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Astronomy is a somewhat weird field in this in other respects. For example, astronomers frequently consider everything that isn't helium or hydrogen a "metal."
by MAGZine 5y ago
Astronomy is a somewhat weird field in this in other respects. For example, astronomers frequently consider everything that isn't helium or hydrogen a "metal."
They just have a very different take on some things, because their way of looking at the universe is different from how we look at earth.
- vagrantJin 5y agoThat strikes me as sbsurd. Sure, the table has mostly metals but there are a lot of gases.
- goldenkey 5y agoEverything's pretty much a plasma when it's burning at millions of degrees.
- matkoniecz 5y agoUniverse is more than 98% hydrogen and helium by mass, with all other being less than 2%. Maybe metal was not the best word for that, but having word for "all elements except hydrogen and helium" is useful in astronomy see https://en.wikipedia.org/wiki/Metallicity https://en.wikipedia.org/wiki/Metallicity
- rob74 5y agoOk, so, maybe they could have, you know, invented a new word? Or picked another one which isn't putting them at odds with the chemists?
- KingOfCoders 5y agoIf it works for them.
- ben0x539 5y agoAstrophysics was probably a thing before chemistry, so maybe the chemists ought to have picked a different word!
- dtgriscom 5y agoTrue, but at that time nobody knew about hydrogen and helium in stars.
- dmurray 5y agoMetal vs gas is a poor choice of dichotomy: every element is a gas at the right temperature and pressure.
- pcl 5y agoI would guess that they aren’t distinguishing on the basis of phase state, but rather atomic number. Astronomers presumably mostly think about matter in the form of a star, in which presumably all the hydrogen and helium would be in some sort of plasma state, and perhaps all the “metals” would be too.
- nicklecompte 5y agoThe reason astronomers use “metallicity” this way is largely historical: (chemical) metals are not as prevalent in stars as non-metallic elements like carbon and nitrogen, but they are much easier to detect in spectral analysis. So historically the “metallicity” of a star really did refer to the heavy metal content (generally Fe), and considering the physical processes involved it’s not unreasonable to extend this to all non-H/He elements in the star. I think it would be “absurd” for astronomers to change this because people who aren’t scientists get confused.
- vagrantJin 5y ago> nicklecompte 1 hour ago | parent [–] | on: Freshly made plutonium from outer space found on o... The reason astronomers use “metallicity” this way is largely historical: (chemical) metals are not as prevalent in stars as non-metallic elements like carbon and nitrogen, but they are much easier to detect in spectral analysis. So historically the “metallicity” of a star really did refer to the heavy metal content (generally Fe), and considering the physical processes involved it’s not unreasonable to extend this to all non-H/He elements in the star. I think it would be “absurd” for astronomers to change this because people who aren’t scientists get confused. My bad yo. Please accept my humble apology in not knowing the historical signifacance of something. I'll be doing my masters in 2022/23, biochemistry/microbiology. I really should have been a bird watcher instead. Who cares about plant proteins anyway? That's not science at all.
- ianai 5y agoIn math, I was taught to always be mindful of the definitions-particularly because they change on context. When studying certain systems different conventions make sense than in other studies. It’s not a judgement call as to what matters absolutely, just what helps the area of study the most. Further, the better flexible you are with working across contexts the better a grasp on the topic you have. (So further, the more ways you can explain a concept or prove a theorem the better you understand the concept.)
- ianai 5y agoThe way it was explained to me, astronomers considered them metals because they’re much more rare than H and He. They’re not made in the core of fusing stars. That might seem trivial, but a huge amount of the universe is H/He compared to the rest of the periodic table.
- Retric 5y agoIn Astronomy STP is the exception not the rule. Not much is a gas at 3 kelvin in deep space, the other common option is stars where everything is a plasma. And that’s ignoring white dwarf’s which are mostly electron-degenerate matter, neutron stars which don’t have chemical elements, and black holes which are even stranger. So, really hydrogen, helium, and everything else is a perfectly reasonable classification as everything else acts the same outside of fusion.
- enkid 5y agoWhat is the typical state of matter at 3 kelvin in deep space?
- eloff 5y agoSolid. Everything except hydrogen and helium would be in a solid state I think.
- evanb 5y agoThat’s not obvious because of the ultra low pressure.
- bigyikes 5y agoAgreed. I haven’t thought about this stuff since taking gen chem in college, so I went and looked up the phase diagram for Neon, as an example. At low pressures, it looks like as little as 15 Kelvin is enough to make Neon a gas.
- Retric 5y agoHowever, deep space is 2.7 Kelvin. Though of course it gets much hotter near stars and even simply being inside a galaxy is enough to hit 10-20 Kelvin.
- Sharlin 5y agoMost matter in deep space is individual ions, atoms, or molecules, so has no well-defined phase. Then there's solid dust particles which are made of all sorts of stuff including silicates, organic compounds, and ices of different elements.
- stjohnswarts 5y agoSometimes it is perfectly adequate to model cows as spheres :)
- tragomaskhalos 5y agoEven more bizarre is the idea of metallic hydrogen: https://astronomy.com/magazine/ask-astro/2018/06/metallic-hydrogen-in-gas-giants https://astronomy.com/magazine/ask-astro/2018/06/metallic-hy...
- freshair 5y agoIs this the reason Hydrogen is grouped with the alkali metals on the periodic table?
- DavidSJ 5y agoThe most immediate reason is that hydrogen is a group 1 element, meaning its outer (in this case, only) shell contains just a single electron, in its s (spherically symmetric) orbital. The electronic structure of an element greatly influences its chemical behavior, so elements in the same group tend to be chemically similar. However, hydrogen is a bit of an odd-ball as group 1 elements go.