A rare star is whizzing across the Milky Way at astonishing speeds, moving at approximately 1.3 million miles per hour (or around 0.1% the speed of light). This L subdwarf star, known as CWISE J124909+362116.0 (or J1249+36 for short), has sparked excitement among astronomers as it might be fast enough to escape the galaxy altogether.
Located just 400 light-years from Earth, J1249+36 is the first hypervelocity star identified within such low mass classifications. The discovery traces its roots back to citizen scientists, who first noticed it during their participation in the Backyard Worlds: Planet 9 project.
These volunteers sifting through fourteen years of data collected by NASA's Wide-field Infrared Survey Explorer (WISE) helped flag this intriguing object, leading to detailed follow-up studies using advanced telescopes. Among those were the Pan-STARRS telescope on Haleakalā and the Keck Observatory on Maunakea, where its astronomical characteristics were unveiled.
This fascinating star is classified as one of the oldest types of stars threading through our galaxy. The research, spearheaded by UC San Diego's Professor Adam Burgasser, has been published in The Astrophysical Journal Letters and is available for preview on arXiv.org.
When first observed, J1249+36 immediately stood out due to its exceptionally high velocity. "This is where the source became very interesting, as its speed and projectile path showed it was moving fast enough to potentially escape the Milky Way," Burgasser remarked.
With the Near-Infrared Echellette Spectrograph (NIRES) at Keck Observatory, investigators measured the star's infrared spectrum, identifying it as an L subdwarf—cooler and less massive than our Sun. Such stars are believed to be remnants of the galaxy's very early generations.
Using this spectral data combined with atmospheric models devised by UC San Diego alumni, they analyzed the makeup of J1249+36. Graduate researcher Efrain Alvarado III expressed enthusiasm over how well their models aligned with NIRES findings, stating, "It was exciting to see our models accurately match the spectrum obtained with Keck's NIRES."
The analysis led astronomers to multiple theories explaining the star's remarkable speed. One scenario proposes J1249+36 was once closely orbiting a white dwarf, which after accumulating too much mass, exploded, propelling J1249+36 at its current velocity.
"If the white dwarf explodes as predicted, its companion star is flung out from the explosion at orbital speed, often with additional burst from the supernova itself," Burgasser explained. Even though this scenario mathematically aligns with the observations, they lack direct evidence due to the explosion occurring millions of years prior.
Another explanation centers around J1249+36 possibly belonging to a globular cluster. Here, interactions with black holes might have created conditions leading to its incredible ejection speed.
“When a star encounters a black hole binary, the dynamics of this three-body interaction can push the star out of the globular cluster,” observed Kyle Kremer, who generated simulations supporting this hypothesis. Yet, locating the original globular cluster remains uncertain.
To unravel these mysteries, researchers aim to analyze the elemental composition found within J1249+36. According to Gerasimov, they seek to identify any chemical fingerprints, which may reveal more about the star's origin.
Irrespective of whether J1249+36's extraordinary speed is due to the remnants of supernova activity or gravitational interactions with black holes, its discovery adds to astronomers' quest to comprehend the Milky Way's past and its cosmic dynamics.
Through continued research, the contributions of citizen scientists, professionals, and students alike carve pathways to connecting the universe's wonders. Volunteers mentioned their efforts alongside key discoveries, citing influences from innovative software created by fellow citizen scientists as critical to finding J1249+36.
Thus, this collaboration highlights the essence of discovery, as it unites enthusiasts and professionals alike driven by curiosity. J1249+36's exhilarating expedition across the Milky Way is more than mere observation; it embodies the shared ambition to understand our universe.
