During a spectroscopic study of stars in the massive young globular cluster NGC 1866 in a Milky Way satellite galaxy called the Large Magellanic Cloud, astronomers discovered a faint planetary nebula. Named Ka LMC 1, the nebula resides near the center of NGC 1866.

The image shows NGC 1866 superimposed with a false color image from the MUSE data cube, where the ionized shell of the planetary nebula Ka LMC 1 is seen as a red ring. The grayscale insets illustrate the different size of the ionized shells of singly ionized nitrogen [N II] and doubly ionized oxygen [O III]. The magnified Hubble image near the center of the ring reveals the presence of a pale blue star -- most probably the hot central star of Ka LMC 1. Image credit: AIP / M.M. Roth / NASA / ESA / Hubble.

The image shows NGC 1866 superimposed with a false color image from the MUSE data cube, where the ionized shell of the planetary nebula Ka LMC 1 is seen as a red ring. The grayscale insets illustrate the different size of the ionized shells of singly ionized nitrogen [N II] and doubly ionized oxygen [O III]. The magnified Hubble image near the center of the ring reveals the presence of a pale blue star — most probably the hot central star of Ka LMC 1. Image credit: AIP / M.M. Roth / NASA / ESA / Hubble.

NGC 1866 is found at the very edges of the Large Magellanic Cloud, which is approximately 160,000 light-years away from Earth.

Also known as ESO 85-52 and LW 163, the cluster was discovered on August 3, 1826 by the Scottish astronomer James Dunlop.

NGC 1866 is a surprisingly young globular cluster situated close enough to us that its stars can be studied individually

In a new spectroscopic study of NGC 1866 stars, astronomers analyzed spectra obtained with the MUSE integral field spectrograph on ESO’s Very Large Telescope.

They made an unexpected and enigmatic discovery: the ionized shell of a planetary nebula.

In a follow-up study, they investigated the nature of this object, named Ka LMC 1, with images from the NASA/ESA Hubble Space Telescope.

“Planetary Nebulae represent a late stage of stellar evolution, when a star has consumed its fuel (hydrogen) for nucleosynthesis, expands as a red giant with shell burning processes, and finally sheds a large fraction of its mass into a huge detached expanding shell, 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 Penn State University and the Space Telescope Science Institute, and his colleagues.

“When the core becomes hotter than 35,000 degrees, it ionizes the shell, which becomes visible in emission lines at selected wavelengths.”

According to the team, their Hubble images revealed the hot central star of the Ka LMC 1 nebula.

“Ka LMC 1 really is a puzzle: for the young cluster age of 200 million years, we require the progenitor star to be quite massive,” said Professor Martin Roth, an astronomer with the Leibniz Institute for Astrophysics Potsdam, the Institut für Physik und Astronomie at the Universiät Potsdam, and the Deutsches Zentrum für Astrophysik.

“But such a star would evolve very rapidly towards the white dwarf cooling track.”

“We have had trouble to reconcile the age of the expanding shell of the planetary nebula with theoretical evolutionary tracks for the central star.”

“The object clearly deserves more detailed observations to unravel its nature.”

“It is one of the rare occasions where stellar evolution can be caught in the act: typically, the time scales are millions, if not billions of years.”

“The massive central star evolution, however, is a matter of only thousands of years — and it can be calibrated against the expansion timeline of the nebula.”

The study was published on November 7, 2025 in the Publications of the Astronomical Society of the Pacific.

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Howard E. Bond et al. 2025. Serendipitous Discovery of a Faint Planetary Nebula in the Massive Young LMC Cluster NGC 1866. PASP 137, 114202; doi: 10.1088/1538-3873/ae1664