M87, the strongest radio-emitting object in the constellation Virgo. M87 is about 60 million lightyears distant, and has a diameter of about 120,000 lightyears, and contains on the order of 2.7 trillion stars. At radio wavelengths, M87 looks like this:

Actually, according to this website the above image was taken at 327 MHz, the lower end of the microwave band. Interstellar communication is questionable with any conceivable technology due to the time lag. However, microwaves could be evidence of power production, conversion, and transmission. There would be no 'encoding' of information, no modulation of the signals.

So what we may have are 2.7 trillion intelligent species, learning from each other "by example". Alien copycats.

Lots more ideas on Microwave Engineering. A communications satellite is basically a microwave transceiver, using microwaves because they pass through the atmosphere with less interference than other types of transmission. I should point out that these types of spacecraft are the only ones that are commercially profitable. Radar uses microwaves. Your wireless LAN also uses microwaves at 2.4 - 5 GHz. Microwaves also make very very popular and convenient cooking appliances, and also work at 2.4 GHz. I think that's important to keep in mind, especially at dinner time. :-)

I would like to see an image of Galaxy M87 taken in the 2.4 GHz microwave band. I wonder if it would look different?