Mergers And Acquisitions In The Cosmos
NASA: We have booster ignition and liftoff of Columbia, reaching new heights for women and X-ray Astronomy.
Martin Elvis: The main thing Chandra does is take these superb, sharp images.
Narrator: News about mergers is usually found in the business section. But many
objects in the Universe, from black holes to clusters of galaxies,
are also prone to mergers. And, like the corporate world, cosmic
mergers are dictated by where the most assets lie. However,
astronomical currency is not judged by money or stock reports, but by
how much mass each object has.
Dr. Nicola Brassington of the Harvard-Smithsonian Center for
Astrophysics explains why so many objects in the Universe are
susceptible to such take-overs.
Scientist: Every object in the Universe that has a mass exerts a gravitational
attraction. The more massive an object, the stronger its gravitational
field. When two objects are close, both will exert a force on the other
and systems will interact. This interaction can range from the two
objects simply passing each other, such as a comet on a sling-shot
trajectory by the Sun, to more extreme interactions, such as two
clusters of galaxies colliding head-on, leading to the creation of
one of the largest objects in the Universe.
Narrator: The Chandra X-ray Observatory, along with many other telescopes, has
found evidence for merging in objects across the Universe. Some of the
most common yet important mergers in the Universe are those between
galaxies. Dr. Brassington describes the state of mergers and
acquisitions of galaxies, including our own.
Scientist:Astronomers believe that nearly every galaxy that exists today has been
formed or shaped by a close encounter or merger with another galaxy in
its past. When two galaxies get caught in the others gravitational
field, they begin to spiral in towards each other, eventually forming a
single, massive galaxy.
This merger can take a few billion years, so it's impossible for
astronomers to observe this process in a single system from start to
finish. Instead, we look at snap-shots of different merging galaxies at
various stages of their evolution with telescopes such as Chandra. We
see these violent collisions not only change the structure of the galaxies, but they
also produce new stars and create massive shock waves that super-heat the gas and
dust within them.
Narrator:Since there can be such a tremendous impact when galaxies merge, one
question to ask is: what about the fate of our own home galaxy?
Scientist: Our own galaxy, The Milky Way, is currently interacting with
neighboring dwarf galaxies, but these systems are too small to significantly
change the properties of the Milky Way. Instead, the Milky Way will
simply eat them up in an act of galactic cannibalism, and, in the
process, fuel the production of new stars in our Galaxy.
However, we think that our closest large neighbor, the Andromeda galaxy,
will collide and merge with the Milky Way in a couple of billion years. When this happens, it will have a huge impact on the Milky Way,
completely changing the properties of the gas and stellar populations.
And, this merger with Andromeda will eventually lead to the
creation of a much larger galaxy, completely unlike the one that we currently reside in.
Narrator: While the collisions of galaxies themselves are fascinating and
important to study, there are also other, even more violent and
powerful, mergers taking place. These occur when entire clusters of
galaxies which are some of the largest structures in the Universe --
ram into each other.
Scientist: These massive systems, formed themselves thruogh mergers of smaller groups
of galaxies, can measure up to the order of a few millions of light
years across, containing thousands of galaxies and trillions of stars.
When two of these enormous objects smash into each other, the energy
involved is phenomenal, surpassed only by the Big Bang. During these
colossal mergers, shock waves heat the gas between the galaxies to
extreme temperatures of around a million degrees Celsius. This makes
the gas glow in X-ray light, which is viewed in detail by both Chandra
and Europe's XMM-Newton observatory.
By studying these extreme mergers, like the one in the so-called Bullet
Cluster, we can learn how these systems evolve over time, and also
gain information about the dark matter that they contain. Dark matter is the
material that is responsible for holding these massive structures together, and
makes up about 80% of matter in the Universe. Dark matter is invisible to
today's telescopes, however, it is still possible to detect this dark matter, but only through the gravity
it exerts on other objects. Clusters and super-clusters, the resulting
product of cluster-cluster mergers, are great places to observe these
effects, enabling the existence of dark matter to be tested and
allowing its distribution to be mapped.
Narrator: So, remember, dont look for news of these cosmic mergers in the
business section. While they may not affect the financial markets,
mergers of cosmic objects are incredibly important. They play a key
role in how objects throughout the Universe, and the Universe itself, have developed and continue to evolve.