That’s not soon enough.

“And that ignores planets made uninhabitable by atmospheric toxicity and/or acidity, deadly temperatures, radiation exposure, and probably many other factors I can’t think of.”
You have it completely backward. Atmosphere of our planet is full of horrible toxic gas that will burn and kill anything that did not evolve to cope with it. Said gas, by the way, was not present on beginning of planet history.

I have talked about this planet and the HZ in general at http://blog.timesunion.com/weather/the-search-for-e-t-in-exotic-climates/1112/ if anyone cares to discuss this in that forum as well.

Thanks!

Ironically, the reality makes my point even more strongly: at 50 Earth masses, 55 Cancri f is heftier than I thought, and so is not earth-like at all. It is far more likely to be a gas giant of some kind.

A “Hot Saturn” seems right – Neptune has 17 earth masses and Saturn has about 95 so think something in between those. Just withoutr the rings or with rings of dust and rock not bright ice.

If the atmosphere of 55 Cancris f is hydrogen and helium – maybe with lots of methane – what would the likely greenhouse effect be? Anyone?

Life in the clouds perhaps as postulated by Clarke for Jupiter – or maybe on moons? Radiation levels could be an issue there but.

Too little info as yet to assess the chances for life really – more studies neeeded. Not likely to be fit for humans though clearly.

We pull lots of astronomical names out of mythic fiction, so I suggest we rename it the M-Class Habitable Zone, where a planet that is very close analog to earth and its present or past atmosphere would have surface liquid water. That would help distinguish the MHZ from other planets that could have surface liquid water in wider orbits with different atmospheres, and also for habitable bodies that haven’t yet been disproven as potential locations for water based life (Europa and gas giant/ice giant atmospheres).

We can terra-form any exo-planet. Just look at the success our science is having with this one.

Sure we can! We can terraform a habitable planet into an uninhabitable one!

The reverse process? Still working the bugs out, I think….

oh, i’m sure it’s habitable – just not necessarily by us.

But not for very much longer, though, if it’s heading into the subgiant phase.

But the thought occurs to me, if 55 Cancri is really cooler and less massive than Sol, it should be expected to have a slightly longer lifespan on the main sequence. So if Sol is projected to have a 10 billion year main sequence lifespan, at 10 billion years old, 55 Cancri ought to have a little bit more time to go….

(According to wikipedia, 55 Cancri is a super-metal rich star (consistent with it having so many heavy planets), which makes estimation of its age and mass less accurate, though.)