Spiral in the Dark

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Image Credit & Copyright: NASA/ESA Hubble Space Telescope & R. Sahai.

Hubble shows us that you should always be on your best behavior because someone’s always watching. When it peered into the cosmos and swung its space eye over to the constellation Pegasus, it caught this star, LL Pegasi doing donuts when it should have been setting an example for the younger stars in its galactic neighborhood.

So in all seriousness, what exactly are we looking at here? LL Pegasi is a carbon star nearing the end of its life and in doing so it’s created a pre-planetary nebula. When a star about the size of the Sun, to about eight times that of the Sun dies, it begins to lose material out into the surrounding region. There isn’t enough available mass to detonate a star that size into a supernova so they just continuously discard mass until only a white dwarf remains. Most of you are probably up to speed on that or at least have a general idea, but what about that perfect spiral structure?

As it turns out, astronomers now believe that shrouded behind this material shell is actually a binary star system. One of those stars is losing its mass in the standard fashion while the two orbit each other. According to the European Space Agency (ESA), the spiral material is expanding outward at 50,000 kph (31,000 mph), which means the time distance between spiral layers is roughly 800 years. You can also infer that the two stars orbit each other at a rate of that same 800 years.

Why the entire object seems to glow, nobody truly knows but the leading theory is galactic light. That’s light from the stars of the Milky Way impacting the structure and rendering it aglow and that’s pretty cool.

Also, the bright star is an unrelated star much closer to us and in the line of sight of LL Pegasi.

NAME: IRAS 23166+1655 (the nebula), AFGL 3068, LL Pegasi.

WHAT IS IT?: Pre-planetary nebula, dying star.

HOW BIG IS IT?: 1/3 of a light year in diameter.

APPARENT MAGNITUDE: Extremely dim.

WHERE IS IT? (General): Constellation Pegasus, the Winged Horse.

WHERE IS IT? (Exact RA/DEC J2000): RA 23h 19m 12s / DEC +17° 11′ 35″.

ESA Hubble page for this image: https://www.spacetelescope.org/images/potw1020a/

NASA APOD page for this image: http://apod.nasa.gov/apod/ap100914.html

SIMBAD data page for this object: http://simbad.u-strasbg.fr/simbad/sim-id?Ident=LL+Pegasi

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