ESA’s Gaia Mission Identifies Stars That May Host Home Of Interstellar Asteroid ‘Oumuamua

M. Kornmesser ESO

One of the key questions about ‘Oumuamua, the first ever interstellar object spotted in our solar system, involves its origin. Astronomers want to know where the space rock came from.

The Max Planck Institute for Astronomy said in a press release that a team of astronomers managed to back track the motion of the interstellar asteroid to identify where it has likely originated.

Using observational data from European Space Agency’s Gaia mission, Coryn Bailer-Jones, of the Max Planck Institute for Astronomy, and colleagues identified four dwarf stars, one of which could be the possible host star of ‘Oumuamua’s home.

The Gaia space observatory collects detailed information about more than a billion stars in the Milky Way galaxy.

Alan Jackson, an astronomer from the University of Toronto who was not part of the research, told NBC News that data from Gaia offer researchers a far better picture of how far away stars are and how they move, which makes tracing back much more accurate.

Using the data of 7 million stars produced by Gaia and 220,000 other stars described in the astronomical literature, Bailer-Jones and colleagues came up with four stars that are possible candidates for the Oumuamua’s home world.

Stars identified as potential home of intestellar asteroid 'Oumuamua
Featured image credit: ESA/Hubble, NASA, ESO, M. Kornmesser

Data suggest that ‘Oumuamua encountered these stars within a couple of light years between one and 7 million years ago.

One of the four is a reddish dwarf star called HIP 3757. It came closest to ‘Oumuamua at least about one million years ago approaching within about 1.96 light-years. This distance is close enough for the cigar-shaped asteroid to have originated from its planetary system if the star has one.

Scientists think that the relative speed of ‘Oumuamua and its host star is likely comparatively slow because objects are typically not ejected from their home system at large speeds.

Unfortunately for HIP 3757, the comparatively large relative speed of around 25 km/s makes it less likely to host the home of ‘Oumuamua. The other candidate is a sun-like star known as HD 292249. It was less close to the asteroid’s trajectory 3.8 million years ago, but with a smaller relative speed of just 10 km/s.

Little is known about the other two but researchers said that each likely came close to the asteroid 1.1 and 6.3 million years ago.

The research did not conclusively identify which of the four stars is the home of the cigar-shaped asteroid. The researchers said that it is even possible that ‘Oumuamua originated from a different star that is too far or too faint to be observed.

“Given that the 7 million stars in Gaia DR2 with 6D phase space information is just a small fraction of all stars for which we can eventually reconstruct orbits, it is a priori unlikely that our current search would find ‘Oumuamua’s home star system,” the researchers wrote in their study, which was accepted for publication by the Astrophysical Journal.