Oumuamua

 

   By Esha Chettri

Physics Department

   On 19^th  October 2017, the first interstellar object visited our solar system. It was later named “ ‘Oumuamua ” and was discovered by Robert Weryk. The fellow astronomer at the University of Hawaii at Manoa, spotted the intriguing object with the Panoramic Survey Telescope and Rapid Response System (Pan- STARRS1) in Hawaii.

   ‘Oumuamua is a Hawaiian word that translated to “scout” is a well-suited name, the strange object is an emissary, a representative of some distant star system we do not know anything about. Prior to entering our solar system, it had been wandering the cold, empty depths of interstellar of the Milky Way for hundreds of millions, or perhaps billions of years, before encountering the sun.

   ‘Oumuamua was originally classified as a comet but the observations later revealed no sign of cometary activity after it passed through the Sun on 9^th September 2017 at an incredible speed of 87.3 kilometres per second. It appeared as a rocky, cigar shaped object with a reddish blue hue. The reflected sunlight from ‘Oumuamua continually dimmed and brightened, telling the astronomers that it was tumbling over in every few hours. Based on the variation of light, the astronomers determined that ‘Oumuamua is up to 400 meters long and highly elongated, estimated to be 10 times more that its width. This aspect is greater than any asteroid or comet observed in our solar system, it may help us find the clues into how other solar systems formed.

    By the time ‘Oumuamua was discovered, it was already on its path to out of the solar system. Given the object’s incredible speed and steep angle relative to the rest of the solar system, ‘Oumuamua was not gravitationally bound to the sun. Hence astronomers were about to monitor the it for merely 11 days. It is already too distant and too dim to be seen with even humanity’s most powerful instruments and no rockets could ever hope to catch up with it. It has left us forever.

     The mysterious visitor had a speed extremely close to the local standard of rest, which is the average velocity of stars in our neighbourhood. However, most of those stars have individual velocities much higher than that. Henceforth it remains a mystery as to why ‘Oumuamua has the speed very close to the average number.

      Lastly, on its way out of the solar system, astronomers were left with one more mystery, ‘Oumuamua seemed to be accelerating, moving away from the sun at a slightly faster pace with every passing day. This wouldn’t be a weird observation for comets as they can have abnormal acceleration profiles due outgassing of materials. This wasn’t the case with ‘Oumuamua as observations revealed no such activity.