Plate Nº 76 · recorded October 30, 2026
Space & AstronomyReported finding
Astronomers Find First Green Star — and It's a Dead One
The white dwarf WD J1330+6435, at 4,240 Kelvin, would glow chartreuse to the naked eye — the first star found shining green, thanks to sodium absorbing its orange light.
By Marcus Bennett4 min read765 words
In brief
- White dwarf WD J1330+6435 has a surface temperature of 4,240 Kelvin and would appear chartreuse green.
- Only 5 of 152 nearby white dwarfs — roughly 1 in 30 — showed colors unexplained by temperature alone.
- Sodium absorbs orange-yellow light and calcium suppresses violet in the star's ultra-dense atmosphere.
- The research, led by Mark Hollands of the University of Warwick, appears in RAS Techniques and Instruments.
- Sodium, calcium and lithium in the atmosphere suggest the star devoured its former planetary system.
By Marcus Bennett
For the first time, astronomers have identified a star that would look green to the naked eye — and it is a dead one. The object, a white dwarf named WD J1330+6435 with a surface temperature of just 4,240 Kelvin, would glow a shade of chartreuse if you could see it up close, according to research led by astrophysicist Mark Hollands of the University of Warwick in the UK.
The findings, published in RAS Techniques and Instruments, suggest that dead stars may be the only stars capable of shining in "forbidden" hues such as green, purple, and cyan.
"Most stars, including most white dwarfs, behave like 'perfect radiators,' so their color is set almost entirely by temperature. But nobody had really looked into what else might be possible for white dwarfs," Hollands said. "It turns out these incredibly dense stars can produce colors nobody expected, and some of them genuinely surprised me."
Why don't green stars exist?
Stars rarely appear pure white. The cosmos holds red, blue, yellow, and orange stars, but green is conspicuously absent from the lineup.
The reason lies in how starlight works. Stars emit light across the entire electromagnetic spectrum, not just the visible band from red to violet. A star's color comes from the balance of wavelengths in that mix, and temperature sets the balance: hotter objects radiate more short, blue wavelengths; cooler objects radiate more long, red ones.
So even when a star's strongest visible emission sits in the green part of the spectrum, all the other wavelengths washing through the mix make it look white or yellow. Think of the red supergiant Betelgeuse, the yellow dwarf Sun, and the blue supergiant Rigel — temperature paints them all.
What makes white dwarfs different?
A white dwarf forms when a star exhausts its fusion fuel and ejects its outer layers, leaving the exposed core behind. No longer powered by fusion, that core shines with residual heat only. It is extraordinarily compact: up to 1.4 solar masses squeezed into a body roughly the size of Earth.
That compression changes the physics of the atmosphere. In the coolest white dwarfs, atmospheric densities can reach those of liquid water — millions of times denser than the Sun's atmosphere. At such densities, atoms crowd together and interact with their neighbors in ways that dramatically alter how they absorb light.
Hollands and his team wanted to know whether that changed the colors these stellar corpses could produce. They selected dozens of white dwarfs already flagged as spectrally unusual, measured the wavelengths each one emits, and calculated how the human eye would perceive them.
The results were a riot: some appeared pink or purple, others vivid blue or cyan — hues ordinary stars cannot produce. But WD J1330+6435 stood out as the weirdest of the lot, and the researchers called its chartreuse green the "most surprising color."
What gives this star its green glow?
The secret sits in that ultra-dense atmosphere. Elements like sodium and calcium, which normally absorb light at narrow wavelength ranges in ordinary stellar atmospheres, can block much broader swathes of the spectrum when packed together in a white dwarf.
That is exactly what happens here. Sodium absorbs a broad band of orange-yellow light, while calcium suppresses violet. With orange and violet removed, green finally claims the starlight.
"The traces of sodium in the atmosphere of this white dwarf absorb the orange part of the spectrum, leaving behind a ghostly green glow," Hollands said. "Imagine standing on a planet and looking up at a green star. It feels like something out of science fiction."
There is a darker wrinkle. Sodium, calcium, and lithium — all detected in the star's atmosphere — are signatures of rocky material. That evidence points to the dead star having devoured the debris of its own former planetary system.
How common are these colors?
Mostly, white dwarfs live up to their name. Of 152 nearby white dwarfs the team examined, only five — roughly one in 30 — showed colors significantly different from what temperature alone would predict.
Not every odd hue signals planetary cannibalism. But the study suggests these colors can act as a diagnostic tool for astronomers studying the chemistry of dead stars and the remains of dead planetary systems, a field known as necroplanetology.
The findings are preliminary in scope — color predictions rely on models of human perception, not direct observation of hue — but they open a new window into what dead stars swallow.
A green star turns out to exist, and it took a stellar corpse to make one.
via warwick.ac.uk (Original)
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News editor covering regulation, policy and their impact on general science news at SciBeat.
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