All Things Space, UFOs, etc.Mercury’s sodium tail is now appearing in special filters Posted on January 15, 2026 by Administrator Mercury’s sodium tail is back! This beguiling phenomenon appears best when Mercury is closest to the sun, or at perihelion. The tail contains sodium atoms, so we can only see it with the help of special filters and long-exposure photographs. Steven Bellavia has now imaged Mercury’s sodium tail five times over the past several years. His latest capture was on Tuesday morning, December 3, 2025.