A team of astronomers led by University of Warwick’s Dr. Mark Hollands has converted white dwarf spectra into the colors a human eye would perceive.
The cool white dwarf WD J1330+6435 has accreted sodium-rich rocky material from its planetary system into its atmosphere; the immense atmospheric density causes the sodium to absorb light over broad range of yellow, orange, and red wavelengths, giving the WD J1330+6435 a ghostly green appearance. Image credit: Mark A. Garlick / University of Warwick.
“Most stars, including most white dwarfs, behave like ‘perfect radiators,’ so their color is set almost entirely by temperature,” Dr. Hollands said.
“But nobody had really looked into what else might be possible for white dwarfs.”
“It turns out these incredibly dense stars can produce colors nobody expected, and some of them genuinely surprised me.”
For the 152 white dwarfs within about 65 light-years of the Sun, the median color matches a blackbody of roughly 6,800 K — very close to the white used on computer screens.
The familiar picture of blue-tinted white dwarfs mostly reflects hot, bright ones that dominate surveys of the faintest sky objects.
Only about 3% of the nearby sample, five stars, strayed far from blackbody colors.
Color-accurate simulated images of white dwarfs. Image credit: Mark Hollands / University of Warwick.
Among known stars, though, the astronomers found some striking examples.
WD J1011+2845, a nearby white dwarf just 48 light-years from Earth, shows a deep salmon pink and is likely the reddest star known in perceived color.
“WD J1011+2845 has a deep convection zone that has lifted carbon from its core to its surface,” the researchers said.
“The resulting carbon molecules distort the star’s light so heavily that almost all of it is squeezed into wavelengths beyond 600 nm, producing a deep salmon-pink glow unlike anything seen in an ordinary star.”
The most surprising color — chartreuse green — comes from WD J1330+6435.
“To our knowledge, no other stars of any kind have been claimed to exhibit a green hue, making white dwarfs so far the only known way to produce a green star,” the scientists said.
“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 added.
“Imagine standing on a planet and looking up at a green star. It feels like something out of science fiction.”
Another cool star, WD J2356-2054, is a vivid blue despite a temperature of only around 4,000 K.
“We examined the chromaticity distribution for the volume-limited 65 light-year local sample of white dwarfs finding a median correlated color temperature of 6,800 K, establishing that, on average, white dwarfs are indeed white in color,” the authors concluded.
“We show how white dwarf spectral models can be used to generate color-accurate images of their stellar disks as they would appear from up close.”
The results were published today in the journal RAS Techniques and Instruments.
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Mark A. Hollands et al. 2026. Any colour you like: the diverse chromaticities of white dwarfs. RAS Techniques and Instruments 5: rzag069; doi: 10.1093/rasti/rzag069
