Supermassive Black Holes
The Universe >
So, you’re thinking of taking a vacation this year to the center of the galaxy. You’ll just load up the luggage, put the kids in the back, and off you’ll go to enjoy the splendors of the galactic nucleus. Here’s my humble travel advice: Don’t do it!
[FAR LEFT: Ground based image of Galaxy NGC7052. NEAR LEFT: The tiny nucleus of the same galaxy (from Hubble) shows the swirling whirlpool of "stuff" referred to in this article. The black hole is WAY down deep inside.]
As splendorific as it may seem, your journey would be a one-way trip.
For starters, it’s more than 30,000 light years away, nearly 200,000
trillion miles. Even Costco doesn’t have enough snack items to keep
you fed for a journey that long.
But most importantly, at the center of our galaxy there is… (cue
the scary music) a supermassive black hole!!! You may recall that a black
hole is an object whose gravity is so intense that not even light can
escape its grasp!
So how do we know there is a star-swallowing, gas-guzzling, dust-devouring,
supermassive black hole there?
All over the universe, whenever astronomers peer deep down into the center
of some distant galaxy, there is nearly always something weird happening
- something dark and sinister.
Remember that a galaxy is a collection of usually hundreds
of billions of stars. At the center of a galaxy, called the nucleus, there
are gas and dust and stars all spiraling around Something in the center.
Careening is a more accurate. Careening out of control is even better.
Objects going around nearby a spiraling center always move faster than
objects out farther away. Think of a round backyard pool with a flock
of rubber duckies floating around in it. Now imagine stirring the waters
gently with some gigantic wooden spoon. The duckies toward the middle
of the pool, near the central “whirl,” will travel faster than
the duckies out near the edge.
Now suddenly a hole opens up at the bottom center of the pool, a hole
that actually empties the water from the pool into some imaginary sewer
drain below. The swirling waters will start picking up speed, spiraling
faster and faster. As the water drains, it will swirl so quickly that
a whirlpool will form. Now the little duckies near the center are swimming
at breakneck speeds as they plunge down to certain ducky death.
This is what we see at the center of galaxies. The stars and gas and dust
there are traveling way faster than they should – unless there is
an open galactic drain at the center that is very small with intense gravity.
It would have to have a mass equal to millions or billions of suns.
But the best telescopes can’t see a thing there. Which is precisely
why a black hole is the prime suspect for our cosmic drain. A black hole’s
intense gravity would spin the place into a frenzy, yet remain unseen.
Even the most supermassive black hole that we suspect is out there is only the size of our solar system. In our tiny human scale that may be huge. But in the grand scale of a galaxy, it is miniscule. For comparison (and in preparation for the SATs), the size of a galaxy is to its central blackhole as a football stadium is to an atom! The black holes are virtually impossible to pick out.
So you see, although a family trip to the center of the
galaxy may sound adventurous, it is really a suicide mission into the
depths of a monster. Once again, the Earth is your friend.
There are images of black hole terror waiting now to scare you at firstlightastro.com/iColumn.
Beware!
Until next time, clear skies!
Have any supermassive questions? Mark Ritter can be reached at ritter@firstlightastro.com
Galaxy size / black hole relationships
View some outstanding
Quicktime movies of central supermassive blackhole in Centaurus A
See a wonderful mpg movie taking you from outside of a galaxy right down to the core. You can feel the swirl. ;)
Posted by Administrator at 2001.03.18 08:43 AM | Comments (0)
