Using data from the ESA Gaia spacecraft, astronomers managed to find a new satellite galaxy of the Milky Way in the constellation Pump. Antlia 2 is not an ordinary dwarf galaxy because there are several times more similar systems.
It is known that the Milky Way rotates around dozens of smaller gravitationally connected galaxies. The list is relatively large, but scientists believe that some are still hiding from our eyes. To expand the list, scientists searched for satellite dwarf galaxies, analyzing a combination of astrometry, photometry, and variability from the Gaia DR2 mission.
The distribution of the Milky Way satellite dwarf galaxies in galactocentric coordinates. The position of Ant 2 is shown as a red filled circle, and the Magellan Clouds are shown in blue. Other dwarf galaxy neighbors are marked black.
The search led to the discovery of a huge, weak, dwarf galaxy Antlia 2 (Ant 2). Nature confirmed spectroscopic observations. The dwarf galaxy is 424,000 light-years away from Earth, and its age is 11.2 billion years. The angular radius of the half light is 9300 light years, and the value reaches -8.5. Astronomers note that in terms of the parameters, the novice converges with the Large Magellanic Cloud (LMC), but its luminosity is 4,000 times weaker. Antlia 2 also exceeds the size of the typical for this group of dwarf galaxies, but its celestial bodies are three orders of magnitude weaker in terms of luminosity. Researchers report that Antlia 2 is the most diffuse of the objects found to date. A dwarf galaxy is even 100 times more diffuse than ultradiffuse galaxies (extremely low luminosity).
A new study indicates that the formation of a dwarf galaxy can proceed under conditions of brightness and density that are significantly smaller than those observed so far. Perhaps in large-scale surveys it will be possible to find even more outlandish objects, and Antlia 2 is only the tip of the iceberg of an unprecedented galactic population.