Post by glactus on Apr 7, 2009 3:49:09 GMT
MyCn18: The hourglass nebula.
The sands of time are running out for the central star of this hourglass-shaped planetary nebula. With its nuclear fuel exhausted, this closing phase of a Sun-like star's life occurs as its outer layers are ejected - its core becoming a cooling, fading white dwarf.
The Hourglass, (also known as MyCn 18) is a young planetary nebula situated in the southern constellation Musca about 8,000 light-years from Earth. Magnitude is variable at 13.
In January 1996 it was designated simply as a small faint planetary nebula, but much improved telescopes and imaging techniques allowed the hourglass shape of the nebula to be discovered.
It is conjectured that MyCn 18's hourglass shape is produced by the expansion of a fast stellar wind within a slowly expanding cloud which is denser near its equator than its poles.
It should be noted that there is another nebula which shares the designation of hourglass, and can be found in the Lagoon Nebula.
Credits: This is a NASA image/ Wide Field and Planetary Camera 2 of the Hubble Space Telescope.