Scientists nicknamed this nebula the 'Cosmic Sea Lemon' — and NASA's Hubble just caught it growing

Scientists nicknamed this rusty-colored cloud of gas and dust, located inside the Trifid Nebula, the "Cosmic Sea Lemon" for its resemblance to a sea slug gliding through space. In April 2026, NASA's Hubble Space Telescope compared a new image of the nebula against one it captured in 1997 — and found that a jet of plasma fired from a young, still-forming star had grown noticeably longer over those 29 years. The jet, part of a feature called Herbig-Haro 399, is embedded in the "head" of the sea lemon, located about 5,000 light-years away in the constellation Sagittarius. Researchers say comparing the two images allowed them to measure the jet's speed, offering new insight into how much energy a forming star injects into the space around it. Credit: NASA, ESA, STScI; N. Bartmann (ESA/Hubble); Leah Hustak, Christian Nieves, Joseph DePasquale, Alyssa Pagan (STScI); Contributors: Subaru Telescope, R. Gendler; Acknowledgement: G. Bacon, J. Muzerolle, F. Summers (STScI)