Remember that once astronomers discovered a galaxy without dark matter? Well, they're back. They found the second, and it actually reinforces the case of the existence of dark matter.
Since the astronomers of the second galaxy were found without any dark matter, the new conclusion, called NGC 1052-DF4 (briefly DF4), confirms that there was no first discovery, NGC 1052-DF2 (short, DF2)  After its discovery, DF2 was in fact a huge surprise, and threw a fairly healthy wrench in our current understanding of the formation and dynamics of galaxies, because dark matter is a vital part of our understanding of galaxies. strange things are not even known to our best instruments at present, but we know that there is something there, some invisible mass that increases the gravitational forces in the galaxies. In the Milky Way, for example, the speed of the outer edge of the galaxy is much faster than it would be if it only affected the detected substance.
Some galaxies seem to have a darker matter than ordinary matter. ; and until the discovery of DF2 it was thought that dark matter is not only a component, but also a need for the formation of galaxies.
So the original document attracted some criticism ̵
"If there is one thing, you always have a small voice in the back of your mind, saying," but what if you make a mistake? "" – said astronomer Peter van Dokum of Yale University.
"Despite the fact that we did all the checks we could think of, we were concerned that nature threw us on the loop and made it possible to do something special, it was something more commonplace."
Then they found DF4, like the DF2, it's an ultra-diffuse galaxy-large enough, scattered and poorly observable – these are the size of the Milky Way, but 100 to 1000 times smaller than stars, so they can be very hard to see.
Both galaxies were also associated with the elliptical galaxy NGC 1052, about 63 million light
And, and DF2, DF4, seems to be completely absent from dark matter. Using a Kek Observatory's LRIS spectrometer, astronomers tracked the orbital motion of seven dense clusters of stars called globular clusters, their velocity was consistent with the gravitational effect of the mass of the estimated normal matter of the galaxy.
"The discovery of a second galaxy with a very small or absent dark matter is as exciting as the initial discovery of the DF2," said Van Dokum.
"This means that the chances of finding more of these galaxies are now higher than we. Since we did not have good ideas about how these galaxies were formed, I hope that these discoveries will encourage more scientists to work on this puzzle.
] The team also conducted further research to confirm the preliminary results for DF2.Using the powerful Keck Cosmic Web Imager (KCWI) of the W. Keck Observatory, they tracked the orbits of 10 globular clusters, and their velocity was also consistent with the absence of dark matter
And since these galaxies there is a table There are, of course, alternative hypotheses for the theory of dark matter, but under these conditions, the existence of these galaxies becomes a more complicated problem, which is, in fact, an argument in favor of its existence – since they prove that normal matter can exist separately. 19659003]. researchers said.
As to why these galaxies do not have dark matter, it remains unresolved. Did they have that and lost it somehow? Were they formed without it from the gas thrown out by NGC 1052? It's hard to say – but perhaps if we find even more galaxies like this, we can start collecting them together.
"We hope that in the future we will learn how often these galaxies exist and whether they exist in other parts of the universe." said astronomer Shani Daniel of Yale University.
"We want to find more evidence that will help us to understand how the properties of these galaxies work with our modern theories. The greatest secrets of our universe are the nature of dark matter."
The study was published in The Astrophysical Journal Letters here and there