NASA ’s Kepler scope has now identify an harebrained 2,326 potential exoplanets . What ’s particularly disgraceful is how many of these planets are gargantuan jumpy planet known as Super - Earths , which defies everything we thought we know about planet constitution .
Of all the recent discovered candidate planets , anywhere from a third to half of them are tops - ground , which are rocky planet larger than Earth but smaller than Neptune . What ’s more , many of them are institute in exceedingly tight law of proximity to their stars . Now , it may be that super - Earths are n’t in reality quite as vulgar as these observation suggest – after all , it ’s easier to recognize major planet stuffy to a Sun , and it ’s easy to see larger rocky planets than smaller ones .
The problem , however , is that the universe of any superintendent - world so near their stars does n’t fit with our understanding of major planet formation , and to retrieve so many ostensibly impossible planets represents a glaring maw in our astrophysical knowledge . Both these major planet ’ existence and their position do n’t fit with our standard planet formation simulation , and this is n’t a matter of simply tweaking the be modelling to accommodate the raw observance – this demand a much cryptic reevaluation of the physics involved .
Part of the job is that astrophysicists developed models of planet geological formation when the only example we had was that of our own solar system , in which there ’s a very clean limning between large gas planets and small bouldery ones , and even Mercury is located at a fairly dependable space from the Sun . This led to theories of “ core accretion ” , which held that the dust and careen in embryonic solar systems were distributed such that only small-scale planet could take shape near the Dominicus , with big rocky planet potential further out and gas pedal giants only potential at much big distances from their star .
But the uncovering , starting in 1995 , of gas titan even big than Jupiter in near proximity to their superstar threw a massive twist in the core accumulation model . stargazer patched this disruption by say that these so - called Hot Jupiters could work far from their star and then migrate much closer in . But they still assumed that any planet declamatory than Earth would either become a gas giant or be swallowed by its star . And that ’s where Kepler is creating massive trouble for astronomers .
Writing for Nature , Eric Hand details the latest findings from Kepler , including a new tinge on just what establish up these superintendent - earth :
For a handful of the superintendent - Earths detected by Kepler , ground - based observations have also determined mass , by tracking the wobble of the innkeeper star stimulate by the major planet ’s gravity . And some of these super - Earths seem to have very blue densities – designate that they may have small jolty core surrounded by large gas envelopes .
Kepler astronomer Jack Lissauer , of Ames , thinks that they may have begun as small cores in the outer voice of their solar system , accreting a large amount of petrol without reach the point of runaway growth that conduce to a dead on target gun giant . Without the gravitational heft of a goliath to hold in gas , such a satellite would have a large , low - density ambience , but it could still arise to super - Earth size by a cooling process that shrivel the atmosphere and allow more gas to be draw in , he say .
But there ’s still a twosome major problem with our current planet formation good example , as Hand explicate . First , these super - Earths are n’t just low density , semi - flatulent worlds . Some are actually very massive and still larger than Earth , and we ’ve got no real path to explain their formation . What ’s more , the superintendent - earth found orbiting very close around their suns – at distances far small-scale than the compass of Mercury – have no line of work existing in our current models , which say they should either be further away or swallowed up by their genius .
One possibility being explore by Norm Murray of the University of Toronto is that it ’s actually the raw materials that transmigrate inwards from the outer solar system , and then the super - Earth really forms in a very skinny but static orbit around its star . It might address the present riddle , but it seems likely that Kepler has plenty more surprises up its sleeves – and it ’s anyone ’s reckon whether our current grasp of astrophysics will be enough to explain them .
ViaNature . creative person ’s construct by Lynette Cook .
AstronomyAstrophysicsNASAScienceSpace
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