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It's weird to see how things come together sometimes in astronomy. By studying a nearby star, astronomers have been able to determine that the very The first stars (and now vanished) of the universe exploded asymmetrically, sending extremely powerful and ridiculously centered beams of matter moving at a speed close to that of light!
How was this sorcery accomplished?
First, let's take a step back – about 13.4 billion years.
When the Universe was very young, it contained only hydrogen, helium and some lithium. All this was in the form of gas scattered in space.
Over time, a few hundred million years after the Big Bang, this gas began to fuse and form the very first stars. These stars were essentially hydrogen and helium, because there was not yet any iron, carbon, oxygen or anything else in it. l & # 39; universe. In truth, this fact dominates astronomy so much that astronomers group all the heavier elements than hydrogen and helium into a catch-all term: metals. I know, I wish they used a different word, but we're stuck with that now. Oxygen may not seem to be a metal, but it is an astronomer. They simply use the word differently from normal people.
Whatever the case may be, these heavier metals change the way these stars form and live their lives; missing heavier elements inside the first generation of stars could develop tremendously*, hundreds of times the mass of the sun, maybe even a thousand times the mass of the sun!
Like today's stars, these first-generation stars melted hydrogen into helium, then carbon, and so on, creating metals in their nucleus. These stars were burning their nuclear fuel extremely fast and exploded in less than a million years. The expanding debris of the supernova, enriched with these heavy elements, then dispersed in the gas around the stars, seeding them with carbon, nitrogen and other elements. The stars born of this gas then began life enriched in metal.
Some of these second-generation stars have exploded, further increasing the amount of heavy elements in the universe. These were massive stars, but some stars born at that time had a lower mass, more similar to the Sun. The lower mass stars use their fuel more stingily, living billions of years. Even tens of billions … which means that they are always there. Today & # 39; hui. After 13 billion years, some of these ancient stars still exists.
To find them, astronomers are looking for stars with extremely low abundance of heavy elements. It's almost impossible to make such stars today, so if you find one, you know it must be old.
Well. Approximately 3,700 light-years away from the Earth is a weak, relatively un-descriptive star called HE 1327-2326. It's a little sun, although slightly less massive. He is also approaching the end of his very long life, beginning his expansion into a red giant. At present, this is called a sub-giant.
It was discovered in the Hamburg / ESO poll in 2005 by astronomers looking for very old stars. It is incredibly low in some metals; the amount of iron in the star is only 0.000006 times that of the Sun!
This is where things are fun. Zinc is an important metal for astronomers studying ancient stars. This first generation of super-massive stars probably made a lot of zinc in their cores, but it was at the bottom near the center of the star. The explosion patterns of these stars show that when the star became supernova, this layer of stars was not destroyed; instead, it collapsed with the rest of the star's core to form a black hole.
When they examined HE 1327-2326, they found that it contained a small amount of zinc, about 0.00004 times the amount of Sun. However, it's still a lot more than you'd expect for such an old star! Where does this zinc come from?
Here is the sneaky piece. The supernova models of this first generation of superstars were based on a strong assumption: that the stars had exploded symmetrically; that is, the debris flew off like an expanding sphere. One of the reasons is that it's much easier to model in a computer; you only have to worry about one dimension (the radial direction, away from the center, if the expansion is perfectly spherical, you can describe it using only that).
But what happens if the explosion is not spherical? We know that some stars explode off-center, for example. And what is even more critical, some stars spin quickly and when their nucleus collapses, this rotation increases enormously (imagine an ice skater who turns his arms in extension, then gets closer, their rotation accelerates). This increase in the spin causes flattening of the material falling into the nucleus, which allows to focus the explosion by projecting two beams of matter and energy tightly focused from top to bottom, screaming from the core. This furrows the upper layers of the star, tears it, and even then, the beams continue to scroll; rays of death walking through the universe.
Nowadays, we call this event a burst of gamma rays and it is one of the most powerful and terrifying things the cosmos can produce.
But they can also save the day! Since they start deep within the star, they can pull out material that would otherwise be locked near the core … including zinc. And of course, models that include the transfer can produce the amount needed to account for what we see in HE 1327-2326.
Hurray! And so an anemic old star (eh, literally) close to the Sun revealed how even more massive old stars exploded near the dawn of the Universe itself. Cared for.
But wait! There is one more thing!
The bundles of material that escaped from the first stars were incredibly powerful and hard to stop. Moreover, the Universe was smaller then, so things were closer together. It turns out that these stars could have sown gas clouds far enough away from them, covering them with heavy metals. Now, billions of years of universal expansion later, these clouds could be in different galaxiesbut still sown by the same star.
I would like to see someone calculate the odds of having an atom or two of one of these dead and cosmically distant stars in our body. It's pretty cool that we have supernovae and kilonovae atoms in us; it would be even cooler.
As Carl Sagan said, we are a star. But it is, perhaps more precisely, that we are stars & # 39; Things.
*There are complex physical reasons for this, but some metals inside a star trap the energy produced, making the star warmer. If a star becomes too massive, it becomes so hot that it rips itself apart. The most massive stars in the Universe now reach a hundred times the mass of the Sun and are incredibly rare.
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