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Galaxies without dark matter are impossible to understand in the current theory of galaxy formation, since its role is fundamental to produce the collapse of gas that forms stars.
In 2018, a study published in the journal Nature announced the discovery of a galaxy that lacked dark matter, which had an extraordinary impact, occupying the front pages of scientific magazines.
Now, according to an article published in the magazine Monthly Notices of the Royal Astronomical Society (MNRAS), a group of researchers from the Instituto de Astrofísica de Canarias (IAC) has solved this mystery through a close look at [KKS2000] 04 (NGC1052-DF2), also known as the 'galaxy without dark matter‘.
In this work, the researchers, puzzled by the fact that all the distance-dependent properties of the galaxy were anomalous, have reviewed the available distance indicators. Using five independent methods to estimate the distance of the object they found that they agreed on one thing: the galaxy is much closer than was contemplated in the original investigation.
The article published in Nature claimed that the galaxy was at a distance of about 64 million light years from Earth. However, this new research has revealed that the actual distance is much less: 42 million light years.
Thanks to these new data, all the properties of the galaxy derived from its distance have returned to normal and they fit within the observed trends traced by galaxies with similar characteristics.
Less mass and stars, but with dark matter
The most relevant data that this analysis has brought to light has been that the number of stars that owns this galaxy is around a quarter of what was originally estimated, while the total mass of the galaxy is about half of that previously estimated. This difference is interpreted by the presence of dark matter, changing the previous conclusions.
The results of this work show the fundamental importance of have precise distances to extragalactic objects. For a long time, this has been (and still is) one of the most difficult tasks in astrophysics: how to measure the distance to objects that we cannot touch.
Ignacio Trujillo et al. "A distance of 13 Mpc resolves the claimed anomalies of the galaxy lacking dark matter", Monthly Notices of the Royal Astronomical Society, Volume 486, Issue 1, June 2019, Pages 1192–1219.