Astronomers have announced the discovery of four white dwarf stars in close proximity to Earth that had previously gone unnoticed. The findings, made by a team from the University of Warwick in collaboration with astronomers from the University of Colorado Boulder, were made possible by observations from the Hubble Space Telescope.
These white dwarf stars are located within 65 light-years of Earth. Their presence was obscured by larger, brighter red dwarf stars in their binary systems. These red dwarf companions effectively "drowned out" the light of the white dwarfs in visible wavelengths, making direct observation impossible until now.
"It's a reminder that even in our own cosmic neighbourhood, we can still find surprises if we look in the right way, at the right wavelengths," said Dr. Mairi O'Brien, a research fellow at the University of Warwick.
One of the identified binary systems, G203-47, has now been confirmed as the ninth closest white dwarf to the Sun. The research team was initially drawn to these four systems due to a significant "radial wobble" observed in their red dwarf companions. This wobble indicates the presence of a massive orbiting object, which in these cases was identified as a white dwarf.
Further analysis revealed unusual activity within these systems. For instance, the red dwarf in the G203-47 system rotates approximately once every 100 days but completes an orbit around its white dwarf companion in just 14.9 days. This orbital period does not align with the star's rotation, a phenomenon that suggests varied evolutionary histories for these binary pairs.
"What's fascinating is that G203-47 shouldn't be rotating this slowly if it formed the same way as similar systems," explained Dr. David Wilson, an associate research scientist at the University of Colorado Boulder. "This suggests that these binaries have had very different evolutionary histories. Some underwent violent, prolonged interactions early on that locked them tidally. Others, like G203-47, experienced gentler, briefer encounters that left them in this unusual state."
Professor Pier-Emmanuel Tremblay from the University of Warwick suggested that the universe may hold more undiscovered binary systems. The team estimates there could be as many as nine or ten additional local binary systems yet to be found. "If we put more targeted effort into observing red dwarfs, perhaps we will find more surprises like this," he stated.
The findings have been published by the Royal Astronomical Society.