The Spiral of LL Pegasi

This weeks OOTW features Alice’s OOTD featured on the 16th of September 2010.

IRAS 23166+1655

This fuzzy cloud lurking in Pegasus may not look like much on the SDSS, but the Hubble space telescope reveals something very beautiful indeed:

Credit: ESA/NASA & R. Sahai

This is IRAS 23166+1655, it may look like a perfect spiral galaxy but it is in fact a pre-planetary nebula, which is a brief burst of nebulosity when a star is in the red giant phase of its life, just before it sheds all of its layers into the interstellar medium as a Planetary Nebula. The cause of the nebula, a carbon star called LL Pegasi, is shrouded by the thick shells of dust and gas that surrounds it and another star, which is gravitationally bound to the other.

As the binaries rotate around each other, making a full turn every 800 years, LL Pegasi throws off beautiful shells of dust and gas on its way round, and because the star throws off the material at different times, it creates the lovely spiral which spreads out for 800 light years! Alice writes in the OOTD that the nebula isn’t lit up by the stars, but is in fact lit up by the galaxy, with one side being brighter than the other because it’s nearer to the plane of the galaxy! 😀

Alice quotes a lovely limerick from Zooite Djj, which I just have to include here:

A HIDDEN STAR SPEAKS OUT
That nebular spiral is curious
(Though the ‘planetary’ label’s quite spurious)
And I’m losing much gas
Which is part of my mass!
So I tell you, it’s making me furious!

You can read more about the spiral here!