Homunculus Nebula

The Homunculus Nebula is a peculiar and possibly unique nebulous structure surrounding the hypergiant star Eta Carinae within the clouds of the sprawling Eta Carinae Nebula. The nebula is the result of an event known as the Great Eruption when, over the course several years, the outer shell of the star began to expand dramatically. By 1841, it had become one of the brightest stars in the sky, before fading away to the point where it became invisible to the naked eye.

The Great Eruption event left the star encased in a curious double-lobed structure, with an approximately spherical 'bubbles' of glowing material expanding outward from each of the immense star's poles. The resulting nebula therefore has a shape like a bloated hourglass, narrowing to a 'neck' around the star's equator, where it is ringed by a skirt of dust. Each of the lobes has a distinct structure of its own, showing a 'hole' in the direction of the star's pole, and a linear 'trench' running across its surface, though the nature and causes of these features remains uncertain at present.

Since the formation of the Homunculus, Eta Carinae has not remained inactive. The lobes of the Homunculus, already approximately a tenth of a light year in diameter, are continuing to grow and expand outward. Some fifty years after the Great Eruption, the star underwent a second 'Lesser Eruption' that created a smaller nebula within the greater Homunculus (known as the Little Homunculus). The hypergiant star within the Homunculus Nebula continues to brighten, and the occurrence of another Eruption event remains a possibility.