The third interstellar visitor (3i) to our Galaxy is throwing up a number of questions regarding interplanetary visitors.
Since it's detection and identification as an interstellar object, 3i has undergone several phase changes as it continues it's rapid journey through teh solar system.
Several of the changes have surprised scientists, who are trying furiously to pigeonhole the object as "Just a comet".
First the object arrives in the solar system with a "coma", surrounded by gas. Initially the gas was identified as Carbon Dioxide, with a small amount of water vapour. With none of the Carbon Monoxide that has been seen with stellar object from our own solar system.
So it was different, but not by a magnitude. Say, 1 on the strangeness level.
It was also noted that the coma was produced further out from the Sun that is normal for stellar comets. That far out, the Sun wouldn't normally have the energy to sublimate CO2 from the surface of the object.
Then further observations noted the presence of nickel in the spectrum of light reflected by the object. Nickel is not unusual in the makeup of asteroids, but again with stellar asteroids it's generally combined with iron. The processes that produced the rocky fragments in our own solar system appear not to be able to produce one without the other.
3i/Atlas now rates a 2 or 3 on the strangeness level.
Initial observations made as the object approached the Sun show that the coma was not forming into the normal comet tail. In fact it was forming an "anti-tail", with the plume of gases and particles heading toward the Sun. After a number of weeks, the force of the Solar wind is now enough to start pushing the plume away from the Sun. but the anti-tail still exists, it's just the output of 3i/Atlas is being pushed away from the Sun after initially being directed toward it.
Strangeness level now at 4
Finally, the Spectrum of light emitted/reflected from the object has shifted from red to green. Not sure what process would cause that, but scientists explain it away by saying the object was coated in red interstellar dust and that the action of the solar wind has stripped the red coating and now the object is showing it's true colour.
Strangeness level now at 5
The latest issue is there are arguments about the amount of light and the type of light the object is emitting. Observations on the polarisation of the light suggests the light is not all reflected. Which means that somehow some of the light we are seeing from the object is actually emitted directly and not reflected. Nothing before has emitted it's own light as far as I'm aware.
Strangeness level now at 6 or even 7
Out of a scale of ten, the object rates at least a 6 for strangeness.
The problem is that not all of the observed effects can be explained by natural phenomena. Scientists are doing a great job of explaining what is happening to 3i/Atlas retrospectively, but no-one has predicted these changes. Which is, to me anyway, this object is so unprecedented.
All we need now is for the larger object to release or split into smaller objects that are captured by the Sun into Solar orbit, or worse still a collision course with the Earth.
Or a course to one of the other planets, like Mars.
Then we'll finally know it's the Alien mothership!
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