Fingering the culprit that polluted the Solar System

Aug 02, 2012
Fingering the culprit that polluted the Solar System
Log10 of the density distribution for model 40-200-0.1 after 2:00 x 104 yrs of evolution, plotted in the z = 0 plane. Contours show the color field plotted at 0.01, 0.025, 0.05, 0.075, and 0.1. The x axis is horizontal and the y axis is vertical. The downward propagating shock wave has compressed the target cloud core and is injecting shock front material through multiple Rayleigh-Taylor (RT) fingers.

(Phys.org) -- For decades it has been thought that a shock wave from a supernova explosion triggered the formation of our Solar System. According to this theory, the shock wave also injected material from the exploding star into a cloud of dust and gas, and the newly polluted cloud collapsed to form the Sun and its surrounding planets. New work from Carnegie's Alan Boss and Sandra Keiser provides the first fully three-dimensional (3-D) models for how this process could have happened. Their work will be published by The Astrophysical Journal Letters.

Traces of the supernova's pollution can be found in meteorites in the form of short-lived radioactive isotopes, or SLRIs. SLRIs—versions of elements with the same number of protons, but a different number of neutrons—found in primitive meteorites decay on time scales of millions of years and turn into different, so-called daughter, elements. A million years may sound like a long time, but it is actually considered short when compared to other studied by geochemists and cosmochemists, which have half-lives measured in billions of years.

This video is not supported by your browser at this time.

When scientists find the daughter elements distributed in telltale patterns in primitive meteorites, this means that the parent SLRIs had to be created just before the meteorites themselves were formed. This presents a timing problem, as the SLRIs must be formed in a supernova, injected into the presolar cloud, and trapped inside the meteoritic precursors, all in less than a million years.

The telltale patterns prove that the relevant daughter elements were not the ones that were injected. This is because the abundances of these daughters in different mineral phases in the are correlated with the abundances of a stable isotope of the parent element. Different elements have different chemical behaviors during the formation of these first solids, and the fact that the daughter elements correlate with the parent elements means that those daughters had to be derived from the decay of unstable parent elements after those solids were crystallized.

One of these SLRIs, iron-60, is only created in significant amounts by nuclear reactions in massive stars. The iron-60 must have come from a supernova, or from a giant star called an AGB star. Boss and Keiser's previous modeling showed that it was likely that a supernova triggered our 's formation, as AGB star shocks are too thick to inject the iron-60 into the cloud. Supernova shocks are hundreds of times thinner, leading to more efficient injection.

Now Boss and Keiser have extended those models to 3-D, so they can see the shock wave striking the gas cloud, compressing it and forming a parabolic shock front that envelopes the cloud, creating finger-like indentations in the cloud's surface. The fingers inject the SLRI pollution from the supernova. Less than 0.1 million years later, the cloud collapses and forms the core of the protostar that became the Sun and its surrounding . The 3-D models show that only one or two fingers are likely to have caused the SLRI pollution found in primitive meteorites.

"The evidence leads us to believe that a supernova was indeed the culprit," said Boss. However, more detective work needs to be done: Boss and Keiser still need to find the combination of cloud and shock wave parameters that will line up perfectly with observations of exploding supernovae.

Explore further: How baryon acoustic oscillation reveals the expansion of the universe

Related Stories

X-ray illumination of supernova ejecta

Jun 24, 2011

(PhysOrg.com) -- Supernovae are the explosive deaths of massive stars, cataclysms that disburse into space the chemical elements produced by nuclear reactions inside the progenitor stars. Understanding chemical ...

Supernova shrapnel found in meteorite

Sep 09, 2010

(PhysOrg.com) -- Scientists have identified the microscopic shrapnel of a nearby star that exploded just before or during the birth of the solar system 4.5 billion years ago.

Image: In the Constellation Cassiopeia

Jul 14, 2010

(PhysOrg.com) -- Tycho's Supernova, the red circle visible in the upper left part of the image, is SN 1572 is a remnant of a star explosion is named after the astronomer Tycho Brahe, although he was not the ...

Space image: New supernova remnant lights up

Sep 13, 2011

(PhysOrg.com) -- Using the Hubble Space Telescope, astronomers are witnessing the unprecedented transition of a supernova to a supernova remnant, where light from an exploding star in a neighboring galaxy, ...

New supernova remnant lights up

Jun 08, 2011

(PhysOrg.com) -- In 1987, light from an exploding star in a neighboring galaxy, the Large Magellanic Cloud, reached Earth. Named Supernova 1987A, it was the closest supernova explosion witnessed in almost ...

Recommended for you

The Great Cold Spot in the cosmic microwave background

20 hours ago

The cosmic microwave background (CMB) is the thermal afterglow of the primordial fireball we call the big bang. One of the striking features of the CMB is how remarkably uniform it is. Still, there are some ...

Mystery of rare five-hour space explosion explained

Sep 17, 2014

Next week in St. Petersburg, Russia, scientists on an international team that includes Penn State University astronomers will present a paper that provides a simple explanation for mysterious ultra-long gamma-ray ...

User comments : 11

Adjust slider to filter visible comments by rank

Display comments: newest first

SnowballSolarSystem _SSS_
1 / 5 (4) Aug 02, 2012
A simpler alternative hypothesis (paradigm shift) suggests that our central collapsing molecular cloud fragmented due to excess angular momentum, forming Saturn, Jupiter and a close binary pair. Then 'core collapse' perturbation lifted the orbits of Saturn and Jupiter at the expense of energy and angular momentum of the close binary pair, causing the binary pair to merge in a luminous red nova (LRN) at 4.567 Ga. Helium burning, r-process and alpha-process nucleosynthesis in the LRN created the short-lived radionuclides of the early solar system and enriched the sun in the stable isotopes, 12C, 14N and 16O, without resorting to a fortuitous local super nova.

