The small red FLIERs are a mysterious byproduct of this process. Some of their observed characteristics suggest that they are like sparks flung outward from the central star late in the very recent past (a thousand years ago). Yet their shapes revealed in these Hubble Telescope images seem to suggest that they are stationary, and that material ejected from the star flows past them, scraping gas from their surfaces. Future Hubble observations will monitor any changes in the positions of FLIERs to resolve this issue. In either case, the formation of FLIERs cannot be easily explained by any models of stellar evolution.
Image Factoids for NGC 6826
Nickname: The Blinking Planetary Nebula
observed by Hubble: Jan 27 1996
distance: 0.7 kpc (2200 l.y.)
HST instrument: WFPC2 (2 orbits) with filters F658N (once-ionized nitrogen, shown in red), F502N (twice-ionized oxygen, shown in green), and F469N (starlight filter, shown in blue).
Credits for the image of NGC 6826
Bruce Balick, University of Washington
Jason Alexander, University of Washington
Arsen Hajian, U.S. Naval Observatory
Yervant Terzian, Cornell University
Mario Perinotto, University of Florence (Italy)
Patrizio Patriarchi, Arcetri Observatory (Italy)