In this week’s image from the Hubble Space Telescope, you can see an unusual type of galaxy, an ultra-diffuse galaxy. The galaxy GAMA 526784 appears as a bright spot in the center of the image and is located about four billion light-years away in the constellation Hydra.
“Ultra-diffuse galaxies like GAMA 526784 have some quirks,” Hubble scientists write. “For example, they may contain very low or large amounts of dark matter, the invisible substance believed to make up the majority of matter in the universe. Observations of ultra-diffuse galaxies found some to have an almost complete lack of dark matter, while others have almost only but consist of dark matter.Another peculiarity of this class of galaxies is their unusual abundance of bright globular clusters, something not seen in other types of galaxies.”
The ultra-diffuse galaxy GAMA 526784 appears as a wafer-thin patch of light in this image from the NASA/ESA Hubble Space Telescope. This wispy object is located in the constellation Hydra, about four billion light-years from Earth. ESA/Hubble & NASA, R. van der Burg; Credit: L. Shatz
This image was collected as part of a Hubble project to learn more about ultra-diffuse galaxies by imaging them at ultraviolet wavelengths. These galaxies can be as large as 60,000 light-years across, which is about the same size as our Milky Way Galaxy but contains only 1% the number of stars as the Milky Way. This has led to them being called the “fluffiest” galaxies.
The low star density of these galaxies makes it difficult to say how they survived, as one would expect them to have split apart. That’s where the dark matter comes in — researchers think those dark matter galaxies may be protected by these dark matter pillows.
But how do you explain the very diffuse galaxies that contain almost no dark matter? Researchers still don’t have a good answer to this question. The only possibility so far is that two of these ultra-diffuse galaxies that do not contain dark matter, NGC 1052-DF2 and NGC 1052-DF4, could have formed at the same time in the same group and that something strange is going on in the specific environment. in which they have formed.