Magazine article Science News

Milky Way Gobbles Its Closest Known Neighbor

Magazine article Science News

Milky Way Gobbles Its Closest Known Neighbor

Article excerpt

Astronomers have discovered that the Milky Way is shredding a tiny galaxy into elongated streams of stars and claiming them for itself. At 42,000 light-years from our galaxy's center, the distorted body stands as the Milky Ways closest galactic neighbor. This marks the second time that the Milky Way has been found guilty of cosmic cannibalism.

Although the 10-billion-year-old Milky Way formed its basic structure long ago by capturing and merging myriad smaller galaxies, the new finding provides fresh evidence that our galaxy is still snacking on small-fry satellite galaxies. In an upcoming Monthly Notices of the Royal Astronomical Society, Rodrigo A. Ibata of the Strasbourg Observatory in France and his colleagues describe the newly discovered dwarf galaxy, dubbed Canis Major for the constellation in which it resides.

Both theoretical models and observations have indicated that the outskirts of large galaxies, such as the Milky Way, grow by gravitationally capturing gas and stars from their smaller galactic neighbors. But in consuming the newly found dwarf galaxy, the Milky Way is adding material to its starlit disk rather than to the outlying regions, Ibata notes.

His team's computer simulations reveal that the Milky Way's disk has been feeding on the dwarf galaxy--tearing out streamers of stars and wrapping them around the Milky Way--for about a billion years and will do so for another billion.

The Canis Major dwarf is a lightweight galaxy, today weighing only as much as a billion suns, or about one-fiftieth as much as the disk of the Milky Way. …

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