We explain what the universe is, its origin and how it is composed. Also, what are its general characteristics, its study and exploration.
The universe is in constant expansion.
What is the universe?
The universe is the vast expanse that contains galaxies, stars, planets, gases, cosmic dust and other components.. It has no known limit and is constantly expanding.
The most accepted theory to explain the origin of the universe is the Big Bang. This theory postulates that all the matter and energy in the universe was concentrated in an extremely small point. During the Big Bang, about 13.81 billion years ago, an abrupt and rapid expansion was unleashed that released an immense amount of energy. As the universe expanded, the temperature decreased, allowing the formation of more complex structures such as stars, planets, and galaxies.
The unit of measurement commonly used to describe distances in the universe is the light year, equivalent to the path that light travels in one year, that is, 9,461 billion kilometers. The observable universe covers enormous dimensions, with galaxies that are millions and even billions of light years away.
See also: Galileo Galilei
Features of the universe
The main characteristics of the universe are:
- It was formed approximately 13.81 billion years ago.
- The most accepted theory about its origin is that of the Big Bang.
- It contains galaxies, stars, planets, gases and cosmic dust.
- It is constantly expanding.
- The visible universe has a diameter of approximately 46.5 billion light years.
- It is composed of atoms and molecules, dark energy and dark matter.
- It has been studied using satellite technology since 1957.
Origin and dimensions of the universe
At the moment, The most accepted explanation for the origin of the universe is called big Bang Theory. This theory holds that almost 14 billion years ago all the matter in the universe was concentrated in a single point. This matter had a very high energy level, which generated a huge explosion (“big bang”) that gave rise to the universe.
The known universe is only a part of the total universe, and is believed to be approximately 46.5 billion light-years across.
Composition of the universe
The universe is made up of three main elements:
- atoms and molecules. It includes stars, planets, galaxies and all objects that we can observe directly.
- Dark matterAlthough it cannot be observed directly, dark matter is thought to make up about 27% of the total universe. It does not interact directly with electromagnetic light and is primarily apparent through its gravitational effects on visible matter.
- Dark energy. It represents approximately 68% of the total universe. Dark energy is responsible for the acceleration in the expansion of the universe and is a phenomenon that is still poorly understood.
Galaxies and star systems
Spiral galaxies have a nucleus from which arms emerge.
Galaxies are the largest scale organizations found in the universe, and can be classified according to their shape into:
- Elliptical Galaxies. They have a defined internal structure with little interstellar matter, that is, with few gases and cosmic dust. Since the stars that make them up are in a very advanced phase of evolution, they are considered the oldest type of galaxy.
- Spiral Galaxies. They have a central core from which arms emerge that form a spiral. In the core there are a large number of stars and very little interstellar matter. On the contrary, interstellar matter is abundant in the arms. Within the observable universe, 75% of galaxies are spirals. A subtype of spiral galaxy is the barred spiral galaxy, which has only two arms. An example of a spiral galaxy is ours, called the Milky Way.
- Lenticular galaxies. It is estimated that they were spiral galaxies that lost their interstellar matter and their arms, so they only preserve the ellipse-shaped nucleus.
- Irregular galaxies. They are those that do not have a defined configuration.
Stars and constellations
The Sun is the closest star to Earth.
Stars are massive celestial objects that emit light and energy due to nuclear reactions in their core.. They are one of the fundamental components of the universe and play a crucial role in the formation and evolution of galaxies.
Constellations are groups of stars in the night sky. which have been identified, named and used as reference points in astronomy and navigation since ancient times. These groupings of stars, when viewed from Earth, appear to form imaginary figures or represent mythological objects, animals or people.
See also: Stars
Planets and celestial bodies
The size of asteroids can be very variable.
The International Astronomical Union (IAU) determines that A celestial object, to be considered a planet, in addition to orbiting around a star and having a spherical shape, must have a “clean” orbit.This means that it should not have any objects of similar size orbiting around it.
In addition to planets and stars, there are other celestial objects in the universe:
- Moons (natural satellites). They are bodies that orbit around the planets. Some planets do not have moons, such as Mercury and Venus; others, like the Earth, have only one; others have many, like Jupiter, with more than ninety.
