December 2018 Newsletter
On October 24, 2017, the first interstellar object, 1I/‘Oumuamua, was discovered by a small telescope in Hawaii. 1I/‘Oumuamua is thought to have originated in another solar system before its journey took it on a brief tour of our own Solar System. As the first interstellar visitor it was given its own special designation, the number 1 for it being the first of its kind and the letter “I” for interstellar. Even the name,’Oumuamua, means “first messenger” in Hawaiian.
The remarkable opportunity that 1I provides is the first direct study of the properties of solar systems beyond that of our own. Asteroids and comets, the by-products of planetary formation, have been studied for centuries in our own Solar System, but we have not yet had the opportunity to make similar observations of asteroids and comets on the outside. Even given the capabilities of modern-day astronomical observatories and satellites we still cannot observe individual objects the size of asteroids around other stars.
When 1l was discovered our research group at DIRAC took on the task of trying to understand as much as possible about it before it left the Solar System. Within days of its discovery, we were given time on the University of Washington’s telescope at Apache Point in Sunspot, New Mexico. We took images of the asteroid as it passed through the desert skies. Right away we went to work analyzing the data. The photometry revealed that 1I had a reddish color, which Lynne Jones, an expert in our group on observations of the Solar System, realized meant that 1I’s surface composition was similar to our Solar Systems asteroids.
Because of bad weather in New Mexico, we only managed to collect a few hours of data; making inferring properties such as the shape and rotation of 1I difficult to calculate. Luckily, we had an expert on statistics and machine learning in our team, Daniela Huppenkothen, who applied sophisticated statistical techniques to tease out the period and amplitude of the variations in brightness of 1I. The results of many analyses by the DIRAC group revealed that 1I was shaped like a skinny potato and probably had some amount of tensile strength holding it together.
Our group’s findings were published in the Astrophysical Journal Letters.
In addition to our observations of 1I, we wanted to know where it might have come from. Together with Drs. Rory Barnes and Tom Quinn, we investigated the evolution of 1I’s galactic orbit before it encountered the Solar System. We started out with the goal of finding out where 1I came from, but further investigation showed that finding a home star is not as straightforward as we thought due to the complex dynamics of the Galaxy. The orbit of 1I before encountering the Solar System was roughly circular making it possible that it migrated large distances within a relatively short time from some other area in the Galaxy so may never know which solar system was its original home.
We wish to acknowledge the support of the B612 Asteroid Institute, the Charles Simonyi Fund for Arts and Sciences, and the Washington Research Foundation in making this research possible.