We’ve recently looked at the effects of massive stars on the debris disks surrounding them. Now the Spitzer Space Telescope has shed new light on just how problematic such environments can be. The huge O-type stars studied by a team of scientists from the University of Arizona’s Steward Observatory (Tucson) are pouring ultraviolet light and powerful solar winds into the protoplanetary disks around Sun-like stars that have the misfortune of being too near to them.
The result: Disruption of the disk through a process called photoevaporation. An O star can be as much as 100 times more massive than the Sun, able to heat a nearby star’s disk to the point that gas and dust boil off. With the disk unable to hold together, the evaporated material is eventually blown away by solar winds. The result creates what researchers are calling a ‘cometary structure’ — the photoevaporation that causes it is something like what happens when a comet forms its tail in its swing through the inner solar system.
Image: The potential planet forming disk of a sun-like star is being violently ripped away by the powerful winds of a nearby hot O-type star in the upper image, from NASA’s Spitzer Space Telescope. Text labels have been added to the identical image in the lower half of this picture. Credit: University of Arizona, Tucson.
“Unfortunately these sun-like stars just got a little too close to the fire,” George Rieke said. Rieke is co-author on the paper and the principal investigator for Spitzer’s Multiband Imaging Photometer (MIPS) instrument. The study should provide useful information on another mechanism for regulating how planets form.
The paper is Balog et al., “Spitzer/MIPS 24 micron Detection of Photoevaporating Protoplanetary Disks,” accepted for publication in The Astrophysical Journal Letters, with preprint available online.
This points out exactly why I suspected solar winds should play such an important role in planetary formation. In our own system, it just seems logical that the solar winds blew the lighter materials farther out (leading to gas giants and lower density planets like Saturn) and left the heavier materials to form the rocky inner planets.
However, I’m now thinking that the heavy iron cores of the rocky planets may have been initially retained by and stewarded together by solar magnetic fields. Does this make sense?
I wonder if the Super-Jupiters might be an exception. Possibly failed binary stars? Two masses in proximity condensing out of one nebula that’s insufficient in mass to create two active stars? It seems that the solar proximity of these planets might indicate a congruent formation with their stars, rather than a subsequent formation, after the star. Does this seem right?
Perhaps there are two (or more) coinciding planet forming conditions in the universe?
That ultra low density super planet, mentioned earlier, seems more likely from this perspective.
Hi Eric
Interesting ideas, though there’s a few problems I can see. Magnetic fields undoubtedly had a role in the disk’s evolution, but they weren’t strong enough to be involved in late stage planet formation. The iron cores formed from molten materials and iron loses its ferro-magnetisation above a certain temperature. The magnetic fields today are generated by currents within the molten cores electromagnetically not through ferromagnetism. However there is some theoretical work which implicates magnetic fields in stopping the hot-Jupiters from crashing into their stars, by stripping the inner disk of mass before its tides could drag the planets in.
Solar winds certainly blew material away, especially the lighter gases and dust, but the main culprit is believed to be radiation from the Sun and, as this new report shows, from nearby giant stars. There’s so many processes going on during star and planet formation that just about any idea is probably a part of the whole – witness the merger of both core-accretion and gravitational collapse in some more recent theories.
Keep working on those ideas.
Adam
Adam,
Thanks for the nice woeds.
I wasn’t thinking about hot ferro-magnetic materials and planetary magnetic fields so much, but rather atomized ferro-magnetic materials in the accretion disc being sheparded together like iron filings around a magnet (the sun being the magnet), thus forming the early proto planets.
Is there a correlation between the solar magnetic field(s) and planetary placement?
Hi Eric
There’s no correlation I know of, but Hannes Alfven had a theory of planet formation that predicted something like that. He was proven wrong on some counts and I haven’t heard much about his ideas for a long time.
Fred Hoyle had the solar magnetic field transfer momentum to the disk and slow the Sun down, which may or may not happen. The whole area is being actively researched so it’s hard to say what will be supported by data.
Adam
Adam,
There’s no correlation I know of, but Hannes Alfven had a theory of planet formation that predicted something like that. He was proven wrong on some counts and I haven’t heard much about his ideas for a long time.
Well no wonder, he’s been deceased for more than ten years.
Fred Hoyle had the solar magnetic field transfer momentum to the disk and slow the Sun down, which may or may not happen. The whole area is being actively researched so it’s hard to say what will be supported by data.
Although both of the men you mention contributed a lot to the study of cosmology, I’m not sure if you mean for your association of my ideas with these men to be a compliment – or an insult. Both apparently suffered from irreconcilable preconceived notions, leading to quite controversial concepts. It should however be stated that Hannes Alfven is a Nobel Laureate.
I think it’s reasonable to consider the magnetohydrodynamics of plasma, but how far one might take this notion in cosmology is certainly debatable.
I’m not so sure about the transfer of angular momentum of the sun into the accretion disc. It seems to me that such a transfer would be more effective with proximity to the sun, therefore the orbits of the inner planets (in particular) should have an apparently correlative distance (step) relationship with the sun. Do they?
Interestingly, the conserved angular momentum of the swirling nebula that preceded the accretion disc must be conserved in the subsequent accretion disc and even the solar system of today. When cosmologists simulate a model of the early sun and it’s accretion disc, do they do it in more of a hydrodynamic way (electrodynamic connectivity), or more so in Newtonian terms (gravitational connectivity)? Do the resultant model simulations differ in their ability to form planets? Is the angular momentum of the solar rotation more consistent with one than the other? Are there obvious correlations between the subsequently formed planets and spacing that should be apparent in the real universe?
I wonder if the Hoyle momentum transfer model were the case, might the planets not so easily form? It seems to me that this might tend to increase the scattering of accretion disc materials. Thereby defeating (or slowing) the necessary clumping required to form planets. Does this seem right?
As usual… the more I learn, the more I want to know. Why is it that when you feed the body the body gets fat and happy, but when you feed the mind the mind simply becomes more voracious?