After analyzing the data from the Spitzer telescope, astronomers found out that the first interstellar object discovered — the Oumuamua asteroid — was almost half the size of what had been thought before. The research results are published in The Astronomical Journal.
Asteroid 1I / Oumuamua was discovered in October 2017. At first, it was considered a comet, but then astronomers agreed that it was an asteroid, with an unusual cigar-like shape. According to previous data, which scientists obtained using Pan-STARRS 1, Hubble and other observatories telescopes, the length of Oumuamua can be no more than 800 meters. In order to obtain new information about it, NASA astronomers in November 2017 aimed a Spitzer infrared telescope at an asteroid.
However, within two months, the telescope could not fix the traces of Oumuamua. Based on this, astronomers concluded that the size of the asteroid is much smaller than those that Spitzer can “see”. To estimate the size of Oumuamua, the scientists decided to find out with the help of three independent models the limiting dimensions of objects that the telescope can fix. They received the results of 100, 140 and 440 meters – that is, the Spitzer would see an object, the maximum dimension of which is from 100 to 440 meters. Thus, it is precisely within these limits that the length of the cigar-shaped Oumuamua lies.
In addition, astronomers have found that the asteroid reflects ten times more light than comets flying into the solar system. Scientists have made this conclusion due to the temperature of Oumuamua: the smaller it is, the more light and heat it reflects.