WD J1330+6435, a white dwarf described as "the first green star", is the subject of NASA's Astronomy Picture of the Day for 22 October 2026. Astronomers have found that trace elements drawn onto some white dwarfs can shift their normally white light into colours such as green, yellow, pink and purple.
Star light, star bright: is there a green star out tonight? Most stars appear as white points of light, with red or blue the only other colours usually noticeable to observers, and those colours mark temperature: blue stars are hotter, red stars are cooler.
NASA's Astronomy Picture of the Day for 22 October 2026 features WD J1330+6435, described as "the first green star". The image, an illustration by Mark A. Garlick of the University of Warwick, shows the white dwarf surrounded by an accretion disk of gas and rocks.
White dwarfs are small, faint stars left behind when a star like the Sun exhausts its nuclear fuel. Astronomers recently found that some white dwarfs would appear yellow, green, cyan, pink or purple rather than white. The cause, the feature explains, is trace elements accreted onto the star: they interact with the stellar atmosphere and shift its normally white colour.
The discovery adds a second influence on a star's appearance. Colour is still a temperature guide, but for these white dwarfs it can also signal what material the star has pulled in. There is one disappointment for skywatchers: the stars in question are too faint to see with the naked eye.
Analysis
Why This Matters
- Star colour is a basic tool of astronomy, usually read as a temperature gauge; these results show that what a star has swallowed can also change its hue.
- WD J1330+6435 and its disk of gas and rocks show debris falling into the star, a record of material in its immediate neighbourhood.
- A literally green star, absent from the familiar palette of the night sky, exists in principle, even if it is too faint to see by eye.
Background
For most stars, colour is a temperature reading: blue means hot, red means cool, and most stars look white. White dwarfs are the small, faint remains of Sun-like stars that have used up their nuclear fuel. The recent finding highlighted by NASA is that some white dwarfs would not look white at all: trace elements accreted onto the star interact with its atmosphere and shift its colour, producing yellow, green, cyan, pink or purple stars.
Key Perspectives
Astronomers: The colour of WD J1330+6435 comes from trace elements interacting with the stellar atmosphere, not from temperature alone. The NASA feature calls it the first green star.
Observers and skywatchers: Whatever their hues, these stars are too faint to be seen with the naked eye, so the colours are descriptions of how the stars would appear, not sights available in the night sky.
Critics and skeptics: The portrait is an illustration, not a photograph. The colours are inferred from how trace elements and the stellar atmosphere would interact, so the palette rests on modelling and calculation rather than direct observation.
What to Watch
- Whether astronomers identify more white dwarfs with shifted colours and how their hues fit the yellow, green, cyan, pink and purple range described.
- The composition of the disk around WD J1330+6435: the gas and rocks shown orbiting the star may be the source of the elements that shift its colour.
- Whether the work leads to colour being used as a quick marker for white dwarfs that are pulling in surrounding material.