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NASA's Hanny's Voorwerp anomaly looks an awful lot like Plate 19 in The Millennial Project by M.T. Savage (an advanced alien civilization):
Above, left: the suggested look-at-a-distance of an advanced civilization in the 1994 book The Millennial Project: How to Colonize the Galaxy in Eight Easy Steps by Marshall Savage. Above, right: Hanny's Voorwerp in 2008
Green is an utterly UN-natural true color for stars in our universe.
-- Why are there no green stars? July 29th, 2008 by Phil Plait
I've been unable to determine how far from us this anomaly is. But it does seem to be pretty far off, with the vast intergalactic void separating it from our own Milky Way. And it's definitely not one of our nearest galactic neighbors. So there's little chance we'd ever get to meet or speak with anyone there-- if they do exist-- even if we could live for a billion years, heading that way in a spacecraft capable of near lightspeed...
For more on the possibilities of advanced star faring civilizations, check out The Rise and Fall of Star Faring Civilizations in Our Own Galaxy.
AUGUST 2008 UPDATE:
"Scientists working at telescopes around the world and with satellites in space were asked to take a look at the mysterious Voorwerp. "What we saw was really a mystery," said Schawinski. "The Voorwerp didn't contain any stars." Rather, it was made entirely of gas so hot — about 10,000 Celsius — that the astronomers felt it had to be illuminated by something powerful. They will soon use the Hubble Space Telescope to get a closer look."
"Hanny's Voorwerp" remains a mystery. It's huge central hole is over 16,000 thousand light years across and Galaxy Zoo astronomers are still puzzling over what caused it."
-- 'Cosmic ghost' discovered by volunteer astronomer 5-Aug-2008; Contact: Janet Rettig Emanuel firstname.lastname@example.org 203-432-2157 Yale University
DECEMBER 2008 UPDATE:
"An eerie green cloud lurking around a nearby galaxy has puzzled scientists since it was discovered last year. New observations reveal that the cloud's ghoulish appearance may have to do with radiation streaming from a black hole inside the galaxy."
"Apparently the more we learn about the Voorwerp, the more intriguing it becomes."
Eerie Green Space Cloud Explained By Clara Moskowitz; 08 December 2008