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Doodler
2004-Aug-25, 03:04 PM
http://www.space.com/scienceastronomy/super_earth_040825.html


Only 14 times Earth's mass, this one could be rocky. Still a biggun' though.

Argos
2004-Aug-25, 03:15 PM
Iīm glad to know resolution is increasing. Soon, terrestrial planets will start poping all around (well, thatīs my wish).

Ut
2004-Aug-25, 04:43 PM
I hope they don't start popping up anywhere near by. Doomsayers, and Nancy, would have a field day.

Grand Vizier
2004-Aug-25, 05:16 PM
I'm still not quite sure why that can't be a high-temperature Neptune/Uranus. Are we certain that a small gas giant can't have migrated inwards to this orbit?

Still, it's a fascinating idea. I suppose even with such high temperatures on the sunlit side, the gravity might be high enough to retain some atmosphere. But if the atmosphere's thin, wouldn't it all condense out on the dark side? (Liquid helium seas, anyone?)

If the atmosphere were dense enough, I believe it's been shown that convection from dayside to night might distribute the heat, keeping the dark side warm enough - even to the point of there being a possible annular zone with habitable temperatures.

Kullat Nunu
2004-Aug-25, 05:40 PM
I'm still not quite sure why that can't be a high-temperature Neptune/Uranus. Are we certain that a small gas giant can't have migrated inwards to this orbit?

It may be a gas giant, but then it probably has to be very unlike to Uranus or Neptune. It must have formed differently, within the orbit of the larger planet.


Still, it's a fascinating idea. I suppose even with such high temperatures on the sunlit side, the gravity might be high enough to retain some atmosphere. But if the atmosphere's thin, wouldn't it all condense out on the dark side? (Liquid helium seas, anyone?)

If the atmosphere were dense enough, I believe it's been shown that convection from dayside to night might distribute the heat, keeping the dark side warm enough - even to the point of there being a possible annular zone with habitable temperatures.

Well, ESO press release (http://www.eso.org/outreach/press-rel/pr-2004/pr-22-04.html) claims that the atmosphere may be "only" tenth of the mass of the planet... So "thin atmosphere" in this case is very dense on terrestrial planet standards. Most likely heat is very effectively transferred everywhere on the planet.

PS. I found an incorrect fact on the Space.com news release:


And a trio of roughly Earth-sized planets was found in 2002 to orbit a dense stellar corpse known as a neutron star.

The planets (actually really strange ones) around PSR1257+12 were found much earlier, in 1992.

bmpbmp
2004-Aug-25, 06:16 PM
this is a good thing right cause 50 light years away aint that far.

Grand Vizier
2004-Aug-25, 06:33 PM
this is a good thing right cause 50 light years away aint that far.

Yeah, that's pretty close by interstellar standards, which means we could hope to know a lot more as better instruments become available. Awful long way by Solar System standards, though.

But most of these extrasolar planets are within 100 light years or less, because the sensitivity of our current instruments limits us to that radius. It won't always be so.

bmpbmp
2004-Aug-25, 06:35 PM
But are they a threat towards earth

Doodler
2004-Aug-25, 06:37 PM
But are they a threat towards earth

](*,)

I don't think so. Even if there were life there, even if it were intelligent, even if it were technologically advanced, I don't even want to speculate on the escape velocity needed from a planet fourteen times heavier than this one.

The Supreme Canuck
2004-Aug-25, 06:38 PM
No more of a threat then the planets, asteroids and comets in this solar system. Far less of a threat, in fact.

Edit: Dang, beat me to it!

bmpbmp
2004-Aug-25, 06:40 PM
Sorry you confused me on the last one

The Supreme Canuck
2004-Aug-25, 06:44 PM
What I mean is that while it is possible for objects in this solar system to hit Earth (happens all the time, in fact) extrasolar planets are so far away that it is a virtual impossibility that they or any object from their solar systems could impact Earth. Simply put, they can't affect us in any real way.

bmpbmp
2004-Aug-25, 06:45 PM
oh ok i get it now thanks

Grand Vizier
2004-Aug-25, 06:57 PM
oh ok i get it now thanks

Sorry, bmpbmp, I didn't realise you were anxious about this one - but I did stress 'interstellar'. You should bear in mind always that the only objects it is worth having even a twinge of anxiety about are asteroids that cross the Earth's orbit. And even then the odds on one being a danger to civilisation are very low.

When it comes to objects beyond our Solar System - this one, Barnard's Star, is one of the fastest moving:

Barnard's Star (http://www.seds.org/~spider/spider/Misc/barnard.html)

...and it's only moving this way at just over 100km/sec. Now that's approximately 1/3,000 of the speed of light. Still it'll come close in about 8,000 years time - and when I say close, that will be less than 4 light years from here. It won't even be visible to the naked eye at the time, being rather a dim star.

