Asteroid Day Brief Apr 11
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What is ‘Oumuamua ?
‘Oumuamua, also known as asteroid I/2017 U1, was discovered for the first time in October 2017 by the Pan-STARRS-1 telescope in Hawaii. It is special because it is the only known asteroid from outside our solar system. For this reason, scientists want to collect as much information as they can get from this interstellar object before it leaves the solar system and pursues its journey through the galaxy. They gathered informations about its nature, shape, even the sounds it makes. The question of its origin however was still unclear, until a team led by Alan P. Jackson published in March 2018 a paper reintroducing their hypothesis.
Where did ‘Oumuamua come from ?
The first hypothesis is that it came from a single star system similar to ours, as purported by Jackson’s team, but it seems unlikely. As we know from our solar system, most of the ejected objects are comets and not asteroids, due to differences in orbit and composition. However ‘Oumuamua has a rocky composition more comparable to that of an asteroid than to the icy composition of a comet. This was the first argument put forward by Jackson’s theory.
The team then suggested that the asteroid was in fact ejected from a binary star system. This consists of two stars orbiting each other, which means that compared to a single star system, the ejection mechanism is much stronger. When an asteroid encounters the secondary star of a binary star system it will accelerate its orbit beyond the escape speed of the primary star, which can be seen as a gravitational kick. Hence, this would explain how asteroid ‘Oumuamua was ejected from its original star system.
What now for ‘Oumuamua ?
The asteroid’s trajectory has been modified by its encounter with the Sun and is now heading towards the Leo constellation, according to Bryce Bolin, Senior Researcher at the University of Washington. “It is difficult to predict precisely where ‘Oumuamua is traveling more than couple 100 Myrs into the future due to the complex gravitational structure of the Galaxy.”
What did we learn from ‘Oumuamua’s visit to our solar system ?
“I am still wondering that myself” answered Bryce Bolin. “’Oumuamua is the first sample that we have seen this close from another star system. From what we can tell, it has a surface composition similar to the asteroids in our own solar system. Asteroids are the chemical remnants of the planet formation process, and the fact that we see an asteroid from another star system having a composition similar to asteroids in our own system implies that perhaps the composition of our own planet formation process is common.”
Stay tuned as we might discover more interstellar asteroids soon.
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“Asteroid Day Briefing” is a on going series of summaries and comments about news around the globe related to asteroid science, engineering and planetary defense. Keep up with the news and subscribe to receive our Asteroid Day Briefing.
Image Credit: European Southern Observatory / M. Kornmesser
