Stellar Remnant WD J1330+6435 Discovered 280 Light-Years Away
Astronomers have identified the first known green star, an object designated as WD J1330+6435 located approximately 280 light-years from Earth in the constellation Draco. The celestial body is a white dwarf, which is an extremely dense stellar remnant that has exhausted its nuclear fuel and cast off its outer layers. While most common stars emit green light, their emissions mix with other colors to produce different perceived hues. This specific white dwarf acquired its unusual visual profile through the ingestion of planetary debris.
Atmospheric Sodium and Calcium Create Emerald Glow
Researchers at the University of Warwick determined that rocky fragments from planets and asteroids once orbiting the star crashed onto its surface, introducing sodium and calcium into its atmosphere. Under normal conditions, sodium absorbs a narrow band of orange light, but inside the dense atmosphere of a white dwarf, those atoms constantly collide with helium. This broadened interaction causes sodium to absorb a much wider swath of the visible spectrum, including yellow, orange, and parts of red. Calcium simultaneously absorbs the violet portion of the spectrum, which contributes to the resulting green coloration with a slight yellowish tint. Lead researcher Mark Hollands stated in an institutional release that standing on a planet to look up at such a star would resemble a science fiction scene.
Spectroscopic Analysis and the Search for Neon Anomalies
Direct visual observation of the green white dwarf remains impossible because these remnants are too small and distant for their true coloration to be observed this way. Scientists instead reconstructed the coloration by analyzing the light coming from the star, breaking the spectrum down into its constituent wavelengths, and running computer models to calculate how the object would appear to human vision at close range. This work was published in the journal RAS Techniques and Instruments, detailing how atmospheric compositions dictate the outward appearance of stellar corpses. The same research initiative identified a white dwarf, WD J1011+2845, located 48 light-years away, which emits a deep salmon-pink glow unlike anything previously seen by experts.
Rarity Across Nearby White Dwarf Populations
Unusual stellar hues represent a distinct minority among dead star populations. Out of 151 nearby white dwarfs examined within roughly 65 light-years of Earth, only five displayed non-standard coloration, pointing to a frequency of roughly one in 30 objects exhibiting atypical pigments. Boris Gänsicke explained to Reuters that the phenomenon operates much like mixing paints on a palette, where removing specific chemical ingredients alters the final perceived hue. While the majority of white dwarfs continue to shine with traditional white light, these contaminated atmospheres demonstrate that planetary systems can dramatically alter the optical signatures of stars long after their primary nuclear fusion has ceased.
White Dwarfs Shine in Various Colors
White dwarfs represent the final evolutionary stage for stars of average mass, eventually leaving behind an inactive core composed of carbon and oxygen after the star has exhausted its nuclear fuel and expanded into a red giant. While typical stars appear orange, white, or blue depending primarily on their temperature, white dwarfs can shine across a broad scale of colors due to physical anomalies in their outer layers. These deviations typically arise in the atmosphere from interactions between helium and trace elements such as iron, magnesium, sodium, and lithium, which vary based on the materials the star encountered during its lifetime. Advanced instruments like the Keck Cosmic Web Imager have further revealed that strange filaments emanate from such stellar remnants, causing the space body to resemble a dandelion.
