Galaxies come in all shapes and sizes. To try to make sense of this, astronomers classify their shapes, such as "Elliptical" or "Spiral" galaxies. The most common type of classification is the "tuning fork", which is illustrated below with some of the galaxies observed by Herschel and Spitzer infrared sateliites. You can click on the galaxies and the labels for more information.
The images were created using observations from the Spitzer SINGS survey and the Herschel KINGFISH survey. Rather than stars, the images show dust between the stars, which is created by dying stars and forms some of the material from which stars are formed. The colour images are made by combining three different wavelenghts.
- Blue: 24μm light from Spitzer MIPS instrument, showing the warm dust that is heated by newly-forming stars
- Green: 100μm light from the Herschel PACS instrument, showing the cool dust
- Red: 250μm light from the Herschel SPIRE instrument, showing the coldest dust, at temperatures just a few tens of degrees above absolute zero.
The colour in the images indicates the temperature of the dust: redder regions are colder, while bluer regions are hotter.
A PDF version of this image can be downloaded here.