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What colour is the universe? April 30, 2011

Posted by Marie in Astronomy, Jodrell Bank, Nebula, Planetary Nebula.

In a long and convoluted story, my last post about the new Jodrell Bank Discovery Centre led a Twitter friend to look at my favourite images page.  This then resulted in a twitter-sation about why the images are so pretty!

The colours in the images are ‘false’; that is,

Credits: Raghvendra Sahai and John Trauger (JPL), the WFPC2 science team, and NASA

if you were to actually be able to travel to see the galaxies or nebulae with your own eyes, you wouldn’t see the colours which are in the images, because our eyes don’t register them.

So I discovered that the people who take the pictures get to choose the colours!

It’s all to do with the chemicals which are detected in the objects, and their wavelengths.  Red indicates the longest wavelength and blue the shortest, with the other colours somewhere in between.

Cats Eye Nebula Credit: NASA, ESA, HEIC, and The Hubble Heritage Team (STScI/AURA) Acknowledgment: R. Corradi (Isaac Newton Group of Telescopes, Spain) and Z. Tsvetanov (NASA).

But however they decide on the colours, they look lovely anyway! Keep an eye on the favourite images page, because I’m adding more all the time. Or if you like, feel free to send me your favourites and I’ll add them to the page.



1. Dave Jones - May 4, 2011

It’s not that our eyes don’t register the colours of these nebulae and galaxies (most of the wavelengths that these images are made from are in the optical range). It’s just that we articially assign different colours to try and make the images look better/clearer. For example, the images above are mostly made from Hydrogen alpha (656 nm), Nitrogen ([NII] 658 nm) and Oxygen ([OIII] 501nm), which equate to two very similar shades of red and a greeny-blue – http://www.spacetelescope.org/static/projects/img/spectra01.jpg

So, to make the images prettier and the distinction between the different emission lines clearer, they are artificially assigned ‘false’ colours, i.e. red, green and blue.

Marie - May 5, 2011

Hi Dave, thanks for the correction. For some reason I had just assumed that the images were not in the optical range. And can I say thanks for being the first actual astronomer to comment on my little blog! 🙂

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