A team of astronomers using the Wide Field Imager on the MPG/ESO 2.2-m telescope at the La Silla Observatory, Chile, has captured a new image of a glowing cloud of cosmic gas and dust known as Gum 15.
This image shows the star-forming region Gum 15. Image credit: ESO.
Gum 15 is located in the constellation of Vela, about 3,000 light-years from Earth.
This object is a striking example of an HII region. Such clouds form some of the most spectacular astronomical objects we can see; for example the Eagle Nebula, the great Orion Nebula, and this less famous example, Gum 15.
Hydrogen is the most common element in the Universe, and can be found in virtually every environment investigated by astronomers. HII regions are different because they contain substantial amounts of ionized hydrogen – hydrogen atoms that have been stripped of their electrons through high energy interactions with ultraviolet photons.
As the ionized hydrogen nuclei recapture electrons they release light at different characteristic wavelengths. It is one of these that gives nebulae such as Gum 15 their reddish glow – a glow which astronomers call hydrogen alpha (Hα).
At the centre of the image of Gum 15 one can see one of the culprits – the star HD 74804.
The clumpy, irregular appearance of Gum 15 is not unusual for a HII region and is again a result of the stars within. HII regions have diverse shapes because the distribution of stars and gas inside them is so irregular.
Adding to Gum 15’s interesting shape are the forked dark patch of obscuring dust visible in the centre of this image and some dim blue reflection structures crossing it. This dust feature makes the nebula resemble a larger and fainter version of the better known Trifid Nebula.
An HII region like this one might give birth to thousands of stars over a period of several million years. Some of these stars cause it to glow and sculpt its shape, and it is these stars that will eventually destroy it.
