Astronomers discover 3I/ATLAS – Third interstellar object to visit Solar System

This one is coming in fast, it has an eccentricity of over 6 with the current fits. For point of reference, 1I and 2I have eccentricities of 1.2 and 3.3.

Right now it is mostly just a point on the sky, it is difficult to tell if it is active (like a comet) yet. If it is not active, IE: asteroid like, then the current observations put it somewhere between 8-22km in diameter (this depends on the albedo of the surface). From what we know, we would expect it to likely be made up of darker material meaning given that range of diameters it is more likely to be on the larger end. However if it is active, then the dust coming off can make it appear much larger than it is. As it comes in closer to the sun and starts to warm up it may become active (or more active if its already doing stuff).

It will not pass particularly close to any planet. It will be closest to the sun just before Halloween this year at 1.35 au, moving at 68 km/s (earth orbits at 29-30 km/s). It is also retrograde (IE, it is moving in the opposite direction of planetary motion), for an interstellar object this is basically random chance that this is the case.

Link to an orbit viewer: https://ssd.jpl.nasa.gov/tools/sbdb_lookup.html#/?sstr=3I&vi...

The next couple of weeks will be interesting for a bunch of people I know.

Source: Working on my PhD in orbital dynamics and formerly wrote the asteroid simulation code used on several NASA missions: https://github.com/dahlend/kete

What planets is it passing between?

It is inside jupiter's orbit now, it will come inside Mars for a time. It is almost on the plane of the solar system, not very inclined.

I linked an orbit viewer above if you want to look.

> It is almost on the plane of the solar system, not very inclined.

Is this also random chance or is there a reason why it's so close to the plane of the solar system?

It is also a factor of where our surveys look on the sky. A lot of asteroid surveys have biases to look at the plane of our solar system (since this is where a lot of asteroids are).

It is probably random chance, however there may be some biases from where they come from on the sky (I know people who work on that, but I don't know much about it).

N=3 does not provide very robust statistics yet, give us another decade or two.

We're going to see a lot more of these in the next couple of years due to the new Vera C Rubin observatory.

Also the ELT [1], I believe. (Both come online this year.)

[1] https://en.m.wikipedia.org/wiki/Extremely_Large_Telescope