Supermassive Black Holes

Drew Lierheimer is a 4th year Finance Student in the Saunders College of Business. This piece is aimed to educate students from grade 6-8 about supermassive black holes in a manner that will peak their interest to pursue the topic further.

I. What is a Supermassive Black Hole (SBH):

As we learned in our last lesson, (the life of a star) we discovered that at the end of their life, higher mass stars tend to collapse. This happens due to a characteristic of the star, which exhausts every last resource needed to function. Once this is done, gravity takes over and forces the star to implode. All of the matter in the star condenses into the smallest (densest) size possible. Sometimes stars will get into such a dense size that they will transform into a black hole. A black hole functions similar to a funnel, the dense mass that was created by the collapse of a star has a strong gravitational pull, which is stronger than the speed of light (the fastest speed capable). As a result, once anything is in the gravitational pull of a black hole, there little hope for its escape.

A supermassive black hole has the same characteristics, as a regular black hole, the only difference, is that a SBH is denser. Due to its density, the black hole has a stronger gravitational pull that allows it to swallow up more matter out into space, which will result into the SBH to continue to gain mass.

There are two ways in which a black hole can transform into a supermassive black hole. One way is to have two black holes collide into each other. This collision would cause both black holed to merge together and create a black hole with enough mass to be one hundred thousand times that of the sun. This collision usually causes all matter around the SBH to be ejected out of its gravitational pull, which means that there is no matter for it to continue its growth resulting in a dormant SBH.

The second way happens when a large black hole or a stellar black hole is formed from a large star collapse. This collapse gives the black hole a mass of three to ten times that of the sun. This stellar black hole then pulls all matter around it into its core, until it has become dense enough to be called a SBH.

The following exercise is aimed at visualizing the basic concept of how a supermassive black hole functions in out universe.

Class Exercise #1: Supermassive Black Hole Visual Concept

Supplies Needed:

· Spandex cloth (10ft X 10ft)

· Dense ball 1 in to .5 in diameter (steel/lead)

· (10) Less dense balls greater and smaller in diameter to dense ball (ping-pong ball, tennis ball, gum ball.etc.)

Instructions: (For teacher to explain)

· Have students line up around the spandex cloth, each holding part of the 10X10 piece at chest height until it is stretched flat between the students.

· The teacher will place the dense ball on the spandex and explain to the students that this acts as the supermassive black hole.

· The teacher then rolls less dense balls by the crater that the dense “ supermassive black hole” ball made.

· Students will watch the path of the less dense balls alter, and eventually fall into the “supermassive black hole”

· As more balls fall into the cave, it will become deeper, which signifies the “ supermassive black holes” gravitational pull is stronger and the SBH is denser, meaning it is harder for the balls to ever leave the hole.

· Students can take turns rolling balls past the “ supermassive black hole” so they can have a better understanding of the principles.

A supermassive black hole has an incredibly large amount of mass, in extremely small volume. This means that the particles are packed extremely tight together. To put it into perspective, the sun, which is in the center of our solar system, has a gravitational pull, which keeps 8 planets revolving round it. A supermassive black hole has few as one hundred times the mass of the sun, in something the size of a pinhead. A SBH is typically found in the center of a galaxy floating around waiting for something to run across its path.

There is a supermassive black hole that resides in the middle of our galaxy (The Milky Way). Its name is Sagittarius A, and it 4 million times denser than the sun. It is a dormant SBH, which means that it is emitting energy that is weaker than SBH’s of comparable mass. Recent studies have shown that Sagittarius A was just as strong as any comparable mass SBH 300 years ago. Scientists don’t know for certain why Sagittarius A has gone dormant, but they assume it is due to a recent (300 years ago) major outburst of energy.

II How We Detect Supermassive Black Holes:

Supermassive black holes can’t be seen since they do not emit the energy inside of them visually. Even though they are “invisible” Scientists believe that they can see a distortion in the visual plane where a SBH is known to be. It is interesting evidence to support the power that a SBH has.

In a more scientific approach, professionals will look at telescope photos of galaxies or areas of high activity and analyze the movement of matter in that activity. Evidence of a swirling effect around a central area is one way of discovering where a SBH is. This swirling effect can create accretion disc & jets (which you will learn about in section IV) Another way scientists find SBH’s is by using an X-ray telescope to measure the amount of energy that a certain area in the universe is emitting. Typically, supermassive areas of energy are correlated to supermassive black holes, since the only think we know that has enough mass to emit such massive amounts of energy is a SBH.

