Space/Science — HabitableZone

Space/Science » in reply to re: How about old OCs?

The Older OCs should contain many Habstars.
Hank — (archived)

Clusters that old will only contain old stars, any which haven't evolved off the main sequence yet (probably the majority) will by definition be suitable targets. Older stars are more common than young ones, and obviously, longer lived. Since the cluster is X billion years old, all stars, hence, any unevolved main-sequence stars, will also be that age, and those will be in pretty much the same condition as when they first formed. Perfect sites for biological evolution.

The more massive, brighter, giants are have already evolved past the point where they fried any worlds surrounding them, and the burned out white dwarfs have already past that stage too and will be lifeless, but the bulk of the remainder should be viable targets. Of course, you won't be listening to individual stars, you'll have the entire cluster and surrounding disk population in your line of sight as well in your reception lobe.

My preliminary review of the field showed 14 known OCs in 1995 with ages exceeding 2.0 billion years, in good agreement with published results in DeLa Fuente Marcos and Turnbull/Tartar. A search through the literature today should turn up many more, there's been a lot of work in this field lately. You really need to read those monographs.

As for frequencies, I would suggest a harmonic of the 21 cm line of neutral hydrogen (approx 1428 MHz), although that sounds like it's outside the range of your equipment. Perhaps a harmonic of one of the other common molecular emission frequencies might fall in your band and be detectable by your gear. If you listen right at the natural emission frequencies, the noise will drown out the ET signal, but they'll know this too and transmit at a harmonic of half or twice the wavelength.

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