This splendid nebula contains a unique scene: two stars orbited by a third


What you are seeing in this stunning image from the Very Large Telescope (VLT) in Chile is something that has never been observed anywhere else: a planetary nebula made up of two closely linked stars orbiting a third outer star.

That third star wasn’t sighted until centuries after the discovery of the nebula itself, known as NGC 246, or sometimes called the Skull Nebula or Pac-Man Nebula – due to the shapes its stars create and the gases swirling around them.

No other nebula seen by our telescopes has such a configuration. These celestial phenomena typically form around one or two central stars, as they eject their outer layers at the end of their life.

neb 2(THAT)

Here we have a white dwarf star and a faint red dwarf star (which you can’t actually see in this image) orbiting each other, and then a third star orbiting the other two. The third star is about four times further away than the other two stars are from each other, which is about 1,900 times the distance between the Earth and the Sun.

If you want to be technical, this is a triple stellar hierarchical system and no other planetary nebula that we are aware of demonstrates the same phenomenon. We have identified around 1,800 of these planetary nebulae, but there are thought to be thousands more out there.

The luminous gas in nebulae can take all kinds of weird and wonderful shapes and appear around stars like our own sun. One day the fiery mass at the center of our solar system could stage a light show similar to this one.

NGC 246 is located in the constellation of Cetus, sometimes known as the whale, about 1,600 light years from Earth. This is a brand new image of the constellation, capturing the wavelengths of light associated with hydrogen (the red parts of the image) and oxygen (the light blue parts of the image).

Snapshots like this help astronomers better understand stars, their composition and evolution. In this case, the FORS 2 instrument was used – the FOcal Reducer and the low dispersion spectrograph – aboard the VLT, and produced a stunning and dramatic image.


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