Forming a large, negatively-charged molecule in space

Astronomers using the Robert C. Byrd Green Bank Telescope found the negatively-charged form of octatetraynyl (C₈H-) in a cold interstellar cloud (middle left) and in the gaseous envelope surrounding an old, evolved star (middle right). This is the largest negatively-charged molecule yet found in space. The scientists believe it probably is formed in steps, illustrated here, proceeding downward.

1. A molecule of C₂H attaches to a molecule of C₆H₂, producing a molecule of C₈H₂ and a hydrogen atom.
2. Radiation (squiggly line) breaks one hydrogen atom from the C₈H₂, leaving C₈H and a hydrogen atom.
3. Finally, an electron attaches itself to the C₈H molecule, freeing a burst of radiation (overall glow seen around the molecule) and leaving the negatively-charged ion C₈H-.

CREDIT: Bill Saxton, NRAO/AUI/NSF

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More Detail: Building From Even Smaller Molecules

Five-Step Chemical Process (PDF File, 1.1 MB)

Caption for PDF Graphic

1. A molecule of C₂H (Ethynyl) attaches to a molecule of C₂H₂ (acetylene), producing a molecule of C₄H₂ (diacetylene) and a hydrogen atom.

2. A molecule of C₂H attaches to a molecule of C₄H₂, producing a molecule of C₆H₂ (triacetylene) and a hydrogen atom.

3. A molecule of C₂H attaches to a molecule of C₆H₂, producing a molecule of C₈H₂ and a hydrogen atom.

4. Radiation (squiggly line) breaks one hydrogen atom from the C₈H₂ , leaving C₈H and a hydrogen atom.

5. Finally, an electron attaches itself to the C₈H molecule, freeing a burst of radiation (squiggly line) and leaving the negatively-charged ion C₈H-.

CREDIT: Bill Saxton, NRAO/AUI/NSF

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