In reading a paper about the Galactic Habitable Zone, it appears that high metalicity in a star is linked to larger planets being located closer to their suns than here - perhaps fatally preturbing orbits within the stellar region that lifebearing planets must occupy. It is thought that this sets an upper boundry as to how metallic a star system can be before life becomes improbable. My question is - if a Jupiter (or larger) size planet had formed closer to Earth in the Sol system, what are the odds (ballpark) that: a) We'd have been thrown out of the solar system, or into the sun. b) We'd have eventually hit the larger planet. c) Earth would be captured as a moon around the larger planet (ie, life could develop). d) Earth's orbit would be unaffected.
Rather more obviously, an Earth was formed closer to Jupiter's orbit. And now we have an asteroid belt there instead. But if Jupiter had formed at the orbit of Earth, probably there would be no other inner planets at all, but that's simply my guesswork.
If this Nearer-Jupiter were too near to the orbit of the Earth, it might well disrupt the formation of the Earth from the primordial planetesimals; too close and the Earth simply would not form. It is possible that a Nearer-Jupiter forming in a solar system which originally contained more matter and consequently more planetesimals than our own would migrate inwards to the inner solar system. The main mechanism for this seems to be exchange of momentum between the giant planet (which may form relatively quickly) and the multitude of moon-sized planetesimals in such a crowded solar system; as the gas giant migrates inwards it will fling the planetesimals and any newly-formed terrestrial planets out of the sysem, so a solar system with a Hot Jupiter is unlikely to contain any Earth-like planets. If you want an Earth-like planet you should hope for a Jupiter out in the middle regions of the solar system, but no closer; Jupiter apparently migrated inwards during the formation of the Solar system but not by very much. On the other hand a crowded solar system such as that around 55 Cancri is difficult to explain by the migration theory; http://www.extrasolar.net/startour.asp?starid=4 there are so many planets in this system that perhaps one or two terrestrials have managed to become sandwiched between them in harmonic relationships with the big planets; this is just speculation on my part, but we may know more before too long.
No, what happened is that the influence of Jupiter prevented the formation of a planet in the zone of the asteroid belt. In other zones, planetesimals merged to form planets, but in the zone of the belt the planetesimals were unable to form a planet
Eburacum, The link you posted was fantastic! I tell you what, the information provided there just makes me feel like the possibilities for life in our galaxy is far greater than I ever thought possible or plausible. Did it do the same for anyone else?
Yes, that's an interesting link. Current models suggest that the orbit of a terrestrial or sub-Saturn mass planet would be stable at around 1 AU, well within Star A's Habitable Zone. If this is so, then high metalicity appears to reduce the chances of an earth-like planet in the habitable zone, but not eliminate it altogether. How did Saturn and Jupiter come to have moons, if not by capturing them or the material necessary to make them?
Jupiter (and Saturn) probably formed a system of moons by accretion, just like a little solar system; From here Just a few of Jupiter and Saturn's moons were captured; this probably happened much later, and requires at least three bodies or an impact for permanent capture. Phoebe is an example of this sort of moon.
I need to catch up! I remember the very first extrasolar planets being announced on John Craven's Newsround (teenage news program) around 1978 or thereabouts. Now we're apparently charting entire systems!
It seems to me that a "Gas Giant" such as Jupiter and Saturn could not form if they were too near to their systems sun. The temperature would be to high. Is my intuition misguided?
Your intuition seems about right; these giants could form in the brief period that the star is forming, and has not yet started to fuse hydrogen; or they could form further out and migrate inwards. This migration seems to occcur by transferring orbital energy between the gas giant and other material in the young system- which material is flun outwards, some perhaps nbecoming the cometary (Oort) belt. Strange things happen when two giants become locked in a harmonic relationship too; Jupiter and Saturn might have been locked in this way briefly, and this seems to have profoundly affected our system... http://www.space.com/scienceastronomy/050525_planet_billiards.html
