**A series of observations with space and space telescopes has discovered a galaxy in which dark matter seems to be absent or almost. If the existence of other galaxies of this type were confirmed, new scenarios would be opened for astronomy and cosmological theories.**

![](https://cdn.pixabay.com/photo/2016/09/08/20/52/starry-sky-1655503_1280.jpg)
[Credits Pixabay](https://pixabay.com/en/starry-sky-star-galaxies-andromeda-1655503/)
[NGC1052-DF2](https://www.nasa.gov/feature/goddard/2018/dark-matter-goes-missing-in-oddball-galaxy) is a spiral galaxy as there are many, about 65 million light years away from us. If it were not for a characteristic that distinguishes it from all the others: it seems to be free of dark matter. The announcement is given [in "Nature"](https://www.nature.com/articles/nature25767?error=cookies_not_supported&code=a661307a-0262-4711-8436-cbc570fbc97a) by Pieter van Dokkum of Yale University and colleagues of an international collaboration. 

With the term dark matter is indicated all the matter of the universe that is not visible because it does not emit and does not reflect the electromagnetic radiation, but it makes its gravitational effects feel. His presence was hypothesized to account for the rotation of galaxies. According to the universal theory of gravitation, the rotational motions of the celestial bodies depend on their mass. And if we consider only ordinary matter, detectable with astronomical observatories, most galaxies could not exist.

https://youtu.be/2y79N4W6In8
Short Video From NASA

But there's more. Dark matter must not only be there, whatever its nature, but must also be very superabundant compared to ordinary matter: the relationship between the respective masses is 30 to 1 in galaxies like the Milky Way, but it can also reach 400 to 1 in the case of dwarf galaxies. 

Despite the numerous theoretical models that account for this elusive "missing mass", dark matter has eluded all attempts to be detected directly. The research of van Dokkum now seems to disrupt the framework of astrophysical and cosmological knowledge. Because in the case of NGC1052-DF2 the accounts of the rotational dynamics also return considering only the visible matter. 

The discovery came after a complex series of observations made first with the Sloan Digital Sky Survey and then with the Dragonfly Telescope Array, made by the group of the same van Dokkum to go hunting for very weak astronomical objects. The galaxy NGC1052-DF2 immediately showed a peculiarity: it has dimensions similar to those of the Milky Way but houses 0.2 percent of the stars hosted in our galaxy. 

New observations made with the Keck and Gemini North ground telescopes, both on the top of the Mauna Kea volcano, on the Hawaiian Islands, have allowed researchers to measure the motions of ten star clusters within the galaxy, and to derive an estimate of the galactic mass. This estimate does not differ much from the visible mass of stars, gas and dust in the galaxy itself. In other words, dark matter is only a fourteenth of what one would expect. 

" If there is dark matter, then it is very little", commented van Dokkum. "The stars of the galaxy realize its whole mass, and there does not seem to be any room for dark matter". 

Furthermore, NGC1052-DF2 does not seem to have a denser central core, an element that is common for other galaxies of the same type. This data, combined with the absence of dark matter, also allows us to see the portion of the universe behind the galaxy, as shown by other observations of the Hubble space telescope: the galaxy is "transparent". 

Astronomers and astrophysicists tried to interpret the collected data and to draw all the theoretical consequences of the case. The first, paradoxical, is that the existence of NGC1052-DF2 should help to exclude the cosmological theories that would refute the hypothesis of dark matter by modifying Newton's law of universal gravitation. According to some of these theories, each galaxy would add a certain amount of mass, the one that is missing to make the accounts come back. But NGC1052-DF2 shows instead that Newton's law is valid in its original form and that dark matter is separated from galaxies. 

Astronomers are already looking for other galaxies similar to NGC1052-DF2: Hubble has already identified 23 candidates. If the possible absence of dark matter were confirmed, new scenarios could be opened both in the experimental field and in the theoretical field.


### References for Further Reading 

[NASA](https://www.nasa.gov/feature/goddard/2018/dark-matter-goes-missing-in-oddball-galaxy)

[SPACE](https://amp.space.com/40119-ghostly-galaxy-almost-no-dark-matter.html)

[PHYS](https://phys.org/news/2018-03-dark-galaxy.amp)