It's kind of hard to get your head around Jupiter. The gas giant has a mass 318 times that of Earth and a circumference 11 times bigger, but is so far away it's sometimes hard to distinguish from a star in the night sky. Jupiter has 66 moons, takes a little under 12 Earth-years to orbit the sun once, and its day is just 10 hours long. It also had the potential to kill the very young Earth 4.5 billion years ago.A team of scientists led by Jason Steffen of the Fermilab Center for particle Astrophysics has been sifting through data from NASA's Kepler space telescope for evidence of Earth-like exoplanets – planets orbiting around distant stars – in the same system as hot Jupiters. Hot Jupiters are planets with about the size and mass of Jupiter, but also orbit so close to their stars that their years are just a few days long. In the 63 solar systems the team surveyed, there isn't one terrestrial planet cohabiting with a hot Jupiter.To find exoplanets, Kepler doesn't look directly at bodies. Rather, it looks at the stars. Big exoplanets like hot Jupiters show up as a dip in the star's light when the disk of the planet passes in front of it. Smaller terrestrial bodies are too small to find this way. Kepler finds these bodies by observing changes in the orbital period of the hot Jupiters. Any slight shift or wobble indicates that a smaller body nearby is tugging on it.The lack of terrestrial planets in these systems suggests that hot Jupiters kill terrestrial planets. The only way a gas giant could end up in such a close orbit to its star is if it migrated there; the ices and lightweight gases would have had to condense to form the gas giant in a cold outer region of the solar system then migrated towards its star, breaking up proto-terrestrial planets in the process.Icy bodies moved away from the Sun to form the Kuiper belt, the region where Pluto orbits. Jupiter’s gravitational influence formed the asteroid belt by keeping the debris in this region from forming into another terrestrial planet. Things in the solar system ended up with Earth in a great spot to host life. But if things had been different in our solar system's early formation, we probably wouldn't be here to study it.If Jupiter had ended up in a more elliptical orbit, it would have tugged the asteroid belt unevenly and left a field of debris extending all the way through the inner solar system. Earth wouldn't have formed. Had there been massive enough spiral gas density waves formed in the protoplanetary disk around our newborn sun, Jupiter might have spiraled inwards, ripping apart proto-terrestrial planets as it went. There's evidence of a fifth gas giant was ousted from our solar system in its early life. If Jupiter had played a game of cosmic pinball with this mythical planet, another gas giant for that matter, and shot it towards the Sun it could have ripped the early Earth apart.Looking at the damage these hot Jupiters do to early Solar Systems, it's easy to think that our chances of finding an exo-Earth are slim. But hot Jupiters are rare in the grand scheme of things. In 2006 the Hubble Space Telescope looked into the heart of our galaxy and found 16 hot Jupiters. Statistically, this means there are 7 billion of these planets in the Milky Way but that's peanuts compared to the estimated 100 billion total planets. We may find our bizarro Earth yet, just probably not sharing a star with a hot Jupiter.
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Earth escaped that fate because our solar system has one ‘cold’ Jupiter. But our solar system wasn't without planetary migration. Our gas giant planets moved, lucky for use they went away from the sun instead of towards it.
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Connections:
- “A Mysterious Gas Giant May Have Shaped Our Solar System”: http://motherboard.vice.com/2011/12/2/a-mysterious-lost-gas-giant-may-have-shaped-our-solar-system—2
- European Exploration of Jupiter is About to Get JUICE-y
- Cosmic Filicide: Rough Way To Go