Watching A Disk of Betelgeuse 

(My Experience)

The only star disk we can see through our naked eyes is the Disk of the star that we revolve around "The sun". Besides that, every star we watch appears as a point source of light. But if we have a good telescope, powerful enough to magnify and resolve, we can see a disk of a Betelgeuse Star. 

The brightness and angular radii of a star in the night sky depend on the size of the star and its distance from the Earth. Betelgeuse is one of the finest and best star disks to resolve due to its immense size (764 times the diameter of the sun!). Although the star is 642 light years away from us, it's huge size makes it the best candidate to resolve if one wishes to see a star disk.  

Unlike other stars, Betelgeuse shows irregular fluctuations in brightness. It's not a variable star. We are unable to predict what is happening there. It might be at the end of its life. Through huge telescopes, it's not very tough to resolve a disk of any given star. Through these photos, we see Betelgeuse diverting from its shape multiple times. Below is the image of the disk of Betelgeuse captured by Alma Telescope in Chile. 

The disk of Betelgeuse rarely appears spherical. Even with my amateur telescope, I had never seen Betelgeuse in a spherical shape like other stars. Most of the time, it appears in the shape of a grain of a corn. The amateur telescope I use touches the right power to resolve the disk of the Betelgeuse. The aperture of my telescope is 11 cm and has the max magnification of 1300x. 

With lower magnification, the Betelgeuse appears just like a normal star through a telescope. But increasing the magnification makes it clear that we are watching a corn grain-shaped star which is nothing but Betelgeuse. The corn grain shape is the characteristic of its weird behavior. If you can see it, you have resolved its disk. And you can say that you are looking at the other sun. 

Observations like these don't always give the clearest images but it's a thing of beauty for those who really know the cosmic distances and our leap to understand the universe.