Posted on 04/09/2003 5:32:48 AM PDT by petuniasevan
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
Explanation: Where is the center of the unusual Egg Nebula? Like a baby chick pecking its way out of an egg, the star in the center of the Egg Nebula is casting away shells of gas and dust as it slowly transforms itself into a white dwarf star. The Egg Nebula is a rapidly evolving pre-planetary nebula spanning about one light year toward the constellation of Cygnus. Thick dust, though, blocks the center star from view, while the dust shells further out reflect light from this star. Light vibrating in the plane defined by each dust grain, the central star, and the observer is preferentially reflected, causing an effect known as polarization. Measuring the orientation of the polarized light for the Egg Nebula gives clues to location of the hidden source. The above image taken by the Advanced Camera for Surveys on the Hubble Space Telescope is false-color coded to highlight the orientation of polarization.
"The Egg Nebula, also known as CRL 2688, is shown on the left as it appears in visible light with the Hubble Space Telescope's Wide Field and Planetary Camera 2 (WFPC2) and on the right as it appears in infrared light with Hubble's Near Infrared Camera and Multi-Object Spectrometer (NICMOS). Since infrared light is invisible to humans, the NICMOS image has been assigned colors to distinguish different wavelengths: blue corresponds to starlight reflected by dust particles, and red corresponds to heat radiation emitted by hot molecular hydrogen."
There is more information at the Hubble Heritage site (and a gallery of photos). Here is the link for the Egg Nebula: Egg Nebula in Polarized Light
Oh, note that the last link called "Egg Nebula" in the APOD article is a PDF file. You'll need Adobe Acrobat reader to view that page.
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