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lpetrich
2012-Oct-16, 12:37 PM
The Extrasolar Planets Encyclopaedia (http://exoplanet.eu/)
Exoplanet Orbit Database | Exoplanet Data Explorer (http://exoplanets.org/)
Numerous planets outside the Solar System have been discovered, and for some curious reason, a large number of them are around Jupiter's mass, but much closer in than one would expect. The usual theory nowadays is that they formed at a larger distance, then spiraled in as a result of their interaction with the still-remaining protoplanetary nebula.

But what happens to the inner planets? Would they still form?
[1004.0971] The Compositional Diversity of Extrasolar Terrestrial Planets: I. In-Situ Simulations (http://arxiv.org/abs/1004.0971) -- no migration
[1209.5125] The Compositional Diversity of Extrasolar Terrestrial Planets: II. Migration Simulations (http://arxiv.org/abs/1209.5125)

Apparently, they can, at least if not too close to one of these wandering giants. However, their composition tends to be more mixed, because of the giants' mixing up the protoplanetary nebula, and Earthlike planets can get much more water than the Earth has, making much deeper oceans.

But if wandering giant planets are so common, then why is it that the Solar System's ones did not migrate? Or did they?

Some planetary scientists are proposing that Jupiter and Saturn spiraled in, then spiraled out again.

A low mass for Mars from Jupiter/'s early gas-driven migration : Nature : Nature Publishing Group (http://www.nature.com/nature/journal/v475/n7355/full/nature10201.html)

Jupiter and Saturn formed in a few million years from a gas-dominated protoplanetary disk, and were susceptible to gas-driven migration of their orbits on timescales of only ~100,000 years. Hydrodynamic simulations show that these giant planets can undergo a two-stage, inward-then-outward, migration. The terrestrial planets finished accreting much later, and their characteristics, including Mars' small mass, are best reproduced by starting from a planetesimal disk with an outer edge at about one astronomical unit from the Sun (1 au is the Earth–Sun distance). Here we report simulations of the early Solar System that show how the inward migration of Jupiter to 1.5 au, and its subsequent outward migration, lead to a planetesimal disk truncated at 1 au; the terrestrial planets then form from this disk over the next 30–50 million years, with an Earth/Mars mass ratio consistent with observations. Scattering by Jupiter initially empties but then repopulates the asteroid belt, with inner-belt bodies originating between 1 and 3 au and outer-belt bodies originating between and beyond the giant planets. This explains the significant compositional differences across the asteroid belt. The key aspect missing from previous models of terrestrial planet formation is the substantial radial migration of the giant planets, which suggests that their behaviour is more similar to that inferred for extrasolar planets than previously thought.
Full text here (http://www.gps.caltech.edu/classes/ge133/reading/grand_tack_nature.pdf)
How Did Jupiter Shape Our Solar System? (http://www.universetoday.com/88374/how-did-jupiter-shape-our-solar-system/)
NASA - Jupiter's Youthful Travels Redefined Solar System (http://www.nasa.gov/topics/solarsystem/features/young-jupiter.html)
Here's a nice presentation: The Grand Tack Hypothesis (http://www.astro.washington.edu/courses/astro557/GrandTack2.pdf), after a sailing maneuver

In it, Jupiter starts out at 3.5 AU, Saturn at 4.5 AU, Uranus at 6 AU, and Neptune at 8 AU. Jupiter spirals in to about 1.5 AU in 100 thousand years (kyr), Saturn quickly follows at about 100 kyr, while Uranus and Neptune don't move very much.

Along with the giant planets are lots of planetesimals, small asteroid-like objects that condensed out of the solar nebula. From 0.3 to 3 AU are S-type (stony) ones, and from 3.5 to 13 AU are C-type (carbonaceous-chondrite) ones. The C-type ones contain water, from where they formed.

Jupiter and Saturn push the S-type objects together, while mixing up S-type and C-type ones as they go. Some S-type ones end up in the outer Solar System, while some C-type ones end up in the inner Solar System.

