One of a kind. That’s the star AFGL 3068, whose true nature was not uncovered until 2006. Its gorgeous if bizarre appearance certainly suggests great mystery. Ironically, however, this unique entity actually solves one of astronomy’s outstanding puzzles.
AFGL 3068 was long known as a bright infrared spot in the constellation Pegasus, but optical telescopes showed nothing there. It’s not that it was too small: The spirals’ dimensions match the angular size of Mars as seen from Earth. Plenty large enough. The problem was the extreme faintness. Only when astronomers successfully pleaded for a long 33-minute exposure using the Hubble Space Telescope’s ultra-sensitive Advanced Camera for Surveys did this geometric oddity materialize out of the blackness.
The only previously known celestial helixes were spiral galaxies. This, however, is neither a galaxy nor some kind of glowing gas. At the center of those nautilus spirals is a binary star system. Located 3,000 light-years away, AFGL 3068 is composed of a red-giant carbon star blowing material into space in a sort of high-intensity stellar wind. It co-orbits a blue-white star lying 103 astronomical units (AU) away from it, or about twice Pluto’s farthest distance from the Sun (1 AU is the Sun-Earth distance). The pair take 800 years to whirl around their common center of gravity.
The red-giant star frenetically sheds material at the rate of one Sun’s worth every 1,000 years, and much of this is carbon, which tends to combine into large molecules — a fine black dust — that thickly surrounds the star, blocking its light. The companion’s gravity pulls the carbon particles in its direction, where much of it escapes into space. As the system revolves, the emitted dust sprays outward into a spiral, like water from a spinning sprinkler.
If you were to float in space near AFGL 3068, you’d feel a dirty blast of soot sweeping past you every 800 years. At a speed of 9 miles (14.5 kilometers) per second, or 32,400 mph (52,200 km/h), this black carbon would definitely ruin your clothes — and the nearest dry cleaner is on 51 Pegasi, hundreds of light-years away. The dark outrushing spiraling material has created five visible turns that now occupy 1/3 light-year.
AFGL 3068 makes light bulbs turn on in astronomers’ brains. Perhaps this sort of binary system creates the perfect concentric shells observed in certain planetary nebulae, like the Cat’s Eye Nebula (
number 22 on our list). The even spacing of those bubbles suddenly makes sense if the mechanism is not bewildering explosions at regular intervals, as was assumed, but rather binary star orbital emissions whose very nature is clockwork precision.