1. Stars
1.1. A star is type of astronomical object consisting of a luminous spheroid of plasma held together by its own gravity. The nearest star to Earth is the Sun. Many other stars are visible to the naked eye from Earth during the night, appearing as a multitude of fixed luminous points in the sky due to their immense distance from Earth. Historically, the most prominent stars were grouped into constellations and asterisms, the brightest of which gained proper names. Astronomers have assembled star catalogues that identify the known stars and provide standardized stellar designations. However, most of the stars in the Universe, including all stars outside our galaxy, the Milky Way, are invisible to the naked eye from Earth. Indeed, most are invisible from Earth even through the most powerful telescopes.
2. Our Solar System
2.1. The Sun
2.1.1. The Sun is the star at the center of the Solar System. It is a nearly perfect sphere of hot plasma, with internal convective motion that generates a magnetic field via a dynamo process.[16] It is by far the most important source of energy for life on Earth
2.2. Planet
2.2.1. A planet is an astronomical body orbiting a star or stellar remnant that
2.2.2. is massive enough to be rounded by its own gravity,
2.2.3. is not massive enough to cause thermonuclear fusion, and
2.2.4. has cleared its neighbouring region of planetesimals
2.3. comets ,meteors and asteroids
2.3.1. A comet is an icy small Solar System body that, when passing close to the Sun, warms and begins to release gases, a process called outgassing. This produces a visible atmosphere or coma, and sometimes also a tail
2.3.2. A meteoroid is a small rocky or metallic body in outer space.
2.3.3. Asteroids are minor planets, especially those of the inner Solar System. The larger ones have also been called planetoids
3. Galaxies
3.1. irregular galaxy
3.1.1. An irregular galaxy is a galaxy that does not have a distinct regular shape, unlike a spiral or an elliptical galaxy.[1] Irregular galaxies do not fall into any of the regular classes of the Hubble sequence, and they are often chaotic in appearance, with neither a nuclear bulge nor any trace of spiral arm structure
3.2. Spiral galaxy
3.2.1. Spiral galaxies form a class of galaxy originally described by Edwin Hubble in his 1936 work The Realm of the Nebulae[1] and, as such, form part of the Hubble sequence. Most spiral galaxies consist of a flat, rotating disk containing stars, gas and dust, and a central concentration of stars known as the bulge. These are often surrounded by a much fainter halo of stars, many of which reside in globular clusters.
3.3. elliptical galaxy
3.3.1. An elliptical galaxy is a type of galaxy having an approximately ellipsoidal shape and a smooth, nearly featureless brightness profile. Unlike flat spiral galaxies with organization and structure, they are more three-dimensional, without much structure, and their stars are in somewhat random orbits around the center