A Lonely Isolated Dwarf Galaxy Offers Clues To Galactic Origins

The Milky Way belongs to a collection of galaxies — as large as Andromeda or as small as a dwarf galaxy — known as the Local Group. Dwarf galaxy Wolf-Lundmark-Melotte's remote location at the edge of this cluster means its development has been undisturbed, which makes it a great candidate for observation by the European Southern Observatory, the ESO said Wednesday.

Large spiral galaxies such as our Milky Way or the Andromeda Galaxy are believed to have been formed from the interactions of smaller galaxies. Galactic mergers, accumulations of gas and dust and other developments, occurred over the course of billions of years. Wolf-Lundmark-Melotte is located three million light-years from the Milky Way. Its location in a lonely section of the Local Group means its evolution has not been influenced by other galaxies or interactions.

ESO likens Wolf-Lundmark-Melotte to an isolated tribe of humans on Earth with no interaction with outsiders. Any changes occurred organically. In the case of the dwarf galaxy, older stars are seen at the edges of the galaxy with younger stars near its center. The intense light near the galactic center is evidence of young stars ionizing hydrogen gas.

Interestingly, the distribution of young and old stars differs from that seen in the Milky Way. Our home galaxy was formed from the inside out with older stars found near the galactic center. That evolution is vastly different from that of Wolf-Lundmark-Melotte. At its very beginning, dark matter pulled together enough hydrogen and helium for the first stars to form.

Dark matter would also pull in dwarf galaxies and clusters of stars to eventually form its galactic center. In an alternate universe where Wolf-Lundmark-Melotte was closer to other galaxies, the older stars at its edges could have been pulled into the center of another galaxy.