The arXiv is a gold-mine of astrophysics papers awaiting publication in the old hard-copy journals. The paper linked to above discusses just how our Sun’s region in the Galaxy seems to have so many metal-enriched stars. Now when astrophysicists say ‘metal’ they don’t mean silvery solids that conduct well. For some reason they call anything not hydrogen or helium, ‘metals’ – including stuff like carbon and oxygen, by-products of helium fusion and the stuff of our Sun’s eventual white-dwarf corpse, plus most of our bodies. Ignoring 10% hydrogen, our bodies are ‘metals’.
So what’s the paper on about? In a ring around the Milky Way’s Black-Heart (BH), between a radius of 7 to 9 kiloparsecs (we’re roughly at 8 kpc), the stars are heavier, on average, in metals than stars further out or somewhat closer to the BH. Very close to the BH the metals count goes way-up, indicating a very violent history of supernova and explosive mixing, and from out of that dangerous region a metal-enriched ‘wind’ descended onto our part of the galactic disk. This produced a whole bunch of stars which had more metals and, from our current knowledge, more heavy planets like Jupiter.
The researchers suggest that this enrichment was a discrete event rather than a gradual build-up. That’s interesting – I’m going out on a limb, but that implies to me that our present planetary system might be the result of a recent galactic event. The chain of inference weakens rapidly but that in turn implies that our appearance, as intelligent beings, might be related to galactic evolution quite strongly. If we only appeared now in galactic history, then perhaps we are amongst the first clade of sophonts to evolve in our Galaxy.
We all know the Fermi Paradox – nuclear energy allows interstellar travel, thus why haven’t aliens from further back in the past already colonized our system? Why isn’t the Galaxy an Artefact and not a seemingly natural system?
Perhaps the answer is: it is, for now, but not forever.