Astronomers studying the remnants of dead stars have identified a white dwarf that may appear green to the human eye. While most stars are orange, white, or blue, some white dwarfs possess unusual atmospheric chemistry capable of creating unexpected hues, according to a study led by astrophysicist Mark Holland from the University of Warwick in England.
Holland and his team analyzed data from 151 known white dwarfs located within approximately 65 light-years of Earth. By examining the light spectra of these stars, which reveal their chemical composition, researchers were able to calculate how these distant objects might look to a human observer.
One of the white dwarfs attracted attention due to its unusual green appearance. Its atmosphere contains elements such as calcium, sodium, and lithium, providing clues about the material accumulated on its surface. These elements could have originated from rocky bodies of a once-existing planetary system.
When an asteroid or another object approaches a white dwarf too closely, the star's intense gravity can tear it apart. The resulting debris falls onto the star, leaving chemical traces that astronomers can study. This makes white dwarfs valuable sources of information about the past, as analyzing the elements in their atmospheres allows scientists to investigate the composition of planetary material that may have existed around other stars.
Other unusual objects and research methodology
The green star was not the only unusual object in the sample. Holland also discovered a white dwarf whose calculated color was close to salmon-pink, possibly due to a high concentration of carbon molecules. Although these colors cannot be observed directly with the naked eye from Earth, they provide a more tangible way to visualize objects that would otherwise remain mere points of light in the vast expanse of space.
The study, published in RAS Techniques and Instruments, also offers a useful method for classifying white dwarfs based on temperature, atmospheric properties, and color. It is important to note that the conclusions are based on existing astronomical data, not the discovery of a previously unknown star. Nevertheless, they offer a new perspective on how scientists interpret the light from these stellar remnants.
Astronomers expect that new spectroscopic surveys will increase the number of white dwarfs whose light will be analyzed in detail. Holland believes that the available sample could increase tenfold, potentially leading to the discovery of more stars with unusual colors. Currently, the possibility of a green star serves as a reminder that the universe is full of surprises; even the remnants of long-dead stars can hold keys to worlds that once orbited around them, allowing astronomers to reconstruct the history of planets across light-years.