The wonderfully named John Learned of the University of Hawaii theorises that alien intelligences could use Cepheid variable stars as nodes on a sort of intragalactic communications network [via @spacearcheology, who retweeted @swadeshine]:
Jolting the star with a kick of energy – possibly by shooting it with a beam of high-energy particles called neutrinos – could advance the pulsation by causing its core to heat up and expand, they say.
That could shorten its brightness cycle – just as an electric stimulus to a human heart at the right time can advance a heartbeat. The normal and shortened cycles could be used to encode binary “0”s and “1”s.
The team says information could thus be shuttled around our galaxy’s network of 500 or so Cepheids – and out as far as the Virgo cluster of galaxies.
Because a civilisation capable of such engineering feats would be sure to turn them to the task of… er, using stars as Morse keys. This guy has made exactly the mistake that Sam Vaknin was on about.
Sounds like a pretty slow Internet. But I’m comfortable with the assumption that if there’s “life” on that scale, it could seek some means of transmitting information.
It seems reasonable to suppose that someone with the technology to do that will most probably also have the means to *directly* send sufficiently powerful pulses of light to her (its?) destination, with enormously greater speed. Fiddling with a star just to generate modulated light is like using a large ship to physically transport an enormous boulder with the content of a message carved on it, instead of sending the message via email: monstruously slower (and inefficient) just because of the unnecessary involvement of great masses of matter. Of course, if the communicating aliens live on a time scale widely slower/longer than ours (or if they *are* the stars, or live in them), this could be not an issue.
Anyway, using an omnidirectional source of light (such as a star) to send messages only makes sense if you want your message to be received by everyone in the galaxy. (Provided, of course, that you have other options: something that can be taken for granted if you are a mega-technology alien civilization). So, if really someone uses variable stars as some kind of galactic Internet, is probably sending out either some message of cosmic (but absolutely *not* urgent) relevance, or… spam!