#galactic centre

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Milky way's galaxy galactic centre.

Ishikawa, Japan.

📷 setting: AI AF-s Nikkor 300mm f-4D IF-ED Nikon D800 ISO:1600

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Dusty Heart

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Centre of the Milky Way

This beautiful image of the centre of the Milky Way, featured on today (1st Oct 21) APOD, shows in detail the dark clouds of dust and gas that obscure our view of the centre, and part of the spiral arms that twist around the centre, but are between us and the centre.

The pink regions are ionized hydrogen gas caused by bombardment of ultra violet light from newly born massive blue giant stars, which causes the hydrogen to glow red, but it also represents stellar nurseries, an active area of star birth.

The central bulge itself, part of the barred shape of our galaxy, is around 10,000 light years end to end, representing billions of older stars, giving it a more yellow/cream colour compared to the rest of the galaxy, which has a more blue hue.

This is because star birth is less common near the super massive black hole, caused partially by the heating of the gas, and as a result, the only stars that exist in this region tend towards the older stars. Blue stars don't live more than a few million years, White stars maybe up to a few billion, yellow stars like our sun can live up to 10 billion years and orange and red dwarfs, well they can last longer than the universe has even existed so far. So the stars that tend to make it to the centre, are older stars that have migrated inwards.

Of course, we can look at our galaxy with very different eyes, here we can see a close up at the centre of our galaxy, right towards Sag A*, the supermassive black hole, but not in visible light, in radio waves, revealing a chaotic area of our galaxy in detail we cannot see in visible light.

Here it is in X ray, the white area just off right of centre is Sag A*. X Rays are commonly used to spot black holes which emit them when material falls in towards the even horizon, but so do stars more generally.

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Abondend Port Building by timkohlbecher

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Sagittarius Star Cloud

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The Centre of our Galaxy

A new image from the centre of our galaxy in ultra violet has been created by the Víctor M. Blanco 4-meter Telescope in Chile. 

The full image covers 250 Million stars, certainly living up to the name of Milky, the centre is so compact, it’s difficult to imagine it as somewhere in space. 

The darker patches are dust and gas from nebulas between us and the background. 

The entire picture at the top comes from the small square highlighted above, in the bulge of stars at the centre of our galaxy. 

It gives a small idea of how large our galaxy is, and how tiny our local neighbourhood of stars is that make up almost all the stars in our nights sky. 

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Globular Cluster at the Centre of the Milky Way

It would seem odd that the first image of the central black hole was not the one in our own Galaxy, but that of galaxy M87, 53 Million light years away, rather than just 25,000 light years away for our own Milky Way’s central black hole.

The reason is simple, we are sitting in the disk of our own galaxy, and between us and the centre are huge amounts of material which obscure it. It’s kind of like being able to see the Sun, 92 million miles away, but not being able to see the centre of your town because of all the tree’s and buildings between you and it. 

However, using filtering techniques and looking at the small amount of EM radiation that can reach us, they have found an ancient group of stars that are not quite behaving as the others, and believe it to be a globular cluster.

Astronomers use the metallicity of stars to gauge their age, stars created in the early universe tend to be almost exclusively Hydrogen and Helium, due to the lack of more complex elements at that time (all created in the fusion and subsequent death of stars), while more recent stars such as our Sun (4.6 billion years old), have much higher rates of elements larger than helium. 

The astronomers also modelled two possible scenarios for how it came to be there, one that a globular cluster had originated within our Milky Way, and simply migrated to the centre over the course of the last 3-5 billion years, or that it was extra-galactic in origin and came via a merger. While they cannot rule out the latter scenario, the models suggest it seems more probable the cluster of stars like many of the globular clusters in our galaxy, had been with us from the start, and simply fell towards the centre.

Source :

https://www.independent.co.uk/life-style/gadgets-and-tech/milky-way-galaxy-stars-discovery-european-southern-observatory-telescope-b672510.html

Original Papers :

https://iopscience.iop.org/article/10.3847/2041-8213/abb245

https://iopscience.iop.org/article/10.3847/2041-8213/abb246

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Milky Way’s Heart