Explanation:
Hanny's Voorwerp,
Dutch for "Hanny's Object", is enormous,
about the size
of our own Milky Way Galaxy.
Glowing strongly in the greenish light produced by
ionized oxygen atoms,
the
mysterious voorwerp is below
spiral galaxy IC 2497 in this
view from the Hubble Space Telescope.
Both lie at a distance of some 650 million light-years in
the faint constellation Leo Minor.
In fact, the enormous green cloud is now suspected to be part of a
tidal tail of material
illuminated by a quasar
inhabiting the center of IC 2497.
Powered by a massive black hole, the quasar
suddenly turned off,
leaving only galaxy and glowing voorwerp
visible in telescopes at optical wavelengths.
The sharp Hubble image also resolves a star forming region
in the voorwerp, seen in yellow on the side near IC 2497.
That region was likely compressed by an outflow of gas driven
from the galaxy's core.
The remarkable mystery object was
discovered by Dutch schoolteacher
Hanny van Arkel in 2007
while participating online in the Galaxy Zoo project.
Galaxy Zoo enlists
the public to help classify
galaxies found in the Sloan Digital Sky Survey,
and more recently in deep Hubble imagery.
Video:
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