Thirteen
little galaxies all in a row: Configuration deviates
from the expected...
Vancouver Sun ^ |
1/6/13 | Randy Shore
A string of 13 dwarf galaxies are in orbit
around the galaxy Andromeda. The galaxies are spread
across a flat plane more than one million light years
wide and 30,000 light years thick, moving in
synchonicity with each other. The phenomenon is unlike
behaviour of other observed galaxies and suggests a hole
in our knowledge of galaxy formation.
A string of 13 dwarf galaxies in orbit around
the massive galaxy Andromeda are not behaving as they
should.
The galaxies are spread across a flat plane more
than one million light years wide and only 30,000 light
years thick, moving in synchronicity with one another,
according to University of Victoria astronomer Julio
Navarro, one of the co-authors of an article on the
phenomenon in the latest edition of the journal Nature.
The view from Earth is of the thin edge of the
plane, so the galaxies all appear to be moving in a
line, Navarro said. Their behaviour is so different from
the usual chaotic orbits of galaxies around each other
that the researchers believe they have revealed a huge
hole in science’s understanding of galaxy formation.
“It’s a very unusual, unexpected configuration,”
Navarro said. “It suggests our thinking about how
galaxies form is totally wrong.”
Computer models suggest that galaxies —
collections of stars formed from dust and gas spread
across the vastness of space — should orbit
independently, almost randomly.
“[Galaxies] are like bees in a beehive,” he
said. “We had thought that galaxies collect stars one by
one from different directions and different orbits.”
But the structure of the synchronous galaxies
orbiting Andromeda is much more like a mature solar
system.
In solar systems, planets are created from
debris and come to move in a plane-like formation over
the course of hundreds of millions of orbits around a
star. The same process led to the rings of rubble around
Saturn.
But the dwarf galaxies of Andromeda are spread
across a distance so vast that they haven’t completed a
single orbit.
“Somehow they have a plane-like structure
similar to a solar system, but with a completely
different origin and we don’t know what that origin is,”
Navarro said.
Twelve of the 13 dwarf galaxies — they range in
size from 10 million to 100 million stars — are on one
side of the orbital plane, as if they are held by a
string being swung from Andromeda.
“This looks like they are all moving together
and they all know where to go, like some pre-existing
structure has been sucked in by Andromeda,” he said.