Solar System Gets A Revised Birth Certificate
    By News Staff | November 4th 2012 03:30 AM | 1 comment | Print | E-mail | Track Comments
    We're not that special, says new research led by the Centre for Star and Planet Formation at the Natural History Museum of Denmark, University of Copenhagen.

    About 4.567 billion years ago, our solar system's planets spawned from an expansive disc of gas and dust rotating around the sun. While similar processes are witnessed in younger solar systems throughout the Milky Way, the formative stages of our own solar system were believed to have taken twice as long to occur. It turns out that is not the case, according to a new paper.

    Using improved methods of analysis of uranium and lead isotopes, their study of primitive meteorites led them to date the formation of two very different types of materials, calcium-aluminum-rich inclusions (CAI's) and chondrules, found within the same meteorite. By doing so, the chronology and overall understanding of our solar system's development has been altered, they conclude in their Science article.

    They took a closer look at the first three million years of the solar system's development by analyzing primitive meteorites composed of a blend of our solar system's very oldest materials. In part, the study confirmed previous analyses demonstrating that CAI's were formed during a very short period of time. The new discovery is that the chondrules were formed during the first three million years of the solar system's development as well. This stands in contrast with assumptions that chondrules only started forming roughly two million years after CAIs. 

    "By using this process to date the formation of these two very different types of materials found in the same meteorite, we are not only able to alter the chronology of our solar system's historical development, we are able to paint a new picture of our solar system's development, which is very much like the picture that other researchers have observed in other planetary systems,"  James Connelly of the Centre for Star and Planet Formation said in a statement.

    Showing that chondrules are as old as CAIs addresses a long-standing question of why chondrule formation should be delayed by up to 2 million years after CAIs. The answer – it is not.

    "In general, we have shown that we are not quite as unique as we once thought. Our solar system closely resembles other observable planetary systems within our galaxy. In this way, our results serve to corroborate other research results which indicate that earth-like planets are more widespread in the universe than previously believed," says Professor Martin Bizzarro, head of the Centre for Star and Planet Formation.


    This is not news since at least some chondrules were always understood to have formed concurrent with CAIs, but it doesn't explain why most chondrules show no evidence of live short-lived radionuclides (SRNs), which is interpreted as chondrules as having formed 2-3 million years later after live SRNs decayed.

    But if SRNs were formed in our own solar system rather than being acquired from beyond, then nothing prevents some or even a majority of chondrules from being older than the SRN-bearing CAIs.

    An alternative hypothesis suggests that the short-lived radionuclides formed by nucleosynthesis right here in our own solar system when the central, close-binary stellar pair merged to form our Sun in a luminous red nova (LRN) at 4.567 Ga. (Thus, our solar system may have originally formed as a multiple star system.) And chondrules may have formed prior to the stellar merger when one or more 'Trojan planets' merged with the larger A-star in the common envelope phase of the central binary pair as they spiraled inward.

    These 'Trojan planets' are hypothesized to have formed by gravitational collapse [also called gravitational instability (GI)] at L4/L5 Lagrangian points, located 60 degrees ahead and behind the smaller B-star in its orbit around the close-binary barycenter. (GI requires stable points where vortexes can form, and these stable conditions are only met at L4 and L5 Lagrangian points.)

    The Trojan pairs, Uranus-Neptune, Jupiter-Saturn and Venus-Earth, may have also formed by GI and escaped the stellar realm by core-collapse perturbation with the B-star, but the final pair of Trojan planets formed after Venus-Earth may have succumbed to the 'spiral-in' of the central binary pair and were consumed by the larger A-star in two, mini planet-sized LRNe before 4.567 Ga