Astronomers working with the Hubble Space Telescope’s Advanced Camera for Surveys have identified a new dwarf galaxy. Russian researchers located an until now unknown dwarf galaxy (named KKs3) around 7 million light-years away toward the southern constellation of Hydrus.
This discovery is unusual because KKs3 is actually well within the relatively well mapped “Local Group” of 50 known galaxies where the Milky Way and Andromeda galaxies are found. In fact, finding the new galaxy has led astronomers to begin to wonder how many other close-by dwarf galaxies have gone undiscovered.
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More on dwarf galaxies
With just one ten-thousandth of the mass of our galaxy, the “dwarf spheroidal” galaxy does not have the features viewers typically expect such as spiral arms.
Dwarf galaxies are unusual as they do not have the gas and dust required to create new stars. That means most dwarf galaxies are ancient, and observing them is something like a cosmic archeological dig. By the same token, because they are so old, the stars of dwarf galaxies are dim, making it difficult to detect them.
Dwarfs are usually found in orbit with larger galaxies, and astronomers believe their star-forming gases were stolen by larger neighboring galaxies. However, KKs3 is not especially close to another galaxy; it is completely isolated and is one of just two known isolated dSph galaxies. The other isolated dSph galaxy in the Local Group was discovered in 1999 and is named KKR 25.
Researchers believe that isolated dSph galaxies were formed differently than larger, orbiting galaxies. Isolated dSphs were not impacted by the gravitic forces of their neighbors, so they likely held onto nearly all of their star-forming gases, but then consumed nearly all of the material in an early burst of star formation. Given the lack of interstellar gas, astronomers have to scan intergalactic space very carefully so not to miss the faint stars of dSph galaxies.
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“Finding objects like Kks3 is painstaking work, even with observatories like the Hubble Space Telescope. But with persistence, we’re slowly building up a map of our local neighborhood, which turns out to be less empty than we thought,” commented Dimitry Makarov, of the Special Astrophysical Observatory in Karachai-Cherkessia, Russia.
“It may be that are a huge number of dwarf spheroidal galaxies out there, something that would have profound consequences for our ideas about the evolution of the cosmos,” he continued.