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TOPIC: Solar System formation
Blobrana


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Posts: 131433
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Protoplanetary disc
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Effect of a planet in the distribution of dust in a protoplanetary disc
An international team, led by astronomers of the Astrophysical Research centre of Lyon (UMR, CNRS, University of Lyon I, Higher Teacher training school of Lyon) has just carried out a study of the gas reaction of and dust in protoplanetary discs. Applying a series of 3D simulations to a protoplanetary disc which has already a planet, these researchers show that the size of dust, or mass of the planet, plays a part in determining the morphology of the disc... and thus determents the formation of a second planet.
The study is published in Astronomy and Astrophysics.

proto_2
Expand (215kb, 1005 x 510)
Dust free lanes created by a planet in the dust of a protoplanetary disc. The solid particle component have sizes of 1cm, 10cm and 1m, (from left to right). The disc surrounds a young star  of the same mass as the Sun. The planet has the same mass and the same orbit as Jupiter.
Credit CRAL

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-- Edited by Blobrana at 15:18, 2007-11-07

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Blobrana


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Posts: 131433
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RE: Solar System formation
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 Our solar system started out as a star at the centre of a vast, disk-shaped nebula of dust and gas. By conventional thinking, the extreme heat near the sun could melt dust and form new minerals, but all of these high-temperature minerals could only drift inward toward the sun, not outward. That led to different types of minerals in the inner and outer reaches of the nebula. But the Stardust spacecraft threw a wrench in this theory by returning high-temperature minerals to Earth from comet Wild 2.
Planetary scientist Fred Ciesla of the Carnegie Institution of Washington's Department of Terrestrial Magnetism in Washington, D.C., thinks he's found a solution to the conundrum. For computational simplicity, past modelling treated the nebula as a one-dimensional object. In such simulations, all gas and dust is assumed to behave the same way, whether it is near the nebula core or far above or below its midplane. But Ciesla performed more computationally demanding, two-dimensional simulations. In these, most nebular material still flows inward toward the sun; but near the midplane, the inward flow ceases or even reverses, letting the outward diffusion of material to the comet-forming region proceed. Ciesla presents his findings in the 26 October issue of Science.

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One of the most remarkable particles found in the Stardust collection is a particle named after the Inca Sun God Inti. Inti is collection of rock fragments that are all related in mineralogical, isotopic and chemical composition to rare components in meteorites called "Calcium Aluminium Inclusions" or CAI's for short. CAI's are the oldest materials that formed in the solar system and they contain a remarkable set of minerals that form at extremely high temperature. In addition to these same minerals, Inti also has tiny inclusions that may have been the first generation of solids to condense from hot gas in the early solar system. These include compounds of titanium, vanadium and nitrogen (TiN and VN) as well as tiny nuggets of platinum, osmium, ruthenium, tungsten and molybdenum. In certain chemical environments and at high enough temperature in the early solar system these exotic materials were the only solid materials that could survive without being vaporised.

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Blobrana


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Posts: 131433
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Neon marker
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The detection of ionised neon was discovered in data obtained from two Spitzer Legacy Program teams: From Molecular Cores to Planet Forming Disks (c2d) and The Formation and Evolution of Planetary Systems (FEPS); and one Guaranteed Time Observing program called Spitzer IRS_Disks.
Pascucci and the FEPS team first presented the detection of Neon II emission towards four circumstellar disks at the 2006 conference "The Planet-Disc Connection." Their paper on the topic was published in the July 2007 edition of Astrophysical Journal.
The detection of Neon II toward 15 sources from the c2d sample is part of Lahuis' PhD thesis study. Meanwhile, the detection of Neon II around disks where planets have already formed in the Spitzer IRS_Disks study was the focus of Espaillat's PhD thesis.

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Neon Signs in Space
A recent detection of neon gas in planet-forming disks may help us better understand how planets form and whether or not life may exist elsewhere in the cosmos.

Listen (2.66mb, mp3,  Running Time: 4:38)

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Blobrana


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Posts: 131433
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RE: Solar System formation
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Astronomers have observed neon in disks of dust and gas swirling around sunlike stars for the first time.
University of Arizona astronomers who collaborated in the observations say that neon could show which stars retain their surrounding dust-and-gas disks needed to form planets and which stars might already have formed planets.

"When I saw the neon, I couldn't believe it. I was just amazed. We were not expecting to see neon around low-mass stars like our sun" - Astronomer Ilaria Pascucci, University Arizona Steward Observatory.

Pascucci is a co-investigator on a Spitzer Space Telescope Legacy project called "Formation and Evolution of Planetary Systems, known as FEPS, headed by Steward Observatory's Michael R. Meyer. The project used an infrared spectrometer to conduct a sensitive search for planet-forming gas around 35 young, solar analogue stars.
Neon showed up in disks of four sunlike stars in Spitzer's FEPS data. The discovery was a surprise because "we didn't realise that solar analogue stars could radiate enough high-energy (X-ray and ultraviolet) light to ionise neon".

