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New Class of Stars Are Totally Metal, Says Astrophysicist
KentuckyFC writes Stars form when clouds of gas and dust collapse under their own gravity, generating enough heat and pressure to fuse the atoms inside them together. When this cloud of dust and gas is the remnants of a supernova, it can contain all kinds of heavy elements in addition to primordial hydrogen, helium and lithium. Now one astrophysicist has calculated that a recently discovered phenomenon of turbulence, called preferential concentration, can profoundly alter star formation. He points out that turbulence is essentially vortices rotating on many scales of time and space. On certain scales, the inertial forces these eddies create can push heavy particles into the calmer space between the vortices, thereby increasing their concentration. In giant clouds of interstellar gas, this concentrates heavy elements, increasing their gravitational field, attracting more mass and so on. The result is the formation of a star that is made entirely of heavy elements rather than primordial ones. Astrophysicists call the amount of heavy elements in a star its "metallicity". Including preferential concentration in the standard model of star formation leads to the prediction that 1 in 10,000 stars should be totally metal. Now the race is on to find the first of this new class of entirely metal stars.
or Kerrang! They're full of metal stars
When did Nathan Explosion become an astrophysicist?
First metal star should be named after them.
Every time I hear about a (cool) new kind of star like this i get all teh happi feelz
It reminds me of the Cosmos where Sagan elucidates how everything and everyone we've ever known is made of "star stuff" & our composition reflects our star's composition
So...what kind of planets & planetoids would a **METAL STAR** make???
Thank you Dave Raggett
... they're called Class \m/ stars.
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Let's take TFA at face value, and assume one in 10k stars start their evolution as count as "metallic" stars.
Hydrogen main sequence stars burn for a a few million years (for the class O supergiants) to literally trillions of years (for the class M all-but-failures). Helium burning, in a star with sufficient mass, lasts between a few hundred thousand to a few dozen million years.
The subject of TFA starts after helium burning normally finishes - Next on a typical star comes carbon, lasting for only a few hundred years; Then comes neon lasting for a single year, oxygen at half a year, and silicon finishes its run in a single day.
So whether or not a star begins life with a high concentration of trans-lithium metals, it will have a very, very short lifetime; That one-in-ten-thousand creation ratio therefore reduces to more like one-in-a-trillion among those stars still shining in our nighttime sky.
Stellar fusion can occur with atomic elements up to iron. There are a number of metals that are lighter than iron. If I'm reading this right, stellar fusion could conceivably be triggered by heavier metallic elements if they were "selected for" by the properties of vortices during the formation process.
The world's burning. Moped Jesus spotted on I50. Details at 11.
What astronomers mean for the word "metal" isn't what the rest of us mean.
As mentioned in the link to Metallicity, the all metal stars could be composed of carbon, nitrogen, oxygen, etc. Basically anything other than hydrogen and helium.
Additionally, in astrophysics the term "metal" includes many elements which are not metals in any other field. Astrophysically, metals are any element other than hydrogen or helium, so in addition to ordinary metals like sodium and lithium non-metallic elements such as carbon and oxygen are counted as metals.
Unless it's made of a light metal...then we'll name it Warrant.
My
If I'm reading TFA correctly, it basically means that stars formed from one molecular cloud have very different metallicities - anywhere between the mean metallicity of the molecular cloud and the "purely metal" extreme. If this is actually true, there may be far reaching implications for the research of stellar clusters. One of the basic assumptions in this field is that all cluster stars created from a given molecular cloud have very similar chemical compositions.
Helium is not!
If you read the article, however, it would point out that astronomers use a skewed definition of "metal", as any element heavier than lithium.
At birth, stars contain little helium, but is is constantly generated by fusing hydrogen.
If you start with metals like sodium and potassium, plus what we normally call non-metals, like carbon and oxygen, then you won't get around to generating helium until you fuze something radioactive that emits an alpha particle.
In astrophysics, the term "metal" normally applies to any element heavier than lithium. Carbon, silicon, even gasses like oxygen and nitrogen, are "metals". We're not talking about star remnants that are primarily iron or lead or uranium. Gold would be right out.
And we have been studying stellar spectra for a century now. The must be much rarer than 1 in 10,000 or we would have already found one. They must be exceedingly rare.
My rights don't need management.
The iron doesn't "want" to come apart, and doesn't.
The star is a fine balance of gravitational attraction that compresses of all its parts to the point of fusion at the center, and the expansion of the star as the pressure of fusing energy at the center wants to expand the star.
At first, hydrogen is converted to helium and that process is so energy-rich that the star doesn't struggle much to hold off the collapsing effect of gravity.
As other elements are converted from one to the other, the fusion process is less efficient in producing energy and the star struggles even more to fight off gravity and becomes more dense
At the last stage of the star's life, when it produces iron, the star hits a brick wall. Fusion is not robust enough to convert iron into the next element.
What happens next is amazing because gravity finally overcomes the expanding process of fusion.
The star collapses very quickly, and THAT enormous pressure jams particles together so violently that heavier, more complex elements than iron are made through fission, and at the same time, the star is exploding.
The iron atoms do not come apart. They ride the shock wave.
It little behooves the best of us to comment on the rest of us.