Grandpa's Selected Letters
Super Massive Black Hole Sagittarius A*

I’m back again. Hi kids.

Well it’s Monday morning again, and, your great grandmother Katherine is here with me. She is in the kitchen on her laptop computer paying bills, bills and more bills. It reminds me of a "Black Hole" sucking up all our money and time, and us swirling round and round in the holes' event horizon. We are also waiting to be crushed as we get sucked into the hole. In our case, the super Black Hole sucking us is the govenment. Your great great grandmother Betty (100 years old) is napping in her spaceship bedroom unaware of impending danger. So today I want to write about a Super Black Hole at the center of our Milky Way called Sagittarius A*.

The Galactic center of our Milky Way is dominated by one resident, the supermassive black hole known as Sagittarius A* (Sgr A*). Supermassive black holes are incredibly dense areas in the center of galaxies with masses that can be billions of times that of our sun. They act as intense sources of gravity which suck in dust clouds, gas clouds, planets, stars and other material such as spaceships. This material is crushed and disappears into the black hold never to be seen again. A black hole is like a whirl pool in the ocean sucking in trapped ships as they go round and round the outside of the whirl pool until finally disappearing into the deepness of the whirling funnel never to be seen again. Another way of visualizing a black hole is to imagine an immense vacuum cleaner sucking in every object that gets caught in its suction. Black holes are called black because even light rays cannot escape a black hole. Light rays are sucked into a black hole and are never seen again, as a result, black holes are invisible to see or photograph.

Evidence of a black hole at the center of our galaxy was first presented by physicist Karl Jansky in 1931, when he discovered radio waves coming from the center of our Galaxy, but, telescopes of the day could find nothing visible. Jansky suggested the existence of a large amount of dark matter was at the center of our galaxy emitting radio waves. The dark matter turned out to be a super massive black hole, which astronomers named SAGITTARIUS A*. This black hole weighs more than four million suns. Earth is only 26,000 light years from SAGITTARIUS A*. This black hole is one of very few black holes in the universe where we can actually witness the flow of matter being sucked into the darkness of the hole. We know the black hole is there because telescopes can see stars being sucked into the blackness of the hole and all the star’s light disappearing.

In our galaxy alone there are 1.5 trillion stars that can be seen. Remember each star is a sun with planets circling the star (sun). The supermassive black hole known as Sagittarius A* is at the center of our galaxy and may eventually suck in all of our galaxy’s 1.5 trillion stars including our star (the sun) with Earth orbiting it. Does that scare you? Don’t worry because if we are destined to be sucked into Sagittarius A* that won’t happen for millions of years from now. By that time, we (the human race) will be on other galaxies living on other planets orbiting other stars.

Gravitational Waves:

Now lets’ talk about the Gravitational Waves produced by black holes. Black holes, it turns out, emit gravitational waves. These waves are part of what scientist refer to as the space-time continuum. The universe is contained in a space (a vacuum) with the space containing trillions of galaxies and black holes. Think of space as an ocean and the galaxies as ships in a vast ocean of space. So what are gravitational waves? These are waves like waves in an ocean of water but are invisible to see. Remember humans build instruments to see what our eyes can’t see. So we built instruments to detect (see) gravitational waves. Now the bows of ships at sea create ocean waves as the ship moves through the water. Well objects in space such as galaxies, stars, planets, comets, and space ships also create bow waves which are invisible gravitational waves in space. Even Earth as it orbits the Sun creates gravitational waves (though small in magnitude) as it plows through the vacuum of space around the Sun.

So what creates the biggest gravitational waves in the whole universe? One guess. You are right. A black hole creates the biggest gravitational waves in the universe. Scientists have built gravitational wave detectors here on Earth which can detect the invisible space waves coming from black holes. Scientists can now use gravitational wave detectors to detect black holes. That’s amazing. There are trillions of black holes in the universe and all are dangerous to humans.

Event Horizon :

So now lets’ talk about the Event Horizon surrounding a black hole. The Event Horizon is the area surrounding the mouth of the black hole that is the danger zone. The Event Horizon is hundreds of thousands to millions of miles wide. Objects when entering this danger zone can still escape the pull of the black hole if they turn around or escape to the side and back out into space. Halve way through the Event Horizon and there is no escape. The object will be sucked in and devoured. Even light passing through the Event Horizon will be devoured.

Your Space Ship:

So now image you are in a space ship traveling through the space-time continuum. As your space ship approaches a large object like a star or planet your space ship may start to be tossed up, down and sideways by the gravitational waves produced by the object your space ship is approaching. Think of it as an airplane flying through a storm. Although most of the time these disturbances will be slight unless the object you are approaching is the Event Horizon of a black hole. The Event Horizon will be emitting huge gravitational waves which will batter the space ship. Your instruments in the space ship will detect these gravitational waves and warn your crew of an approaching black hole and you are in the danger zone. Turn around and get out before your space ship is sucked into the hole, crushed and disappears forever. So the good news is that the Event Horizon of a black hole gives your space ship warning time to escape. How’s that for amazing?

You know a great scientist by the name of Albert Einstein predicted the existence of black holes and gravitational waves when he developed his “Theory of Relativity” in 1917. His Theory of Relativity is all complicated mathematical equations that proves there is a space-time continuum, and, not only are there Gravitational Waves, but, light actually will curve when pulled or bent by the force of gravity. Another great scientist, Stephen Hawkens, in 1990 developed the mathematical proof establishing the existence of an Event Horizon surrounding the mouth of a black hole. Many more scientists helped expand mankind’s knowledge of the universe we live in.

Again what’s the lesson here? You live in the greatest country in the history of mankind which allows you to learn, study, work hard and achieve your dreams.

For mankind to move into space, mankind needs educated skilled smart people strong in spirit, mind and body. What you will learn is going to be based on the discoveries of thousands of hard working scientist before you. God gave you a intellect, now use it. Also a great adventure awaits you so be prepared.

More on the Event Horizon

By the way, as I understand it, the Event Horizon surrounding the mouth of the black hole also emits jets of x-rays, gamma rays, radio waves and magnetic waves, as well as, gravitational waves. The event horizon contains a swirling mass of space matter, swirling and swirling, in a gigantic whirl pool of matter being sucked into the mouth of the Black Hole. These jets of x-rays, gamma waves, radio waves and magnetic waves can also be used to detect black holes. In short, the Event Horizon is a very electrically stormy place very dangerous to space ships and the people inside these ships. Amazing stuff, amazing science. Be prepared and educate yourself to the wonders of the universe.

For a minute, imagine the dangers and hardships faced by Christopher Columbus when, in 1492, he crossed the unknown ocean to discover the American content. Remember up until that time, Columbus’s crew thought the world was flat and they would sail off the edge and disappear much like being sucked into a black hole. To his crew in 1492 that was scary stuff. The ocean to be explored today is now the space of the universe. Scary and exciting. Be prepared for the adventure.

Your great grandfather

Don

P.S. Check out the Black Hole illustrations below.