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The strange structures of the Saturn nebula

The spectacular planetary nebula NGC 7009, or nebula Saturn, emerges from the darkness as a series of irregularly shaped bubbles, illuminated in glorious blue and pink tones.

The Saturn nebula is located about 5,000 light-years away, in the constellation of Aquarius (the water-bearer). Its name derives from its strange form, similar to the ringed planet that we all know seen of song.

But, in fact, planetary nebulae have nothing to do with planets. The Saturn nebula was originally a low mass star that expanded to red giant at the end of its life and began to release matter from its outermost layers. This material was dragged by strong stellar winds and excited by the ultraviolet radiation generated by the hot core that they were leaving behind, creating a circunestellar nebula of hot colored powder and hot gas. At the heart of the Saturn nebula are the remains of the star, visible in this image, which is in the process of becoming a white dwarf.

In order to better understand how planetary nebulae acquire these strange shapes, an international team of astronomers, led by ESO’s Jeremy Walsh, has used the MUSE (Multi Unit Spectroscopic Explorer) instrument to penetrate into the dusty veils of the nebula Saturn. MUSE is an instrument installed in one of the four Telescope Units of the Very Large Telescope at ESO’s Paranal Observatory in Chile. It is so powerful because it not only creates an image, but also collects information about the spectrum (or gamma) of the object’s light at each point in the image. The team used the MUSE instrument to produce the first detailed optical maps of gas and dust distributed throughout a planetary nebula. The resulting image of the Saturn nebula reveals many intricate structures, including an inner elliptical bubble, a bubble or outer layer, and a halo. It also shows two currents, previously captured, that extend from the two ends of the long axis of the nebula and end in bright ansae (the Latin word for “wings”).

Mapping the structures of gas and dust in planetary nebulae will help understand their role in the life and death of low-mass stars, and will also help astronomers understand how these planetary nebulae acquire such strange and complex shapes.

But MUSE’s capabilities extend beyond planetary nebulae. This sensitive instrument can also study the formation of stars and galaxies in the early universe, as well as mapping the distribution of dark matter in clusters of galaxies in the near universe. MUSE has also created the first 3D map of the Pillars of Creation in the Eagle nebula (eso1518) and has obtained images of a spectacular cosmic clash in a nearby galaxy (eso1437).

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