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Sun’s Origin

Stellar Nursery Secrets: Uncovering Sun’s Origin

It’s not quite clear where the sun was created. There seem to be a lot of competing theories on the Sun’s Origin, according to some recent ones.

Could the Sun be an only child? Or perhaps it came from a (very) large family.

If you think your family reunions are awful, just try to picture them with a few thousand of your most bitter siblings. After all, our story is also about the sun’s origin. While we have made great strides in understanding the birth of stars, we still have some fundamental questions about the star closest to home.

The sun may be so close we can reach out and touch it, but time is still working against us when it comes to understanding how it came to be. Our star, which formed 4.6 billion years ago, is now well into middle age and has strayed far from its birthplace, an unknown and long-gone “stellar nursery” of gas that eventually cooled and condensed into stars.

What evidence do meteorites provide about the sun’s origin? 

While we were unable to locate the nursery in question, we did acquire some useful information. Surprisingly, we have evidence of it in the form of meteorites, some of which retain information about the conditions present during the solar system’s conception. Meteorites include isotopes of elements like potassium that can tell us where they formed in the presolar nebula, and differences amongst meteorites can be used to infer the conditions of the nebula before the formation of planets.

An international team of astronomers analyzed the sun’s origin using meteorite data and cutting-edge computer simulations. They used data from meteorites and cutting-edge computer simulations to determine what conditions were likely present when the sun was born.  Their research suggests that the Sun not only had many siblings but also was born in a very urban area.

What is the process of star formation in nebulae?

When the interior of these cosmic clouds, known as nebulae, collapses onto a central pile-like point, a star is born. There is a wide range of sizes and types of nebulae, from faint black globules to enormous, massive molecular clouds. The formation of a star in any given nebula is a story of nature rather than nurture.

Barnard 68 (B68)
Credit: ESO

Barnard 68:

The neighboring nebula Barnard 68 is a dark clump of frigid gas and dust, composed of microscopic grains of silicates (rocky stuff) and complex carbon molecules like soot, and is only a few hundred light-years away from Earth. It’s a favorite of mine since it looks like a black hole in the sky, blocking out the brightness of the stars behind it.

With a diameter of only 0.5 light-years (3 trillion miles), it contains barely enough matter to create a single star marginally more massive than the sun. It’s probably in the midst of this transformation right now, and in as little as 200,000 years it may become a star.

Orion B:

On the other end of the spectrum is the Orion B molecular cloud complex, which is over a thousand light-years away and many hundreds of light-years broad; it is a genuinely massive region of active star formation. It’s robust enough to produce an incredible number of stars, at least 100,000 sun-like ones. The famous Orion nebula is just a small fraction of this enormous stellar factory, visible to the naked eye and the birthplace of hundreds of stars.

These massive clouds are uncommon yet produce stars at an industrial rate, while smaller clouds are more common but produce fewer stars. The Sun may have formed in any type of star nursery, and it would be impossible to know from these numbers alone.

How are sibling stars in a nebula affected by the presence of massive stars?

The stars formed in each of these nebular environments are, nevertheless, quite distinct from one another. Sibling stars in a nebula that are still developing are profoundly affected by the presence of massive stars. Like the solar wind, but turned up to 11, they can release torrents of subatomic particles. These winds can deposit heavy metals like aluminum and magnesium onto stellar embryos. A new combination of these metals, such as iron and cobalt, are then flung very far when these stars explode as supernovae.

What can the early solar system’s chemical composition reveal about the sun’s origin?

Large stars, however, are unusual. It’s estimated that only one in a hundred stars is large enough to have such influence and that tiny nebulae simply don’t succeed. That means, in theory, we could find out what kind of birthing room the sun was born in by analyzing the early solar system’s chemical composition.

This question was at the heart of the recently released study. In particular, astronomers focused on aluminum-26 and iron-60. While iron-60 is forged in the thermonuclear hell of an exploding star, aluminum-26 is produced within massive stars and expelled in their winds. Both elements decay into magnesium and cobalt, so measuring the amounts of these daughter elements in meteorites from the early solar system can reveal the sun’s origin.

What did the new study suggest about the sun’s origin?

The new study uses the physics of nebulae and star formation to model the birth of a sun-like star in different circumstances, from nebulae with relatively few stars (a proxy for smaller clouds) to enormous nebulae with many thousands. Then, they compared the virtual yields to those measured in meteorites by calculating the elemental composition of the emerging proto-proxy-presolar disk in each scenario.

Their findings suggest that the young sun was assaulted by stellar winds and supernovae while it was still in its natal disk. This suggests that the solar nursery was more analogous to the Orion complex than it was to Barnard 68.

That is to say, the sun was probably more of a city slicker than a country bumpkin. We can’t prove this as easily now that its nebular nursery has been destroyed. After all, there’s nowhere to go but forward.

What about the thousands of other stars that the sun shares a family tree with? 

They were probably huddled together like a litter of puppies when their sun was young, but now they’re dispersed across the cosmos after striking out on their own. However, astronomers do actively seek them out, specifically stars that are the same age and composition as the sun.

Reuniting is highly improbable. We’ll just have to make one if we want to see a family photo book.

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