Astronomers discover that our galaxy is a suburb of a supercluster of 100,000 large galaxies they have called
Laniakea
In what amounts to a back-to-school gift for pupils with nerdier
leanings, researchers have added a fresh line to the cosmic address of
humanity. No longer will a standard home address followed by "the Earth,
the solar system, the Milky Way, the universe" suffice for aficionados
of the extended astronomical location system.
The extra line
places the Milky Way in a vast network of neighbouring galaxies or
"supercluster" that forms a spectacular web of stars and planets
stretching across 520m light years of our local patch of universe. Named
Laniakea, meaning "immeasurable heaven" in Hawaiian, the supercluster
contains 100,000 large galaxies that together have the mass of 100
million billion suns.
Our home galaxy, the Milky Way, lies on the
far outskirts of Laniakea near the border with another supercluster of
galaxies named Perseus-Pisces. "When you look at it in three dimensions,
is looks like a sphere that's been badly beaten up and we are over near
the edge, being pulled towards the centre," said Brent Tully, an astronomer at the University of Hawaii in Honolulu.
Astronomers
have long known that just as the solar system is part of the Milky Way,
so the Milky Way belongs to a cosmic structure that is much larger
still. But their attempts to define the larger structure had been
thwarted because it was impossible to work out where one cluster of
galaxies ended and another began.
Video from Youtube
Tully's team gathered measurements on the positions and movement of
more than 8,000 galaxies and, after discounting the expansion of the
universe, worked out which were being pulled towards us and which were
being pulled away. This allowed the scientists to define superclusters
of galaxies that all moved in the same direction (if you're reading this
story on a mobile device, click here to watch a video explaining the research).
The work published in Nature
gives astronomers their first look at the vast group of galaxies to
which the Milky Way belongs. A narrow arch of galaxies connects Laniakea
to the neighbouring Perseus-Pisces supercluster, while two other
superclusters called Shapley and Coma lie on the far side of our own.
Tully said the research will help scientists understand why the Milky Way is hurtling through space
at 600km a second towards the constellation of Centaurus. Part of the
reason is the gravitational pull of other galaxies in our supercluster.
"But
our whole supercluster is being pulled in the direction of this other
supercluster, Shapley, though it remains to be seen if that's all that's
going on," said Tully.
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