Scientists Discover First-Ever Green Star 280 Light-Years Away After It ‘Eats’ Planetary Debris

Astronomers have identified the first documented green star, a white dwarf named WD J1330+6435, about 280 light-years from Earth in the constellation Draco. Its unusual chartreuse-green appearance developed after rocky debris from planets that once orbited it entered its atmosphere.

The same study identified WD J1011+2845, a white dwarf about 48 light-years away that has a rare salmon-pink color and may be the reddest star recorded.

Published in the journal RAS Techniques and Instruments, the research examined 151 white dwarfs to investigate how their atmospheric chemistry affects their visible colors. The results offer a closer look at the unusual ways the remains of stars can appear after their main life cycle ends.

How the Green Star Got Its Color

A white dwarf is the compact core left behind when a low- or medium-mass star runs out of nuclear fuel and sheds its outer layers. These objects are typically white, but their atmospheric composition can change their appearance.

Researchers focused on the green white dwarf after finding evidence that material from its former planetary system had accumulated on its surface. The debris contained elements including calcium, lithium and sodium.

Mark Hollands, an astrophysicist at the University of Warwick in England and lead author of the study, explained the initial finding.

“We first became interested in this white dwarf because bits of planetary material have fallen onto its surface, enriching its outer layers in elements including calcium, lithium and, in particular, sodium,” Hollands said.

Why Sodium Makes the Star Look Green

In ordinary stars, sodium absorbs a narrow range of orange light. In this white dwarf’s extremely dense atmosphere, sodium atoms are repeatedly struck by surrounding helium atoms. These interactions change their energy levels, allowing them to absorb yellow, orange, and some red wavelengths instead of just a narrow band of orange.

That difference changes the color of the light reaching an observer, giving the star its green appearance.

“The end result is that the sodium atoms no longer absorb one very narrow wavelength of orange; they absorb the yellow, orange, and some of the red wavelengths. And what you’re left with is a star that has a beautiful chartreuse green glow, something that wouldn’t be possible for sun-like stars,” Hollands said.

Boris Gänsicke, a University of Warwick astrophysicist and co-author of the research, highlighted the extreme density of white dwarfs. A typical one contains about half the Sun’s mass in a space roughly the size of Earth.

“Because white dwarfs are super-dense stars, they are roughly the size of the Earth, but contain about 165,000 times its mass; even a small amount of sodium blocks out a large amount of the orange light coming out of the star,” Gänsicke said.

The Salmon-Pink Star Has a Different Origin

The second unusual object, WD J1011+2845, gets its color from carbon rather than sodium. Located in the constellation Leo Minor, it displays a salmon-pink hue that researchers believe may be the reddest recorded for a star.

In this case, the carbon comes from deep inside the white dwarf rather than from material falling onto its surface.

“Rather than something hitting the star, in this case the carbon comes out from its deep interior,” Gänsicke said.

To study the objects, researchers combined observations from the Sloan Digital Sky Survey, which used a telescope in New Mexico, with models of white dwarf spectra. Their analysis showed that carbon-rich white dwarfs generally appear pink or purple, while those polluted by planetary debris tend toward yellow. Cooler objects with atmospheres containing hydrogen and helium can look cyan or pale blue.

What Astronomers Learned From the Study

The research connects visible color to the chemical elements present in a white dwarf’s atmosphere. By examining the light these objects absorb, astronomers can identify differences in their composition and better understand the processes affecting them.

Green stars have featured in science fiction, including the comic-book film Supergirl. This discovery provides a documented astronomical example of a color long associated with imaginary worlds.

Hollands reflected on the unexpected result: “It does show that the universe is sometimes just as weird as anything science fiction can conjure up.”