Astronomers have confirmed the discovery of four dead stars hidden within 65 light-years of Earth. The stars had remained unnoticed for decades because they were concealed by the bright light of nearby companion stars.
The discovery was made by scientists from the University of Warwick and the University of Colorado Boulder using the Hubble Space Telescope. Their findings were published in the Monthly Notices of the Royal Astronomical Society (MNRAS).
The newly identified objects are white dwarfs, the remains of sun-like stars after they have used up all of their nuclear fuel. Scientists say our own sun is expected to become a white dwarf in about 5 billion years.
The four white dwarfs had gone undetected because each orbits a red dwarf, a smaller star that shines brightly enough in visible light to hide the white dwarf from view.
Dr. Mairi O’Brien, a research fellow at the University of Warwick and the study’s lead author, said nearby isolated white dwarfs are usually easy to identify. However, these four could only be detected through observations in ultraviolet light.
One of the most significant discoveries was the binary system G 203-47, located about 25 light-years from Earth. It is now considered the ninth-closest known white dwarf system to the sun. In this system, the red dwarf orbits the white dwarf every 14.9 days while rotating on its own axis only once every more than 100 days.
Dr. David Wilson of the University of Colorado Boulder said this difference suggests binary star systems can evolve in different ways. Some may form through violent events, while others, such as G 203-47, likely developed through gentler and shorter interactions.
Professor Pier-Emmanuel Tremblay of the University of Warwick said there could be another nine or 10 similar binary systems nearby because only a small percentage of known red dwarfs have been thoroughly examined for hidden companions.
He added that some of these undiscovered objects could be brown dwarfs, which failed to gain enough mass to become full-fledged stars.