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PostPosted: Wed May 16, 2012 9:24 pm 
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http://scienceblogs.com/startswithabang/2012/05/exoplanet_bullies_make_earth-l.php

According to this article, hot Jupiters make little rocky worlds impossible in their systems. From my limited knowledge in this area, it all seemed to make sense. I was wondering what your thoughts were on this, EDG.

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PostPosted: Thu May 17, 2012 4:20 am 
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They do indeed mess things up for the inner system (even if a world forms after they pass through on their migration, it'll still be affected by the hot jupiter's gravitational influence). Makes sense to me, though I wouldn't say it's "impossible"... just a hell of a lot harder!

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PostPosted: Fri May 18, 2012 7:26 pm 
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I thought several systems that had been discovered had hot jupiters AND other planets farther out? Sure everything we know is the bigger stuff but still, if a super-earth can exist in several systems, I don't see why an Earth-sized world would be "impossible", rare maybe, but not impossible.

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PostPosted: Fri Jul 20, 2012 12:56 pm 
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Looks like Gliese 581g is back on the menu - and it's the most habitable planet we've discovered so far!

http://phl.upr.edu/press-releases/fivep ... planetsnow

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PostPosted: Fri Jul 20, 2012 1:52 pm 
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Well, I have to admit that GL381 throws all my assumptions about habitable planets out the window.

It appears that this Red Dwarf planet might have TWO habitable planets.

WTF!?!??!?!

I thought Red Dwarfs had too small of a habitable zone to have multiple planets within it, but not only are there two planets within the habitable zone, but they are both super-Earths.

Maybe Traveller didn't get things that wrong after all (except for the fixed orbits stuff) and there are LOTS of habitable planets around these Red Dwarf stars. If this is true, then there could be orders of magnitude more habitable planets in our galaxy than previously thought.

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PostPosted: Thu Sep 20, 2012 1:29 am 
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Cyborg IM1 wrote:
Well, I have to admit that GL381 throws all my assumptions about habitable planets out the window.

It appears that this Red Dwarf planet might have TWO habitable planets.

WTF!?!??!?!

I thought Red Dwarfs had too small of a habitable zone to have multiple planets within it, but not only are there two planets within the habitable zone, but they are both super-Earths.


As long as planets are spaced by ratios rather than fixed distances, the variation in the width of the habitable zone with the luminosity of the star doesn't matter. The inner and outer edges are set by temperature limits and the square-cube law, and vary in strict proportion.

On the other hand, according to Dole the problem with red dwarfs is tidal locking. Tidal force goes with the cube of distance rather than the square, so all planets orbiting in the life zones of the cooler M stars, and those in the inner parts of the life zone of most Ks and the rest of the Ms will get tidally locked to their stars before they can develop a breatheable atmosphere. Dole calculated a diminished life zone of which the inner edge is defined by tidal locking rather than excessive heat, but that is not the life zone that is meant in these discovery reports.

These planets might have habitable temperatures. It is even possible that one star might have three planets with habitable mean temperatures. But I'm old-fashioned: I don't call a planet "habitable" until I know not only that it is warm and cool enough, but also that it has a breatheable atmosphere, significant open water, minimally violent weather and vulcanism, bearable surface gravity, not too much ionising radiation at teh surface, and enough insolation in the B+V band to support [genetically-engineered] crops.

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PostPosted: Tue Oct 16, 2012 11:01 pm 
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Holy Dooley!


There is a planet with a mass comparable to Earth orbiting Alpha Centauri B! http://www.spacedaily.com/reports/Nearest_Star_Has_Earth_Mass_Planet_999.html

It's awfully close, and must be blisteringly hot, but it's there. And it's detectable. Detectable! That's mind-boggling. Astronomy deserves to be known for fantastically precise measurement as it is for huge magnitudes.

Detecting a planet of the mass of Earth in the life zone of a Sol-like star is going to be tougher, but I have little doubt that it will soon be possible.

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PostPosted: Wed Oct 17, 2012 12:46 pm 
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Heard about this last night! VERY EXCITING.

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PostPosted: Thu Oct 18, 2012 2:00 am 
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Yes, indeedly. High time we sent a robe that way, what?

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PostPosted: Thu Oct 18, 2012 3:45 am 
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Vile wrote:
Yes, indeedly. High time we sent a robe that way, what?


Yes, because those poor overheated aliens really need a dressing gown around now :-P

Seriously though, this is really exciting stuff. I asked Geoff Marcy (one of the original planethunters) if he knew of anyone looking for planets around Alpha C and Sirius a few years ago when he came to give a talk at UVic, and he said that it'd be really hard to extract a decent planetary signal from the data.... i guess now the technology has caught up! :-)

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