Astronomers wonder if ‘Oumuamua might be an extraterrestrial solar sail

Artist’s impression of the first interstellar asteroid/comet, “Oumuamua”. This unique object was discovered on 19 October 2017 by the Pan-STARRS 1 telescope in Hawaii. Credit: ESO/M. Kornmesser  Read more at: https://phys.org/news/2018-11-oumuamua-extraterrestrial-solar.html#jCp
Artist’s impression of the first interstellar asteroid/comet, “Oumuamua”. This unique object was discovered on 19 October 2017 by the Pan-STARRS 1 telescope in Hawaii. Credit: ESO/M. Kornmesser

Remember ‘Oumuamua? It was the object that was detected by the Panoramic Survey Telescope and Rapid Response System-1 (Pan-STARRS-1) that appeared to be the first interstellar asteroid humanity has seen. A study by two astronomers from the Harvard Smithsonian Center for Astrophysics (Shmuel Bialy and Prof. Abraham Loeb) now suggests that ‘Oumuamua might be a light sail of extra-terrestrial origin.

The object was first spotted about 40 days after it made its closest approach to the Sun, which indicates that it hadn’t outgassed prior to closest approach — something that a comet would do. However, as it started leaving the solar system, it increased in velocity instead of slowing down as it should have. While most modern theories would see that increase as a side effect of comet outgassing, it would have also affected the spin of ‘Oumuamua — something that was not observed.

So what could have caused ‘Oumuamua to accelerate on its way out of the solar system? Bialy and Loeb postulate that a light sail just 0.3 to 0.9 mm in thickness could survive a journey through the entire galaxy, making it possible that it’s a probe from interstellar space. Since no radio transmissions emanated from ‘Oumuamua, it could be that it’s a defunct solar sail that’s just cruising the galaxy and being blown about by gravity and stellar radiation. In an interview with Universe Today, Loeb said that:

The alternative is to imagine that `Oumuamua was on a reconnaissance mission. The reason I contemplate the reconnaissance possibility is that the assumption that `Oumumua followed a random orbit requires the production of ~10^{15} such objects per star in our galaxy. This abundance is up to a hundred million times more than expected from the solar system, based on a calculation that we did back in 2009. A surprisingly high overabundance, unless `Oumuamua is a targeted probe on a reconnaissance mission and not a member of a random population of objects.

Loeb might be excused for his enthusiasm with the extraterrestrial origin theory; he’s the head chair of the Breakthrough Starshot Advisory Committee, a group that wants to send thousands of small light sails on an accelerated journey to nearby stars.

You can read the paper by Bialy and Loeb here.

 

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One thought on “Astronomers wonder if ‘Oumuamua might be an extraterrestrial solar sail

  1. Interesting idea. That would be an amazing coincidence, though, that an old and defunct space probe just happened to come our way. Unless someone sent it our way on purpose, of course.

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