As usual with the corporo-media any new astronomy find that can be hyped into some form of sensationalism is pushed for all it's worth. Meanwhile, much more solid and less speculative science - such as the recent experiments generalizing Snell's law of optics to phase angle,i.e.

http://brane-space.blogspot.com/2011/11/re-thinking-of-snells-law.html

Are given short shrift or escape any attention, even on page 34.

Now, as an astronomer, space physicist I am, of course, intrigued by any genuine news that there could possibly be other habitable worlds out there. But, I am also cautious, maybe overly so. I know how difficult it is for random processes of planet formation, or solar system formation, to result in one or more orbs of the right mass to end up in the proverbial "Goldilocks zone" or the habitable region which would make life as we know it possible.

Hence, I do have some moderate enthusiasm for the latest discovery of an apparently "Earth like" planet which has been dubbed Kepler 22b that orbits a sunlike star in the Constellation Cygnus, 600 light years distant. Now so far as we know currently, only two datums are available: the period of the planet - 290 days, and the diameter, estimated to be 2.4 times that of Earth, or about 19,000 miles in diameter.

http://brane-space.blogspot.com/2011/11/re-thinking-of-snells-law.html

Are given short shrift or escape any attention, even on page 34.

Now, as an astronomer, space physicist I am, of course, intrigued by any genuine news that there could possibly be other habitable worlds out there. But, I am also cautious, maybe overly so. I know how difficult it is for random processes of planet formation, or solar system formation, to result in one or more orbs of the right mass to end up in the proverbial "Goldilocks zone" or the habitable region which would make life as we know it possible.

Hence, I do have some moderate enthusiasm for the latest discovery of an apparently "Earth like" planet which has been dubbed Kepler 22b that orbits a sunlike star in the Constellation Cygnus, 600 light years distant. Now so far as we know currently, only two datums are available: the period of the planet - 290 days, and the diameter, estimated to be 2.4 times that of Earth, or about 19,000 miles in diameter.

Assuming the planet is orbiting a sun-like star (essentially a "twin" of our Sun to hear the planet finders tell it) then we can use Kepler's 3rd law (a^3 ~ P^2) to obtain the semi-major axis of the orbit, or the mean distance from its sun. This would work out to be about 0.86 AU or 79 million miles. Roughly 7 million miles beyond the mean distance of Venus from our Sun.

(Bear in mind this doesn't mean Kepler 22b is a hellhole like Venus, because Venus' conditions are not derived from its distance from the Sun, but by an incipient runaway greenhouse effect - which is why we want to avoid it here on Earth!)

What we don't know is the **mass**, and that's important because if the density isn't as high as for the Earth (5.5 g/cm^3) it may not be habitable by ordinary mammalian bipeds because of not being able to retain an atmosphere. We can make the calculations here, assuming the planet is a near sphere, and taking its effective radius as 1.5 x 10^7 m so its volume will be: V = 1.4 x 10^22 m^3. Then for an Earth-like density (D), the mass would be:

M = D x V = (5500 kg/ m^3) (1.4 x 10^22 m^3) = 7.7 x 10^25 kg

The surface gravity, or acceleration of gravity at the surface, can be found from:

g = G M/ R^2

where G is the Newtonian gravitatonal constant, G = 6.7 x 10^-11 N-m^2/kg^2

And g = 10.2 m/s^2

Now, we know the weight is defined: w = mg

(Bear in mind this doesn't mean Kepler 22b is a hellhole like Venus, because Venus' conditions are not derived from its distance from the Sun, but by an incipient runaway greenhouse effect - which is why we want to avoid it here on Earth!)

What we don't know is the **mass**, and that's important because if the density isn't as high as for the Earth (5.5 g/cm^3) it may not be habitable by ordinary mammalian bipeds because of not being able to retain an atmosphere. We can make the calculations here, assuming the planet is a near sphere, and taking its effective radius as 1.5 x 10^7 m so its volume will be: V = 1.4 x 10^22 m^3. Then for an Earth-like density (D), the mass would be:

M = D x V = (5500 kg/ m^3) (1.4 x 10^22 m^3) = 7.7 x 10^25 kg

The surface gravity, or acceleration of gravity at the surface, can be found from:

g = G M/ R^2

where G is the Newtonian gravitatonal constant, G = 6.7 x 10^-11 N-m^2/kg^2

And g = 10.2 m/s^2

Now, we know the weight is defined: w = mg

Of course, the converse might also be true, and this exciting new world might be a gas planet, with no definable surface but only layers of differing atmospheric density, which is not even comprised of oxygen, but more likely methane and ammonia. In that case, it would be an even worse candidate for any hypothetical colonization (assuming the recent superluminal neutrino discovery is for real, and portends FTL travel, allowing us to maybe get to Kepler 22b in 30 years!)

An easy way to arrive at this is simply to apply a ratio of the planet's surface gravity to Earth's which in this case is:

g'/ g = (10.2) / (9.8) = 1.04

In other words, to find a person's weight on the new planet (again, using the assumption it has Earth's density) simply multiply one's Earth weight by a factor 4.85. Hence, a 100 pound woman will weigh 104 pounds, and a 200 pound man will weigh 208 lbs, etc..

Of course, the converse

Clearly then, it doesn't make too much sense to get all worked up

http://brane-space.blogspot.com/2011/09/tackling-intermediate-astronomy_15.html

If the mass, together with the radius-volume computations shows a planet with a density equal to water or less (e.g. 0.687 g/ cm^3 in the case of Saturn), all bets are off....and we had better start looking for other candidates!

g'/ g = (10.2) / (9.8) = 1.04

In other words, to find a person's weight on the new planet (again, using the assumption it has Earth's density) simply multiply one's Earth weight by a factor 4.85. Hence, a 100 pound woman will weigh 104 pounds, and a 200 pound man will weigh 208 lbs, etc..

Of course, the converse

**might also be true**, and this exciting new world might be a gas planet, with no definable surface but only layers of differing atmospheric composition and density, which is not even comprised of oxygen, but more likely methane and ammonia. In this case, life like our own would not survive there, so it wouldn't be an "Earthlike planet" in that sense.Clearly then, it doesn't make too much sense to get all worked up

**until we can obtain the mass**, probably using a method not too dissimilar from the one used for binary star systems, e.g.http://brane-space.blogspot.com/2011/09/tackling-intermediate-astronomy_15.html

If the mass, together with the radius-volume computations shows a planet with a density equal to water or less (e.g. 0.687 g/ cm^3 in the case of Saturn), all bets are off....and we had better start looking for other candidates!

Stay tuned!

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