University of Warwick astronomers identify green and pink white dwarf stars
By modeling human colour vision from stellar spectra, researchers found that high atmospheric density creates green, pink, and purple white dwarfs.
Astronomers from the University of Warwick have discovered that white dwarf stars can display colors outside the traditional blackbody spectrum, including green, pink, cyan, and purple, according to eurekalert.org eurekalert.org
eurekalert.orgeurekalert.orgOpen source ↗. The findings were established using human color vision models applied to observational spectra and published in the journal RAS Techniques and Instruments.
Atmospheric density and spectral shifts
For standard stars, color correlates directly with temperature as a blackbody radiator, ranging from red and orange to white and pale blue. However, in cool white dwarfs, atmospheric density reaches approximately 1 gram per cubic centimeter, which is millions of times denser than the Sun's photosphere. In these extreme conditions, trace elements such as carbon, sodium, and calcium interact with the surrounding dense helium plasma, causing broad absorption across wavelengths and shifting the visible hue away from standard stellar profiles.
Using simulated human color perception based on archival spectral data, the team discovered that star WD J1330+6435 appears chartreuse green. This object, with an effective temperature of roughly 4,000 degrees Celsius, accreted rocky debris containing calcium, lithium, and sodium from its destroyed planetary system. The high density broadens sodium absorption over yellow, orange, and red bands, leaving a green emission profile. The authors reported no other known stars that would appear genuinely green to human vision.
Carbon dredging and population statistics
The team also characterized WD J1011+2845, located 48 light-years away, which appears deep salmon-pink eurekalert.org
eurekalert.orgeurekalert.orgOpen source ↗. In this object, deep convective motions dredge carbon up from the core into the helium atmosphere, where diatomic carbon molecules absorb blue, green, and yellow light, shifting the remaining output past 600 nanometers.
In a volume-limited sample of 151 white dwarfs within 20 parsecs (roughly 65 light-years) of Earth, five exhibited non-standard colors: two yellow and three pink. This indicates that approximately one in thirty white dwarfs exhibits unusual coloration. The remaining 146 stars showed a median color temperature of about 6,800 Kelvin, corresponding to white, correcting observational biases that favored blue white dwarfs in brightness-limited surveys.
