{ "@context": "https://schema.org", "@type": "NewsArticle", "@id": "https://badiyaa.com/first-green-star-white-dwarf-wd-j1330-6435/#article", "mainEntityOfPage": "https://badiyaa.com/first-green-star-white-dwarf-wd-j1330-6435/", "headline": "A white dwarf 284 light-years away may be the first green star; sodium soaks up its orange light", "description": "Warwick astronomers ran the star's spectrum through a model of human color vision and got chartreuse; only 5 of 151 nearby white dwarfs showed any unusual color.", "datePublished": "2026-10-18T16:01:00+01:00", "dateModified": "2026-10-18T12:55:52+01:00", "author": { "@type": "Organization", "name": "Badiyaa Editorial Desk", "url": "https://badiyaa.com/author/editorial-desk/" }, "publisher": { "@type": "NewsMediaOrganization", "@id": "https://badiyaa.com/#organization", "name": "Badiyaa", "url": "https://badiyaa.com/", "logo": { "@type": "ImageObject", "url": "https://badiyaa.com/wp-content/uploads/2026/10/badiyaa-logo-color-600x60-1.png", "width": 600, "height": 60 }, "email": "badiyaavideo@gmail.com", "publishingPrinciples": "https://badiyaa.com/editorial-policy/", "correctionsPolicy": "https://badiyaa.com/corrections/", "actionableFeedbackPolicy": "https://badiyaa.com/contact/", "ownershipFundingInfo": "https://badiyaa.com/about/#ownership", "sameAs": [ "https://www.facebook.com/profile.php?id=61595518283625", "https://www.instagram.com/badiyaa.com.ai/", "https://www.threads.net/@badiyaa.com.ai" ], "parentOrganization": { "@type": "Organization", "name": "Rezilient Digital", "url": "https://www.rezilientdigital.com/", "address": { "@type": "PostalAddress", "streetAddress": "Fl No 3, Nav Shyam Sadan, Plot No 38, Pestom Sagar, Chembur", "addressLocality": "Mumbai", "addressRegion": "Maharashtra", "postalCode": "400089", "addressCountry": "IN" }, "sameAs": [ "https://www.linkedin.com/company/rezilientdigital" ] } }, "isAccessibleForFree": true, "inLanguage": "en-US", "wordCount": 934, "image": [ "https://badiyaa.com/wp-content/uploads/2026/10/Illustration_of_Rocky_Debris_around_a_White_Dwarf.webp", "https://badiyaa.com/wp-content/uploads/2026/10/Illustration_of_Rocky_Debris_around_a_White_Dwarf-1024x576.webp" ], "articleSection": "Science", "keywords": "astronomy, stars, University of Warwick, white dwarf", "articleBody": "A burned-out star called WD J1330+6435, about 284 light-years from Earth, would glow chartreuse green if a person could see it up close, according to astronomers at the University of Warwick in England. Their model puts the peak of its visible light at around 500 nanometers, in the green part of the rainbow, and the team knows of no earlier credible report of any green star. That breaks the usual rule. For ordinary stars, color is almost purely a readout of temperature: cool ones look orange, Sun-like ones white, the hottest pale blue. WD J1330+6435 sits at roughly 7,200 degrees Fahrenheit (about 4,000 degrees Celsius), a temperature that would normally produce an orange star. How the Warwick team turned 36 spectra into colors The work is described in Any colour you like: The diverse chromaticities of white dwarfs, by Mark Hollands, Boris Gänsicke and Pier-Emmanuel Tremblay of Warwick with Detlev Koester of the University of Kiel in Germany. It was posted on October 13, 2026 and accepted by the journal RAS Techniques and Instruments; Warwick announced the result on Thursday, October 15. No white dwarf (the dense, Earth-sized core a Sun-like star leaves behind) is near enough for anyone to look at its disc. So the group worked from spectra, the record of how much light a star gives off at each wavelength, and ran them through a model of human color vision. Chromaticity, the term in the title, simply means perceived color. For metal-polluted stars, the oddest group, they recomputed 36 objects with an updated version of Koester’s atmosphere code. Why sodium at the density of water turns a star green The trick is pressure. The coldest white dwarf atmospheres reach about 