From the Hubble Space Telescope
M2-9 is a striking example of a bi-polar or butterfly nebula. It is 2,100 light-years away in the constellation Ophiuchus. If the nebula is sliced across the star, each side of it appears much like a pair of exhausts from jet engines. Indeed, because of the nebula's shape and the measured velocity of the gas, in excess of 200 miles per second, the description as a super supersonic jet exhaust is quite apt. Ground-based studies have shown that the nebula's size increases with time, suggesting that the stellar outburst that formed the lobes occurred just 1,200 years ago. The central star in M2-9 is known to be one of a very close pair which orbit one another at perilously close distances. It is even possible that one star is being engulfed by the other. The gravity of one star pulls weakly bound gas from the surface of the other and flings it into a thin, dense disk which surrounds both stars and extends well into space.
The disk measures approximately 10 times the diameter of Pluto's orbit. Such a disk can successfully account for the jet-exhaust-like appearance of M2-9. The high-speed wind from one of the stars rams into the surrounding disk, which serves as a nozzle. The wind is deflected in a perpendicular direction and forms the pair of jets that we see in the nebula's image. This is much the same process that takes place in a jet engine. In this image, neutral oxygen is shown in red, once-ionized nitrogen in green, and twice-ionized oxygen in blue.
Image Title: Hubble Sees Supersonic Exhaust from Nebula
based on press release for PHOTO NO.: STScI-PRC97-38
Credits: Bruce Balick (University of Washington), Vincent Icke (Leiden University, The Netherlands), Garrelt Mellema (Stockholm University), and NASA
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Last Modified On: Tuesday, December 19, 2000