Tag Archives: Galaxy

Can a hydrogen atom make a galaxy glow red?

Why are galaxies red? This is due to one element and only one – Hydrogen.

Hydrogen is nature’s smallest element and is, perhaps, the purest representation of what an atom actually is. The name Hydrogen actually comes from Greek words ‘hydro’ and ‘gen’ – which when put together mean “water-generator”.

 Diagram of Hydrogen – one electron and one proton

Hydrogen was extensively studied by scientists such as Niels Bohr. Bohr’s simple atomic model had an electron orbiting a proton, just like in the diagram shown above. This is analogous to the Earth orbiting around the Sun. However the Bohr model is highly simplistic as quantum mechanics tells us that we never quite know exactly where the electron is.

Hydrogen also has very specific energy “shelves” where electrons are allowed to be. Despite the short comings of Bohr’s model the energy levels of these shelves can be calculated very accurately from the model.

So, in order to move an electron from one shelf to the next we need a very specific amount of energy. This is due to the discretization of angular momentum which meant an electron in the Bohr model could only exist at certain distances from the proton. If you give the atom more energy the electron will jump up to a higher shelf – at this point it’s in an excited state.

Electron jumping down to a lower energy shelf

Electron jumping down to a lower energy shelf [Image courtesy of http://phys.org]

If you let it sit there it will re-emit energy in the form of light and the electron will jump back down to a lower shelf. Now, if an electron jumps from the 3rd shelf to the 2nd shelf the electron emits visible light. This emission is so powerful that it can be seen throughout many galaxies:

Elliptical galaxy NGC-2937 (As seen in an earlier post on The False Vacuum!)
Elliptical galaxy NGC-2937 (Image credit: NASA)

It’s THAT emission that causes the glowing red lines in the galaxy shown above. In the case of the galaxy shown above (where in a previous blog post we looked at where its unusual shape came from) the clear red lines are where the galaxy is forming stars. This red glow from Hydrogen shows us very clearly where stars are being formed in the night sky.

So there you have it. These red lines splashed across the night sky are a visible sign that new stars are born and shows how hydrogen can make a galaxy glow  a deep red.

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Man has now left the solar system!

It’s an amazing day today. Voyager 1, a tiny little spacecraft built 36 years ago, has now left the solar system and is travelling out towards the rest of our galaxy! This is the first man-made object to have left our solar system.

Voyager 1 awaiting payload entry into a Titan-Centaur-6 rocket

Voyager – 1 awaiting payload entry (Credit to Wikimedia Commons)

Voyager’s technology, once considered cutting edge, is now outclasssed by any mobile phone. It carries an eight-track tape recorders and 240,000 times less memory than your old iPhone 3 used to have. Once designed only for a 4 year trip to Saturn the success of Voyager-1 has taken NASA experts by storm.

“I don’t know if it’s in the same league as landing on the moon, but it’s right up there. Star Trek stuff, for sure”

– Donald Gurnett, Professor of Physics at the University of Iowa

I think it goes to show NASA can do it – Johnson style!