21 Nov 2017

At http://spaceweather.com (November 20th) we have news of another round of solar wind making a rendevous with the Earth in the next few days, coinciding with a mild November here in the UK. We also have an image of an 'interstellar asteroid' first seen by the Pan-STARRS telescope weeks ago when it was thought to be an interstellar comet. It is now classified as an asteroid as it has failed to bring on a cometary show as it approached the Sun. It is passing through the solar system ...

   see also https://phys.org/print430401999.html ... where the asteroid has been given a monicker - Oumuamua. It is dark red in colour. Apparently, it may be metallic but is certainly rocky, and is about 400m inlength - a sort of flying cigar that is rotating. When it passed closest to the Sun it exhibited no display or any evidence of flaring (as a comet would). Is this another example of an EU dud? It is now heading back into interstellar space. Its surface is reddened due to the effects of irradiation from cosmic rays.

The big question of course is how often do interstellar objects pass through our solar system. This one was only spotted by Pan-STARRS and the inference is that other space telescopes do not pick up small asteroids such as this. One estimate, which is provisional, is that at least one a year enters and passes through the solar system (which would include comets as well as asteroids). They simply have not been picked up before so we might be in for a surprise. The interesting thing to note here is that an object passing through would not have time to adopt a safe orbit.