If you see, in the spectrum of a planet host star, strange chemical elements, it can be a signal from a civilization which is there.
I have no doubt that Brian May would have had a brilliant career in science had he completed his Ph.D. in 1971.
There are many unidentified bands in the spectra of stars. Wide bands are produced by some complex molecules in the interstellar space.
When discs form around stars, there is interaction of angular momentum between disc, planets and parent star, and this interaction affects the rotation of the parent star, and that will affect the lithium abundance.
It's not very fun to do spectroscopy.
Connection between life and radioactive nuclei is straightforward. No life without tectonic activity, without volcanic activity. And we know very well that geothermal energy is mostly produced by decay of uranium, thorium, and potassium.
Let me mention that not all sun-like stars host planets - perhaps about 30% of them are planet-builders. It's not so easy to form a planet!
Spectroscopy can probably answer the question, 'Is there anybody out there?' Are we alone?
The one way to discover about aliens is to tune your radio telescope and listen to the signals.
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