Scientists have known the universe is expanding for over eight decades. During this period, many speculated that gravity would eventually slow and halt the expansion then the universe would probably start to contract. This common view held that the universe repeatedly oscillated between Big Bang and Big Crunch. Then, in the late 1990’s, some scientists realized that the brightness of exploding stars in very remote galaxies were not following the predicted theoory. They concluded that the expansion of the universe was not decelerating. It is speeding up.
Stars that explode are called supernova. Based on their mass, some suns end their lives by self-destructing in a cataclysmic event that unleashes tremendous amounts of energy and produces a ball of light that briefly outshines all the stars in its galaxy. Many supernovae share common characteristics based on the matter that is inside the sun when it explodes. This matter can be identified by studying its spectrum of light, much like the rainbow of colors that we see when light passes through a prism. Each element within the star absorbs parts of its rainbow of colors and these can be identified even though the light comes from an object located tremendously far away and in the distant past. Based on this, scientists can surmise how bright a supernova should appear and recently they began to see that many were dimmer than expected.
M83, pictured here, has been a hot spot for supernova. Until very recently, more supernova had been discovered in this galaxy than in any other- a total of six in the past eighty five years and more will probably be discovered over time. This is ten times the rate predicted by theory. M83 was first seen about 250 years ago and is located in the southern constellation of Hydra. It is relatively close to Earth, only 15 million light years distant, and is part of a group of thirteen or more galaxies that include the mysterious Centaurus A.
M83 can be quite challenging to observe or photograph from mid-northern latitudes because it is very close to the horizon. However, it is easy to view from points halfway below the Earth’s equator. From those locations, this galaxy is actually quite bright and can be seen with binoculars or a small telescope high in the sky.
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This gorgeous picture of M83 was produced by Michael Sidonio on April 22, 2006 from his outdoor imaging area at Mt Campbell Observatory, in Googong, New South Wales, Australia. CLICK HERE for a larger image. Michael used a six inch refractor and a 1.5 mega-pixel camera to record his almost three hour total exposure.
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