Betelgeuse Dimming Irregularly

What if a "ship" was travelling from there to here by the shortest route? It would occasionally "eclipse" the sun from the solar system that it is coming from and the effect would become greater as time progressed (years not days).

I believe you are proposing an occultation for this observation. Betelgeuse is a relatively close star but it is still 700 light years away. I would not expect an occultation of a solid "ship" to dim part of the surface as the image shows nor such a large part of the surface. A dust cloud, like the ones seen in this famous NASA image Pillars of Creation, streaming across our line of sight might partially shade this star.

We already know that Betelgeuse is traveling through an interstellar medium at 30 km/s and that this creates a bow shock four light years wide. That media might contain more opaque material that partially blocks the surface. I wonder if the orientation of the bow shock and the dimming region relate?

This gorgeous image (By Rogelio Bernal Andreo - http://deepskycolors.com/astro/JPEG/RBA_Orion_HeadToToes.jpg, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=20793252) shows an earlier image of the entire Orion constellation and the large but dim nebula that this constellation appears in our sky.

There is less material around the red star in the upper left region but in the resolution of this image the surface of Betelgeuse is smaller than one pixel.

Yes, I suppose that occultation is the correct term.

If the ship were at 50% of the way here, it would need to be around 25% of the star diameter to occlude 50% of the star's output.

If the ship is say 0.7 light years away from us, then it would need to be less than 0.05% of the star diameter to occlude 50% of the star. Maybe possible if they are using a solar sail.

Check my maths, at 0.7 light years of a total 700, that's 0.1% for total "eclipse", so .05% for a 50% eclipse.

Is there any indication of the timeframe of the observed changes? are they happening in terms of days/weeks/months or years?

The time frame is within a year, as my original post shows. I don't know if any intermediate images exist between those two but here is the first non-point source image of any star that's not our sun.

This is from 2017 is by the Atacama Large Millimeter/submillimeter Array (ALMA) and is a false color image of the radio telescope data.

The collection of astronomers known as AAVSO have tracked the visible magnitude of Betegeuse and other variable stars. Here is their chart for the past year plus a few months..

Betelgeuse is an enormous star. 0.05% of its diameter is 617,000 kilometers. I trust your math but this means an enormous ship 1 kilometer in diameter would have to be 10 million kilometers away from us. That's between Mars and Earth. It would also have to track with the line of sight path during our one quarter of the way travel around the sun.

I don't think this is a local occultation.

OK, so I'm shot down in flames, but at least that theory seems positively discounted, so we need to identify another that does satisfy the model and the laws of optics.

So what if Betelgeuse is two stars collapsing into each other while rotating. Major diameter is the pair in profile, minor diameter is the pair in line. Heck if the pattern is different on each second pass, then the pair are of slightly different sizes.

If as someone else proposed "She's gonna blow", then it might have already happened and we will see that as time passes.

The angular size of Betelgeuse is about 50 mas (milliarcseconds).

https://en.wikipedia.org/wiki/Betelgeuse

A "spaceship" which would occult half of this would be about 25 mas across. One radian equals 206264806.71915 mas, so if the diameter of the "spaceship" is D, the distance is (206264806.71915 / 25) x D = 8250592 x D.

So, for example, if it were a mile across, it would be 8.25 million miles away.

She's getting ready to blow, sometime in the next 100 centuries, a short time for a star, a long time for a man. (Sorry, Niel)

Maybe when this one blows it will put us out of our misery.

could be right.

Er, actually those changes took place about 700 years ago in Earth terms...