Astronomers have narrowed down four stars where 'Oumuamua, the interstellar object that zipped through the Solar System in 2017, was suspected to be ejected.
Using the data collected by Gaia, a space observatory of European Space Agency, a group of researchers were able to trace back the origin of the mysterious space rock.
Mysterious Visitor From Far Away
Astronomers, who are based in Hawaii, first discovered 'Oumuamua in October using the Panoramic Survey Telescope and Rapid Response System or Pan-STARRS as it came near the orbit of the Earth. Its name translates to "messenger from afar, arriving first."
Since it was sighted for the first time, scientists have been curious about the origins of the long, cigarette-shaped space rock. It is the first known object that has come from outside of the Solar System.
A previous study found that instead of an asteroid as initially thought, 'Oumuamua is actually a comet.
Since comets are believed to be leftovers from the dawn of star systems, it is possible that 'Oumuamua began its journey when it was ejected while planets were being formed. To find where the interstellar visitor came from, scientists from NASA, ESA, and the Max Planck Institute needed to not only trace back the space object's trajectory but also go back in time.
Where 'Oumuamua Came From
"Gaia is a powerful time machine for these types of studies, as it provides not only star positions but also their motions," explained Timo Prusti, a project scientist behind Gaia.
The astronomers looked at the data from the observatory's second release which revealed positions, distance, and motions for more than 1 billion stars within the Milky Way Galaxy. For the study, they needed the radial velocities or how fast an object is moving toward or away from Earth.
To find the home of the comet, the team considered about 7 million stars from the data collected by Gaia. They also used an additional 220,000 stars from existing astronomical literature.
They were able to pin down four dwarf stars where 'Oumuamua might have come from. Two of the stars are identified as HIP 3757 and HD 292249, but little is known about the other two stars. All four had a close encounter with the comet between 1 and 7 million years ago.
"While it's still early to pinpoint 'Oumuamua's home star, this result illustrates the power of Gaia to delve into the history of our Milky Way galaxy," added Timo.
The researchers hope to further pinpoint the exact home of 'Oumuamua when Gaia releases its next sets of data. A planned release in 2020 will have more samples of radial velocity which can be used to reconstruct the trajectories of more celestial bodies in the sky.
The study is published in the Astronomical Journal.