All along, the Milky Way has unknowingly had a shy cosmic neighbor: A tiny galaxy has been discovered in our Solar System’s home. And now, astronomers are wondering just how many of these diminutive dwarfs are secretly nestled in the intergalactic undergrowth.
Using the Hubble Space Telescope’s Advanced Camera for Surveys (ACS), a Russia-led group of researchers were able to pinpoint dwarf galaxy KKs3. The small sector is approximately 7 million light-years away in the direction of Hydrus, a small constellation in the deep southern sky.
Now that may sound far away, but KKs3 is actually contained within the famous Local Group of around 50 known galaxies that the Milky Way and Andromeda galaxies live in.
Weighing only one ten-thousandth of the mass of our galaxy, the “dwarf spheroidal” galaxy does not include familiar features like spiral arms and is a comparative lightweight. Its discovery, however, has led the astronomical community to contemplate just how many other dwarf galaxies like KKs3 have gone uncovered.
Dwarf galaxies are particularly interesting because they lack the gas and dust needed for new generations of stars to be created. Seemingly, dwarf galaxies are ancient—an observation of their stars is similar to a cosmic archeological dig. And since dwarfs are so old, the stars they contain are also very dim, making them very difficult to detect to begin with.
“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,” said Dimitry Makarov, of the Special Astrophysical Observatory in Karachai-Cherkessia, Russia.
Moreover, these dwarfs are usually found orbiting larger galaxies; the Milky Way and Andromeda, for instance, are known to have several satellite dwarf galaxies. As such, researchers believe their much larger galactic neighbors steal their star forming gases; what’s more, large galaxies are even believed to have cannibalized many dwarf galaxies during their development. Yet, KKs3 does not appear to be in close proximity to another galaxy; it is completely isolated, joining a very exclusive club of only two known isolated dwarf galaxies that includes the KKR 25.
“It may be that are a huge number of dwarf spheroidal galaxies out there,” Makarov said, adding, “something that would have profound consequences for our ideas about the evolution of the cosmos.”
In the meantime, the team will continue to seek out more nearby dwarf galaxies as they wait for improved telescopes beyond the Hubble Space Telescope, like the James Webb Space Telescope (JWST) and the European Extremely Large Telescope (E-ELT), which are to hit the market in a few years.