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New Neighbor Discovered Close to Our Milky Way

kks03_free

Image credit: Hubble Telescope negative image of KKs3 and a much closer globular cluster

As KKs 3, the dwarf galaxy, has been newly discovered, we have a new resident in our galactic neighborhood. The discovery of such galaxy has been released in The Monthly Notices of the Royal Astronomical Society and its photo has been captured by the Hubble Space Telescope.

Although it is the new discovery, KKs 3 is not definitely “new” in the technical sense, because it has possibly existed in the area since the time when the Milky Way came into being. However it got our attention until recently. With its discovery, the number of the membership of the Local Group goes up to 55, and it is regarded as one of members that are most distant from Earth.

It has to be admitted that some rare features of Kks 3 have aroused particular interest from scientists. Generally speaking, most dwarf galaxies are located near larger galaxies which could cannibalize their gas and dust, thus encouraging star formation in the predator galaxy. However, being so isolated, KKs 3 has been discovered to be low on gas and dust, despite of the fact that it has no obvious object to steal these raw materials. At present, it is not clear whether at certain previous time KKs3 had lost its gas and dust to a large object, with which it has parted ways ever since, or whether it never had much to begin with: and what little it did have has been used up for making stars.

According to I.D Karachentsev and his colleagues from Russia’s Special Astrophysical Observatory, most stars (taking up 74% of the total number) were formed at an early epoch more than 12 Gyr ago.

It is estimated by I.D Karachentsev that the stellar mass is at 23 million times bigger than that of the sun. Taking the Sagittarius Dwarf Galaxy, our nearest galactic neighbor by comparison, it is nearly a thousand times in regard to its mass. So KKs 3 is only five to six times bigger in mass than that of Omega Centauri, the largest of the globular clusters which orbit the Milky Way.

As standing in Hydrus, the location of KKs3 is so far south that it could not be observed by most northern hemisphere telescopes, and it appears that KKs3 is located next to a much nearer globular cluster (left object in the image above), thus making its nature obscure until recently. As the second isolated dwarf spheroidal galaxy has been found in the Local Group, it is hoped by astronomers that it would be much helpful in explaining in which way the small, isolated galaxies have developed.

Talking of this discovery, Professor Dimitry Makarov of the Special Astrophysical Observatory said, as struggling very persistently, they were slowly working out a map of our local neighborhood, which have been found to be less empty than previously thought. It is guessed that the huge number of dwarf spheroidal galaxies might exist there, which would cause the remarkable changes of scientists’ ideas about how the the cosmos have evolved.

Journal reference: Karachentsev, I. D., et al. “A new isolated dSph galaxy near the Local Group.”Monthly Notices of the Royal Astronomical Society: Letters 447.1 (2015): L85-L89.

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