Theory Proposes New View of Sun and Earth's Creation

Spaceref ^ | May 20, 2004

[SteveH]

Theory Proposes New View of Sun and Earth's Creation

Spaceref

May 20, 2004

Like most creation stories, this one is dramatic: we began, not as a mere glimmer buried in an obscure cloud, but instead amidst the glare and turmoil of restless giants.

Or so says a new theory, supported by stunning astronomical images and hard chemical analysis. For years most astronomers have imagined that the Sun and Solar System formed in relative isolation, buried in a quiet, dark corner of a less-than-imposing interstellar cloud. The new theory challenges this conventional wisdom, arguing instead that the Sun formed in a violent nebular environment - a byproduct of the chaos wrought by intense ultraviolet radiation and powerful explosions that accompany the short but spectacular lives of massive, luminous stars.

The new theory is described in a "Perspectives" article appearing in the May 21 issue of Science. The article was written by a group of Arizona State University astronomers and meteorite researchers who cite recently discovered isotopic evidence and accumulated astronomical observations to argue for a history of development of the Sun, the Earth and our Solar System that is significantly different from the traditionally accepted scenario.

If borne out by future work, this vision of our cosmic birth could have profound implications for understanding everything from the size and shape of our solar system to the physical makeup of the Earth and the development of the chemistry of life.

"There are two different sorts of environment where low-mass stars like the Sun form," explained ASU astronomer Jeff Hester, the essay's lead author. "In one kind of star-forming environment, you have a fairly quiescent process in which an undisturbed molecular cloud slowly collapses, forming a star here... a star there. The other type of environment in which Sun-like stars form is radically different. These are more massive regions that form not only low-mass stars, but luminous high-mass stars, as well."

More massive regions are very different because once a high-mass star forms, it begins pumping out huge amounts of energy that in turn completely changes the way Sun-like stars form in the surrounding environment. "People have long imagined that the Sun formed in the first, more quiescent type of environment," Hester noted, "but we believe that we have compelling evidence that this is not the case."

Critical to the team's argument is the recent discovery in meteorites of patterns of isotopes that can only have been caused by the radioactive decay of iron-60, an unstable isotope that has a half life of only a million and a half years. Iron-60 can only be formed in the heart of a massive star and thus the presence of live iron-60 in the young Solar System provides strong evidence that when the Sun formed (4.5 billion years ago) a massive star was nearby.

Hester's coauthors on the Science essay include Steve Desch, Kevin Healy, and Laurie Leshin. Leshin is a cosmochemist and director of Arizona State University's Center for Meteorite Studies. "One of the exciting things about the research is that it is truly transdisciplinary, drawing from both astrophysics and the study of meteorites - rocks that you can pick up and hold in your hand - to arrive at a new understanding of our origins," noted Leshin.

When a massive star is born, its intense ultraviolet radiation forms an "HII region" - a region of hot, ionized gas that pushes outward through interstellar space. The Eagle Nebula, the Orion Nebula, and the Trifid Nebula are all well-known examples of HII regions. A shock wave is driven in advance of the expanding HII region, compressing surrounding gas and triggering the formation of new low-mass stars. "We see triggered low-mass star formation going on in HII regions today," said Healy, who recently completed a study of radio observations of this process at work.

The star does not have much time to get its act together, though. Within 100,000 years or so, the star and what is left of its small natal cloud will be uncovered by the advancing boundary of the HII region and exposed directly to the harsh ultraviolet radiation from the massive star. "We see such objects emerging from the boundaries of HII regions,'' Hester said. "These are the 'evaporating gaseous globules' or 'EGGs' seen in the famous Hubble image of the Eagle Nebula."

EGGs do not live forever either. Within about ten thousand years an EGG evaporates, leaving behind only the low-mass star and its now-unprotected protoplanetary disk to face the brunt of the massive star's wrath. Like a chip of dry ice on a hot day, the disk itself now begins to evaporate, forming a characteristic tear-drop-shaped structure like the "proplyds" seen in Hubble images of the Orion Nebula. "Once we understood what we were looking at, we realized that we had a number of images of EGGs caught just as they were turning into proplyds," said Hester. "The evolutionary tie between these two classes of objects is clear."

Within another ten thousand years or so the proplyd, too, is eroded away. All that remains is the star itself, surrounded by the inner part of the disk (comparable in size to our Solar System), which is able to withstand the continuing onslaught of radiation. It is from this disk and in this environment that planets may form.

The process leaves a Sun-like star and its surrounding disk sitting in the interior of a low density cavity with a massive star close at hand. Massive stars die young, exploding in violent events called "supernovas." When a supernova explodes it peppers surrounding infant planetary systems with newly synthesized chemical elements - including short-lived radioactive isotopes such as iron-60.

"This is where the meteorite data come in," said Hester. "When we look at HII regions we see that they are filled with young, Sun-like stars, many of which are known to be surrounded by protoplanetary disks. Once you ask the question, 'what is going to happen when those massive stars go supernova?', the answer is pretty obvious. Those young disks are going to get enriched with a lot of freshly-made elements."

