Dusty SunflowerA ghostly halo of dust and gas surrounds the spiral galaxy M63, aka the Sunflower galaxy, in a recently released picture taken in 2005.
The image—made using a remote-controlled, privately owned telescope in New Mexico—was captured during a recent survey of spiral galaxies, which found telltale remnants of galactic digestion.

Larger spiral galaxies—each containing hundreds of billions of stars—are thought to grow by "eating" neighboring dwarf galaxies, which contain just a few billion stars.As the smaller, satellite galaxy is pulled toward the hungry spiral, gravity distorts and shreds the dwarf, so that within a few billion years the smaller galaxy is reduced to wisps and tendrils called tidal streams. Over a few billion more years, the faint streams of stars are assimilated into the spiral.Tidal streams and other structures linked to galactic feeding frenzies have been seen around our own Milky Way galaxy and its immediate vicinity since 1997. (Related: "Eight New Neighboring Galaxies Found.")

But the new survey, led by David Martínez-Delgado of the Max Planck Institute for Astronomy, is the first to show that these structures exist around much more distant spirals, backing up this theory of galaxy evolution.

"This process could be also very important in elliptical galaxies," Martínez-Delgado said in an email. "But we are only studying nearby spiral galaxies with a mass similar to our galaxy in the local universe ... [so] that we can understand the formation of the Milky Way."—Victoria Jaggard

Image courtesy R. Jay GaBany and D. Martínez-Delgado, MPIA