shaped galaxies were discovered with all the gradations of a large number of hot stars and dust. As early as the 1930s, elliptical dwarf galaxies were discovered in the constellations of the Furnace and the Sculptor with extremely low surface brightness, so small that these galaxies, some of the closest to us, are barely visible in the sky, even in their central part. On the other hand, in the early 60′s of the twentieth century, many distant compact galaxies were discovered, of which the most distant in appearance are indistinguishable from the stars, even in the strongest telescopes. They differ from stars in a spectrum in which bright lines of radiation are visible with huge redshifts corresponding to such great distances at which even the brightest single stars cannot be seen.

Unlike ordinary distant galaxies, which, due to a combination of the true energy distribution in their spectrum and the redshift, look reddish, the most compact galaxies (also called quasi-star galaxies) have a bluish color. As a rule, these objects are hundreds of times brighter than ordinary supergiant galaxies, but there are also weaker ones. According to the theory of the Russian astronomer IS Shklovsky, radio galaxies of a nonthermal nature have been found in many galaxies when electrons and heavier charged particles moving at speeds close to the speed of light (so-called synchrotron radiation) are inhibited in a magnetic field. Such particle velocities are obtained as a result of grand explosions inside galaxies.

Compact distant galaxies with powerful non-thermal radio radiation are called N-galaxies.

Star-shaped sources with such radio radiation are called quasars (quasi-stellar radio sources), and galaxies with powerful radio radiation and having noticeable angular dimensions are called radio galaxies. All these objects are extremely far from us, which makes them difficult to study. radio galaxies, which have a particularly powerful non-thermal radio radiation, have a predominantly elliptical shape, and there are spiral.

radio galaxies are galaxies in which the nuclei are in the process of decay. Ejected dense parts continue to fragment, possibly forming new galaxies – sisters, or satellites of smaller galaxies. In this case, the speed of scattering of fragments can reach huge values. Studies have shown that many groups and even clusters of galaxies disintegrate: their members move away from each other indefinitely, as if they were all caused by an explosion.

Supergiant galaxies have luminosities 10 times the luminosity of the Sun, quasars are on average 100 times brighter; the weakest of the known galaxies, the dwarfs, is comparable to the usual globular star clusters in our galaxy. Their luminosity is about 10 luminosities of the sun.

The sizes of galaxies are very diverse and range from tens of parsecs to tens of thousands of parsecs.

The space between galaxies, especially inside clusters of galaxies, apparently contains sometimes cosmic dust. Radio telescopes do not find a significant amount of neutral hydrogen in them, but cosmic rays penetrate it in the same way as in electromagnetic radiation.

The galaxy consists of many stars of different types, as well as star clusters and associations, gas and dust nebulae, and individual atoms and particles scattered in interstellar space. Most of them occupy a lenticular volume with a diameter of about 30 and a thickness of about 4 kiloparsecs (about 100 thousand and 12 thousand light years, respectively). A smaller part fills an almost spherical volume with a radius of about 15 kiloparsecs (about 50 thousand light years).

All components of the galaxy are connected into a single dynamic system that rotates around a small axis of symmetry. To the terrestrial observer inside the galaxy, it is represented in the form of the Milky Way (hence its name – "Galaxy") and the whole set of individual stars visible in the sky.