Stellar explosion helps scientists explain 13-billion-year-old mystery of Milky Way's elements

Scientists have resolved a13-billion-year-old mystery of the Milky Way's elements with the help of astellar explosion in space.

The Milky Way began to form relatively soon after the Big Bang explosion that marked the beginning of the universe some 13.8 billion years ago.

Until now, it was believed that neutron star mergers were the only way heavy elements (heavier than Zinc) could be produced.

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But the discovery of an ancient star SMSS J2003-1142 in the Milky Way's halois providing the first evidence for another source for heavy elements, including uranium and possibly gold.

The study published in Natureshows the heavy elements detected in SMSS J2003-1142 were likely produced, not by a neutron star merger, but through the collapse and explosion of a rapidly spinning star with a strong magnetic field and a mass about 25 times that of the Sun.

This stellar explosion is called 'magnetorotational hypernova' by astronomers.

A star-formation binge in the Milky Way spanning the time when the solar system was born more than 4.5 billion years ago was apparently precipitated by the collision between our galaxy and a smaller one called Sagittarius, scientists said on Tuesday.

Such collisions typically do not involve stars smashing head-on, they said, but can foster conditions for star formation by, for example, amping up the amount of gas in a galaxy or having gas clouds come together.

The galaxies first crashed more than 6 billion years ago. Since then, Sagittarius - a “dwarf” galaxy 10,000 times less massive than the Milky Way - has twice passed through our galaxy’s immense disk containing most of its roughly 100 billion stars. All three galactic interactions were associated with a burst of Milky Way star formation.

Data from the European Space Agency’s Gaia space observatory revealed a prolonged star-formation episode from 6.2 billion to 4.2 billion years ago associated with the initial crash. Two other star-formation surges linked to the galactic collision peaked 1.9 billion years ago and 1 billion years ago, each lasting a few hundred million years.

“It is not really an impact like a car crash,” said astronomer Tomás Ruiz-Lara of the Instituto de Astrofísica de Canarias in Spain, lead author of the research published in the journal Nature Astronomy. “Some parts of Sagittarius and the Milky Way intersect, but stars do not crash. A star-star collision would be really, really rare.”

The collision disrupted our galaxy’s steady pace of star formation.

“First, we have the addition of material, gas, from Sagittarius that increases the amount of gas in our galaxy to form new stars. Second, you have the collision between gas clouds from Sagittarius and the Milky Way triggering star formation,” Ruiz-Lara said.

“Third, gravitational instabilities induced by the interaction are able to trigger star formation,” Ruiz-Lara added, by causing “ripples” in the density of the gaseous interstellar medium.

(With inputs from agencies)