So always check the distance scale before you get worried. (I would assure you that if any local asteroid looks really dangerous, we will be discussing it here in no uncertain terms. )

dvb
2004-Aug-25, 07:05 PM
But are they a threat towards earth

](*,)

I don't think so. Even if there were life there, even if it were intelligent, even if it were technologically advanced, I don't even want to speculate on the escape velocity needed from a planet fourteen times heavier than this one.

Wouldn't the top of the planets atmosphere be closer to the surface in a higher gravity environment? If this were to be the case, a rocket wouldn't have to be launched as high to go into orbit as it would on the earth. Once you're outside the atmosphere, there's no friction, so you can manage a much lower orbit.

This is all based on my first assumption though. Am I correct? 8-[

Avatar28
2004-Aug-25, 07:53 PM
Wouldn't the top of the planets atmosphere be closer to the surface in a higher gravity environment? If this were to be the case, a rocket wouldn't have to be launched as high to go into orbit as it would on the earth. Once you're outside the atmosphere, there's no friction, so you can manage a much lower orbit.

This is all based on my first assumption though. Am I correct? 8-[

Possibly. But you would also have to get to a much higher speed to maintain said orbit. It's getting the speed more than the altitude that's the problem. Just off the top of my head, orbital velocity for a low orbit (say, something equivalent to what the shuttle uses) would probably be 100,000 mph or so. Actually, maybe more than that even, but I've not done the math so I'm probably way off.

earthman2110
2004-Aug-25, 08:09 PM
So always check the distance scale before you get worried. (I would assure you that if any local asteroid looks really dangerous, we will be discussing it here in no uncertain terms. )

:D haha

dvb
2004-Aug-25, 08:13 PM
Wouldn't the top of the planets atmosphere be closer to the surface in a higher gravity environment? If this were to be the case, a rocket wouldn't have to be launched as high to go into orbit as it would on the earth. Once you're outside the atmosphere, there's no friction, so you can manage a much lower orbit.

This is all based on my first assumption though. Am I correct? 8-[

Possibly. But you would also have to get to a much higher speed to maintain said orbit. It's getting the speed more than the altitude that's the problem. Just off the top of my head, orbital velocity for a low orbit (say, something equivalent to what the shuttle uses) would probably be 100,000 mph or so. Actually, maybe more than that even, but I've not done the math so I'm probably way off.

You bring up a very good point here.

Would it not also require a higher velocity to maintain orbit, assuming that the planet is also larger in circumference than the earth?

Ilya
2004-Aug-25, 09:01 PM
Possibly. But you would also have to get to a much higher speed to maintain said orbit. It's getting the speed more than the altitude that's the problem. Just off the top of my head, orbital velocity for a low orbit (say, something equivalent to what the shuttle uses) would probably be 100,000 mph or so. Actually, maybe more than that even, but I've not done the math so I'm probably way off.

It's counterintuitive, but both escape velocity and orbital velocity and proportional to the square root of the planet's mass. Increasing mass 14 times increases orbital velocity "only" 3.75 times - so Space Shuttle would have to go 67,000 mph instead of 18,000 mph. But that assumes the same radius...


Would it not also require a higher velocity to maintain orbit, assuming that the planet is also larger in circumference than the earth?

Larger circumference means greater distance from the planet's center means LOWER orbital velocity. Again, it is inversely proportional to the square root of the distance, so if the planet is twice Earth's radius, orbital velocity will decrease as square root of 2 - down to 48,000 mph. Still no prize :)

Avatar28
2004-Aug-25, 10:06 PM
Larger circumference means greater distance from the planet's center means LOWER orbital velocity. Again, it is inversely proportional to the square root of the distance, so if the planet is twice Earth's radius, orbital velocity will decrease as square root of 2 - down to 48,000 mph. Still no prize :)

Okay, so my first thought of about 50,000 mph would have been better then. Figures. :-?

dvb
2004-Aug-25, 10:06 PM
Cool!

Thanks for the explanation Ilya. :)

Joe87
2004-Aug-26, 12:15 AM
So what would the surface gravity on this planet be? If it's proportional to the orbital velocity, it would be 2.8 g's. Not a very pleasant place for us to live, although evolution would surely be able to generate organisms that could easily cope, given that life got started there.

Ilya
2004-Aug-26, 12:23 AM
So what would the surface gravity on this planet be? If it's proportional to the orbital velocity, it would be 2.8 g's. Not a very pleasant place for us to live, although evolution would surely be able to generate organisms that could easily cope, given that life got started there.

