1. Howard says

    of course each planet is millions of light years away. So each one is currently millions of year older now. So each planet that is judged likely to support life has already destroyed itself in the name of god.

  2. Håkon says

    I feel lucky to be alive in such a momentous era. I wonder how our ancestors would have felt, knowing that there were so many other worlds out there.

  3. AggieCowboy says

    @Howard: Considering that the Milky Way Galaxy is only 100,000 light years in diameter and 1000 light years thick…your calculations are a bit off.

    The most distant planet identified to date is approximately 21,500 light years from Earth. It is a single planet system that is (likely) a rocky ball of ice roughly 5.5 times the size of Earth orbiting a red dwarf, OGLE-2005-BLG-390L, at a distance 2.6 AUs.

    @Globalpost: Watch your facts, Milky Way is the name of our galaxy, Sol is the name of Earth’s parent star, thus we live in the Sol (or Solar) System. Space Geeks will eat you for lunch for such a error.

  4. ggrr says

    At 2.5 the Earth’s mass, any atmosphere would dissipate into space given the weak gravitational hold. It would also require an iron core for a magnetosphere against cosmic rays and its solar wind, which is the reason why Mars lost all its air.

  5. Gregory in Seattle says

    Keep in mind that Earth itself could not support life (as it exists now) for almost 8/9ths of its existence, so being the right size and having the right distance from its sun means very little.

  6. Bill says

    @ggrr : Are you trying to set a record for the number of errors that can be crammed into three lines?

    FYI the gravitational field (Newton’s version is more than adequate here) is proportional to the planet’s mass and inversely proportional to the square of its radius. If a planet with a mass 2.5 times that of ours can’t keep its atmosphere, why do we have one?

    Both Jupiter and Saturn are not believed to have iron cores, but rather liquid metallic hydrogen cores, and both have a magnetic field. Iron isn’t required. The earth’s magnetic field is not the result of a permanent magnet, but rather due to having a rotating molten core that is conductive. Meanwhile Venus has an induced magnetic field due to the interaction of the solar wind with Venus’ ionosphere, but it is much weaker than ours. Yet in spite of being closer to the sun and less massive than the earth, it has kept its atmosphere.

  7. AggieCowboy says

    @GGRR: You need to add ‘molten’ in there. Mars likely has a solid core and, therefore, can no longer generate a magnetosphere.

    Nor is an iron core required. Super-Earths may be too massive to have differentiated layers, but can generate magnetospheres by a different mechanism.

  8. Bill says

    @ggrr : if you really want to know the mechanisms, read up on magnetohydrodynamics.

    Before you can even begin to understand Maxwell’s equations and the Navier-Stokes equations, you’d have to know far more physics than is covered in basic courses that explain Newton’s law of gravity, so you have a lot of work to do.

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