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Blobrana


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Posts: 131433
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Orbital eccentricity
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acj.jpg
Numerical simulations conducted by Jacques Laskar revealed that the maximum orbital eccentricity of the inner planets changes considerably over time. Thus over billions years, each planet would cut a broad swath (colored bands) around its mean orbit (white lines). Indeed, Mercurys orbital eccentricity can, in principle, become large enough that it risks collision with Venus. Although the orbits of other terrestrial planets will never cross in this way, they largely fill the inner solar system when one considers their long-term variations.
(Adapted from Laskar 1996.)

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Blobrana


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Posts: 131433
Date:
Oort Cloud
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Title: The Formation of the Oort Cloud in Open Cluster Environments
Authors: Nathan A. Kaib, Thomas Quinn
(Version v2)

We study the influence of the initial stellar environment on the formation and current structure of the Oort cloud. To do this, we have run four different simulations of the formation of the Oort Cloud for 4.5 Gyrs, each containing 20,000 particles. In each simulation, the solar system spends its first 100 Myrs in a different open cluster environment before transitioning to its current field environment. We find that, compared to forming in the field environment, the inner Oort Cloud is preferentially loaded with comets while the Sun resides in the open cluster and that most of this material remains locked in the interior of the cloud for the next 4.4 Gyrs. On the other hand, the outer portions of the Oort Cloud in each of the simulations are all similar. Depending on the initial stellar density of the cluster environment, the internal structure of the present day Oort Cloud will vary widely.

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Blobrana


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RE: Solar System formation
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Creationists who bang the pulpit about the Universe being young tend to use old, outdated, and long-debunked arguments. The astronomy ones just crack me up. Sometimes they are based on faulty data, sometimes on twisting or misinterpreting the results, sometimes on outright lies. They are most pernicious, perhaps, when there is a kernel of truth in what they say though generally they leave out a HUGE amount of information that shows they are wrong. One argument has to do with angular momentum. This is a tendency for a rotating object to stay spinning unless acted upon by a force of some kind (that "acted upon" part is important later). Mathematically, it depends on how big an object is and how fast it spins.

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Title: A CORRELATION BETWEEN PREMAIN-SEQUENCE STELLAR ROTATION RATES AND IRAC EXCESSES IN ORION
Authors: L. M. Rebull, J. R. Stauffer, S. T. Megeath, J. L. Hora, and L. Hartmann

Early observations of T Tauri stars suggested that stars with evidence of circumstellar accretion disks rotated slower than stars without such evidence, but more recent results are not as clear. Near-IR circumstellar disk indicators, although the most widely available, are subject to uncertainties that can result from inner disk holes and/or the system inclination. Mid-infrared observations are less sensitive to such effects, but until now, these observations have been difficult to obtain. The Spitzer Space Telescope now easily enables mid-infrared measurements of large samples of PMS stars covering a broad mass range in nearby star-forming regions. Megeath and collaborators surveyed the Orion Molecular Clouds (~1 Myr) with the IRAC instrument (3.6, 4.5, 5.8, 8 µm) as part of a joint IRAC and MIPS GTO program. We examine the relationship between rotation and Spitzer mid-IR fluxes for ~900 stars in Orion for stars between 3 and 0.1 Solar masses. We find in these Spitzer data the clearest indication to date that stars with longer periods are more likely than those with short periods to have IR excesses suggestive of disks.

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Blobrana


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Posts: 131433
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Solar system bodies arranged from large to small
This is an interesting illustration of bodies in our Solar system which are larger than 200 miles (322 km) in diameter. They are laid out from the largest to the smallest.

IMAGE (40kb, 1600 x 145)

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Blobrana


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Posts: 131433
Date:
irregular Satellites of the Planets
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Title: irregular Satellites of the Planets: Products of Capture in the Early Solar System
Authors: David Jewitt, Nader Haghighipour

All four giant planets in the Solar system possess irregular satellites, characterized by large, highly eccentric and/or inclined orbits that are distinct from the nearly circular, uninclined orbits of the regular satellites. This difference can be traced directly to different modes of formation. Whereas the regular satellites grew by accretion within circumplanetary disks the irregular satellites were captured from initially heliocentric orbits at an early epoch. Recently, powerful survey observations have greatly increased the number of known irregular satellites, permitting a fresh look at the group properties of these objects and motivating a re-examination of the mechanisms of capture. None of the suggested mechanisms, including gas-drag, pull-down, and three-body capture, convincingly fit the group characteristics of the irregular satellites. The sources of the satellites also remain unidentified.

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-- Edited by Blobrana at 11:48, 2007-03-06

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Blobrana


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Posts: 131433
Date:
Origins
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 Origins, a project to study how the solar system formed, begins this month.
The Natural History Museum is leading the network of European institutions, including the Ondrejov observatory in the Czech Republic, in their quest to learn more about the beginnings of our planetary system.
The multi-disciplinary team includes cosmochemists, astrophysicists, astronomers and cosmic-mineralogists, similar to the network of scientists at NASA. The European Commission awarded a four-year 2.6 million Euro grant to the project last month.

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