We explain what the Milky Way is, how it originated and its dimensions. In addition, we explain what its characteristics and structure are.
The Milky Way is observable with the naked eye from our planet.
What is 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 cluster of about forty different galaxies called the Local Group. The Milky Way and Andromeda are the two brightest galaxies in the group.
From our planet, the Milky Way is observable with the naked eye as a band of blurry white light that is found throughout the celestial sphere. It is brightest towards its center, towards the constellation of Sagittarius. This has allowed its observation since ancient times, when it was thought to contain all the stars in the universe.
In the 17th century, Galileo Galilei was the first to observe it with a telescope. However, the American astronomer Edwin Hubble was the one who delimited it and studied it in greater depth in the 20th century.
Where does the name “Milky Way” come from? The name “Milky Way” comes from Latin and means “way of milk” or “milky path”. The designation is linked to the white, luminous appearance of the band of stars seen in the night sky. The association with milk derives from Greek mythology. According to legend, Hera was to breastfeed Heracles (better known by his Latin name, Hercules), a son of Zeus who had been born as a result of infidelity. However, Hera was not willing to do it, but one day she woke up and discovered that Heracles had been made to suckle on her breast. Faced with this, she abruptly removed it, so that the milk continued to come out, causing some drops to spill out and form the bright stripe in the sky known as the Milky Way.
See also: Astronomy
Characteristics of the Milky Way
The Milky Way has the following characteristics:
- It is the galaxy where the solar system and our planet Earth meet.
- It was formed 13.6 billion years ago.
- It has an approximate diameter of 100,000 light years.
- It is estimated that it has between 100,000 and 400,000 million stars.
- Galileo Galilei was the first to observe it from Earth with a telescope.
- It is part of a group of galaxies called the Local Group.
- It is made up of three parts: halo, disc and bulb.
- It is believed that at its center there is a large supermassive black hole.
Origin of the Milky Way
The Milky Way, like other galaxies, formed after the Big Bang, approximately 13.6 billion years ago.As the universe expanded and cooled, larger structures formed. In this context, the Milky Way began to take shape as denser regions attracted additional matter around them through gravitational force.
Subsequently, matter continued to accumulate into a rotating disk known as the galactic disk. The galaxy’s spiral structure, with its characteristic arms, developed over time due to gravitational interactions and internal dynamics.
Along its history, The Milky Way has experienced mergers with smaller galaxies and the continued formation of stars and planetary systems.
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Dimensions and location of the Milky Way
It is estimated that there are between 100,000 and 400,000 million stars in the Milky Way.
The Milky Way has an estimated average diameter of 100,000 light years.It is estimated that there are between 100,000 and 400,000 million different stars in it. Our solar system is located on the outskirts of the galaxy, about 28,000 light years from the center.in one of the arms of the spiral of the galactic disk.
Movement of the Milky Way
The Milky Way completes a rotation on its axis approximately every 225 million years.
The Milky Way has two main movements in space:
- Galactic rotation. The Milky Way rotates on its axis, just like a rotating disk. It takes between 200 and 250 million years to complete an orbit around the galactic center. This movement is what gives shape to the galaxy’s disk.
- Translation around the galactic center. In addition to rotation, the Milky Way moves in an orbit around the galactic center. This orbit is complex and is thought to involve gravitational interactions with other Local Group galaxies, such as the Andromeda galaxy.
Parts of the Milky Way
Most of the young stars are contained in the disk.
The Milky Way is divided into three parts: halo, disk and bulge.
- HaloIt is a spherical structure surrounding the galaxy and has a low concentration of stars and gas clouds. Instead, it contains groups of old stars that orbit the galaxy as satellites. It also has abundant dark matter, which gravitationally influences the movement of the galaxy.
- Disk. This is where most of the young stars are contained, as it is the region with the highest concentration of gas and where star birth processes still occur. The arms of the galactic spiral are also located there.
- Bulb. It is the central region of the galaxy, with the highest stellar density. It has a flattened spherical shape and has a rotating movement similar to the rotation of the planets.
The galactic center
It is believed that there is a large black hole in the galactic center.
At the center of the Milky Way lies a dense and complex region called Sagittarius A* (Sgr A*). A supermassive black hole is thought to reside at the heart of this region.
Observations indicate that Sgr A* has a mass equivalent to millions of times the mass of the Sun, which is consistent with the typical characteristics of a supermassive black hole. However, due to the amount of dust and gas in the central region of the galaxy, the light is obstructed and this makes it difficult to observe.
Evidence for the presence of such a black hole has been gathered by studying the motion of stars near that region. These stars orbit around an invisible point with an extremely large mass at the center, which would be consistent with the Presence of a supermassive black hole at the center of the Milky Wayalthough there are still debates about it.
The Milky Way in culture
Rubens painted The birth of the Milky Way based on the myth of Hercules and Hera.
The Milky Way has been present in the human imagination about the sky and space since AntiquityThe Aztecs saw in it the cloud serpent Mixcóatl, and the Vikings thought it was the gateway to Valhalla, the realm of warriors fallen in combat.
On the other hand, Spanish pilgrims have used the position of the Milky Way in the sky as a reference to reach Santiago de Compostela, which is why it is often named the “Camino de Santiago”.
The Milky Way has also been depicted many times in fine art. An emblematic case is the painting The birth of the Milky Way, by Rubens, who used the myth of Hercules and Hera to create it.
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