A huge set
of new Hubble Space Images show galactic collisions in action and the variety
of peculiar forms that merging galaxies can take.
The series
of 59 new photographs, released today on the 18th anniversary of the
Hubble Space Telescope's
launch, are the largest collection of Hubble images ever released together.
Galaxy
mergers are now known to be more common than was previously thought. They were even
more common in the early universe than they are today. The early universe was
smaller, so galaxies were closer together and therefore more prone to smash-ups.
Even apparently isolated galaxies can show signs of past mergers in their
internal structure.
Our own
Milky Way contains the debris of the many smaller galaxies it has brushed
against and devoured in the past. And it hasn't stopped munching away at its
neighbors: It is currently absorbing the Sagittarius dwarf elliptical galaxy.
The Milky
Way isn't the top predator though, as our giant neighbor, the Andromeda galaxy,
is expected to devour the Milky Way in about two billion years. The future
resulting elliptical galaxy has already been dubbed "Milkomeda."
Though colliding
galaxies rush towards each other at hundreds of kilometers per hour, the
interactions can take hundreds of millions of years to complete.
This game
of celestial bumper cars is driven by the gravitational pulls that galaxies
exert on one another. Typically the first sign of a collision is a bridge of
matter connecting two galaxies as gravity's first gentle tugs tease out dust
and gas. As the outer reaches of the galaxies begin to interact, long streamers
of gas and dust, called tidal tails, sweep back to wrap around the galactic
cores.
As the cores
approach each other, the conflicting pull of matter from all directions can
result in shockwaves
that ripple through interstellar clouds. Gas and dust are siphoned off to fuel
bursts of star formation that appear as blue knots of young stars. Given the
vast distances between stars in a galaxy — the nearest star to us is 4.3
light-years away — stars rarely collide when galaxies merge.
The Hubble
images capture galaxies in various stages of the collision process and show the
variety of new and unusual shapes the mergers can create, including mergers
that look like an owl in flight and a toothbrush.
advertisement