Then Jupiter and Saturn get locked in a 3:2 resonance, with Jupiter at 1.5 AU and Saturn at 2 AU, and their interactions with the protoplanetary disk push them outward. As they go outward, they push Uranus and Neptune outward as those planets get into resonances with them. They also leave behind the asteroid belt as they go.

Inside 3.5 AU, it's mostly S-type asteroids, while outside 3.5 AU, it's mostly C-type asteroids.

Mars ends up relatively small, since it does not have as much starting material as the Earth.

The C-type planetesimals supply water to the inner planets, making the Earth's oceans.

It's also a good setup for the Nice model (http://en.wikipedia.org/wiki/Nice%20model) of outer-planet migration. Saturn, Uranus, and Neptune keep going further out, and they scatter lots of planetesimals outward to form the Kuiper Belt. The Nice here is not the English word, but Nice, France, where the model was developed.

The origin of the giant planets is still not very well understood, it must be said.


For some somewhat technical background on planetary-system formation, check out Scott Tremaine's home page (http://www.sns.ias.edu/~tremaine/lectures/)

Hornblower
2012-Oct-16, 03:51 PM
The Extrasolar Planets Encyclopaedia (http://exoplanet.eu/)
Exoplanet Orbit Database | Exoplanet Data Explorer (http://exoplanets.org/)
Numerous planets outside the Solar System have been discovered, and for some curious reason, a large number of them are around Jupiter's mass, but much closer in than one would expect. The usual theory nowadays is that they formed at a larger distance, then spiraled in as a result of their interaction with the still-remaining protoplanetary nebula.

But what happens to the inner planets? Would they still form?
[1004.0971] The Compositional Diversity of Extrasolar Terrestrial Planets: I. In-Situ Simulations (http://arxiv.org/abs/1004.0971) -- no migration
[1209.5125] The Compositional Diversity of Extrasolar Terrestrial Planets: II. Migration Simulations (http://arxiv.org/abs/1209.5125)

Apparently, they can, at least if not too close to one of these wandering giants. However, their composition tends to be more mixed, because of the giants' mixing up the protoplanetary nebula, and Earthlike planets can get much more water than the Earth has, making much deeper oceans.

But if wandering giant planets are so common, then why is it that the Solar System's ones did not migrate? Or did they?

Some planetary scientists are proposing that Jupiter and Saturn spiraled in, then spiraled out again.

A low mass for Mars from Jupiter/'s early gas-driven migration : Nature : Nature Publishing Group (http://www.nature.com/nature/journal/v475/n7355/full/nature10201.html)

Full text here (http://www.gps.caltech.edu/classes/ge133/reading/grand_tack_nature.pdf)
How Did Jupiter Shape Our Solar System? (http://www.universetoday.com/88374/how-did-jupiter-shape-our-solar-system/)
NASA - Jupiter's Youthful Travels Redefined Solar System (http://www.nasa.gov/topics/solarsystem/features/young-jupiter.html)
Here's a nice presentation: The Grand Tack Hypothesis (http://www.astro.washington.edu/courses/astro557/GrandTack2.pdf), after a sailing maneuver

In it, Jupiter starts out at 3.5 AU, Saturn at 4.5 AU, Uranus at 6 AU, and Neptune at 8 AU. Jupiter spirals in to about 1.5 AU in 100 thousand years (kyr), Saturn quickly follows at about 100 kyr, while Uranus and Neptune don't move very much.

Along with the giant planets are lots of planetesimals, small asteroid-like objects that condensed out of the solar nebula. From 0.3 to 3 AU are S-type (stony) ones, and from 3.5 to 13 AU are C-type (carbonaceous-chondrite) ones. The C-type ones contain water, from where they formed.

Jupiter and Saturn push the S-type objects together, while mixing up S-type and C-type ones as they go. Some S-type ones end up in the outer Solar System, while some C-type ones end up in the inner Solar System.

Then Jupiter and Saturn get locked in a 3:2 resonance, with Jupiter at 1.5 AU and Saturn at 2 AU, and their interactions with the protoplanetary disk push them outward. As they go outward, they push Uranus and Neptune outward as those planets get into resonances with them. They also leave behind the asteroid belt as they go.