"When you then pick up a meteorite and find a mix of materials that can only be easily explained by a nearby supernova, you realize that you are looking at the answer to a very longstanding question in astronomy and planetary science," Desch added.

"So from this we now know that if you could go back 4.5 billion years and watch the Sun and Solar System forming, you would see the kind of environment that you see today in the Eagle or Trifid nebulas," said Hester.

[SteveH]

Here's an image:

(OK, so I really found the article from that other conservative EBB...;-)

[farmfriend]

.

[Consort]

There are probably many ways for suns and planets to form.

[P.O.E.]

From what I remember iron is about as high on the table a sun will create (and my memory is rusty on that, so to speak). So supernova is the machine for the higher elements. Makes me wonder if we are the first such experiment.

[MonroeDNA]

Nice post!

[aimhigh]

..a new theory..

.. anything but God... anything but God... anything but God... anything but God... anything but God... anything but God... anything but God... anything but God..

[JSteff]

As the Pope said once (along these lines).. creationism and evolution are not mutually exclusive.

The Lord created and put in motion all that still goes on creating. Maybe the beauty of all it is that we ended up being one, maybe the only one, of those solar systems that allowed life.

Did the Lord make anything easy for us? Did he give us nuclear power, antibiotics, or open heart surgery? No, he gives us the things to do this but leaves us to discover and use them the best we can.

How we use them determines whether we have learned what he taught us in the beginning.

[PatrickHenry]

PING. [This list is for the evolution side of evolution threads, and some other science topics like cosmology. FReepmail me to be added or dropped. Long-time list members get all pings, but can request evo-only status. New additions will be evo-only, but can request all pings. Specify all pings or you'll get evo-pings only.]

[Shryke]

creationism and evolution are not mutually exclusive.

I happen to agree, but.....what does evolution have to do with this article?

[RadioAstronomer]

A star uses the weak force to “burn” (nuclear fusion). Three processes we observe are proton-to proton fusion, helium fusion, and the carbon cycle. Here is an example of proton-to-proton fusion, which is the process our own sun uses: (two protons fuse -> via neutrino interaction one of the protons transmutes to a neutron to form deuterium -> combines with another proton to form a helium nuclei -> two helium nuclei fuse releasing alpha particles and two protons). The weak force is also necessary for the formation of the elements above iron. Due to the curve of binding energy (iron has the most tightly bound nucleus), nuclear forces within a star cannot form any element above iron in the periodic table. So it is believed that all higher elements were formed in the vast energies of supernovae. In this explosion large fluxes of energetic neutrons are produced which produce the heavier elements by nuclei bombardment.

[RightWhale]

Somebody, possibly at a table of proto-astronomers having coffee in the break room between classes, said there were several supernovas in our region over a period of time, and we now reside in a hollow region swept free of dust about 500 light years in diameter.

[longshadow]

I'll ask the obvious question: where is the remnant of the massive star that went supernova that seeded our solar system with all that iron 60 whose daughter products they find in the meteorites? Shouldn't we have a "Crab Nebula" sort of thing sitting in our galactic backyard if this is accurate? Or, are they suggesting after 4 billion years, all evidence of it would have long since dissipated?

[RightWhale]

An old supernova would be nothing but a small burnt-out cinder by now, all the dust blown away or condensed into planets and comets. Crab nebula is very recent, just this morning in astronomical time.

[PatrickHenry]

I'll ask the obvious question: where is the remnant of the massive star that went supernova that seeded our solar system with all that iron 60 whose daughter products they find in the meteorites? Shouldn't we have a "Crab Nebula" sort of thing sitting in our galactic backyard if this is accurate?

I don't know what a 4-billion-year-old nebula would look like from the inside, and that's probably our perspective. It probably clouds our "outlook" a bit, but unless one is looking at a nebula from the outside, its existence may not be obvious.

[longshadow]

An old supernova would be nothing but a small burnt-out cinder by now, all the dust blown away or condensed into planets and comets.

I suspected that might be the case ....

[JSteff]

Re-Read Post 6

[Dimensio]

Huh?

What does a religious concept like a god have to do with scientific theory?

[Shryke]

Re-Read Post 6

Done. I repeat, how are these two concepts related? And how did evolution get into the mix?

[<1/1,000,000th%]

I'll ask the obvious question: where is the remnant of the massive star that went supernova that seeded our solar system with all that iron 60 whose daughter products they find in the meteorites?

That's the first thing I thought. There should be a nearby neutron star or a black hole. Maybe it's a massive star flyby?

[longshadow]

That's the first thing I thought. There should be a nearby neutron star or a black hole. Maybe it's a massive star flyby?

As was already pointed out, the enormous time since the event pretty much wipes out the observable evidence. Even if a remnant were still in the neighborhood, it's doubful we'd know unless it was radiating energy..... and I don't know if neutron stars cam last 4+ billion years without depleteing virtually all of its angular momentum.