What are white dwarf stars?

Summary Unlike most stars, which usually look white, blue or orange some of these stars may have unusual colours. Most stars appear white, blue or orange but some white dwarfs may have unusual colours because of the elements found in their outer layers. Scientists also found elements such as iron and magnesium in the outer layers of some white dwarfs. These materials are commonly found in rocks suggesting that rocky objects may once have existed near these stars. AI Generated Summary Scientists have studied a rare type of star that could appear green to the human eye. Unlike most stars, which usually look white, blue or orange some of these stars may have unusual colours. Studying them could help researchers learn more about stars and planets that existed in the past. According to a report published by CNN, the research was led by astronomer Mark Hollands from the University of Warwick in the United Kingdom and his colleagues. The team examined 151 white dwarf stars located relatively close to Earth. Some of these stars showed unusual colours. The findings were published in the scientific journal RAS Techniques and Instruments. What are white dwarf stars? White dwarfs are the remains of stars that have reached the final stages of their lives. Stars similar to our Sun may also become white dwarfs when they use up most of their nuclear fuel. These stars are relatively small but extremely dense. Although they no longer produce energy in the same way as younger stars they can continue to shine for billions of years. Most stars appear white, blue or orange but some white dwarfs may have unusual colours because of the elements found in their outer layers. Why could some stars look green? The researchers found that certain white dwarfs contain elements such as calcium, sodium and lithium. These elements can affect the light coming from a star and change how its colour appears. Scientists also found elements such as iron and magnesium in the outer layers of some white dwarfs. These materials are commonly found in rocks suggesting that rocky objects may once have existed near these stars. However the presence of these elements does not necessarily mean that a planet once orbited every star studied. What can these stars tell us about ancient planets? When a rocky object moves too close to a star the star's strong gravity can break it apart. The remains may then fall onto the star and mix with its outer layers. By studying these materials scientists can learn about the chemical makeup of objects that once existed around the star. This method may help researchers understand what ancient planets asteroids and other rocky bodies were made of even when those objects no longer exist. Scientists also find a star that may look pinkish orange The research also identified another white dwarf that could appear pinkish orange to the human eye. Scientists believe that its colour may be linked to a high amount of carbon in its outer layers. Professor Agnes Kim from the University of Scranton in the United States who was not involved in the research said the study builds on existing scientific knowledge. Although it may not reveal an entirely new phenomenon the method used to understand stellar colours is interesting. She noted that it is fascinating to imagine how these stars might look if they were close enough to observe directly. How do scientists identify the colours of distant stars? These stars are too far away for scientists to examine them directly. Instead, researchers study the light they emit. They use a method called spectroscopy which separates light into different wavelengths. By examining these wavelengths scientists can identify elements in a star and learn more about its properties. The colour and temperature of a star along with the elements found in its atmosphere can help researchers classify it and understand why it looks different from other stars. More white dwarf stars could be studied in the future Mark Hollands and his team plan to study more white dwarf stars to find out whether other examples with unusual colours exist. Many stars have not yet been examined in enough detail to reveal all their properties. New scientific instruments may help researchers collect better information about stars located much farther from Earth. Hollands estimates that the number of white dwarfs with detailed light records could increase by around ten times in the future. He also suggested that the number of potentially green looking white dwarfs could grow from one or two known examples to around 10 or 20 as more stars are studied. However this is a prediction, not a confirmed discovery. Final Thoughts •What does this discovery mean? The study offers another way to investigate white dwarf stars and the rocky objects that may once have surrounded them. By examining unusual colours and the elements found in these stars scientists can gather clues about their history and the possible remains of ancient planetary systems.