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Black Holes: By the Numbers (Text Version)


"Abandon all hope, ye who enter here." The Italian poet Dante Alighieri wrote these words in his fourteenth century poem Inferno about a journey through hell. The same foreboding could apply to black holes.

If anything gets too close to a black hole, it is dragged inside and never leaves. This is because a black hole's gravity is so strong that even light cannot escape. Click ahead and learn a few facts about these eerie formations in space.

You can look at our slideshow as an interactive or scroll through the images below.


United Kingdon, with snow and without snow

Slide 1: 2 › Larger image

There are two main kinds of black holes and the difference between them is mass.

The first kind is a stellar black hole and it occurs when a single massive star runs out of fuel. Small stellar black holes are more than three times the mass of our sun!

The other kind of black hole is called a supermassive black hole. These super-sized black holes are formed as the result of many black holes combining into one enormous black hole. They have millions to billions of times the mass of our sun. These black holes reside at the centers of galaxies and can consume other stars and gas from around their neighborhood.

How does a star become a black hole, or part of a supermassive black hole? A star burns energy in the form of nuclear fuel. This energy pushes outward and balances the inward pull of gravity created by the mass of the star. When a star runs out of fuel, it can no longer generate any push against the gravity of all its mass. The gravity forces everything toward the center of the burned out star and the core collapses into a black hole. The outer layers of the star explode in what is called a supernova.

About this image: This artist's concept shows one of the most primitive supermassive black holes (central black dot) ever discovered. The black hole, dating back 13 billion years, was discovered by NASA's Spitzer Space Telescope.


Lake George, NY, in different times of year
Slide 2: -459 › Larger image

Black holes are extremely cold. Those that begin as stars not much larger than our sun have a temperature close to absolute zero, which is equivalent to -459.67 degrees Fahrenheit or -273.15 degrees Celsius. Bigger black holes are much, much colder. Even so, these very cold objects can be surrounded by extremely hot material. The tremendous pull of gravity from black holes draws in gas and stars that pass relatively close by. These materials collide and heat up to hundreds of millions of degrees before they get slowly drawn into the black hole.

About this image: X-rays and radio waves were used to detect this black hole, which is actively pulling in large quantities of gas (bright orange oval in the center). Data from the NASA's Chandra X-ray Observatory and the Very Large Array were used to create the image.


Effects of the Rainy Season Along the Nile
Slide 3: 1 › Larger image

Anything pulled into the black hole is eventually crushed into one single point. This point is called the singularity and is the very essence of the black hole.

The tremendous gravity coming from a black hole is what pulls objects in. However, it is not like a vacuum cleaner that sucks up anything. An object has to be close enough to be drawn in by the black hole's gravity.

About this image: This illustration represents the area close to a black hole. Once anything passes into the black sphere, it eventually gets pulled to the singularity.


Sea Ice in the Arctic Circle
Slide 4: Hundreds › Larger image

Black holes discovered in our Milky Way Galaxy numbers in the hundreds. However, astronomers suspect there may be thousands in space.

About this image: This panel of illustrations from the European Space Agency depicts a star that travels too close to a black hole. As it nears, the star is stretched and quickly torn apart. Most of the yellow gaseous debris escapes but a small amount is captured and forms a rotating disk of gas that is heated before being swallowed by the black hole.


Water Storage in the Amazon
Slide 5: 15 › Larger image

If you are wondering if our sun will ever become a black hole, you can relax. Astronomers believe a black hole begins as a star that is much larger than our sun (at least 15 - 20 times the mass of our star, the sun).

Our star will eventually become a white dwarf, a very dense object that produces no new energy.

About this image: Cygnus X-1 is a relatively nearby black hole. It is about 6,000 light years from Earth. Discovered in 1964, it was the first object to be identified as a black hole. This X-ray image was taken by the Chandra X-ray Observatory.


Air Temperature at Earth's Surface
Slide 6: 26,000 › Larger image

About 26,000 light years from Earth, at the center of our Milky Way Galaxy, is a supermassive black hole called Sagittarius A*.Although it "feeds" on the winds blown off dozens of massive young stars that are nearby, it is on a limited diet. The stars are relatively far from Sagittarius A* and its gravity is weak at the stars' location. Sagittarius A* doesn't consume much since the nearby stars' high-velocity winds are hard for it to capture and swallow.

About this image: The Chandra X-ray Observatory produced this X-ray image of Sagittarius A*. The colors are based on different X-ray bands.


Classroom and Reference Material

› Black Hole Math (high school classroom activity)

› Chat With a NASA Astronomer

› Ask an Astrophysicist: Black Holes

› No Escape: The Truth About Black Holes

› Black Hole Rescue

Science consultant: Varoujan Gorjian, Research Astronomer, NASA/JPL and Spitzer Space Telescope