Why is our galaxy called the Milky Way?

We have many unofficial names for cosmic landscapes. Sometimes they are named after the shape we see, such as the Horsehead Nebula. Sometimes they have names that are 'borrowed' from their constellations, for example, Galaxy Fairy (Andromeda). But what about our galaxy, the Milky Way? Why does the star strip cross the night sky?

The structure illustration of the Milky Way.(Photo: NASA)

First, let's talk a little bit about the Milky Way. Astronomers believe it to be a striped spiral galaxy - a spiral-shaped galaxy that has a straight line of stars crossing its center, as you can see in the image above. If you fly over the Milky Way at the speed of light, it will take you about 100,000 years.

The galaxy is part of a collection of galaxies called Local Groups . We are on the journey to collide with the largest and most massive member of that collection, the Tien Tien galaxy (also known as M31). The galaxy is the second largest galaxy, and the third Triangulum Galaxy (M33). It is known that this group has about 30 members.

To visualize its enormous size, you should be happy to hear that Earth is not located somewhere close to the Milky Way's heart and its extremely violent supermassive black hole. NASA says we are about 165 million billion miles away from that black hole, which is in the direction of the constellation Sagittarius (Sagittarius).

The magnetic field of the Milky Way is made by Planck satellite of ESA.(Photo: ESA)

The name of our galaxy actually originates from the appearance of a milk stream as it squeezes through the night sky. While tracing the arms of the galaxy is a challenge when viewed from our urban centers of light pollution today, but if you take it to the remote areas, the Milky Way actually catches The head occupies the whole sky. The ancient Romans called our galaxy Via Lactea, literally 'Milk Road'.

And according to the website Astronomy Beautiful Everyday, the Greek word for 'galaxy' (galaxy) is also derived from 'milk '. It is difficult to say if it was due to coincidence, because the origin of the name Milky Way and the Greek etymology for galaxies have long since disappeared from prehistoric times, although some sources of information says the name is derived from the appearance of the Milky Way.

It takes thousands of years to understand the nature of what we are watching. Back in the Aristotle period, according to the Library of Congress, the Milky Way was believed to be the ' place where celestial bodies interact with the Earth'. Without telescopes, it's more difficult to say than that, but that began to change in the early 17th century.

Stunning views of our galaxy.If there are alien civilizations out there, can we find them?(Photo: ESO / S. Guisard)

An important observation early on, like the textbook, was from the great astronomer Galileo Galilei. (He is famous for discovering the four satellites of Jupiter - Io, Europa, Callisto and Ganymede - he sees them through telescopes.) In Sidereus Nuncius in 1610, Galileo stated that the observations of he showed that the Milky Way is not a uniform band, but that certain packets contain denser star density.

But the true nature of the galaxy dodges us for a while. Other early observations ensued: those stars were part of our Solar System (Thomas Wainwright, 1750 - a later claim proved false) and the stars on this side. The galaxy is denser than the other side (William and John Herschel, late 18th century).

It was not until the 20th century that astronomers learned that the Milky Way was only one of many galaxies in the sky. This conclusion comes after several development steps: conducting remote 'spiral nebula' observations shows that their speed is moving farther away than our galaxy's escape velocity (Vesto Slipher, 1912 ); observations that a 'new star' in the Tien Nu galaxy is fainter than ours (Herber Curtis, 1917); and most famously, Edwin Hubble's observations of galaxies show that they are actually very far from Earth (1920s).

Hubble images in ultraviolet, visible and infrared light regions.Photo: NASA, ESA, H. Teplitz and M. Rafelski (IPAC / Caltech), A. Koekemoer (STScI), R. Windhorst (University of Arizona), and Z. Levay (STScI)

In fact, the number of galaxies is more than we can imagine a century ago. Using the Hubble Space Telescope, weekly astronomers independently exploited this powerful astronomical station to observe every tiny piece of the sky.

Hubble provided a number of 'deep-field' images of distant galaxies billions of light-years away. It is difficult to estimate how many galaxies are 'out there' , but estimates appear to indicate at least 100 billion galaxies. That number will keep astronomers busy all the time.