It takes a nice safe environment for planets to form, according to new data gathered by the Spitzer Space Telescope. The powerful infrared observatory recently observed powerful O-type stars in the process of stripping away nearby planet-forming disks. The gigantic stars can have as much as 100 times the mass of the Sun, and generate killer solar winds. In one case, the planetary disc takes on a comet-like appearance, as planetary material is blown away from the star.

A star must live in a relatively tranquil cosmic neighborhood to foster planet formation, say astronomers using NASA’s Spitzer Space Telescope.

A team of scientists from the University of Arizona’s Steward Observatory, Tucson, came to this conclusion after watching intense ultraviolet light and powerful winds from O-type stars rip away the potential planet-forming disks, or protoplanetary disks, around stars like our sun. At up to 100 times the mass of the sun, O stars are the most massive and energetic stars in the universe. They are at least a million times more powerful than the sun.

According to Dr. Zoltan Balog, lead author of the team’s paper, the super-sensitive infrared eyes of Spitzer are ideal for capturing the “photoevaporation” of these planet-forming disks. In this process, immense output from the O star heats the disks that are surrounding nearby sun-like stars so much that gas and dust boil off (much like the evaporation of boiling water), and the disk can no longer hold together. Photon (or light) blasts from the O star then blow away the evaporated material, potentially stripping the sun-like stars of their ability to form planets.

“We can see that these systems take on a cometary structure as they are being blown away and destroyed,” said Balog.

“No other telescope has ever captured the photoevaporation of a protoplanetary disk in this much detail,” adds Dr. Kate Su, who is a co-author on Balog’s paper.

According to Su, the photoevaporation process is very similar to the one that forms the tail of a comet as it swings by the inner solar system, only a lot more violent and on a far larger scale.

“Every time a particle of light from the O star hits a dust grain in the nearby protoplanetary disk, the light particle pushes the dust grain away from its host star,” said Su. “This is very similar to how comet tails form.”

“Unfortunately these sun-like stars just got a little too close to the fire,” adds Dr. George Rieke. Rieke is also a co-author on the paper and the principal investigator for Spitzer’s multiband imaging photometer instrument, which made the new observations.

Ultimately, the astronomers hope to determine whether all stars have planets, and if not, how a star loses the ability to form them. The Spitzer findings will help astronomers understand what regulates the process of planet formation.

Team members say that originally they were looking for “diskless stars” in their survey, stars that had ventured too close to an O star and no longer had any disk left. With so many O stars in the region, they didn’t expect that a protoplanetary disk would survive for very long. However, they found something different — stars that had recently blundered into the hostile neighborhood of an O star and were still in the process of losing their disks.

“To see protoplanetary disks in an area where no one expected to see one is very exciting,” said Balog. “But to see a disk in the process of evaporating is even more thrilling.”

Balog’s paper was recently accepted for publication in Astrophysical Journal. He is currently is at the University of Arizona on leave from the Department of Optics and Quantum Electronics, University of Szeged, Hungary.

Original Source: Spitzer News Release 

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Since stars are now said to be 150 times larger than the sun when born, we should expect that no planet formation is possible within a collapsing nebula, so that leaves planet formation after the star forms and blows away all remaining gas with its solar-wind. Eruption of iron rich molten rock goes into orbit around the star, eventually rolls up into a planetisimal core, then over 2 or 3 billion years has spiralled away from the scene of its birth, where, meantime a replenishment of more iron rich rock accumulates and rolls up to form the core of the next planet. Also the above article would suggest that there is no such thing as a protoplanetary disc.

Isn't this incredible - I can't find that report claiming that 'said to be 150 times larger than the sun when born' on the www. [Can anyone help?] Although, a nebula, no matter what size, will collapse violently into a star, it must at the same time create a very rough neighbourhood.

Before a nebula collapses, lets assume that it is a ball of gas that has grown around an old planet, that's if there is nothing nearby to distort it. It reaches pressure 0 on the already liquid planet, which causes it to explode. The concussion of that primal explosion impacts with unbelievable violence upon the compressed gas and solids above it, probably for several hundred million kilometers where implosion as well as explosion will result. There will be a void left where implosion has created elements higher up the atomic scale that now will almost instantly be refilled with the unaltered gas above.

The impact of this next event will probably be more violent than the first and a lot of new elements will be combined to make newer ones higher still on the atomic scale. How many of these violent impacts will occur I wouldn't hazard a guess, but eventually a change will take place as the primarily iron content of the growing star will cause it to magnetically gain sufficient polarity to start pulling remaining gas and solids into an equatorial disc. As this stuff comes together from both hemispheres, more violent impacting will take place as it is lured toward the equatorial and is pulled together also by it's own collective gravity.

Any sign of angular momentum at this stage obviously does not exist, so the only place for this stuff to go is either up or down. Seems to me it would be down, right within the equatorial, and would start at bottom of the radius. The matter would be molten, and with the squeeze above, plus the lack of angular momentum, it would virtually pour into the equator of the forming star.

Any collection of the solids into planetals prior to this are doomed, so if the established theory has any credence at all, they would have to form after that event. But there is more to come.

Since it seems that the equatorial pour would be from a disc right around the star, one might assume that it poured in a sort of a swirl, that made it semi-orbital. Perhaps, but could it gain sufficient orbital momentum to separate out into planetals? The progressive pattern of our planetary orbits as they fit with Bode's law, doesn't appear to fit that scenario. Getting a whirlpool thrust of ninety degrees as the stuff is in direct fall does not seem likely.

However, the Establishment have never been able to give a satisfactory answer as to how the outer planets gathered up their mass, so perhaps I'm shooting myself in the foot by offering this alternative. although it seems very dicey to me, and I am still of the opinion that the planets came into being, one by one, after the whole nebula absorption, and the new star's solar wind blew away all the left over gasses. Or perhaps I'll get the Nobel Prize for solving the shaky ground problem in the established theory. hehehehe.

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