III Inside a Supermassive Black Hole:

Most questions directed towards SBH’s inquire about what is inside. The quick answer is no one knows, and will ever know. What scientists do know is that no light can escape once inside of one. Since their gravitational pull is so strong it distorts the light, which disallows any light to pass through the event horizon.

The event horizon is the point at which there is no return for matter being sucked into a SBH. It is the point at which an outside observer can no longer interact or see any of the matter entering the black hole. At some point the object being pulled into the black hole is brought in at a speed faster than the speed of light, which means light that the object is displaying to an outside observer is not fast enough to “out run” the force pulling against it so it loses “contact” with anything outside the SBH. This being said, to an outside observer, may think they are seeing an actual object on the outside of the SBH, but in actuality it isn’t there. Since light only travels at a certain speed, It will take a while for an outside observer to notice when the matter has been captured by the SBH.

Once an object makes it to the event horizon, it is instantly inside of the SBH. Since the size of the SBH is so small and dense (the size of a pin head) there is nothing to see inside of it. In essence, “there is so much stuff inside a black hole, that there isn’t anything”. This means and everything that enters the event horizon of am SBH does not exist anymore. This is a strange concept to wrap your head around, but if you think of something that can swallow whole galaxies that are millions of light years in size into something the size of a pin, then you can think that there is no room for anything, and that matter must not exist anymore. There is not physical proof that this is what happens, but it is what scientists have calculated should happen inside a black hole.

IV Accretion Discs & Jets:

The pull of some supermassive black holes is so extreme; it rarely pulls any matter into its “core”. Since the SBH acts as a funnel, it is constantly swirling large amounts of matter around at a fast pace towards its small entrance. A combination of theses elements leads to the creation of an accretion disc. This disc is made up of space matter that is trapped in limbo waiting to be lost into a black hole forever. At some points the amount of matter that enters the back hole at one time is too great that the SBH’s “spits” it out back into the universe. This action will be seen as a jet shooting from the center of the SBH (see exhibit 1 in appendix)

The following exercise will help illustrate the concept of an accretion disc and the jets that form around a black hole.

Exercise #2: Accretion Disc & Jets Visualization

Supplies Needed: For Each Student

· 1 inch diameter foam ball

· 2 pieces of 100 lb. card stock

· 1 pair of scissors

· 1 roll of scotch tape

· 1 bottle of Elmer’s liquid glue

· 1 drafting compass

· 1 ruler

Instructions:

· Take the scissors and cut the foam ball into two equal halves.

· Take the compass and draw a 5-inch diameter circle on both sheets of card stock.

· Cut both circles out of the sheet of card stock.

· Take one circle and glue it in between the two halves of foam ball (make sure the flat sides of the halves are on either side in the center of the paper)

· Take the ruler and draw two perpendicular lines through the center of the second circle cut out (so it looks like A big +).

· Cut along the lines that were drawn, to make the circle into 4 separate pieces.

· Take one of the four pieces and curve the two straight sides into each other and fasten them with the scotch tape. (This should look like a cone)

· Repeat previous step with a second cut out.

· Fasten the two cones to each end of the foam ball (the curved side of the ball)

The end result should look like this:

This model should help visualize what happens around a SBH when matter is being attracted. You can see the disc around the ball acting as the accretion disc and the cones on the top and bottom of the foam ball act as the jets that shoot out from either end of the SBH.

V. Function within a universe:

A supermassive black hole can’t be characterized as having a specific purpose, like you would assign to a toothbrush. It can however, teach us lessons about fundamental forces within our universe.

Since the discovery of SBH’s, scientists have developed technologies in order to explore more about SBH’s. For example the investigation of gravitational waves, which scientists believe are created due to black holes, has led to the development of a device called an interferometer, whose purpose is to help sense and analyze the structure of gravitational waves.

VI. Conclusion:

Supermassive Black Holes are amazing in their functioning principles. They seem to go against everything that we know about physics, but still the proof of their existence is apparent. Hopefully up and coming scientists like yourselves will uncover the next discovery in supermassive black holes, which will bring us closer to fully understanding what a supermassive black hole is.

Appendix

Exhibit 1: Black hole with accretion disc and jets.

http://www.dailygalaxy.com/my_weblog/2009/01/supermassive-bl.html