- AsteroidsThey are rocky or metallic bodies that orbit the Sun, but are smaller than the planets. The Asteroid Belt, between Mars and Jupiter, is a region with a large number of these celestial bodies.
- CometsThey are bodies composed of ice, dust and gases that develop a bright tail when they approach the Sun.
- MeteorsThey are small rocky or metallic particles that enter the Earth’s atmosphere and burn up. They are also called shooting stars.
It may help you: Asteroid Belt
The Milky Way
The Milky Way is the galaxy where our solar system is located, along with billions of other stars and their planetary systems. It is located in a group of galaxies called the Local Group. It has an estimated average diameter of 100,000 light years and is estimated to contain between 100 and 400 billion different stars.
It was formed after the Big Bang, approximately 13.6 billion years ago. Throughout its history, the Milky Way has experienced mergers with smaller galaxies and the continued formation of stars and planetary systems.
The Milky Way is visible to the naked eye from our planet as a blurry white band of light that spans the entire celestial sphere. This has allowed its observation since ancient times, when it was thought to contain all the stars in the universe.
The solar system
The solar system is the planetary system in which the Earth is located. All human exploration of the universe so far is limited to the solar system. Its center is the Sun, whose gravitational force has created the orbits of eight planets. In order of proximity to the Sun, these planets are:
Terrestrial planets. They are those that are composed of rock and metal.
- Mercury. It is the closest planet to the Sun and the smallest in the system. It doesn’t have satellites.
- VenusIt is a planet similar to Earth in size, mass and composition, although it has no satellites.
- LandIt is the densest planet in the solar system. Its only natural satellite is the Moon, but it currently has many artificial satellites created by humans.
- Mars. It is a planet with a reddish appearance due to the iron oxide on its surface. It has two moons: Phobos and Deimos.
Gas planets. They are those that are composed of ice and gases.
- JupiterIt is the largest planet in the solar system, 318 times larger than Earth.
- SaturnIt is the planet with the most visible rings. The rings are a set of millions of particles that rotate around the planet. Uranus and Neptune also have them, although they are less visible from Earth.
- UranusIt is a planet that was only classified as such in 1781, due to the slowness of its orbit.
- Neptune. It is a planet seventeen times larger than Earth and was first observed in 1846.
Black holes
The images of black holes that we know are only representative, because we cannot see them.
Black holes are regions of the universe where gravity is so intense that nothing, not even light, can escape its pull.. They are formed by the gravitational collapse of a massive star at the end of its life cycle.
Black holes remain one of the most fascinating cosmological phenomena in the study of the universe. For this reason, new studies and discoveries are constantly being made about them. At the end of March 2023, the European Space Agency (ESA) announced the discovery of the closest black hole to Earth, located 1,560 light years away.
Space exploration and the search for extraterrestrial life
Humanity has observed the universe visible from Earth since ancient times. In the 20th century, technological advances made it possible to do so from space as well. Space exploration began with the launch of Sputnik 1 in 1957 by the Soviet Union. (USSR).
The subsequent space race between the United States and the USSR led to successive explorations. Thus, in 1961, Yuri Gagarin was the first man to travel to outer space, and, in 1969, Apollo 11 reached the Moon, at which time Neil Armstrong and Buzz Aldrin became the first humans to walk on its surface. .
Later, the Voyager and Pioneer space probes explored the solar system and provided information about the planets and their moons. Likewise, the Hubble space telescope, launched in 1990, provided images of space that are very important for understanding the universe.
The search for extraterrestrial life has been a constant goal in space exploration. For example, NASA’s Viking mission, launched in the 1970s, searched for signs of life on Mars.
In addition, research into planets outside our solar system has experienced a boom with the discovery of thousands of them thanks to space telescopes such as Kepler and TESS. These are searched for signs of habitability, such as the presence of water. Likewise, the SETI (Search for Extraterrestrial Intelligence) program uses radio telescopes to listen for radio signals coming from space in search of possible transmissions from extraterrestrial beings.
The end of the universe
The most accepted explanation for a possible end of the universe is called the Big Freeze.This theory is based on the fact that our universe is expanding ever faster,…