The artistic vision of Oumuamua - a guest from outside the solar system. Astronomers used IRAC on the Spitzer Space Telescope to limit the infrared radiation from Oumuamua and estimate its size.
A year ago, scientists discovered an unusual object moving in space near the earth's orbit. Several days of observations showed that this is not an ordinary asteroid or comet, because the route was not supported by the gravity of the solar system. It turned out, we face the first interstellar body, which received the name Oumuamua.
Astronomers have long suspected the existence of comets and asteroids in other planetary systems. Perhaps Oumuamua flew in from one of them. Most modern models of the solar system assume that such small bodies are remnants of the era of planetary formation. The study of a rare guest allowed us to obtain information about the similarities and differences in the formation of the system of planets.
Oumuamua has become an important and valuable object for the scientific community. Supervisory companies were fast, because he was rapidly moving away and was weak to detect. Surveys have shown that the object is reddish in color, with no visible spectral signs or hints of gas or dust. All this reveals the nature of a primitive (D-type) asteroid, although it is difficult to find a suitable analogue in the solar system. The variable light curve indicated an extremely elongated shape (length is 6 times longer than width). The IRAC camera on the Spitzer space telescope is now at a distance of 155 million miles from Earth, therefore it is endowed with a completely different viewing angle from Oumuamua than earth telescopes. Scientists sent a camera to a place where, according to calculations, the object should have been a year later, but the 30-hour review did not show anything. But the emission limit was so low that it allowed us to limit several physical properties.
For example, the absence of an IR signal indicates the absence of gas or dust (which is characteristic of a comet). Given the exact composition and reflectivity, we can say that the size reaches a minimum of 240 m (can reach up to 725 m). The object is now too far away for any terrestrial telescope. It again becomes an interstellar mystery, recalling that space is capable of many surprises.