What do we know about the characteristics of stellar objects, 13,3 billion light years away from us? To receive light from objects like MACS0647-JD, I suppose, it has to has extraordinary dimensions and intensity of electromagnetic radiation. What are the mass, the dimensions and other characteristics for this objects?
Holger, 

I highly recommend you check out the NASA story on the discovery MACS0647-JD, which includes many dimensional facts (mass, distance, age, etc.) and comparisons:

http://hubblesite.org/newscenter/archive/releases/2012/36/full/

From the article: 


  The estimated total mass of the stars in this baby galaxy is roughly
  equal to 100 million or a billion suns, or about 0.1 percent to 1
  percent the mass of our Milky Way's stars.




Measuring the mass of a galaxy is very tricky indeed (especially one as far as 13.3 billion light-years from earth!), but there are a couple different methods that can one can use, see here:

PSU Astro Measuring Mass of Clusters 

And this Physics Stackexchange thread as well:

https://physics.stackexchange.com/questions/123/how-does-one-measure-the-mass-of-a-galaxy-and-other-such-large-quantities