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For decades, dark matter and its nature and location have remained elusive to cosmologists. Recently, a team of astronomers conducted a study to locate the mysterious substance, but the results show that there is not as much dark matter as previously theorized.
“Our calculations show that it should have shown up very clearly in our measurements. But it was just not there!” Christian Moni Bidin of the Astronomy Department at la Universidad de Concepción in Chile says in the European Southern Observatory (ESO) press release. Moni Bidin also headed the study and was the lead author of the team research paper, published in The Astrophysical Journal.
Dark matter is impossible to be seen or detected. It constitutes 74% of the mass in the Universe. How it is distributed around the Universe is unknown. Astronomers believe that dark matter is what causes and exerts the gravitational force around objects made of normal matter (i.e. everything that is not dark matter or dark energy), such as planets, stars, and galaxies.
In the past, astronomers considered that one certain location of dark matter would be around galaxies: a model known as the Standard Halo Model demonstrates how galaxies form and evolve. This model also states that they rotate as quickly as they do due to dark matter, which is thought to collect around the galaxies as a halo.
Working with the 2.2-meter MPG/ESO telescope at ESO’s La Silla Observatory in Chile, the team produced a model in hopes of finding the amount, mass, density, and distribution of dark matter around the Sun (the nearest best bet for finding the substance) and our very own galaxy (the Milky Way). Utilizing a hypothesized amount of dark matter based on a past model, they measured the motions of hundreds of stars (sometimes created from the influence of dark matter) as far as 13,000 light-years away from the Sun.
But what the team observed was a lack of dark matter instead; the conjectured density was significantly lower. “The mystery of dark matter has just become even more mysterious,” Moni Bidin states.
He and his colleagues will further investigate and analyze their results. According to their paper, if matters are consistent, the distribution of dark matter would have to
“reconcile the results with the DM paradigm. The interpretation of these results is thus not straightforward. We believe that they require further investigation and analysis, both on the observational and the theoretical side, to solve the problems they present.”
“Despite the new results,” Moni Bidin continues, “the Milky Way certainly rotates much faster than the visible matter alone can account for. So, if dark matter is not present where we expected it, a new solution for the missing mass problem must be found.”