Imagine a lawn sprinkler spinning wildly, tossing out two S-shaped streams. At first it appears chaotic, but if you stare for a while, you can trace its patterns. The same S-shape is present in the Butterfly Nebula, except in this case it is not water in the air, but gas blown out at high speed by a star. And the “S” only appears when captured by the Hubble camera filter that records near-infrared emission from singly ionized iron atoms.
“The S-shape in the iron emission from the Butterfly Nebula is a real eye-opener,” Kastner said. The S-shape directly traces the most recent ejections from the central region, since the collisions within the nebula are particularly violent in these specific regions of NGC 6302. “This iron emission is a sensitive tracer of energetic collisions between slower winds and fast winds from the stars,” Balick explained. “It’s commonly observed in supernova remnants and active galactic nuclei, and outflowing jets from newborn stars, but is very rarely seen in planetary nebulas.”
“The fact that the iron emission is only showing up along these opposing, off-center directions implies that the source of the fast flows is wobbling over time, like a spinning top that’s about to fall,” added Kastner. “That’s another tell-tale sign of the presence of a disk, which directs the flow, and also a binary companion.”
Hubble image of Butterfly Nebula
Source: NASA