White dwarfs are usually described as hot, pale remnants of stars like the Sun. A ScienceDaily report on work from the University of Warwick describes a less familiar possibility: some white dwarfs could look pink, yellow, cyan or even green because of the chemistry in their atmospheres.
The standout example is WD J1330+6435. The researchers’ calculations suggest that this white dwarf, reported to have a temperature of about 4,000 degrees Celsius, would appear chartreuse green to human vision. The report calls it the first known star credibly identified as genuinely green, while making clear that this is an inference about its appearance rather than a color seen directly by astronomers.
That distinction matters. The source says no white dwarf is close enough for astronomers to distinguish its color directly with the human eye. Instead, researchers analyzed spectra: measurements that separate starlight into its component wavelengths. They then processed those measurements through a model of human color vision to calculate how each star would appear. The green appearance is therefore model-inferred from starlight measurements, not a direct visual observation or a photograph showing the star’s color.
The proposed explanation is that a white dwarf’s atmosphere can be so dense that small amounts of elements absorb light in ways that differ from those in less dense environments. The report gives an approximate density of 1 gram per cubic centimeter for material in the coolest white dwarf atmospheres, comparable to water and millions of times denser than the Sun’s visible surface. Under those conditions, elements such as carbon, calcium and sodium can interact with surrounding helium plasma and affect a broader range of wavelengths than they otherwise might. For WD J1330+6435, the report attributes the green appearance particularly to sodium absorbing orange light.
The team also examined a sample of 151 white dwarfs within 20 parsecs of Earth. Five had unusual colors: two yellow and three pink. From this, the researchers estimated that about one in 30 white dwarfs across the Universe might have an unexpected color. That is an extrapolation reported by ScienceDaily; the captured account does not give its uncertainty range or enough detail to assess how the estimate was derived.
The other 146 stars had a reported median color temperature of about 6,800 Kelvin, corresponding to white light. The report says this finding challenges the impression that white dwarfs are usually blue: hotter, bluer examples are brighter and can be overrepresented in surveys that select stars by brightness. A nearby sample can offer a different picture of the broader population.
The reported result adds atmospheric chemistry to the usual temperature-based explanation of stellar color. It also has limits: this account is a ScienceDaily report, not the underlying research paper, and the packet does not include the paper’s methods, data, or uncertainty analysis. The spectrum-based color calculation supports a predicted appearance, but how robust that prediction is—and how common unusually colored white dwarfs are—needs more detail than the report provides.