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Cosmic Poltergeist Messed Up Milky Way
Sunday, September 22, 2013 7:49
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Objects: strange stellar layers
Likely culprit: a dead dwarf galaxy
The dwarf galaxy was doomed, but it wasn’t going down without a fight. Even as it was being ripped apart by the Milky Way it struck back with enough force to set our galaxy’s bones rattling. Its ghost may still haunt us, as the vibrations from its death throes subtly move things around in the Milky Way.
That’s one possible explanation for the cosmic poltergeist that has rearranged stars in the Milky Way, making odd stellar layers within the galaxy’s spiral disc. The dwarf galaxy is a key suspect because its remains lie eerily close to the most disturbed zones.
Under attack (Image: Anita Stizzoli/Getty)
Over time gravitational tugs from the Milky Way’s regular matter and dark matter should smooth out the vertical distribution of stars in its disc, so that its northern and southern halves are more-or-less mirror images of each other. This damping effect should happen within 100 million years of the galaxy’s formation, a blink of an eye compared with the more than 10-billion-year lifetime of the Milky Way.
