Planetary influences on young stellar disks

December 14, 2015, Harvard-Smithsonian Center for Astrophysics
Planetary influences on young stellar disks

A newborn star typically has a disk of gas and dust from which planets develop as the dust grains collide, stick together and grow. Stars older than about five million years lack evidence for these disks, however, suggesting that by this age most of the disk material has either been converted into planets or smaller bodies, accreted onto the star, or dispersed from the system. Transition disks bridge this period in disk evolution: They have not yet been disbursed, and warmed by the star, can be detected at infrared or millimeter wavelengths. Their infrared colors can be used to characterize their properties. They often show inner dust cavities, which astronomers have sometimes interpreted as evidence of the presence of planets that have cleared out their orbits.

The models of planet-disk interactions, however, indicate that dust cavities are only an indirect consequence of planet clearing. What actually seems to occur is that the planet creates a gap in the gas, and the gas distribution at its outer edges then traps the small and produces a dust ring that is frequently asymmetric. There is some uncertainty in this picture because other mechanisms could produce a dust cavity or dust ring, including selective evaporation of dust grains by starlight, or instabilities in the itself. Determining the inside the cavity can help to distinguish between these mechanisms.

CfA astronomer Sean Andrews and his colleagues used the ALMA millimeter-wavelength telescope array to study transition disks in four relatively nearby young stars. This powerful new facility can measure dimensions in these disks as small as twenty-four astronomical units (one AU is the average distance of the Earth from the Sun), and can do so for both the small dust grains and the warm gas. In all four disks the scientists were able to model the gas distribution. They found that the gas cavity was as much as three times smaller than the cavity, and that the density inside the cavity drops by at least a factor of one thousand compared to the surface density. The results strongly suggest that the cavities were indeed produced by orbiting planets.

Explore further: Transition discs in Ophiuchus and Taurus

More information: "Resolved Gas Cavities in Transitional Disks Inferred from CO Isotopologs With ALMA," N. van der Marel, E.F. van Dishoeck, S. Bruderer, S.M. Andrews, K.M. Pontoppidan, G.J. Herczeg, T. van Kempen, and A. Miotello, A&A, in press (2015). arxiv.org/abs/1511.07149

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FredJose
1 / 5 (5) Dec 15, 2015
A newborn star typically has a disk of gas and dust from which planets develop as the dust grains collide, stick together and grow.

There is unfortunately nothing "typical" about newborn stars whatsoever since no one has detected or observed a star being born. There is no documented and verified observational evidence for this supposed typification at all.
Hence this story about the surrounding disk of gas and dust is just so much speculation, so much hot air and just so much story telling as a Hansel and Gretel tale.
This is poor science if indeed it can be called science.
From the physical structures we actually can observe as well as the mechanics involved, it should be quite clear that planets need to have been formed very quickly indeed or else they would have disintegrated or completely disassembled again. As it stands, they needed to have all their ingredients in the right place at the right time at the right temperature and chemical mix or else nothing would result.
FredJose
1 / 5 (4) Dec 15, 2015
A newborn star typically has a disk of gas and dust from which planets develop as the dust grains collide, stick together and grow.

Has ANYONE ever seen a cloud of dust particles collide and stick together and then grow like a snowball rolling along the ground? If you've ever observed dust balls of fluff in an uncleaned building, you'll know that they don't ever gather together into even small rocks. Even in places that have abandoned for centuries. So how much less will dust particles stick together in space where there is no gravity, no pressure or some kind of binding agent to ensure adhesion? This accretion story of planetary birth is more lame than a dead duck and really defies very well established principles of mechanics.
Captain Stumpy
5 / 5 (3) Dec 16, 2015
...since no one has detected or observed a star being born...This accretion story of planetary birth is more lame than a dead duck and really defies very well established principles of mechanics
@fred
- we can determine the facts about a crime scene based upon the forensic evidence without "being there to observe it happening" too

- you also say
At least Christians have a the concept of an intelligent, all powerful and live mover as first cause
without a shred of evidence or the ability to substantiate your own claim, but somehow following the logical rules of physics based upon known observed evidence and extrapolating a result is not logical?

this isn't the first time you've made this accusation. you ignored the evidence and replies then, why should anyone consider posting evidence to you now?
especially considering your acceptance of religious doctrine without hesitation as "logical"...

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