So scientists were more than a bit surprised to find a galaxy that has little to no dark matter at all. To resolve the discrepancy, the team scrutinized the galaxy with the Hubble Space Telescope, the W.M. Keck Observatory and the Gemini Observatory, the latter two on Mauna Kea in Hawaii. "I spent an hour just staring at this image", van Dokkum said as he recalled first seeing the Hubble image of NGC 1052-DF2. "It's so rare, particularly these days after so many years of Hubble, that you get an image of something and you say, 'I've never seen that before'".
Closer monitorings utilizing the Hubble and also 10-meter Keck telescopes revealed that the item, now described NGC1052- DF2, belonged to a lately uncovered course of things called ultra-diffuse galaxies.
Even though the galaxy is mostly empty, they found clusters of densely grouped stars.
"If it's true that a galaxy exists where there is hardly any dark matter, I think that's a problem for all theories about galaxy formation", says Erik Verlinde, a theoretical physicist at the University of Amsterdam who has proposed an alternative to dark-matter-dominated gravity and was not involved in the research. Van Dokkum's group suggests it may have formed as a large, nearby galaxy concentrated a huge amount of gas, creating a "mini-whirlpool" from where the stars formed.
This discovery makes all the current theories on the distribution of dark matter and its influence on galaxy formation redundant or partly false.
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In other words, the question arises: if a galaxy did not start from dark matter, which then gravitationally attracted common matter, how did it form?
In Dragonfly images, NGC 1052-DF2 looked like a standard ultra-diffuse galaxy. Dark matter seems to be needed to draw in sufficient material to form the galaxy and its stars, and halos of dark matter keep galaxies from spinning apart as they rotate. In one, a sudden explosion of massive star-birth inside the galaxy could have cleared out all of its gas and dark matter. So the enigma of NGC 1052-DF2, may not be an enigma for long. So how do astronomers know they exist? The researchers then set about measuring the movements of the clusters as a way to estimate the galaxy's total mass.
The newly discovered galaxy is called NGC1052-DF2, or DF2 for short.
These ideas, however, still do not explain how this galaxy formed. This large, fuzzy-looking galaxy is so diffuse that astronomers can clearly see distant galaxies behind it. The researchers, led by Mr. Peter van Downey of the University of Yale, USA, made the relevant publication in Nature magazine and relayed by the Athenian News Agency. They can't agree on what it's made of, how much a single particle weighs, or the best way to construct a Play-Doh diorama of it. "So finding the opposite, namely an absence of dark matter really came out of the blue for us", he added. Thus, this leaves no speculative room for the existence of dark matter.
More work has to be done by the team which is conducting this research and after that, the actual occurrence of the galaxy and the non-occurrence of the dark matter will be proved. This is only expected if dark matter is bound to ordinary matter through nothing but gravity. NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope.