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APOD: 2026 August 4 – Curious Cometary Knots in the Helix Nebula
ScienceAPODAPOD: August 4, 2026 –...Today's APODArchiveSubmissionsIndexSearchCalendarRSSEducationAboutDiscuss APOD Astronomy Picture of the Day 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. Curious Cometary Knots in the Helix Nebula What causes unusual knots of gas and dust in planetary nebulas? Seen also in the Ring Nebula, the Dumbbell Nebula and NGC 2392, the knots' existence was not initially predicted, and their origins are still not well understood.
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