University of Warwick astronomers discover first known green star

Astronomers from the University of Warwick have identified the first known star that would appear green to the human eye. The discovery, published in RAS Techniques and Instruments, focuses on a white dwarf named WD J1330+6435 located in the constellation Draco, approximately 280 light-years from Earth.

While stellar color is typically determined by temperature—with hotter stars appearing blue and cooler stars appearing orange or red—this white dwarf exhibits a unique chartreuse green hue. Researchers found that the star’s extreme density and chemical composition cause this deviation. The white dwarf has absorbed rocky debris from its former planetary system, enriching its atmosphere with elements such as calcium, lithium, and sodium.

Specifically, the high density of the atmosphere causes sodium atoms to collide constantly with helium atoms, altering their energy levels. This process allows the sodium to absorb a broad range of light in the yellow, orange, and red spectrums, leaving behind a ghostly green glow. The study suggests that white dwarfs can display a much wider variety of colors than previously thought, including pink, purple, and cyan, depending on the specific materials they have consumed.