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Comment by vlovich123 | Hacker News Reader

Is our solar system considered metal poor?

'Metallicity' in that sense is used to describe stars and the Sun, being a relatively young star is metal rich.

Edit: 'young' is confusing here as pointed out in sibling comments - young compared to the age of the universe rather than young in terms of stage of stellar evolution. To make this even more confusing, this is 'population I' - younger and more metal rich unlike older, metal-poor 'population II' stars.

https://en.wikipedia.org/wiki/Stellar_population#Chemical_cl...

Ah ok. So this is about the composition of just the star and not anything about the broader system.

Almost pretty much the same thing really.

Consider that our sun contains 99.86% of the mass of our Solar System.

Bear in mind the headline is about total spectrum of elements in entire galaxies ... eg: as in looking at our galaxy, the entire milky way, from a distance that makes it dwindle to a near point and difficult to estimate how many stars make it up.

Of all the many galaxies that we can see, this is a story about a handful that are mostly hydrogen and helium .. more so than what we see as typical for galaxies.

Almost pretty much the same thing really.

Consider that our sun contains 99.86% of the mass of our Solar System.

If you dumped that into a Sun-sized metal-poor star, it would probably pass for metal-rich.

Given our sun is a population I or heavy-element-rich star that'd almost certainly be the case ... the elements that didn't fall into our sun to make it so remained in orbit and are also heavy element rich (obviously relatively more so that the mostly H-He sun).

A Sun sized metal poor star wouldn't be surrounded by large amounts of orbiting heavy elements .. that would suggest even larger amounts failed to orbit and fell into that star.

( I'll freely confess to being decades out of date on the conjectured life of stars though, these days I mainly do geophysics related to astrophysics (cancelling out ground effects from SKA type projects) )

Oh I just meant that amount of metal for some (entirely made up) stars would already be pretty metal. The sort of astro out of an Asimov joke story.

But as the black hole approached, Hieronymus noted there was no gravitational effect. He studied it more closely and announced, with a chuckle, that it was not a black hole after all.

“It’s nothing,” he said. “Just an ordinary asteroid someone has painted black.”

Being able to identify both is a feat.

Yeah although like most things in exoplanetary astronomy, the relationship between metallicity and planetary systems is an area of active research with various not-totally-intuitive findings:

https://www.space.com/31456-rocky-planet-found-unlikely-star...

https://www.nature.com/articles/s41467-023-37195-4

That Neptune sized planet sure is close to its star. Interesting

Oh they get even bigger and closer and we've seen a bunch of those because they're more readily detectable:

https://en.wikipedia.org/wiki/Hot_Jupiter

We have Black Sabbath, Iron Maiden, KISS, Slayer, and Megadeth. I'd say we are doing alright!

No. I believe a metal poor solar system wouldn't have rocky planets.

But our sun is quite young afaik (middle aged) and earth is not much younger so it’s weird to hear the reasoning that metal-poor systems implies young system…

I’m assuming the poster misspoke and meant that metal-poor stars have formed when the universe was relatively young, not that the stars are young. It’s also my understanding that a planet such as ours could only have formed a bit later, after enough supernovae had formed all the carbon and iron and so on that we need to live.

Making matters confusing is the fact that the phrase "a young galaxy" is commonly used to refer to a galaxy formed when the universe was young – if it’s far away (high redshift, z >> 1) and as such we see it the way it was when the universe was young!

This specific study, however, looked for more nearby galaxies (z < 1, we see the light that was emitted a few billion years ago) so these galaxies (as we see them) are in fact "old".

I think essentially all existing galaxies either formed >10 Gy ago or are the results of galaxy mergers – so in that sense there are no "young", recently-formed galaxies in the universe at all as the raw material was long ago used up. As such in astro-talk "young galaxies" can fairly unambiguously mean "far-away galaxies". But formally they’d be called high-z or high-redshift galaxies.

> after enough supernovae had formed all the carbon and iron and so on that we need to live.

And let’s not forget some of the atoms we see around us have been through even more violent events than supernovae.

Population II systems must be very boring.

Here, “young” means measured from the Big Bang.

Our sun is made from the stuff of previous stars.

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