> a kind of new matter with unusual property There should be more planets with photosynthesis than intelligent life. Better first step would be to accumulate

> a kind of new matter with unusual property There should be more planets with photosynthesis than intelligent life. Better first step would be to accumulate a long list of planets with anomalous oxygen levels and then focus on those targets for radio analysis or similar. Oxygen is very active chemically and without photosynthesis you don't get much of it in an atmosphere. Theoretically some civilizations could be strongly exhibitionistic or perhaps try to spread a religion or just otherwise be very attention seeking. Just like some human individuals are. If you wanted to gain the attention of every astronomer for thousands of light years, right now we have the tech to dump a couple hundred tons of some weird elements into the sun and for "awhile" until solar wind blows it away the sun would suddenly glow ridiculous anomalously brightly in argon or whatever nonsense element. There was a scientific paper on this general idea and I can't find it. There's a little bit of everything everywhere so if you have sensitive enough instruments you could in theory detect stuff in the sun. I mean, this is literally how we discovered helium... and the astronomers would completely flip their lids if suddenly out of nowhere a hundred tons of iridium instantly appeared in the solar spectra for no apparent reason. Also they'd be able to tell it was relatively pure refined substance, if it was a mere huge asteroid it would have normal asteroid composition, but WTF here's 99% pure ball of I don't know, krypton ice. An extremely exhibitionistic civilization could also dump some kind of organic dye into the sun. It won't last long and there won't be much signal, but it'll look weird as heck in spectrograms for a little while.