The asteroid come from another world. Interview with young ESA astrophysicist Marco Micheli
For the first time in history, an international group of astronomers has observed an asteroid coming from interstellar space, which travelled for millions of kilometres before starting its long journey within our solar system.
This important discovery, appeared in the journal Nature, involved the Italian researcher Marco Micheli, astrophysicist at the ESA NEO Coordination Centre in Frascati, the European Space Agency’s centre that studies Near-Earth Objects, i.e., asteroids travelling close to the Earth.
Can you tell us about the history-making discovery of the asteroid that has been named ʻOumuamua?
Telescopes located in different parts of the world every day explore the sky in search of new asteroids due to pass near the Earth and continuously identify new ones, which are announced to the international community of astronomers through a website, to allow further data and observations to be collected. On 19 October 2017, the Pan-STARRS telescope, located in Hawaii, detected one of these asteroids, which was made known to astronomers around the world. At that point, using the Optical Ground Station-OGS telescope in Tenerife, Canary Islands, I decided to make further observations and collect new data on this celestial object, which showed that its orbit was different from that of any asteroid in our own solar system. It was a hyperbolic orbit, and therefore this object must have come from another solar system.
How important is this discovery for astronomy?
For the first time in history we have observed an object coming from outside our solar system, which has travelled through the galaxy and ended up following its trajectory around our sun. We know asteroids that travel the opposite direction, that is, are ejected from our solar system, and we had long anticipated that we would be able to observe an object coming from outside. But until now this had never happened.
What characteristics have you observed in the new asteroid?
Apparently, ʻOumuamua didn’t appear to be different from other known asteroids and it looks very much similar to the typical rocks that orbit in the solar system at greater distances from the Earth. It spins on its axis about every 7 and a half hours, which is quite common. However, it shows a great variation in brightness during its rotation, by a factor of 10: this has led us to hypothesize that its length is roughly ten times its width, so its shape is highly elongated. Also, ʻOumuamua travels at a higher speed than any other celestial object in our solar system: this depends on the fact that it comes from outside and it shows that it will leave, without becoming ‘attached’ to a solar orbit.
You are currently working as a researcher at the ESA SSA-NEO Coordination Centre, the European Space Agency’s programme dedicated to the detection of the nearest and most dangerous asteroids to Earth. What made you choose this job?
My passion for astronomy started when I was a child, when I convinced my mother to take me to the astronomical observatory in my home town, Brescia. When I was 14, I attended a summer course organized by Unione Astrofili Bresciani (the local Amateur Astronomer Society) and there I decided that all I wanted to do in life was ‘hunt’ for asteroids. This passion accompanied me until after high school, when I was accepted at the Physics Faculty of Scuola Normale of Pisa. After graduation, I decided to do a PhD in astronomy at the University of Hawaii, where I specialized and met many of the researchers involved in this important scientific discovery. I then received an important job offer from ESA and I took the opportunity to go back to my home country and work at the ESA Centre in Frascati.
What advice would you give to a young person with your own passion for astronomy, who would like to dedicate his/her life to the study of the cosmos?
Personally, I would advise them to take a degree in physics because it is a well-rounded degree that provides an excellent background in many areas. The specialization in astronomy can come later, for example, with the PhD. What is even more important, however, is the experience abroad, which allows you to broaden your horizons and create new contacts, and which gives you the opportunity to join international research teams, such as the team that has made this important discovery published by Nature.