During a spectroscopic study of the stars of the massive young globular cluster NGC 1866 in the Milky Way's satellite galaxy called the Large Magellanic Cloud, astronomers discovered a faint planetary nebula. The nebula, named Ka LMC 1, is located near the center of NGC 1866.
The image shows NGC 1866 superimposed on a false-color image from the MUSE data cube, with the ionized shell of planetary nebula Ka LMC 1 visible as a red ring. Grayscale insets illustrate the different sizes of ionized shells of singly ionized nitrogen. [N II] and doubly ionized oxygen [O III]. An enlarged Hubble image near the center of the ring reveals the presence of a pale blue star – most likely the hot central star Ka LMC 1. Image credit: AIP / MM Roth / NASA / ESA / Hubble.
NGK 1866 lies at the very edge of the Large Magellanic Cloud, which is approximately 160,000 light-years from Earth.
The cluster is also known as ESO 85-52 and LW 163. discovered 3 August 1826 Scottish astronomer James Dunlop.
NGC 1866 is a remarkably young globular cluster located close enough to us that its stars can be studied individually.
In a new spectroscopic study of the stars NGC 1866, astronomers analyzed spectra obtained with the MUSE integrated field spectrograph on ESO's Very Large Telescope.
They made an unexpected and mysterious discovery: the ionized shell of a planetary nebula.
In a follow-up study, they explored the nature of this object, named Ka LMC 1, using images taken by the NASA/ESA Hubble Space Telescope.
“Planetary nebulae represent a late stage of stellar evolution when the star has used up its fuel (hydrogen) for nucleosynthesis, expands as a red giant with envelope burning processes, and finally loses most of its mass into a huge separated expanding envelope, before the remaining core contracts, becomes very hot, and finally dims to become a white dwarf,” said first author Dr. Howard Bond, an astronomer at Pennsylvania State University and Space Telescope Science Institute. and his colleagues.
“When the temperature of the core exceeds 35,000 degrees, it ionizes the shell, which becomes visible in emission lines at selected wavelengths.”
Hubble images revealed the Ka Nebula's hot central star, LMC 1, the team said.
“Ka LMC 1 really is a mystery: for a young cluster 200 million years old, we require the progenitor star to be quite massive,” said Professor Martin Roth, an astronomer at the Leibniz Institute for Astrophysics Potsdam, the Institute of Physics and Astronomy at the University of Potsdam and the German Center for Astrophysics.
“But such a star would evolve very quickly toward the white dwarf cooling path.”
“We had difficulty reconciling the age of the planetary nebula's expanding shell with the theoretical evolutionary paths of the central star.”
“The object clearly deserves more detailed observation to unravel its nature.”
“This is one of the rare cases where stellar evolution can be caught in action: time scales are typically millions, if not billions of years.”
“However, the massive central evolution of a star is a matter of just thousands of years – and can be correlated with the time scale of the nebula's expansion.”
study was published on November 7, 2025 in the magazine Publications of the Pacific Astronomical Society.
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Howard E. Bond etc.. 2025. Accidental discovery of a faint planetary nebula in the massive young LMC cluster NGC 1866. PASP 137, 114202; two: 10.1088/1538-3873/ae1664
