‘Oumuamua: interstellar rock or alien spacecraft?
It was a typical day for astronomer Robert Weryck back in September 2017. He was using the Haleakalā Observatory in Hawai’i to search for unexpected activity in the sky. That night, he discovered something so unexpected, he did not immediately realize how revolutionary it was. While countless rocks and asteroids surround the solar system, this body had a shape and trajectory so unique that it made it stand out from the rest. Sadly, this long, red, cigar-shaped object was seen once and never again because it flew out of the solar system! After tracing back its path, astronomers discovered that it is an interstellar object, or in other words, it is a visitor from outer space. Hence its name ‘Oumuamua, which means “scout” in Hawaiian. For some scientists, this scout is a naturally made interstellar asteroid, but for others, it is interpreted as an alien-made spacecraft.
If ‘Oumuamua had been observed in more detail, maybe this debate would have been solved by now; however, the quick passage of this object through our system gave barely any information to study it. Supporters of the asteroid-type hypothesis have come up with different ideas to explain the observed properties. One possibility is that ‘Oumuamua is made of metals that have turned red due to high energy particles found everywhere in space called cosmic rays. Other scientists suggest that it is made of a combination of carbon, hydrogen, and other non-metal elements found in our bodies. Many different theories, such as being made of frozen hydrogen, have been disproven over time. As for its place of origin, astronomers have come up with a wide range of possibilities. Almost four years later, there is still no consensus about what this object could be!
On the other side of the debate, some scientists have searched for any signs of life that could have come from the scout object. The first efforts were made by the Search for Extraterrestrial Intelligence (SETI) Institute using the Allen Telescope Array, a group of radio telescopes trying to listen for unexpected signs that might be of artificial origin. Other efforts through the Green Bank Telescope in West Virginia did not receive any abnormalities from ‘Oumuamua.
Although this debate started more than three years ago, astronomer and professor at Harvard University Avi Loeb brought it back to the spotlight when he published a book last January. Trying to raise his book to fame, Avi has created controversy around ‘Oumuamua and how astronomers are not open to the possibility of this interstellar object being a light sail made by extraterrestrial life. This and other remarks said by Avi have unfortunately created a ripple effect within the astronomy and astrobiology fields due to his dismissal of all the efforts to think outside the box and look for multiple ways to search for extraterrestrial life that the community has done, creating uneasiness and discomfort through many scientists (but this is topic for an upcoming post).
In the end, Oumuamua is long gone, and the mystery remains. We might never know if it was an interstellar asteroid or an alien spacecraft, but the fact that we received a foreign visitor during our lifetime makes this event a special one even for non-astronomers.
Héctor Delgado Díaz is an astronomer and astrobiologist who is passionate about the search for extraterrestrial life. He studies the efficiency of each observation technique used to look at planets outside the solar system (exoplanets) and creates simulations of how the atmospheres of the exoplanets would look like through the lens of space telescopes.