We explain what celestial bodies are and the characteristics of planets, stars, constellations, nebulae, comets and more.
What are celestial bodies?
The celestial bodies are all natural objects that are part of the universe and that they can interact with another body, due to the force of gravity (orbiting it or being orbited).
In cases where there is no force of gravity influencing it, the celestial body is considered a “wandering body” that wanders through space, without orbiting around any star.
Planets
the planets are celestial bodies that revolve around a star such as Earth, Mars, Jupiter, etc and they make a translational movement around the Sun, always counterclockwise. The planets also perform a rotation movement that consists of rotating around their own axis.
Planets differ from stars because the latter have a greater amount of mass (density). For this reason, planets cannot carry out thermonuclear fusion processes that would allow them to emit their own light, as stars do. Planets only reflect the light they receive from the luminous star they orbit.
In addition to their density, they differ from other celestial bodies due to their size, since Its diameter must be greater than 1,000 kilometers. Bodies with similar characteristics but smaller size can be, for example, asteroids. the planets are usually surrounded by atmospheric gaseous layers of varying density.
stars
Stars are celestial bodies that represent enormous engines of cosmic energy that produce heat, light and radiation (such as ultraviolet rays and x-rays).
were formed by the condensation of hydrogen and cosmic dust and are capable of radiating their own light through nuclear fusion reactions. They must have a minimum amount of mass for the temperature and pressure conditions to trigger these reactions.
Stars live billions of years and, in general, the larger they are, the closer they are to extinction. They vary greatly in size and are classified in a range from “dwarfs” to “supergiants” (which can have a diameter 500 times larger than that of the Sun). The life cycle of a star can be summarized as follows:
- New star. After millions of years of the gas cloud becoming large enough and beginning to contract, nuclear fusion begins in which hydrogen is converted to helium. The contraction stops and the star emerges.
- Red giant It is the stage in which the star becomes larger and begins to consume its fuel. A slow process is triggered in which it contracts, a lot of heat is generated (especially in the core of the star) and by burning the last available fuel, the star goes extinct.
- Planetary nebula It is the stage in which the extinct star begins to shed layers because it can no longer contain them. The center of the star becomes a “white dwarf” (extremely dense star) and, once it has consumed all its energy, it stops shining and becomes a “black dwarf.”
- Supernova When the instance of a “planetary nebula” occurs with very large stars (for example, 40 times larger than the Sun), it is called a “supernova.” The stage of shedding layers of the star is called a “neutron star.” When the star stops shining, it can become a “black hole” in space.
Continue in: Stars
Constellations
The constellations are groups of stars that present an imaginary shape in the night sky and are created by humans. They are usually named with terms from Greek mythology, for example, the constellation of Orion whose name refers to a hunter, and that of Andromeda whose name corresponds to a maiden.
The stars that make up a constellation are not necessarily associated by their location, that is, can be found hundreds of light years away from each other. The fact that they form a group is arbitrary; in fact, different cultures have devised different constellations linking only some of the stars.
The zodiac (a word of Greek origin that means “circle of animals”) is a strip in space through which the Sun and the planets transit. This strip is located around the “celestial equator” (which corresponds to an imaginary projection of the line of the terrestrial equator in space).
It is divided into twelve equal parts, each representing a different figure: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpius, Sagittarius, Capricornus, Aquarius and Pisces. Hence the name “zodiacal constellations” arises.
Nebulae
The nebulae are concentrations of gas in which hydrogen, helium and star dust predominate which are widely dispersed, but due to the force of gravity they can come together to form a group. The larger the nebula, the greater the force of gravity it develops.
Nebulae are crucial to the universe because stars are born within them from the condensation and aggregation of matter. There are also other nebulae that are made up of remains of extinct stars.
In its final stage, the clump of gases and dust becomes so large that it collapses under its own gravity. That collapse causes the material in the center of the cloud to heat up until the core gives rise to a new star.
Nebulae are distributed throughout space, between stars and other celestial bodies. The best-known nebula is called “Helix.” and is made up of the remnant of an extinct star and may have been similar to the Sun. It is located about 700 light years from Earth.
Natural satellites
natural satellites They are solid celestial bodies that orbit a larger object. The bodies that orbit the planets are called “moons.”
Although their composition is somewhat uncertain, several moons made up of rocky sediments and ice, among other elements, have been detected. Planets can have different numbers of moons each other, with the exception of Earth, which only has one, and Mercury and Venus, which have no known moons to date.
Natural satellites originate from various processes. Some, passing close to the planet's orbit, were captured and attracted by its gravitational force. Others originated from clouds of gas and dust that formed around a planet as a result of the detachment caused by a collision between an asteroid and a planet.
kites
Comets are remains that come from the beginnings of the Solar System, about 4.6 billion years ago. consist of ice structures covered with organic material. It is possible that they could provide relevant data about the formation of the Solar System.
Some theories assume that comets brought water and other organic compounds (elements essential for life) to Earth when it was not yet a planet, but was in its initial stage of formation.
The comets are characterized by having a visible trail that is made up of dust and plasma (ionized gas). Most travel at a safe distance from the Sun, however, some have crashed into the luminous star or passed so close that they broke up and evaporated.
The orbit of comets changes constantly. It originates in the region of the outer planets and is usually affected or influenced by these major planets. Some comets end up in orbits close to the Sun and others are sent out of the Solar System.
Meteors
Meteors are luminous celestial bodies that form when meteoroids (solid bodies from space), enter the earth's atmosphere and due to friction they burn when passing through the upper atmospheric layers, disintegrating before reaching the surface of the planet.
Meteors travel at high speed and leave a trail (sometimes persistent). That is why they are often called “shooting stars” but they should not be confused with stars. differ from comets because they do not penetrate the Earth's atmosphere while meteors do.
According to current terminology, they are distinguished as follows:
- Meteoroid They are particles of dust and ice left behind by comets, or from debris during the formation of the Solar System.
- Meteor They are luminous phenomena made up of meteoroids that manage to pass through the Earth's atmosphere and disintegrate before impacting the surface.
- Meteorite They are meteoroids that pass through the Earth's atmosphere, but reach the surface of the planet because their large size does not allow them to completely disintegrate when they pass through the atmospheric layers.
References
- “Celestial body” in My solar system.
- “What do you know about the stars?” in National Geographic.
- “Life cycle of stars” in EIS.edu.es.
- “Nebula” at Spaceplace.nasa.gov.
- “What is a satellite” at NASA.
- “Comets” at NASA.
- “Meteor” in Astromia.
