Our sun is a solitary star, but many stars in the galaxy have companions.
In some systems, stars interact in fascinating ways. One of these stories involves a star called the “blue lurker,” recently studied by NASA’s Hubble Space Telescope in the open star cluster M67, located about 2,800 light-years away.
The blue lurker’s past is dramatic, shaped by its connection to two other stars in a rare triple-star system.
At first glance, this star might seem like an ordinary sun-like star, but its unusually fast spin rate and unique history make it stand out.
The term “blue lurker” might sound like a comic book villain, but it actually describes a rare type of star.
Though it’s part of a special group called “blue stragglers,” it doesn’t appear blue to the naked eye. Its color blends in with other stars, making it appear as if it’s “lurking” among the ordinary stellar population.
The blue lurker spins much faster than most sun-like stars. While normal stars like the sun take about 30 days to complete one rotation, the blue lurker spins in just four days.
This rapid spin puzzled astronomers, but it turned out to be a clue to its incredible history.
Astronomers discovered that about 500 million years ago, the blue lurker’s two companion stars merged into one massive star.
This merger created a giant star, which eventually shed some of its material onto the blue lurker. As it absorbed this material, the blue lurker’s spin rate dramatically increased.
Today, the blue lurker orbits the remnant of this merger—a hot, dense white dwarf. Using ultraviolet spectroscopy, Hubble revealed that this white dwarf is unusually heavy, with a mass of 0.72 times that of the sun.
It is also extremely hot, with a surface temperature of about 23,000°F, nearly three times the sun’s surface temperature. This white dwarf’s high mass and temperature provide evidence of its violent past as the product of two stars merging.
Emily Leiner, an astronomer from the Illinois Institute of Technology, has been studying the blue lurker and its companions. “This star is exciting because it’s an example of how stars interact in a triple system,” she said. “We know these multiple star systems are fairly common, but it’s very complicated to understand their evolution.”
Triple-star systems make up about 10% of all sun-like stars, and their interactions can produce extraordinary outcomes, such as mergers or even explosive events. What makes this case special is how much astronomers have been able to piece together about its history.
“This is one of the few triple systems where we can tell such a detailed story,” Leiner added. “It’s rare to find systems like this where we can trace the entire evolutionary journey.”
The study of the blue lurker sheds light on how stars interact and evolve in complex systems. As researchers continue to study triple-star systems, they hope to uncover even more fascinating stories hidden in the stars. Leiner’s findings were presented at the 245th meeting of the American Astronomical Society.
Source: ESA.