The simplest theory most often turns out to be right.
Torbjorn_Larsson_OM
5 / 5 (3) Aug 02, 2012
@ SSS:

That is not the simplest theory, the supernova theory predicts the initial protoplanetary disk properties simpler. Supernovas aren't fortuitous but the usual molecular cloud environment:

"Molecular clouds host supernova remnants
- Natural association: birth place of massive stars ending as SNe" [ http://scineghe08...ouds.pdf ]

It would then be less likely if lower mass long lived star formation wasn't triggered by SNes.

As for planet formation, the separated Nice model is very predictive and so accepted. There are no contender that comes even close.

I don't understand why anyone would suggest a 2nd gen planetary system (after the original binary merged), which would be rarer than 1st gen as binaries are a subset of stars. But it is impossible to square with the solar system especially, there are no traces of an earlier protoplanetary disk.
Pressure2
1 / 5 (4) Aug 02, 2012
Quote from article: "This presents a timing problem, as the SLRIs must be formed in a supernova, injected into the presolar cloud, and trapped inside the meteoritic precursors, all in less than a million years."

Now to the simplest one of all: The sun itself was the percursor supernova. Timing problem solved.
Shootist
4 / 5 (8) Aug 02, 2012
Now to the simplest one of all: The sun itself was the percursor supernova. Timing problem solved.


Oliver, is that you?
thermodynamics
5 / 5 (3) Aug 02, 2012
It can't be Oliver. He is not ranting about neutron pressure and iron cores (yet).
Caliban
not rated yet Aug 02, 2012
Quote from article: "This presents a timing problem, as the SLRIs must be formed in a supernova, injected into the presolar cloud, and trapped inside the meteoritic precursors, all in less than a million years."

Now to the simplest one of all: The sun itself was the percursor supernova. Timing problem solved.


Only one small problem with these proposed proto-solar system nova/supernova theories: in either case, the shockwave/radiation pressure would have cleared out the entire volume of the present-day solar system, and probably much more, besides -ie, no material in the neighborhood from which the present day solar system could have formed.

The "nearby" supernova better fits the observations, even if it is a bit more complex as a proposed mechanism.

SnowballSolarSystem _SSS_
1 / 5 (5) Aug 02, 2012
Torgjorn,

SNe:
I'll grant your point that giant molecular clouds are host to > concentrations of SNe.

Nice Model (NM):
And I agree that the intrusion of Neptune into the Kuiper belt explains the LHB, but I disagree with the cause since the NM has nothing to say about timing. Alternatively, exponential 'orbit inflation' of a wide binary companion, Proxima (Centauri), by perturbation of its original close binary pair out to 270,000 AU, explains timing. At 4.567 Ga and 75 AU, Proxima's inner planetary resonant nursery was forming the Kuiper belt, like Jupiter formed the asteroid belt. On a log plot, the barycenter of the solar system crosses Neptune at 4.0 Ga, and the present-day barycenter at 33,750 AU aligns the aphelion of OOC comets, explaining the missing perturbator, Tyche. Barycenter works, Tyche doesn't for an Oort cloud perturbator since a 1-3 Mj mass Tyche at 20,000 AU could be detected by planetary deflection of the zero-gravity barycenter.

2nd Gen:
?, 1 disk, 1 gen
SnowballSolarSystem _SSS_
1 / 5 (4) Aug 02, 2012
Correction,
planetary deflection BY the zero-gravity barycenter.
Pressure2
1 / 5 (6) Aug 03, 2012
It is not necessarily a problem Caliban. Sure most of the lighter elements would be expelled but some in not most of the heavier elements would not. How can we know this? Because a neutron star is the remnants and a lot of heavy nuclei would almost certainly be in low orbits around a neutron star. It would not be like an on-off switch.
Torbjorn_Larsson_OM
not rated yet Aug 05, 2012
@ SSS:

"And I agree that the intrusion of Neptune into the Kuiper belt explains the LHB, but I disagree with the cause since the NM has nothing to say about timing."

What timing? It fits the LHB, since the Jupiter/Saturn resonance that kick start the process fits nicely the delay between disk formation and LHB.

You get back to the correlation between protoplanetary disk and a supernova seeding it. This isn't the responsibility of the Nice model, and the separation makes the physics simpler.

The correlation between protoplanetary disk and a supernova seeding, and compacting, the previous molecular cloud is the very one you grant. Simple as that.

@ Pressure2:

As I already noted, a 2nd gen disk looks different from what we see, and specifically our disk doesn't show traces of a 1st gen disk.
SnowballSolarSystem _SSS_
1 / 5 (4) Aug 06, 2012
Torbjorn,

"It fits the LHB, since the Jupiter/Saturn resonance that kick start the process fits nicely the delay between disk formation and LHB."

I've got 3 of a kind which beats "nicely", hands down.

The SS barycenter at 30 AU, 4000 Ga falls on a straight line on a natural log plot between 75 AU, 4567 Ma and 270,000 AU, 500 Ma when lunar spherules reached a min., implying exponential perturbation between the close and wide binary pairs.

If Proxima's close binary pair merged at 500 Ma, the increase in lunar spherules count since then could be caused by eccentricity pumping of outer Oort cloud comets near the SS barycenter (29,600 AU) as a vector cross product between the barycenter Sun axis and the galactic-center Sun axis. So the SS barycenter could be the hypothesized planet Tyche.

"The correlation between protoplanetary disk and a supernova seeding, and compacting, the previous molecular cloud is the very one you grant. Simple as that."

I'm missing your point.