Star Vistas

There are many different types of nebulae.  Some are great glowing regions of ionised gas, rather like hug Neon signs in space, except the glowing gas is usually Hydrogen rather than Neon.  THe bright red glowing gas regions you will see in Star Vistas are ionised Hydrogen atoms emitting red light at 656.3nm, also called Hydrogen-alpha.  The North America and Pelican nebulae in Cygnus aew examples of these emission nebulae.

Bright blue reflection nebulae are caused by dust particles scattering short wavelength (blue) light from a nearby star much more efficiently than longer wavelength (red) light.  THe eerie-looking M78 in Orion is a fine example of a reflection nebula.

Some nebulae are not “lit up” by a nearby star, so the gas in these regions simply acts as an absorber of light giving rise to dark nebulae.  Perhaps the most famous of all dark nebulae is the Horsehead nebula in the constellation Orion.  Take a close look at the Horsehead panoramic image in Star Vistas and you will see emission, reflection and dark nebulae all in close proximity to one another.

Finally there are a class of objects known as planetary nebulae.  These are the remains of supernova events and typical examples are the tiny planetary NGC2438 seen in the M46 open cluster image, and the much larger Dumbbell nebula, M27, both can be seen in Star Vistas.

As you look at the images in Star Vistas note the different types of nebulae, galaxy and star cluster that you see.  Note the very bright reflection nebulosity that surrounds the Pleiades in the M45 image.  This is something not visible to the naked eye, or even with the aided eye!