Calcium in our bones and teeth likely came from special star explosions, scientists study how process happened

Thanks to an amateur astronomer, 70 scientists from 15 countries were able to witness this calcium-spewing explosion or supernova in action and study it extensively


                            Calcium in our bones and teeth likely came from special star explosions, scientists study how process happened
(Aaron M Geller, Northwestern University)

The origins of calcium on our planet, including in our teeth and bones, are traced to stars that ended their life dramatically in an explosion. But about half of them come from a type of blast, which is extremely rare. The elusive nature meant that astronomers could not unravel its secrets. But thanks to an amateur astronomer, 70 scientists from 15 countries were able to witness this calcium-spewing explosion or supernova in action. This helped them gain insights into how they generate copious amounts of the bone-forming element.

“These events are so few in number that we have never known what produced calcium-rich supernova,” said first author Wynn Jacobson-Galan, who began working on the study at UC Santa Cruz and is currently a graduate student at Northwestern University. “By observing what this star did in its final month before it reached its critical, tumultuous end, we peered into a place previously unexplored, opening new avenues of study within transient science.”

Normally, stellar objects make small amounts of calcium by slowly burning helium throughout their lives. Calcium-rich explosions, on the other hand, produce massive quantities -- within seconds. Once stars near their end, they explode and eject elements into space, thereby shaping the cosmos. The dying star in question is located in Messier 100 galaxy, about 55 million light-years away from Earth. Catching the explosion in action was an amateur astronomer named Joel Shepherd. On April 28, 2019, Shepherd used his new telescope to view the galaxy. The following day he spotted a bright orange dot and alerted others.

Hubble Space Telescope image of SN 2019ehk in its spiral host galaxy Messier 100. The red arrow points to the supernova. (Charlie Kilpatrick, UCSC)

“As soon as the world knew that there was a potential supernova in M100, a global collaboration was ignited,” Jacobson-Galan said. “Every single country with a prominent telescope turned to look at this object.”

The astronauts used three telescopes --NASA’s Swift Satellite, W.M. Keck Observatory in Hawaii, and Lick Observatory -- to observe the supernova dubbed SN 2019ehk. “In the world of transients, we have to discover things very, very fast before they fade,” Raffaella Margutti, assistant professor of physics and astronomy at Northwestern, said. “Initially, no one was looking for x-rays. Daichi noticed something and alerted us to the strange appearance of what looked like x-rays. We looked at the images and realized something was there. It was much more luminous than anybody would have ever thought. There were no preexisting theories that predicted calcium-rich transients would be so luminous in x-ray wavelengths.”

The researchers concluded that a collision between the star's matter and loose material in the outer shell created bright X-rays. The overall explosion led to intensely hot temperatures and high pressure, driving a chemical reaction that produces calcium, they said. “The explosion is trying to cool down,” Margutti explained. “It wants to give away its energy, and calcium emission is an efficient way to do that.”
 
Using Keck, the Northwestern team discovered that SN 2019ehk emitted the most calcium ever observed in a singular astrophysical event. “It wasn’t just calcium-rich,” Margutti said. “It was the richest of the rich.”

The study was published in the Astrophysical Journal.

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