Utilizing near-ultraviolet spectroscopy from the NASA/ESA Hubble Space Telescope’s Space Telescope Imaging Spectrograph (STIS), astronomers have uncovered four white dwarf stars orbiting a nearby red dwarf star. These fascinating binary systems are located within 20 parsecs (65 light years) of the Sun, with one of the white dwarfs ranking as the ninth closest to our solar system.
An artist’s impression of a red dwarf and white dwarf binary companion peeking out from behind. Image credit: Mark A. Garlick / University of Warwick.
Astronomers have dedicated decades to studying star neighborhoods, yet white dwarfs remain notoriously elusive.
The newly identified systems—G 203-47, GJ 207.1, LHS 1817, and Wolf 1130—exhibit significant radial wobbles, indicating they are orbited by a massive companion.
Mairi O’Brien, an astronomer at the University of Warwick, stated, “Isolated white dwarfs are typically easy to spot nearby, but these four stars were obscured by their red dwarf companions, which overwhelmed their light.”
“This discovery emphasizes that even within our local universe, hidden surprises await those who investigate at the right wavelengths.”
Astronomers leveraged Hubble/STIS data to achieve comprehensive insights from these four systems.
While white dwarfs are generally prominent in ultraviolet observations, red dwarfs’ intense flares can mimic white dwarf signals, complicating the search.
The team implemented a custom calibration technique to confirm the presence of the four white dwarfs formally.
Among these, G 203-47 stands out as particularly enigmatic. Despite being just 25 light-years away, it took 27 years from initial radial wobble observations to identify its companion white dwarf. This system is now officially recognized as the ninth closest white dwarf to the Sun.
G 203-47 is unique; typical red dwarfs rotate every 100 days, whereas white dwarfs in this system orbit every 14.9 days.
Normally, gravitational tidal forces cause body synchronization, ensuring that the same faces always meet, akin to the Moon and Earth. However, the red dwarf’s slow rotation precludes this.
“Interestingly, if G 203-47 formed like similar star systems, its slow rotation is unexpected,” said Dr. David Wilson, an astronomer at the University of Colorado Boulder.
“This suggests that these binary systems have vastly different evolutionary paths.”
“Some underwent violent interactions early in their existence, while others, like G 203-47, had gentler encounters, creating an unusual configuration.”
These four new white dwarfs have enabled researchers to refine their census of white dwarf populations within 65 light-years.
Significantly, population models had predicted the existence of around four to five closely orbiting white and red dwarf pairs, and the scientists discovered exactly four, aligning with theoretical projections.
Professor Pier Emmanuel Tremblay from the University of Warwick noted, “About 30% of red dwarfs within 20 parsecs have been systematically studied for hidden white dwarf companions.”
“We hypothesize that there could be nine to ten additional binary systems in our local stellar vicinity waiting to be discovered.”
“With more focused observations of red dwarfs, we are likely to uncover more intriguing findings.” The team’s paper is published today in Royal Astronomical Society Monthly Notices.
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Mairi W. O’Brien and others. 2026. Direct detection of white dwarfs in four WD+dM post-common envelope binaries within 20. MNRAS 550 (2): stag1195; doi: 10.1093/mnras/stag1195
Source: www.sci.news
