Astrophoto: Centaurus A by Johannes Schedler
Written by R. Jay Gabany
Natural disasters are, unfortunately, something that we must contend with. For example, a flash flood can plunge towns into unexpected chaos, a hurricane strike can suddenly devastate an entire region and science has found evidence of an ancient asteroid impact that curtailed the rein of the dinosaurs by affecting climate across our planet. But these kind of events occur on an even greater scale - natural circumstances can lead to catastrophes that engulf whole galaxies such as seen in this picture.
This is an image is an astronomical relic. The light used to produce this picture left its source over 10 million years ago when mammals ruled the earth but mankind had not yet taken our first steps. The events depicted began about 100 million years earlier than that, however. We are viewing a scene that would be horrific for anything located close by or within it because this is a picture of two galaxies that have collided!
This image is a portrait of the the mysterious galaxy named Centaurus A, which is located in the southern constellation of the same name. Centaurus A received this designation in 1949 when it was discovered to be a powerful source of radio waves. It has since be recognized as a strong source of X-rays, also. This galaxy is faintly visible for a few weeks from the mid-northern lattitudes although it rarely ventures far above the haze at the horizon. Below the equator, however, this object is almost overhead for many and can be observed with moderate sized telescopes under dark skies quite easily.
Galaxies come in all shapes and sizes but they can be broadly grouped into three categories: spiral, elliptical, and irregular. Spiral galaxies are the most beautiful type with their long arms of gas, dust and stars gracefully bent around their central areas. Elliptical galaxies appear to be large, oblong balls of light that shine from their billions of older constituent stars and are generally featureless except for their enormous size. The irregular galaxy group is the category for everything else. Irregular galaxies are distinguished by their lack of any real organization and, for all intents and purposes, appear as a randomly shaped collection of gas, dust and stars.
Centaurus A does not easily fit into any of these designations because it is the result of a merger between an elliptical and spiral galaxy. The dark threads that stretch across the large ball of light are all that remains of the dust lanes from spiral galaxy that ventured too close and was swallowed by a much larger elliptical island universe.
As if a train wreck of galactic proportions isn't enough, Centaurus A's set of calamities also includes a stellar monster that is feeding at its center.
When the material inside a star can no longer support the thermonuclear reaction that causes it to shine, the star will begin to die. Stars that are similar to the size of our sun will become bloated, as their end draws near, then throw off most of their outer layers in a huge expanding bubble that exposes their small inner cores. Over time the core will become colder and dimmer as it fades to black.
Some larger stars will become supernovas and explode with a tremendous force that briefly outshines the combined light of all the stars in their galaxy.
Stars that are many times more massive than our sun will end their lives very strangely- they will simply begin to shrink until they are only a few miles in diameter. At this point, all of the material that once was a star is squeezed into a very small space so that each thimble-full weighs as much (or more) as the Earth. These stars are called black holes and they have such powerful gravity that nothing which ventures near can escape being pulled into it. Black holes do not shine because even light, itself, is trapped by the grip of its enormous gravity.
At the center of Centaurus A resides a black hole that is over a billion times more massive than our sun and it is slowly devouring the central area of this unusual galaxy! As material is drawn into the black hole, it is shot out at either of its poles as twin jets of energy. This image cannot show the two jets that are shooting from the top and the bottom of Centaurus A because the jets are only visible in infrared, X-ray and radio waves.
This picture was taken on between May 25 and 27, 2006 from Hakos, Namibia by Johannes Schedler using 5.5 inch refractor telescope and an 11 megapixel astronomical camera. Johannes resides in south-eastern Austria but he took his telescope and camera with him on an astronomically-oriented vacation to Africa and exposed this five hour photograph plus many more.
Do you have photos you'd like to share? Post them to the Universe Today astrophotography forum or email them, and we might feature one in Universe Today.
Written by R. Jay GaBany
Filed under: Astrophotos
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