A big question for Astronomers
Astronomers are puzzled as to what holds a distant galaxy together that appears to be devoid of dark matter.
The galaxy, known as AGC 114905, is about the same size as the Milky Way and is 250 million light-years away from Earth. This faraway galaxy, on the other hand, has a thousand times fewer stars than our own galaxy.
According to theoretical models, dark matter, the enigmatic invisible substance, must hold such sparse galaxies together. According to estimations, this accounts for around 85% of all matter in the universe. However, when astronomers used the Very Large Array in New Mexico to measure AGC 114905, they discovered that it contained none.
AGC 114905 was not chosen by coincidence by the team, chaired by Pavel Mancera Pia. Pia is an astronomer at the University of Groningen and the Netherlands Institute for Radio Astronomy in the Netherlands (ASTRON).
Conclusions by previous Observations
Previous research suggested that this galaxy, along with five others, may be deficient in dark matter. However, the results were so contrary to theory that Mancera Pia and his colleagues decided to repeat the measurements.
Despite 40 hours of measurements with one of the world’s most powerful radio telescopes, the researchers discovered no dark matter.
“Of course, this is exactly what we expected and hoped for because it verifies our past findings,” Mancera Pia said in a statement. “The problem today is that the theory predicts that dark matter must exist in AGC 114905, but our findings show that it does not. In fact, the gap between theory and observation is widening all the time.”
AGC 114905 isn’t the first galaxy without dark matter that astronomers have identified. A team lead by Yale University astronomer Pieter van Dokkum discovered NGC 1052-DF2 in 2018. It’s roughly 60 million light-years away from Earth and doesn’t appear to have any dark matter. The scientists noted in a new statement that the methodology and measures employed in Mancera Pia’s recent study are more robust than that work.
The researchers believe that another, more massive galaxy nearby may have drained their galaxy of its dark matter. The remarkable thing is that no galaxy in the vicinity of AGC 114905 appears to be capable of such a feat.
Meanwhile, the scientists are looking into a second ultra-diffuse dwarf galaxy from their original group of six. If they get no marks of the dark matter in that galaxy as well, it will strengthen the dark matter poor galaxies case, said the scientists in the statement.