Super-Jupiters having large earthlike moons is a pretty neat concept. I wonder if someday we will be able to check these planets for moons, just as we hope to look for other earthlike worlds?

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A question was asked by ASEI...

Super-Jupiters having large earthlike moons is a pretty neat concept. I wonder if someday we will be able to check these planets for moons, just as we hope to look for other earthlike worlds?

...currently there is no way of directly imaging the moons. Planets swamp the light of their moons. However watching for eclipses and seeing the planet and its moons by their shadows as they dim their star slightly is feasible with a modest space telescope like the planned Kepler mission.

qraal

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I have been asking about "super comets" APOD has this to say about Star CW Leonis

I had read something about the detection of water around another star.

On the Earthly moons around a Juipiter, it does come down to the planet being able to protect itself from the magnetic field of the Joivian planet.

But yeah, it is a neat concept.

Any planetary system with more than one readly habitable planet in the system would certainly encourage interplanetary travel, especially if it were close, like a neighboring moon.

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It would be real nice to find out Big Blue has one or more habitable moons, but for it's distance I'd rather see something closer inhabitable, like Epsilon Eridani which is where the planet Vulcun is supposed to be.

Of coarse right now either are just as impossible to visit, but I don't believe that will always be so. When we finally reach out, it will be to the nearest stars first.

I thought Vulcun was supposed to be closer to Sun than Mercury, this other planet vulcan is a big plus to trekkies, but nothing like the original.

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The planet Vulcun in Star Trek is not in our Solar System. That Vulcun was a hypothetical planet which has never been proven to exhist.

But Vulcun in Star Trek is an rocky planet orbiting Epsilon Eridani, and it would be closer to it's star then Mercury is to our Sun.
This is because the star Epsilon Eridani is an orange K type star. It's life zone is much closer to the star then ours is.

Since we have yet to begin to discover Earth sized planets, it's not out of the question that an Earth like planet could be in that star's life zone.

Live long and Prosper.

I didn't think the habital zone aroung Epsilon Eridani would need to be so close to the star?

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No; the habitable zone (visual wavelengths) for Epsilon Eridani is 0.5 AU, much further out than Mercury is from our sun;

if you add the warming effect of infra-red radiation you get a bolometric habitable zone of about 0.6 AU, nearly as far out as Venus.

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Hi All

Planetwatcher wrote...

It would be real nice to find out Big Blue has one or more habitable moons, but for it's distance I'd rather see something closer inhabitable, like Epsilon Eridani which is where the planet Vulcun is supposed to be.

Of coarse right now either are just as impossible to visit, but I don't believe that will always be so. When we finally reach out, it will be to the nearest stars first.

my reply...

Vulcan is actually thought to be located around 40 Eridani (also known as Keid) some 16.5 light years away, though I have seen discussions of it being even further away. Since no one is too sure how fast warp speeds really are the fact that Vulcan is four days away from Earth at top warp doesn't help.

Gene Roddenberry is said to have backed Keid/40 Eridani as Vulcan's home star. Interestingly Vulcan is also said to not have a moon, tho in the movies other planets are clearly visible - implying that it is actually a moon itself of a Jovian planet. In light of our current discussion that's a pleasant coincidence.

qraal

Live Long and Prosper

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So, let's talk about habitable moons of super-jovian planets a bit more.

In an earlier post, I commented that tides would be a problem - that a habitable world would have to have surface water, and that proximity to a super-jupiter would cause massive tides that might make the place uninhabitable. I think I've changed my mind.

Not that there wouldn't be massive tides. But those tides would undoubtedly have spun the moon down until it was tidally locked.

We want a moon that's far enough from the planet to be outside the radiation belts, and therefore it will have a relatively long "month". But it will also be tidally locked, which will give it a very long "day". For instance, Callisto's "day" is 16 days long. I wonder how habitable such a world would be?

Well, I would expect the climate to vary quite a bit between night and day. Almost as much as it varies between summer and winter here on Earth, perhaps more. Probably any life there would evolve a sleep cycle conducive to their night/day cycle, hibernating through the long cold night period and activating during the hot day period.

There is also the variation in position due to orbiting the gas giant. I suppose that any life originating on such a world would become very good at hibernating!

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The planet would have its own active core and thus magnetosphere wouldn't it Thorn? Thus protecting the Moon/Moons for the radiation of the Super-Juipiter?

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Your analysis of mountains is wrong in two ways. First, a larger planet with HIGHER surface gravity would have SMALLER mountains. Seems counterintuitive, but it makes sense if you realize that gravity is the force which keeps mountains small. Mars, for example, has the larest known mountains (and valleys) in the solar system. Also, by nature more massive planets collect thicker atmospheres, so even a very large mountain would not be high enough to produce a significant atmospheric pressure variation from foot to summit. Gravity works against us, making mountains smaller and the atmosphere thicker. On the other hand, high atmospheric pressure is less of an impediment to habitability than you woudl expect. Life thrives in the deepest parts of the ocean where pressures reach thousands of atmospheres. The high pressure is not an issue since it is a uniform force in all directions.

But, anyway, I agree the moons are a good candidate. But one thing you need is a magneosphere. Gas giants tend to have large magnetoshperes, so if you are inside the parent's magnetosphere you are ok. Without a magnetosphere you would lose your atmosphere.

But, a large moon might have a magnetosphere of its own. The driving force of a magnetosphere is a liquid iron core. Mars has no magnetosphere since it's core, although it is iron, probably cooled and stoped producing a magnetic shield billions of years ago. Mars cooled faster than earth because it is smaller and the ratio of volume to surface area is much lower.

So, we need to find a very large moon of HD 28185, much larger even than MArs, or it will cool to quickly. We probably need something close to the mass of earth. Again, earth seems to be "just right" for what we need. Happily, we would expect a massive planet like HD 28185 to collect very large moons, possibly the size of earth or larger. IF it does, there is a very good chance that world would have a magnetosphere, liquid oceans, mild climate, etc. Great real estate indead!


There are some other similar exosolar planets which also seem to be getting the cold shoulder from astronomers. HD 108874 b, for example, has low eccentricity and appears to be in the stars HZ.

PS, http://www.extrasolar.net/evmain.html is an awesoem site for extrasolar planets, and here is a link for

HD 108874 b
http://www.extrasolar.net/planet.asp?PlanetID=196

and

HD 28185
http://www.extrasolar.net/star.asp?StarID=130