Astronomers from the European Southern Observatory have taken the best look yet at the Saturn Nebula, and now they are are using the data to understand how such a stunning structure formed.
The Saturn Nebula, also known as NGC 7009, is a large planetary nebula 5,000 light-years away. But don’t let the “planetary” adjective confuse you, the nebula has very little to do with planets and a lot to do with the aging stars at its center.
The Saturn Nebula formed when a low-mass star expanded into a red giant. This is usually the beginning of the end for stars. The stars swells up and the outer layers begin to be blown away by the intense radiation and strong stellar winds coming from the interior of the star. Over time, the hot gas is pushed so far away, a nebula is formed and, at its center, a bright hot stellar core. For NGC 7009, the stellar core is over 55,000°C (99,000°F).
The broad picture of such an astronomical object is clear, but the details are a lot more complex. To understand the intricate interaction that formed such an elaborate shape, researchers used the MUSE (Multi Unit Spectroscopic Explorer) instrument on the Very Large Telescope. MUSE provided the chemical and physical information of every pixel in the image.
MUSE allowed the team to create the first optical map of the gas and dust distribution. The team was able to identify an elliptical inner shell, an outer shell, an expanding halo, and two streams pushing through the gas and dust of the nebula. These two structures called ansae (which is Latin for handles) give the nebula its Saturn-like appearance.
The observations have provided a lot of data, so the researchers now need to work out how all of that fits together. Among the intriguing tidbits, the team discovered that there is very little dust at the inner shell rim. The shell is an expanding shock wave that is destroying dust in its wake, but it’s not clear exactly how. It could be just smashing into dust grains and breaking them apart or heating them so much that they simply evaporate away.
Planetary nebulae only last for a few tens of thousands of years – a blink in cosmic terms. More work such as this will be necessary to truly comprehend how these objects form.