Why White Dwarf Stars Can Appear in Unexpected Colors

What colors can white dwarf stars really be?

White dwarfs are the dense remnants left after Sun-like stars reach the end of their lives. Their name reflects the early examples astronomers found, which were hot and appeared white or pale blue ¹.

But white and blue are not the only possible appearances. A University of Warwick report says white dwarfs can show a wider range of colors, including a star that would appear green to human eyes ¹. The report does not give a complete list of colors or say how common each appearance is.

Why does one white dwarf look green?

The reported star is called WDJ1330+6435. According to the research summary, it has taken in sodium-rich rocky material from its planetary system. This process is called accretion: material falls onto and becomes part of a star ¹.

The summary says the star’s atmosphere is so dense that sodium absorbs light across broad parts of the yellow, orange and red ranges. With less of that light reaching an observer, the star can appear ghostly green ¹. The appearance is not described as a green surface; it is the color of the light seen from the star.

Does a star’s color always show its temperature?

For many stars, color gives a useful clue about temperature. The Warwick report describes cooler stars as orange, stars like the Sun as white, and the hottest stars as pale blue ¹.

That rule does not explain every apparent color on its own. In the reported white dwarf, sodium in the atmosphere changes which parts of the star’s light are absorbed ¹. So astronomers need to consider what the atmosphere contains as well as the star’s temperature.

How do astronomers identify a white dwarf’s color?

The research summary explains the proposed cause through the star’s atmosphere and the wavelengths of light sodium absorbs ¹. A wavelength is a way of describing a particular part of light. Different wavelengths correspond to different colors.

The supplied report does not set out the observing instruments, the full analysis, or the exact method used to determine how the star would look to a human eye. It does describe the finding as research from University of Warwick astronomers and says it was published in a journal of the Royal Astronomical Society ¹. The available source excerpt does not provide the paper’s title or publication details.

What does this discovery tell us—and what remains unclear?

The finding shows why a white dwarf’s name should not be taken as a promise that every one looks white. Atmospheric material can alter the light that escapes, producing an appearance that differs from the familiar white or pale-blue examples ¹.

The information provided here is limited. It does not establish how often white dwarfs have unusual colors, whether other examples have been confirmed, or whether the green appearance is visible without instruments. It also does not provide enough detail to assess the full evidence beyond the research summaries ¹².