Our galaxy has entered a new scale.  It turned out to be much lighter than expected

However, studying the Milky Way from within the Milky Way is a difficult task. When we look at other galaxies millions of light-years away, we see them in their entirety. Using telescopes, we are able to study its structure, distinguishing nuclei, spiral arms, structures created as a result of the close passage of another galaxy and many other features of its structure. The Milky Way is more difficult. Since we are inside a disk filled with billions of stars, all we see around us is an endless forest of stars. Determining their three-dimensional distribution in space becomes a serious challenge. The same applies to the entire galaxy cluster. Even knowing the mass of the Sun and the Solar System, based on those stars in our galaxy that we can see and how they move in space around the galactic center, is very difficult. When we add to this equation dark matter, which we cannot see at all and whose influence on the mass of the galaxy is enormous, the puzzle becomes very difficult to solve.

Despite the serious limitations that we cannot and will not be able to overcome (we will never see the Milky Way from the outside), scientists decided to calculate the correct mass of our galaxy.

Read also: The Milky Way Galaxy is more distinct than we thought. It’s about her neighborhood

As a general rule, the mass of a galaxy can be measured from its rotation curve. If we measure the speed of a star in a galaxy, and then identify the star from the center of the galaxy, we will know the amount of mass within the orbit of that star. However, the problem is that while this works effectively in other galaxies, in our own galaxy it is not easy to choose a star for such measurements. If we wanted to search for a star located on the other side of the galaxy from us, we would not find it at all, because between us and it are billions of stars and a lot of gas and dust.

For this reason, scientists have so far measured the mass of our Galaxy based on studies of the motion of hydrogen clouds that emit radiation with wavelengths of 21 cm. Instead, the speed of globular clusters orbiting the Milky Way was measured. All these measurements indicate that the mass of our galaxy is about one trillion solar masses.


inside Latest research project Scientists used the latest data from the Gaia satellite, which measures the positions, distances and movements of more than 1.5 billion stars in the Milky Way. Even though it’s only 1 percent. The stars in the galaxy, then, according to the study authors, are enough to accurately calculate the rotation curve.

Read also: The Milky Way Galaxy is not what you think. We were so wrong

However, the result of the calculations was a big surprise to the researchers. It turns out that the data indicates that the mass of our galaxy is “only” 200 billion solar masses, or only 20 percent. Previous estimates. Taking all uncertainties into account, the maximum possible mass of the Milky Way is 540 billion solar masses, which is half of what was suspected. Given that we know approximately the amount of regular matter in our galaxy, it must be assumed that there is much less dark matter than expected.

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