Structure of Saturn Nebula more complex than initially thought

Astronomers have observed the ‘star death’ in finer detail then ever before


The Saturn Nebula, also known as NGC 7009, is located in the constellation of Aquarius. Image credit: ESO/J. Walsh

The Saturn Nebula, a planetary nebula approximately 5000 light years away, has been intensely studied by the European Southern Observatory (ESO)’s Very Large Telescope (VLT). The Multi Unit Spectroscopic Explorer (MUSE) instrument has been able to map the gas and dust within the system, and this will help astronomers make sense of what happened to this antecedent low-mass star remnant.

Contrary to the name, planetary nebulae have absolutely nothing to do with planets. The Saturn Nebula – named after its resemblance to the planet Saturn – was once a low-mass star, and as it came to the end of its life, it swelled up to become a red supergiant. In an explosive fashion, the outer layers of the star were blown out by strong stellar winds and fuelled by ultraviolet radiation, leaving behind a shining remnant white dwarf in the middle.

Jeremy Walsh, an ESO astronomer, and his team have taken advantage of the VLT’s MUSE instrument to precisely map the planetary nebula in an attempt to understand its intricacies. The MUSE instrument has recently been installed on one of the four unit telescopes that comprise the VLT at ESO’s Paranal Observatory in Chile. The instrument has been a revelation since its installation, as it’s powerful enough to not only image a celestial object, but it will gather details of it’s spectrum at any point in the image.

The VLT’s MUSE instrument is capable of splitting up the different wavelengths the Saturn Nebula, revealing its chemical composition. Image credit: ESO/ J. Walsh

The results have shown that there are many complex layers to the Saturn Nebula, as it has shown to include an elliptical inner shell, an outer shell, a halo and two axes at either end of the nebula ending in bright ansae, which is Latin for handles. The team also found a wave-like feature in the dust that has perplexed the astronomers. The dust is usually evenly distributed throughout the nebula, but there is a distinct lack of dust in the rim of the inner shell. Astronomers believe that the dust is being destroyed in this region, and they have a few explanations for it. The first is that the shockwave smashes into the dust and obliterates every particle of ‘dirt’, the second is that there may be a shockwave that brought about a strong heating effect that evaporated the dust.

By mapping the whole gas and dust structure of the Saturn Nebula, this will help astronomers understand the life of a low-mass star. Not only that, but also this analysis will hopefully unmask how the planetary nebulae obtain their unique shapes.

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