**7. The classical model of the birth and evolution of a solar system**

From the three new Neptune-like planets [Schwarzschild 2004] the scientists conclude the following:

i. The shock waves of a Supernova explosion sets a giant cloud of gas and dust , passing nearby, into a spinning mode. The rapid spin cannot be accommodated by one hydrostatic star hence it results into the fragmentation of the cloud into binary or multiple star system. Even the new multiple system cannot accommodate the excess angular momentum and the individual clouds are flattened out as pancake shaped disc of accretions. The central part collapses into a proto-star surrounded by a thick disk of gas and dust. From these Keplerian debris disks the planets are born. The solar insolation is causing the photoevaporation of gas out of the system and the dust particles are spiraling inward due to Poynting-Richardson Drag and settling down in the midplane of the disc. Thus gas is blown out and the host star vicinity is filled with heavy suspension of dust particles larger than a micron size. These micron size dust randomly collide and stick together building up km-sized planetismals. But before the build up can take place the random collision may result in repeated breakups preventing the formation of planetismals. But if there is heavy dust suspension, with the gas blown out, runaway gravitational accretion takes place resulting into full scale terrestrial planets.

So there are two scenarios:

a. The first scenario is the earliest stage of planet formation when the protostar is not experiencing full scale thermonuclear fusion . At that stage there is a very light density suspension of dust in a thick envelope of gas. The gravitation is too weak and

Enigma of the Birth and Evolution of Solar Systems

most others were herded into the asteroid belt;

in the new planetary-satellite model this naturally occurs.

**8. The extra-solar planets which donot fit in any model** 

and Saturn

Orbital period=3.35d; Orbital radius = 0.05AU;

of total mass=1.63MΘ ;

Primary star mass=1.06M<sup>Θ</sup> ;

Mass= 1.14MJ ;

list of the exoplanets and the reasons why they have become an enigma.

Gas Giants in 100 times smaller orbit as compared to the orbit of Jupiter

Hot Jupiter orbiting the primary star;

Secondary system is a binary system

Orbital radius of secondary with respect to the primary= 12.3AU; Orbital period of the primary and

no unfinished middleweights planets.

is the following:

Name of the extra-

'Pegasi' exoplanets

HD 188753 (triple star system)

May Be Solved by Invoking Planetary-Satellite Dynamics 85

 Gas Giants in outer regions would cause icy embryos to veer inward and collide with newly evolved rocky planets. In the process water is transferred to the inner rocky planet; Gas Giants also act as bodyguards for these small watery worlds. There are large chunks of residual rock an ice which are on the loose and which would smash the inner rocky planets in next 100 million years. Gas Giants with its powerful gravitational fields took direct hit from these marauder chunks, some were flung out of the system and

iii. According to gas instability theory there is an abrupt formation of gas giants. The gravitational instability in the circumstellar disc leads to gas-giant formation. There is

iv. In classical theory the explanation given for the infernally tight orbits of the hot jupiters

These must have formed much farther away beyond the snow-line which is about 1AU. Subsequently the tidal interaction with the protoplanetary disc caused the hot Jupiter to spiral in. This protoplanetary disc itself dissipates off due to Poynting-Robertson drag and due to photo- evaporation. So the inward migration must be fast before the dust-gas protoplanetary disc dissipates off [Schwarzschild 2004]. This is too contrived a situation. But

Lately many exoplanets have been discovered apart from hot-jupiters which donot fit any Model of planet birth and evolution and hence present a conundrum. Table (7) presents the

solar system Description Reason for enigma

Gas Giants can form only beyond snowline which is at 1AU. Then how come hotjupiters are in orbits of a less

Gliese 436- a=0.028AU Mu Arae - a = 0.084AU Rho Cancri-a=0.04AU

which will prohibit the formation of a gas giant;\*

A close and massive secondary will truncate the circumstllar disk around the primary to a radius of 1.3AU and the disk will be heated to temperatures

than 1 AU ?

gravitational accretion is prevented. But snowline criteria is not applicable as thermonuclear furnace is not switched on yet. Hence the dust is coated with ice which is amorphous and hence sticky (Ordinary ice is a open-pack hexagonal crystalline structure and is non-sticky whereas ice at -230ºc is fluffy amorphous structure. If small ceramic ball is covered with fluffy, amorphous ice falling from a height of 12 cm it bounces to 1 cm whereas ball covered with crystalline ice bounces to 8 cm. The colder, more disordered ice absorbs more of the energy of the impact because the molecules rearrange themselves during the collision. Therefore the dust particles coated with amorphous ice will stick together rather than rebounce). Through collision and agglomeration (or sticking), km-sized planetismals are formed which are then set on the path of gravitational accretion. Once 10ME cores have formed the gravitational field is strong enough to cause the wrapping of these icy-rocky cores with thick envelopes of gas resulting first into gas giants and subsequently into ice giants.


