Exploding Stars Likely Shaped the Destiny of Planet Earth

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An infrared image of the Ophiuchus star-forming nebula reveals new stars wrapped up in the clouds of gas they are forming in. The Ophiuchus cloud is the closest star-forming region to our solar system, only 407 light-years away.  (NASA/Spitzer)

Scientists are investigating the origin of our planet and solar system by examining other, younger stars and planetary systems currently being formed.

They are looking at a star-forming region in the constellation Ophiuchus. The area is a window into the origins of other solar systems, and the vast cloud of dust and molecules in which they form.

Nascent stellar embryos are providing insight into the raw ingredients that shaped the course of our planet’s development. Researchers are peeking inside the cosmic kitchen to observe how Earth might have been cooked up.

Star-forming nebula Rho Ophiuchi, captured by NASA's WISE spacecraft. The colors represent different wavelengths of infrared light, revealing thermal emissions from stars and surrounding clouds of gas and dust in the nebula. (NASA/JPL-Caltech/UCLA)

Scientists have long suspected that supernovas — the titanic death-blasts of massive stars — contributed to the special sauce that created Earth, but the new data from Ophiuchus gives researchers the ability to apply rigorous mathematical analysis and direct observations to test that hypothesis.

Early findings suggest it might have been multiple exploding stars that created our solar system.

Ophiuchus observations

Several observatories, including from NASA, the European Space Agency, and Chile, took new measurements of multiple wavelengths of light from the star-forming region.

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Researchers from UC Santa Cruz and elsewhere are examining the observations, which show abundance of aluminum-26, an isotope of the element aluminum.

Isotopes are heavier forms of elements, containing more neutrons in an atomic nucleus than the ordinary atom. They are often unstable and prone to decaying into lighter elements, a radioactive process that releases heat. A nuclear power system generates heat from the decay of radioactive atoms in a similar way.

Though most of the aluminum-26 originally infused in our solar system’s primordial star-forming cloud has long since decayed, the elements it broke into remain, preserved in meteorites fallen to Earth.

An infrared composite image from the Ophiuchus star-forming nebula. The gas and dust clouds of the nebula are shown in relation to dense proto-stellar embryos, where new star systems are being born. (João Alves/ESO)

The amount of a radioactive isotope like aluminum-26 that is present during a planet’s formation may be crucial to its development, and the amount of heat released by their decay could determine how wet or dry the planet becomes. And though aluminium-26 has been detected throughout the Ophiuchus complex, its abundance in each forming star system was found to vary enormously.

So what does the math say? Which spice shelves might the mystery chef who cooked up our solar system have grabbed from?

Using a numerical analysis, the researchers calculate a 59% probability that the aluminum-26 in a star system’s mix is supplied by a supernova, and a 68% chance that the material originates from multiple supernovas, as opposed to a single star explosion.

In other words, for nature to cook up a solar system with rocky, water-bearing planets like Earth, likely more than one massive star had to perish in spectacular fashion, billions of years ago.

This finding is important for understanding how our planet was formed and what other worlds might be like in the galaxy around us.

Are there other planets like ours out there? A clearer understanding of the confluence of conditions and materials that produced our solar system can offer insight.

“There is nothing special about Ophiuchus as a star formation region,” said João Alves of the University of Vienna, a co-author of the Ophiuchus paper. “It is just a typical configuration of gas and young massive stars, so our results should be representative of the enrichment of short-lived radioactive elements in star and planet formations across the galaxy.”

Reverse engineering the recipe for our solar system

It’s difficult to peer 5 billion years into the past to understand exactly what conditions shaped our solar system, planet, and life on Earth.

The Eagle Nebula, a stellar nursery 5,700 light-years from our solar system, hides nascent proto-planetary systems within its gas clouds. The visible-light image (left) was captured by NASA's Hubble Space Telescope and nicknamed the "Pillars of Creation." A near-infrared image (right) reveals what's inside: A proto-star can be seen swaddled in the nebula at the topmost tip of the pillar on the left. (NASA)

Scientists can piece together forensic evidence, traces of material and remnant surface features of planets, moons, asteroids and comets preserved over eons. But this reconstruction of the past can be like an episode of "Crime Scene Kitchen," where investigators puzzle over what dishes were cooked up by examining scraps of food left on the cutting board and burned residues in the oven. 

For decades scientists have believed that our solar system was formed by clouds of interstellar gas and dust condensing under gravity, enriched with oxygen, iron, uranium and other special chemical elements, atoms heavier than the hydrogen and helium that make up most of a star-forming cloud.

The new, direct observations of forming star systems give the researchers solid numbers to work with, mathematical tools that give more definite shape to the nebulous ideas of the past few decades.