It took quite a while for astronomers to discover a tiny neighboring galaxy hiding near the Milky Way, but thanks to an image taken by NASA's Hubble Space Telescope, an international team of scientists has discovered the dwarf galaxy located just a mere 7 million light years away.
Igor Karachentsev from the Special Astrophysical Observatory in Russia, together with colleagues, discovered the dwarf galaxy dubbed KKs3 using the Advanced Camera for Surveys (ACS), the primary imaging instrument onboard the Hubble Space Telescope, in August this year.
Although the galaxy has just been discovered, the researchers found that 74 percent of KKs3's star mass was formed in the early years of the universe about 12 billion years ago. They likewise found that the galaxy weighs only 1/10000 of the mass of Milky Way.
"According to our calculation, the total stellar mass of the galaxy is 2.3 × 107 M⊙, and most stars (74 per cent) were formed at an early epoch more than 12 Gyr ago," the astronomers wrote in their report published in the Monthly Notices of the Royal Astronomical Society on Dec. 21.
KKs3 is a dwarf spheroidal galaxy (dSph galaxy). These systems lack certain features such as the spiral arms that can be found in the Milky Way. They do not also have the raw materials necessary for the formation of a new generation of stars, so they leave behind older and dimmer relics.
The raw materials, such as gas and dust, appear to have been stripped out from these galaxies by massive galaxies nearby so most dSph objects can be found near bigger cosmic companions. This makes KKs3 a rare find because it is the second known isolated dSph in the cosmic community called Local Group, a cluster of over 54 galaxies, including our very own Milky Way and the Andromeda Galaxy.
The other similar type of galaxy is the KKR 25, which was discovered by the same group of researchers in 1999. Astronomers are interested in findings dSph objects because these could shed light on how galaxies form in the universe.
"We're slowly building up a map of our local neighborhood, which turns out to be less empty than we thought," said research team member Dimitry Makarov, also from the Special Astrophysical Observatory. "It may be that there is a huge number of dwarf spheroidal galaxies out there, something that would have profound consequences for our ideas about the evolution of the cosmos."
