Work

Any colour you like: the diverse chromaticities of white dwarfs

Year: 2026

Type: article

Abstract: ABSTRACT Main-sequence stars have perceived colours ranging from orange to white to blue with increasing effective temperature. This is because their atmospheric opacities cause only minor deviations from blackbody colours when integrated over the broad-band sensitivity curves of the human visual system. White dwarfs can have much denser atmospheres, reaching $\sim 1$ g cm$^{-3}$ for the coolest known objects. If metals such as carbon, calcium, or sodium are present in these ultradense atmospheres, extreme broadening of atomic and molecular opacities can produce optical spectra that diverge significantly from blackbodies. We investigated how the combination of temperature and chemical composition can affect the perceived colours (chromaticity) of white dwarfs. While we found that most white dwarfs are similar in colour to blackbodies, we also demonstrate examples of known stars that would appear yellow, green, cyan, pink, or purple if viewed close enough for their stellar discs to be resolved. We examined the chromaticity distribution for the volume-limited 20 pc local sample of white dwarfs finding a median correlated colour temperature of $\approx 6800$ K, establishing that, on average, white dwarfs are indeed white in colour. Finally we show how white dwarf spectral models can be used to generate colour-accurate images of their stellar discs as they would appear from up close.

Source: RAS Techniques and Instruments

DOI: 10.1093/rasti/rzag069

Authors: Mark A Hollands, Boris T Gänsicke, Pier-Emmanuel Tremblay, Detlev Koester

Institutions: University of Warwick, Christian-Albrechts-Universität zu Kiel

Language: English

Topic: Stellar, planetary, and galactic studies

Subfield: Astronomy and Astrophysics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $1,732

Funders: University of Warwick, European Commission, H2020 European Research Council