SETI bioastro: Come see the end of our galaxy...

From: Larry Klaes (
Date: Tue Apr 18 2000 - 15:36:49 PDT

Subject: Astrophysicist maps out our own galaxy's end (Forwarded)
Date: Tue, 18 Apr 2000 12:31:51 -0400
From: Andrew Yee <>
Organization: UTCC Campus Access

University of Toronto


Prof. John Dubinski
U of T Department of Astronomy
ph: (416) 978-8494; email:

Janet Wong
U of T Public Affairs
ph: (416) 978-6974; email:

April 14, 2000

Astrophysicist maps out our own galaxy's end

Computer simulations produce spectacular images of Milky Way colliding
and merging with neighbour

By Janet Wong

The gigantic clouds of gas and matter that pelted the Milky Way in its
infancy are mere fenderbenders compared to the catastrophic collision
set to occur with the Andromeda galaxy in several billion years --
and one U of T astrophysicist has mapped the fallout.

"We're on a collision course right now," says John Dubinski, professor
of astronomy at U of T and the Canadian Institute for Theoretical
Astrophysics, who led the project with co-author Lars Hernquist of the
Harvard-Smithsonian Center for Astrophysics. "Within three billion years,
the Milky Way will be swallowed up and merged with the Andromeda galaxy."

The 2.2-million-light-year gap between the Milky Way and Andromeda is
closing at about 500,000 kilometres an hour, he explains. That pace
will quicken as the two galaxies near each other.

According to Dubinski, merging galaxies are not uncommon. In fact,
this type of interaction plays a key role in helping build larger
galaxies and structures in the universe. While mergers of galaxies
are less frequent now than in the early days of the universe, it is
still an ongoing process, and one in which our own Milky Way and its
big sister, the Andromeda galaxy, are active participants, he notes.

Dubinski simulated this Milky Way-Andromeda interaction by following the
motion of more than 100 million stars and dark matter particles as the
gravitational forces of the two galaxies force them to collide. The
simulation was a feat of parallel computing that took four days to
complete on the San Diego Supercomputing Center's 1152-processor
IBM SP3 "Blue Horizon" -- one of a new class of supercomputers that
can perform more than one trillion arithmetic operations per second.

In the end, the simulation required the equivalent of three years of
continuous operation on a single workstation.

The result is a high-resolution computer animation of the collision and
merger of the two galaxies from start to finish and some very detailed
snapshots of the structure and dynamics of a galaxy merger.

"We just used the Milky Way and Andromeda galaxies as a test case,"
says Dubinski. "It's the first time we've been able to develop a full
picture of tens of millions of stars in two separate galaxies merging
and interacting. The power of these new machines will allow us to
improve the dynamic range and reliability of our simulations of
galaxies and large-scale structures in the universe."

Perhaps even more intriguing is the fact that life on Earth -- whatever
it may be -- will probably live through and witness the entire merger
over the one billion-year dance of the two galaxies, he says. The
reason is that the expected lifetime of our sun is projected to last
another five billion years. Plus, the likelihood of stars and planets
slamming into each other is very low because the distance between them
is so vast. The interaction will be "collision-less," with the most
significant effect involving huge gravitational distortions of the
systems as they coalesce.

At some point three billion years hence, the night sky will be
completely filled by the approaching Andromeda galaxy and when the
two galaxies intersect there will be two bands of light arching
overhead -- looking like two Milky Ways, says Dubinski. With the
merger, two possible fates await the sun and Earth -- we could be
flung into the depths of intergalactic space and escape the galaxy
forever or hurled into the centre of the merging pair where new
stars will be formed.

And for those on Earth, it will be a spectacular display of galactic
fireworks, he says. Massive stars near the sun will be exploding as
supernovae at such a rate that the night sky will be bright enough
to read a newspaper.

For MPEG movie of the Andromeda-Milky Way encounter: [6.3 MB]

[Janet Wong is a news services officer with the Department of Public


Computer simulations produce spectacular images of Milky Way colliding
and merging with neighbour.

Andrew Yee

This archive was generated by hypermail 2b30 : Wed Mar 28 2001 - 16:07:53 PST