Astronomers have identified the first star exhibiting a distinctly green hue, challenging longstanding assumptions about the range of colors stars can display. The discovery, led by researchers at the University of Warwick, reveals that certain white dwarf stars—dense stellar remnants formed when stars exhaust their fuel and shed their outer layers—can glow in unexpected colors, including green, pink, cyan, yellow, and purple.

The star in question, designated WD J1330+6435, is located roughly 284 light years from Earth. While traditionally white dwarfs are named for their white appearance, scientists have now found that their color can vary significantly due to the interactions between trace elements in their atmospheres and the star’s dense plasma. These stars are roughly the size of Earth but possess densities millions of times greater than that of the Sun’s visible surface.

WD J1330+6435’s atmosphere contains helium along with chemical elements such as sodium, calcium, and lithium. The presence of sodium absorbs light in the yellow, orange, and red parts of the spectrum, while calcium absorbs violet and blue light. When the remaining wavelengths were modeled according to human optical perception, the star’s color appeared as a “ghostly” chartreuse green—a shade comparable to the herbal liqueur of the same name.

White dwarfs are generally not visible to the naked eye and appear as point sources even through telescopes, making direct observation of their color impossible. Instead, scientists rely on detailed analysis of the star’s emitted light spectrum and chemical composition to infer what their colors would look like if seen from close proximity.

According to the research, temperature remains a primary factor influencing stellar color, with hotter stars appearing blue or white and cooler stars tending toward orange. However, white dwarfs deviate from this simplistic model because their dense atmospheres influence how trace elements absorb light. This phenomenon results in the broader palette of colors now observed in some white dwarfs.

Researchers estimate that approximately one in 30 white dwarfs exhibits such unusual coloration. While this may seem a small fraction, given the vast number of white dwarfs in the universe, the implication is that many oddly colored stars exist but go unnoticed due to their faintness and small size.

One of the study’s lead scientists, Dr. Mark Hollands, highlighted the surprise of these findings, noting that the interplay of chemical elements under extreme atmospheric conditions allows these dense stars to produce colors not previously anticipated. Another researcher, Professor Boris Gänsicke, underscored that despite the diversity, the median white dwarf remains white in appearance.

This discovery broadens astronomers’ understanding of stellar remnants and could influence future studies about the composition and evolution of stars after their main sequence stage. It also suggests that the visible colors of stars in the night sky might be more diverse if closer observations were possible. The findings were published in the journal RAS Techniques and Instruments.