Inside 3.5 AU, it's mostly S-type asteroids, while outside 3.5 AU, it's mostly C-type asteroids.

Mars ends up relatively small, since it does not have as much starting material as the Earth.

The C-type planetesimals supply water to the inner planets, making the Earth's oceans.

It's also a good setup for the Nice model (http://en.wikipedia.org/wiki/Nice%20model) of outer-planet migration. Saturn, Uranus, and Neptune keep going further out, and they scatter lots of planetesimals outward to form the Kuiper Belt. The Nice here is not the English word, but Nice, France, where the model was developed.

The origin of the giant planets is still not very well understood, it must be said.


For some somewhat technical background on planetary-system formation, check out Scott Tremaine's home page (http://www.sns.ias.edu/~tremaine/lectures/)My bold. They may appear to be disproportionately common because they are the easiest type to detect.

lpetrich
2012-Oct-16, 06:35 PM
But if wandering giant planets are so common, then why is it that the Solar System's ones did not migrate? Or did they?

My bold. They may appear to be disproportionately common because they are the easiest type to detect.
Maybe, but has anyone tried to estimate how many "hot Jupiters" there are?

One must first define what one means by that.

At a minimum, a "hot Jupiter" ought to be inside the "snow line", about 2.7 AU for a solar-luminosity star, where the temperature is about 150 - 170 K (The “Snow Line” in Protoplanetary Disks « ISM and Star Formation (http://ay201b.wordpress.com/the-snow-line-in-protoplanetary-disks/)). Outside the snow line, it's easier for a giant planet to get started.

Going in a more strict direction, How Many Hot Jupiters? - AstroWright (http://www.personal.psu.edu/jtw13/blogs/astrowright/2012/07/how-many-hot-jupiters.html) states

But in reality 51 Pegasi b is a member of a pretty select class of object. There are "only" 23 exoplanets discovered with radial velocities that have periods shorter than 10 days and masses above 0.4 times that of Jupiter. Of these, 2 transit (HD 189733 b and HD 209458 b, the latter being the first planet known to transit its host star). This is consistent with the rate expected from geometry of about 10% (that is, since orbital planes are random, only 1 in 10 hot Jupiters will just happen to transit).

The actual frequencies of hot Jupiters around normal stars is surprisingly hard to figure out. Kepler reports a very low rate: around 0.5% of stars have hot Jupiters (many of these may be false positives, so the true Kepler rate may be only 0.3%), but the Keck planet search reported a higher number that is consistent with the other radial velocity surveys: more like 1.2%. What's going on?
If one uses a strict definition like this, then Jupiter-mass planets closer to the snow line might be called "warm Jupiters" instead.

I haven't been able to find estimates of how many warm Jupiters there are, however. They are more difficult to detect than the very hot kind, so it will be more difficult to do statistics on them.

RogerG
2012-Dec-20, 02:46 PM
When the planetisimals are forming, I can understand the central 'core' driving the lighter gaseous components out beyond the ice-line but what is happening to the dust heavier than H/He beyond the ice-line? Within, we have the 'heavy' metal cores (planetisimals) begining to form for the future terrestrial planets BUT is there similar material forming like planetisimals in the Jupiter/Saturn region or has gravity "dragged" these heavy elements onto/into the central core? The asteroid belt seems to contain some heavy elements but are there similar items either beyond or incorporated into Jovian/Saturnaian moons/asteroids?
All the SF writers have miners working the asteroid belt but what happens to heavy elements beyond 5, 10, 20 and 30 Au?

Robert Tulip
2012-Dec-24, 11:22 PM
Have you seen the hypothesis that the migration of Neptune past Uranus caused the late heavy bombardment (http://lunarscience.nasa.gov/articles/nlsis-swri-team-investigates-wandering-gas-giants-and-late-heavy-bombardment-moon/)?

The NASA link has a very cool simulation of the expulsion of Neptune by the Jupiter:Saturn 1:2 resonance (http://lunarscience.arc.nasa.gov/images/702.gif).