Actually, it's worse. Force (or acceleration) of gravity is directly proportional to the mass (not to square root of mass), and inversely proportional to square of distance. So with 14 times mass, and twice radius, gravity is 14/4 = 3.5 g. Don't ask me why orbital velocity and force of gravity are not proportional to each other - the answer requires rather hairy differential equations, which I used to understand (as in "back in grad school").

One Day More
2004-Aug-26, 06:28 AM
So what would the surface gravity on this planet be? If it's proportional to the orbital velocity, it would be 2.8 g's. Not a very pleasant place for us to live, although evolution would surely be able to generate organisms that could easily cope, given that life got started there.

Actually, it's worse. Force (or acceleration) of gravity is directly proportional to the mass (not to square root of mass), and inversely proportional to square of distance. So with 14 times mass, and twice radius, gravity is 14/4 = 3.5 g. Don't ask me why orbital velocity and force of gravity are not proportional to each other - the answer requires rather hairy differential equations, which I used to understand (as in "back in grad school").

3.5...rather Jupiter with 2.36 though it's a gaseous giant! :wink:
Anyway, would there be ANY organism on Earth that could have a chance there. On that rocky planet-not Jupiter. How 'bout Sperm Whales? They dive outrageously deep: about 1000 feet or something equalling to about 50 atmospheres! :o Correct me if I'm wrong tho.

Edited to clarify which planet I meant.

eburacum45
2004-Aug-26, 06:40 AM
If we assume an Earth-like density, the gravity works out to be 'only' 2.4 gee, diameter 30800 km, escape velocity 27 km/sec.

A high gravity, hot world; perhaps with hydrogen in the atmosphere too.
A cross between Jupiter and Venus.

Not really very Earth-like.

ZaphodBeeblebrox
2004-Aug-26, 06:43 AM
If we assume an Earth-like density, the gravity works out to be 'only' 2.4 gee, diameter 30800 km, escape velocity 27 km/sec.

A high gravity, hot world; perhaps with hydrogen in the atmosphere too.
A cross between Jupiter and Venus.

Not really very Earth-like.

Yeah

Perhaps even a Chthonian World (http://www.orionsarm.com/worlds/Sisyphos.html), right?

eburacum45
2004-Aug-26, 07:10 AM
Yes, thanks for the plug, by the way...
but I think this planet (which hasn't got a name, but we could call it Mu Arae a, or alternately Mu Arae d)

will not be as hot, and will have a thicker atmosphere, and there are other planets in this system
http://www.solstation.com/stars2/mu-arae.htm
(called b and c, by the way)

Chthonian planets are thought to eject other planets from the system as they spiral in, so it probably isn't one of them. But this stuff is all very tentative; every new planet adds lots of data.

Kullat Nunu
2004-Aug-26, 12:31 PM
Yes, thanks for the plug, by the way...
but I think this planet (which hasn't got a name, but we could call it Mu Arae a, or alternately Mu Arae d)

Mu Arae d, Mu Arae a is the star.


Chthonian planets are thought to eject other planets from the system as they spiral in, so it probably isn't one of them. But this stuff is all very tentative; every new planet adds lots of data.

Indeed. I think this planet may be a member of yet another new class of planets, and that is very exciting.

eburacum45
2004-Aug-26, 04:25 PM
a or d, I am going to call it Semele, after the woman who was burned by getting to close to Zeus;
http://www.forteantimes.com/forum/attachment.php?s=4703d2032542ccc8579ce328d7075a97& postid=433087

Ilya
2004-Aug-26, 07:56 PM
If we assume an Earth-like density, the gravity works out to be 'only' 2.4 gee, diameter 30800 km, escape velocity 27 km/sec.

I assumed that with higher mass density would increase as internal materials were more compressed. Granted, the figure "twice the radius" (i.e. 8 times volume) was completely arbitrary, I am willing to bet that with composition identical to Earth, such planet will have LESS than 14 times volume.


A high gravity, hot world; perhaps with hydrogen in the atmosphere too.
A cross between Jupiter and Venus.


Sounds very much like Uranus.

Ilya
2004-Aug-26, 08:01 PM
3.5...rather Jupiter with 2.36 though it's a gaseous giant! :wink:
Anyway, would there be ANY organism on Earth that could have a chance there. On that rocky planet-not Jupiter. How 'bout Sperm Whales? They dive outrageously deep: about 1000 feet or something equalling to about 50 atmospheres! :o Correct me if I'm wrong tho.


Temperature would be the biggest problem. Lack of oxygen, second. If you assume the 14-Earth mass planet at reasonable distance from the Sun, and with oxygen-bearing air...

Then first, water-breathing animals will not even notice the difference. Second, small land animals such as insects deal very well with high gees. Whether they can deal with high pressure is a different story - and depends on just HOW high the pressure is.