Astronomers have described their discovery of four new hidden white dwarf stars “local” to Earth as a “surprise”.<\/p>\n
The University of Warwick team used the Hubble Space Telescope to pinpoint the small, dim stars orbiting in double systems within 65 light years of Earth. <\/p>\n
The four white dwarf stars in this “nearby region” of space each have larger and brighter red dwarf companions that had previously concealed them.<\/p>\n
University of Warwick research fellow Dr Mairi O’Brien said: “Nearby isolated white dwarfs are usually easy to find, but we couldn’t see these four stars directly in visible wavelengths because their red dwarf companions were drowning out their light.”<\/p>\n
“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.”<\/p>\n
One of the stellar binaries, known as G203-47, is now officially the ninth closest white dwarf to the Sun.<\/p>\n
The Warwick team, working with astronomers from the University of Colorado Boulder in the US, was interested in the four nearby systems because of a “substantial radial wobble”.<\/p>\n
This describes a phenomenon where a star wobbles back and forth, indicating a massive companion object is orbiting.<\/p>\n
Co-author Dr David Wilson, research associate at the University of Colorado Boulder, explained their findings revealed some unusual activity.<\/p>\n
For instance, G 203-47’s red dwarf rotates once every 100 or so days, but orbits its white dwarf every 14.9 days, meaning they are not tidally synced.<\/p>\n
“What’s fascinating is that G 203-47 shouldn’t be rotating this slowly if it formed the same way as similar systems,” Wilson said.<\/p>\n
“This suggests that these binaries have had very different evolutionary histories. <\/p>\n
“Some underwent violent, prolonged interactions early on that locked them tidally. Others, like G 203-47, experienced gentler, briefer encounters that left them in this unusual state.”<\/p>\n
Prof Pier-Emmanuel Tremblay from the University of Warwick added the team thought there could be as many as nine or 10 additional local binary systems not yet discovered.<\/p>\n
“If we put more targeted effort into observing red dwarfs, perhaps we will find more surprises like this,” he said.<\/p>\n