AFGL 4104 or Roberts 22
Credit: NASA, ESA, and R. Sahai (Jet Propulsion Laboratory)
They say the flap of a butterfly's wings can set off a tornado on the
other side of the world. But what happens when a butterfly flaps its
wings in the depths of space?
This cosmic butterfly is a nebula known as AFGL 4104, or Roberts 22.
Caused by a star that is nearing the end of its life and has shrugged
off its outer layers, the nebula emerges as a cosmic chrysalis to
produce this striking sight. Studies of the lobes of Roberts 22 have
shown an amazingly complex structure, with countless intersecting loops
and filaments.
A butterfly's life span is counted in weeks; although on a much
longer timescale, this stage of life for Roberts 22 is also transient.
It is currently a preplanetary nebula,
a short-lived phase that begins once a dying star has pushed much of
the material in its outer layers into space, and ends once this stellar
remnant becomes hot enough to ionise the surrounding gas clouds and make
them glow. About 400 years ago, the star at the centre of Roberts 22
shed its outer shells, which raced outwards to form this butterfly. The
central star will soon be hot enough to ionise the surrounding gas, and
it will evolve into a fully fledged planetary nebula.
Information about the nature, age, and structure of Roberts 22 was presented in a paper using Hubble data back in 1999, published in The Astronomical Journal.
Source: ESA/HUBBLE - Space Telescope
