In the veins of the Butterfly Nebula

Thanks to the Gemini South telescope in Chile, we have taken unprecedented details of knots and strands of molecular hydrogen in the “wings” of the bipolar planetary nebula NGC 2346, known for some time as Butterfly Nebula. It is a star in a short but highly spectacular phase of its life cycle.
A group of researchers from the National Optical Astronomy Observatory (NOAO) US, including Italian Letizia Stanghellini, using the 8-meter Gemini South Telescope located in Chile, have obtained the highest-resolution image ever acquired of the planetary nebula NGC 2346. Discovered by William Herschel in 1785, this bipolar nebula is located at a distance of 2,300 light years from our Sun, in the direction of the constellation Monoceros, and is also known as the Butterfly Nebula for its hourglass shape.


Credit: Image from GeMS/GSAOI Multi-Conjugat Adaptive Optics System

The new observations show details about the Butterfly Nebula “wings” of size comparable to that of our solar system, really tiny in astronomical scale. In the image you can appreciate details of nodes and filaments of molecular hydrogen that no other ground-based telescope or space has so far been able to make in a manner so sharp.
In fact, molecular hydrogen in the lobes of the bipolar NGC 2346 was identified nearly 30 years ago, although previous observations suggested that it was disposed in a compact form donut. The filamentary structure observed in the new images corresponds to the mechanism of formation that the same research team proposed a model that describes how a bubble of hot gas around the central star bursts and fragments accordingly shell surrounding gas. The nodes of gas probably represent a common phenomenon that occurs when two fluids of different densities are in contact, and the lighter liquid pushes the heavier fluid.
The authors have developed computer simulations to understand how it should be the interaction between the gases in different densities, producing a movie that shows the evolution over time. “This film shows in sequence the model results in a period of about 9,000 years,” explains Arturo Manchado the NOAO, first author of the study. “The blue color corresponds with the emission of molecular hydrogen. The animation starts from a torus initial cold gas to the equator, which becomes less and less visible as the outer body is fragmented, leaving behind only the larger aggregates. ”
Before reaching the final stages of its life cycle and turn into “butterfly”, NGC 2346 was a double star system, with two big just to turn about the common center of mass. The more massive of the two stars has exhausted its fuel faster than his partner of lower mass, before swelling into a red giant, and then gradually losing the outer layers to become a white dwarf star with a mass between 0, 3 and 0.7 times that of the sun. The symmetrical shape of the butterfly wings of this bipolar nebula was probably carved by the pair of star, although this hypothesis has yet to be confirmed. With an orbital period of 16 days, the two stars are located closer than the Sun is in the Mercury.
The observations were carried out with the new system to obtain images in the band of near infrared equipped with adaptive optics of the telescope Gemini South during the initial test of this tool. Adaptive optics is a new technique that allows the real-time correction of the “flicker” of astronomical images caused by turbulence of the terrestrial atmosphere.

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