The fierce ultraviolet radiation given off by the young stars of NGC 3324 has carved this giant cavity in space. And, thanks to our old friend pareidolia, that boundary between different gases looks an awful lot like a person's profile.
In fact, the astronomers at the La Silla Observatory in Chile's Coquimbo Region have taken to calling this the Gabriela Mistral Nebula, after a Chilean poet who won the Nobel Prize in 1945. (Actually, there is a bit of a resemblance.) For anyone who enjoys seeing large, illusory profiles and who missed out on seeing New Hampshire's Old Man of the Mountain, this is a more than worthy substitute. So what created the stark boundary between the different parts of the nebula? In a statement, the European Southern Observatory explains:
A rich deposit of gas and dust in the NGC 3324 region fuelled a burst of starbirth there several millions of years ago and led to the creation of several hefty and very hot stars that are prominent in the new picture. Stellar winds and intense radiation from these young stars have blown open a hollow in the surrounding gas and dust. This is most in evidence as the wall of material seen to the centre right of this image. The ultraviolet radiation from the hot young stars knocks electrons out of hydrogen atoms, which are then recaptured, leading to a characteristic crimson-coloured glow as the electrons cascade through the energy levels, showing the extent of the local diffuse gas. Other colours come from other elements, with the characteristic glow from doubly ionised oxygen making the central parts appear greenish-yellow.
For more, check out the ESO website.