White dwarfs can glow in a surprising range of colors, including one documented for the first time in new research demonstrating how these dead stars can defy their namesake
A recent paper published in RAS Techniques and Instruments describes the first known white dwarf that would appear green to the human eye, along with an assortment of similar stars in other colors.
Generally, cooler stars appear reddish or orange, transitioning toward white and eventually blue as their temperatures increase. However, the new research reveals a much broader range of colors that can occur among these small, dense stellar remnants.
White Dwarfs
These dense objects are the remnants of once Sun-like stars that burned out long ago. Despite being relatively small and technically “dead,” they can remain extremely hot. As a result, many glow in the white-to-blue portion of the visible spectrum, hence their name.
The new research, however, reveals that their colors can also include green, pink, cyan, yellow, and purple, offering a surprising variety of hues that would become apparent if we could observe these distant objects more closely.
“Most stars, including most white dwarfs, behave like ‘perfect radiators,’ so their colour is set almost entirely by temperature. But nobody had really looked into what else might be possible for white dwarfs,” said Dr Mark Hollands, Warwick Prize Fellow in the Astronomy and Astrophysics Group, University of Warwick, who led the work. “It turns out these incredibly dense stars can produce colours nobody expected, and some of them genuinely surprised me.”
What Colors a White Dwarf?
The unusually dense atmospheres of white dwarfs play an important role in determining their colors. Under these extreme conditions, elements such as carbon, calcium, and sodium can interact with helium-rich plasma, absorbing specific wavelengths of light in ways that would not occur in the less dense atmospheres of Sun-like stars. As certain wavelengths are absorbed, the star’s apparent color shifts, much as though a filter had been placed over its light.
Pink or purple hues can result from carbon-rich atmospheres, while yellow colors may arise from elements deposited by asteroids and comets. In relatively cool white dwarfs, interactions involving hydrogen and helium can also produce a cyan appearance.
The first identified green white dwarf, WD J1330+6435, has an atmospheric temperature of approximately 4,000°C. Its unusual coloration results from a combination of calcium, lithium, and sodium, likely originating from rocky material drawn in from its planetary system.
“The traces of sodium in the atmosphere of this white dwarf absorb the orange part of the spectrum, leaving behind a ghostly green glow,” Dr. Hollands said. “Imagine standing on a planet and looking up at a green star. It feels like something out of science fiction.”
Modeling Star Color
This remarkable assortment of colors isn’t commonly visible in our night sky, since most white dwarfs are too distant and faint for their colors to be readily distinguished by the human eye.
Instead, astronomers use spectroscopy to separate starlight into its component wavelengths, revealing information about a star’s temperature, composition, and other physical properties. For the new research, the team processed these measurements using a model that simulates human color vision, allowing them to determine how the stars would actually appear to an observer.
Despite the intriguing findings, the familiar white coloration remains far more common. Of the 151 white dwarfs examined within approximately 65 light-years of Earth, only five displayed unusual colors.
“One in thirty might not sound like a huge fraction, but across the entire population of white dwarfs in the Universe, that is still a lot of oddly coloured stars out there,” Professor Boris Gänsicke, Department of Physics, University of Warwick, concluded. “Yet if we take the median across a representative population of white dwarfs, we found that the average white dwarf really is white.”
The paper, “Any Colour You Like: The Diverse Chromaticities of White Dwarfs,” appeared in RAS Techniques and Instruments on October 14, 2026.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.