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Sagittarius A* Animations
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Images of the Milky Way's Supermassive Black Hole
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During 2012, Chandra collected about five weeks worth of observations on Sagittarius A* (Sgr A*, for short), the supermassive black hole at the center of the Galaxy. This sequence begins with wide-field X-ray images around our Galactic Center. Next, it fades to a composite of the region around Sagittarius A* as seen in X-rays by Chandra (blue) and infrared emission from Hubble (red and yellow). The view then zooms to a Chandra-only image just half a light year across. The diffuse X-ray emission here is from hot gas captured by the black hole and being pulled inwards. Less than 1% of this material reaches the black hole's event horizon, or point of no return, because much of it is ejected.
[Runtime: 00:29]

(Credit: Wide-field X-ray: NASA/CXC/SAO; Close-up X-ray: NASA/UMass/D.Wang et al., IR: NASA/STScI)

Click for low-resolution animation
Tour of Sagittarius A*
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Scientists have long known that the giant black hole at the center of the Milky Way is a particularly poor eater. Unlike some of its more distant galactic cousins including quasars, the Milky Way's black hole doesn't seem to be consuming much material, and, as a result, it is remarkably dim in X-ray light by comparison. To find out why our black hole behaves as it does, scientists used Chandra to observe the black hole - known as Sagittarius A* -- for over five weeks worth of time. This is one of the largest amounts of time that Chandra has ever looked at the same object. Sagittarius A* is a black hole with about 4 million times the mass of the Sun. At just 26,000 light years from Earth, Sagittarius A* is one of very few black holes in the universe that's close enough where we can actually witness the flow of matter nearby. The researchers found out that Sagittarius A* actually consumes less than about 1% of the material it has available to it. While they are still working out th e details of how and why the black hole is so finicky, astronomers now have a new piece of the puzzle thanks to these new X-ray data from Chandra.
[Runtime: 01:20]

(Credit: NASA/CXC/A. Hobart)

Click for low-resolution animation
Beyond the Horizon
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For a long time people believed that the Earth was flat and that if you sailed too far you'd fall over the edge! It seems funny they could have thought that, because now we're lucky enough to have pictures of our entire planet and we can see its shape (take a look at image 2). But it took some pretty impressive technology to get these pictures, which wasn't available to our ancient ancestors. Did you know you have to travel about 20,000 kilometres from Earth to be able to see the entire planet?

Now imagine how far into space you'd have to travel to fit all the 300 billion stars of the Milky Way (our Galaxy) into one shot! This is way beyond our abilities at the moment, but we can photograph small sections of the Galaxy. This picture from the Chandra X-ray Observatory shows the very centre of the Milky Way. This is the most chaotic and dangerous part of the Galaxy, and home to a supermassive black hole.

Anything that gets too close to a black hole is pulled into it with such a strong force that it has no chance of escape. The boundary that marks the point of no return is called the event horizon. Past this not even light will return: this monster will pull it in forever. The blue haze in this picture includes piping-hot gas floating perilously close to the event horizon of our Galaxy's supermassive black hole. But astronomers have found that just a tiny amount of this gas will be gobbled up by the black hole, and the rest will be "spat out" before it gets too close.
[Runtime: 02:03]

(Credit: NASA/CXC/April Jubett)

Return to Sagittarius A* (August 29, 2013)