I cropped this from the image above. A couple of things to notice: the pink/orange object is called NGC 604 and is a glowing cloud of hydrogen heated by a great cluster of hot stars at its centre. It is the same kind of object as the Orion Nebula but 40 times the size!
Note the graininess of the image; the telescope has resolved the brightest of the giant stars in the galaxy from a distance of 3 million light-years.
A long time since my last blog post! Busy at work, at home and studying. To calm my nerves I've been processing pictures of little bits of the heavens. Not my own images - the summer night sky is getting too bright - but data collected by various sky surveys and available online through the ESO Online Digitized Sky Survey.
A number of surveys are available and offer various degrees of sky coverage; from 45% of the sky (in blue filtered light) to 99% (in red and infrared). The web interface allows selection of a target or specific coordinates. The images can be displayed as a GIF or downloaded as GIF or FITS. The FITS file format contains a wider range of pixel intensities than GIF. I use FITS Liberator to select the best "window" to view the FITS data.
The images are scans of photographic plates taken by some very big telescopes. Many of them were obtained with the 1.2 metre UK Schmidt Telescope in Australia during the early 90s. Being scanned from the original plates means there are some interesting blemishes in some of the plates. Hairs, fingerprints and other defects can be found if you look carefully enough :-) They can, of course be photoshopped out these days!
Here is what typical GIF images look like:
There are subtle differences to the images; the blue filtered image shows the structure in the spiral arms more easily because of the hot (bluish), young stars there. The red filtered image shows the background glow of the disk - containing many more low mass, cooler (redder) stars.
These are grayscale images. To make a natural colour image we'd need an image taken with a green filter! However, no images in green were taken.
Just for fun...I wanted to see some colour images so I synthesised my own green image. This was done by averaging the pixel intensities in the red and blue images. For example, if a pixel is very bright in blue (say a value of 3000) and dimmer in red (say, 1000) then the I'd interpolate the green value to be (3000+1000)/2 = 2000. Doing this for every pixel generates a synthetic green image.
Armed with the red-green-blue (RGB) images it's a simple matter to blend the images to get a colour image:
The full res version can be viewed here. And you really should look at it! The amount of detail in the images is breathtaking.
So this has become my most recent astronomical diversion. You can see some of my other results on Flickr.
Dr Adrian Jannetta
Guitar strummin' explorer of the universe. Mild mannered maths teacher by day and astronomer by night.