Douglas Lin(University of California, Santa Cruz) says " Many incipient gas giants won't make it to jovian mass before the disk dissipates after a few million years. So we can expect lots of failed Jupiters to show up as Neptune".

The farther the planet is the longer it takes to form. Infact it may be 100 billion years whereas the lifetime of the debris disk may be only several million years.

Computer models of Jonathen Lunine give the following picture:


84 Space Science

b. The second scenario is when gas has been exhausted both by the process of gas giants and ice giants formation and also by photoevaporation. At this stage lack of gas assists runaway gravitational accretion of the thick dust suspension into terrestrial planets. Radioactive dating of the core by Hf-W has established that Earth and Mars were formed 29 million years and 13 million years respectively after the birth of the solar nebula [Cameron 2002, Yin et al 2002, Kleine et al 2002]. There was an extended core formation period. The interior of the planet is heated partly due to Helmholtz Contraction(or gravitational energy release) and partly due to radioactivity particularly that of26Al. Accumlative collision between small bodies produce the planet. When a small body collides into a large body the core of the small body gets embedded into the mantle of the large body. The heat of impact melts the interior and molten iron core of

ii. According to core-accretion theory or dust bunny theory, by agglomeration-accretion a rock or ice core is formed of mass 10 M+ . Beyond that critical mass the core rapidly envelopes itself by gravitationally captured gas from the surrounding circumstellar disk. This process terminates with the formation of a gap in the circumstellar disc. Douglas Lin(University of California, Santa Cruz) says " Many incipient gas giants won't make it to jovian mass before the disk dissipates after a few million years. So we can expect

The farther the planet is the longer it takes to form. Infact it may be 100 billion years

 In the inner part of the solar system debris disk is dense. In this dense part, the gas giants are formed in first million years through a chain of core formation and gas

 In the next ten million years the leftover rock and dust accreted to form the moon – sized embryos. Dust clumps together into gravel, gravels to rock and rocks to hundred

 It churns an orderly set of embryos into an unruly, colliding swarm which through collision and accretion evolves into a set of terrestrial planets like our Earth and Mars in

of planetary embryos moving in tidy, sedate circular orbits. The collisions stop.

gas resulting first into gas giants and subsequently into ice giants.

the smaller body percolates to the core of the larger body.

whereas the lifetime of the debris disk may be only several million years.

Computer models of Jonathen Lunine give the following picture:

Jupiter's influence that is gas giant's influence have two effects:

another 10 to 20 million years but these rocky planets are bone dry;

lots of failed Jupiters to show up as Neptune".

accretion;

gravitational accretion is prevented. But snowline criteria is not applicable as thermonuclear furnace is not switched on yet. Hence the dust is coated with ice which is amorphous and hence sticky (Ordinary ice is a open-pack hexagonal crystalline structure and is non-sticky whereas ice at -230ºc is fluffy amorphous structure. If small ceramic ball is covered with fluffy, amorphous ice falling from a height of 12 cm it bounces to 1 cm whereas ball covered with crystalline ice bounces to 8 cm. The colder, more disordered ice absorbs more of the energy of the impact because the molecules rearrange themselves during the collision. Therefore the dust particles coated with amorphous ice will stick together rather than rebounce). Through collision and agglomeration (or sticking), km-sized planetismals are formed which are then set on the path of gravitational accretion. Once 10ME cores have formed the gravitational field is strong enough to cause the wrapping of these icy-rocky cores with thick envelopes of


These must have formed much farther away beyond the snow-line which is about 1AU. Subsequently the tidal interaction with the protoplanetary disc caused the hot Jupiter to spiral in. This protoplanetary disc itself dissipates off due to Poynting-Robertson drag and due to photo- evaporation. So the inward migration must be fast before the dust-gas protoplanetary disc dissipates off [Schwarzschild 2004]. This is too contrived a situation. But in the new planetary-satellite model this naturally occurs.
