Visit the gallery of my previous images at this link.
How a galaxy appears depends on the color of the light viewed. This image used wavelengths of ultraviolet and visible light. The visible light from this spiral galaxy shows a tightly wound pinwheel shape. That is typical of many spirals.
Viewed in ultraviolet light, the shape can be very different. Ultraviolet light is a shorter wavelength than visible light. It is emitted by stars much hotter than the Sun. They are seen as blue in this image of NGC 6782. The central and outer rings have a lot of these hot stars. Darker lanes of cooler dust can also be seen. Click any image to embiggen.
Known as Stephan’s Quintet, this tight gravitationally bound group was discovered in 1877 by Édouard Stephan. The Hubble greyscale images I used to form this color image show only four of the five members of the quintet. It is one of the most studied galaxy groups.
As noted above, young hot stars show as blue. Older and more mature stars are tinted red in this image giving the glow we see. There is a great deal of activity taking place in this group.
The Bubble Nebula was first observed in 1787 by William Herschel. It is found in the constellation Cassiopeia at a distance of 7100 light years. The star at lower left center, visible through the shell of gas, is 40 times the mass of our Sun. It is driving the expansion of the gases of the shell at 2000 km/s from it. Intense ultraviolet light is illuminating gases nearby to the right and in the more distant upper left. Light travels much faster than the expanding nebular shell of gas.