1 gram per cubic centimeter, as dense as water and millions of times denser than the visible surface of our own star. Packed that tightly against helium, trace atoms smear their absorption over a much wider band of color than they would in a thin gas. WD J1330+6435 has swallowed rocky debris from its own planetary system, which left calcium, lithium and sodium in its helium atmosphere. Sodium blots out orange light and calcium removes violet, so what escapes is weighted toward green. Hollands put it this way: “The traces of sodium in the atmosphere of this white dwarf absorb the orange part of the spectrum, leaving behind a ghostly green glow.” The amounts involved are tiny. The fitted sodium-to-helium ratio is 10 to the power of minus 8.7, which works out to roughly two sodium atoms for every billion helium atoms; calcium comes in at about 1.6 per billion. Once the gas is crushed this hard, a few atoms per billion recolor a whole star. Only 5 of 151 nearby white dwarfs look unusual To see how common odd colors are, the team also took every white dwarf within 20 parsecs (about 65 light-years) of the solar system, a group of 151. Five stood out: two yellow and three pink. That is 5 divided by 151, or 3.3%, which is where the team’s figure of about 1 in 30 comes from. For the other 146, the median color temperature was close to 6,800 kelvin, which reads as plain white to the eye. That corrects a common assumption that white dwarfs are typically blue. Hot, blue ones are brighter, so surveys that pick stars by brightness catch more of them than their true share. The same paper names a possible reddest star on record, WD J1011+2845, 48 light-years away. Convection there has carried carbon up from the core, and the resulting carbon molecules push almost all of its light beyond 600 nanometers, giving a deep salmon-pink. Limits: a noisy spectrum and a color nobody has seen Three caveats matter. First, the green is calculated, not observed; it is what a human eye would register if the star’s disc could be resolved. Second, the authors write that the spectrum of WD J1330+6435 is somewhat noisy, so its true chromaticity could differ slightly. Their confidence rests on a cross-check: a simpler model from their 2021 analysis gave a similar pale green (hex code #EAFFA1). Third, this is not a newly found star. It was analyzed in 2019 and again by two groups in 2021, mainly because its spectrum shows lithium. What is new is the color calculation, built on improved sodium line shapes that pushed the fitted temperature to 4,240 kelvin, close to one earlier estimate. The paper also checks its own claims. Two other stars in the sample of 36, WD J0851+1543 and WD J1351+2645, also come out green but much paler; the first rests on a cleaner spectrum, so the authors call its green status reliable. Even WD J1330+6435 is not uniformly green: their simulated image is most vivid at the center (#D0FFB4) and turns faintly orange in the outermost pixels of the disc. All of this comes from one team, one set of atmosphere models and archival spectra, with no outside group yet repeating the color work. Gänsicke framed the population result plainly: “the average white dwarf really is white.” The next step the authors point to is a search. They describe a vivid blue white dwarf, WD J2356-2054, as a more extreme sodium-rich cousin of the green one at a similar 4,000 kelvin, and expect a continuum of green, cyan and blue stars between the two to turn up in future surveys. The full paper is free to read on arXiv under the number 2610.18966. Further reading arXiv: Any colour you like: The diverse chromaticities of white dwarfs University of Warwick: astronomers reveal the true colours of white dwarf stars Wikipedia: White dwarf Image: NOIRLab/NSF/AURA/J. da Silva, CC BY 4.0 via Wikimedia Commons This article was produced with AI assistance and reviewed by our Editorial Desk. How we work.", "markdown": "https://badiyaa.com/first-green-star-white-dwarf-wd-j1330-6435.md" }