We are from another galaxy in the process of joining with the Milky Way. The Milky Way is actually not our parent galaxy. The mystery of why the Milky Way has always been sideways in the night sky has never been answered -- until now.
Dave Romer - Voyager and Galactic Plane on 07 Jul 2003 - DivX 6-5-1.avi. This movie shows the locations of Voyager 1 and Voyage 2 spacecraft circa 2003 -- above and below the galactic plane respectively.
"This first full-sky map of Sagittarius shows its extensive interaction with the Milky Way," Majewski said. "Both stars and star clusters now in the outer parts of the Milky Way have been 'stolen' from Sagittarius as the gravitational forces of the Milky Way nibbled away at its dwarf companion. This one vivid example shows that the Milky Way grows by eating its smaller neighbors."
The study's map of M giants depicts 2 billion years of Sagittarius stripping by the Milky Way, and suggests that Sagittarius has reached a critical phase in what had been a slow dance of death.
"After slow, continuous gnawing by the Milky Way, Sagittarius has been whittled down to the point that it cannot hold itself together much longer," said 2MASS Science Team member and study co-author Martin Weinberg of the University of Massachusetts. "We are seeing Sagittarius at the very end of its life as an intact system."
Does this mean we are at a unique moment in the life of our galaxy? Yes and no.
"Whenever possible, astronomers appeal to the principle that we are not at a special time or place in the universe," Majewski said. "Because over the 14 billion-year history of the Milky Way it is unlikely that we would just happen to catch a brief event like the death of Sagittarius, we infer that such events must be common in the life of big spiral galaxies like our own. The Milky Way probably dined on a number of dwarf galaxy snacks in the past."
On the other hand, Majewski and his colleagues have been surprised by the Earth's proximity to a portion of the Sagittarius debris.
"For only a few percent of its 240 million-year orbit around the Milky Way galaxy does our Solar System pass through the path of Sagittarius debris," Majewski said. "Remarkably, stars from Sagittarius are now raining down onto our present position in the Milky Way. Stars from an alien galaxy are relatively near us. We have to re-think our assumptions about the Milky Way galaxy to account for this contamination."
The new findings will help astronomers measure the total mass of the Milky Way and Sagittarius galaxies, and probe the quantity and distribution of the invisible dark matter in these systems.
MORE: http://www.viewzone.com/milkyway.html
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