Sept. 25 (UPI) -- The interstellar object 'Oumuamua came from somewhere outside the solar system, but where has remained a mystery.
Scientists at the Max Planck Institute for Astronomy, however, have identified four stellar candidates from which the object may have originated.
Astronomers first spotted 'Oumuamua in 2017. Unfortunately, by the time scientists noticed the oblong visitor, it was already moving away from their telescopes, headed back to interstellar space.
Despite the brief visit, scientists were able to gather enough data related to 'Oumuamua's trajectory to retrace its journey through the Milky Way.
Previous attempts to retrace 'Oumuamua's path failed to account for the object's outgassing. Analysis of the interstellar object suggests 'Oumuamua features characteristics of both an asteroid and a comet. And like a comet, 'Oumuamua's ice was sublimated -- heated and turned to gas -- as it passed by the sun.
The outgassing process caused 'Oumuamua to accelerate slightly. The newest attempts to retrace the object's path were the first to account for this outgassing acceleration.
To determine where 'Oumuamua might have come from, astronomers also turned to stellar data collected by the Gaia mission. Scientists modeled the paths of both 'Oumuamua and thousands of stars, looking for crisscrossing trajectories.
Astronomers identified four stellar candidates moving at slow enough speeds. Fast-moving stars don't usually lose orbital control of large objects.
While all of the stars are plausible homes for 'Oumuamua, astronomers acknowledged they have yet to identify a smoking gun. They may be able to identify more candidates after Gaia's third data release, scheduled for 2021, which will feature a wealth of new data on stellar velocities.
Scientists have previously suggested the interstellar object was ejected from a binary star system, while others have argued 'Oumuamua was slung into interstellar space by interactions between giant planets.
"Ejection of 'Oumuamua by scattering from a giant planet in one of the systems is plausible, but requires a rather unlikely configuration to achieve the high velocities found," researchers wrote in their paper. "A binary star system is more likely to produce the observed velocities. None of the four home candidates have published exoplanets or are known to be binaries."