The Keyhole Nebula is a glowing cloud of gas, dust, and stars some 8000 light years distant toward the constellation Carina.
The nebula contains both bright regions that glow by means of fluorescent emission from ionized gas, and dark regions that obscure background light by means of dense molecular gas and dust.
The Keyhole Nebula is a site of active star formation, containing stars that are ten times as hot and 100 times as massive as the Sun. The entire Carina Nebula is some 200 lights years across, but the Keyhole Nebula portion shown here is only about 15 light years across.
The bright star in the middle is Eta Carinae; the red and yellow spikes in up-down direction are due to the pixels of the detector becoming saturated, so that electrons flow over across several pixels.
Eta Carina is the second most luminous star in the Milky Way, being 5 million times brighter than the Sun.
This image was used in my popsci article Big Bang — an eyewitness account (also available in Danish and Norwegian). You should read it :)
