The standard cosmological model believes that ordinary matter only accounts for about 5% of the universe, while mysterious dark matter and dark energy occupy about 27% and 68%, respectively. However, the nature of dark matter and dark energy is still unknown. It is one of the greatest mysteries of the moment.
Dark matter does not emit any form of radiation, and scientists cannot directly detect it, but it can be judged by gravitation. Scientists have discovered that dark matter plays an important role in maintaining the structure of galaxy clusters and galaxies in the universe, just like a pedestal.
However, the universe is big and there are galaxies. Recently, a study published in Nature pointed out that scientists discovered for the first time a galaxy that contains almost no dark matter.
This peculiar galaxy was named NGC 1052-DF2. Its size is similar to that of the Milky Way galaxy. The number of stars is only one hundredth of that of the Milky Way. It is very dim, like a ghost, a typical super-dispersive galaxy. Although the ultra-dispersive galaxies are not uncommon in the universe, the dark matter-missing hyperdispersed galaxies are unprecedented.
Initially, the researchers took note of NGC 1052-DF2 using a telephoto lens array specifically designed to detect ghost galaxies in the universe. Next, they used the Keck Observatory to measure the movement of 10 globular clusters in the galaxy, and based on this calculations, they came to an astonishing conclusion that NGC 1052-DF2 contains almost no dark matter.
Subsequently, the Hubble Space Telescope and Gemini Observatory revealed more details of NGC 1052-DF2. This ghost galaxy has no obvious core and cannot find signs of supermassive black holes. In terms of appearance, it does not have the spiral structure of the spiral galaxy, and it does not look like an elliptical galaxy.
In addition, the globular clusters of NGC 1052-DF2 are quite weird, twice as large as regular globular clusters. Judging from the globular cluster’s color, the galaxy has a history of about 10 billion years.
So why is the dark matter of this galaxy so scarce? The researchers proposed two kinds of conjecture.
First, NGC 1052-DF2 is a member of the galaxy cluster dominated by the giant elliptical galaxy NGC 1052. The absence of dark matter may be related to the strong disturbance generated at the beginning of the formation of NGC 1052. Second, NGC 1052-DF2 may be created by the strong wind from the outburst of the NGC 1052 supermassive black hole. However, neither of these conjectures can explain all the features of NGC 1052-DF2.
In order to gain a deeper understanding of the galaxies lacking dark matter, the researchers conducted further searches and found that 3 of the 23 other scattered galaxies photographed by Hubble were similar to NGC 1052-DF2. This may be a new subject worth studying.