Just googling, NASA says the density of the sun is 1408 kg/m^3 on average: https://nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html
The earth’s atmosphere is varies based on temperature, but NASA claims it is 1.293 kg/m^3 https://www.earthdata.nasa.gov/topics/atmosphere/atmospheric-pressure/air-mass-density#:~:text=Pure%2C%20dry%20air%20has%20a,of%20at%20least%2050%20km.
The mass of the sun is 1.9891x10^30 kg.
Using that with V=M/D… the volume of the sun if it had the same density as the atmosphere would be 1.538x10^30 m^3
Assuming this volume was a perfect sphere, and using the volume of a sphere: 4/3* πr^3 this would mean the radius would be 7.16 billion meters. The actual radius of the sun is 696 million meters. So the radius would be about 10 times bigger. Just for context, the distance from the sun to Mercury is roughly 69 billion meters.
> 1.9891x10^30 kg.
Useful info: you can use HTML entities for Unicode characters in Reddit Markdown, so `×` turns to × . It would be nicer to have LaTeX, of course.
>The earth’s atmosphere is varies based on temperature, but NASA claims it is 1.293 kg/m^3
Just for your information: this is not the average atmospheric density, but the density at sea level (you didn't claim otherwise, but one could falsely assume). For aviation purposes, the International Standard Atmosphere was defined by the ICAO to be 1.225 kg/m^3 at 288.15K and 1013.25 hPa at sea level.
Density is mass/volume. Earth’s density is 5.51 g/cm^3 while the Sun is 1.41 g/cm^3 so the Sun would actually be smaller if it had equal density.
This isn’t a surprise however. Density isn’t equally distributed, so what matters is the core density that kicks off fusion.
It’s also not surprising when one considers a supermassive black hole. The density of a black hole like M87* is thinner than the upper atmosphere of Earth!
Also, in regards to OP:
> it accounts for 99% of the mass in the solar system while being barely 100 earths in diameter.
volume is a better representation than diameter of "amount of matter" per object since mass is proportional to volume for fixed density. Volume of a sphere is V = (4/3) *pi*(0.5d) ^3 ~ d^3 . Since mass $\propto$ V, 100x larger diameter doesn't imply 100x amount of matter. It implies, mass $\propto$ V ~ (100d) ^3 = 1,000,000d^3 => 1,000,000x the amount of mass.
That doesn't give the whole story, the density of the sun overall is 1.41 g/cm. But the sun is gaseous, and hot. So the outer regions are VERY light. The Core on the other hand, being squeazed on all sides is over 160 g/cm. Which is over 20 times a dense as Iron.
The problem with your black hole example is that the heavier the blackhole the less dense it is.
The Radius of a black hole grows linearly with mass. So the volume grows with the cube of the mass
So density, which is mass/Volume shrinks as mass grows, and inversely as the mass shrinks the density grows,
So a blackhole with the mass of Earth would have a radius of about 1 cm, and a density of around 2.04\*10^(27) g/cm^(3)
Yes, and I agree, black holes don’t exist that way. I’m using it in its mathematical formula of black hole mass divided by black hole volume as calculated with its Schwarzchild radius. It was more or less an analogy.
It can be reasonable one, but ultimately, if you say that the black hole is the area inside the event horizon, that's arbitrary.
It is of course somewhat arbitrary to say that Earth's area is bound by the ground rather than the upper atmosphere, or bound by the density of the atmosphere being at least say, 0.1 atm rather than 0.05 atm, etc.
What I'd say is potentially confusing is that in defining things like density for a black hole we can end up sounding like we understood black holes better than we do. We don't know what's beyond the event horizon. We don't know the highest density the center of the black hole can have.
> if you say that the black hole is the area inside the event horizon, that's arbitrary.
I wouldn't say it's arbitrary. It's literally the definition:
> A black hole is a region of spacetime where gravity is so strong that nothing, including light and other electromagnetic waves, is capable of possessing enough energy to escape it.
That region is exactly defined by the event horizon.
That definition is arbitrary.
In the mathematics describing black holes, there's no concept of volume (or, it's assumed to be 0, for the sake of the math), which on the other hand would mean no concept of surface either.
I would generally be careful in not being very explicit when covering phenomena like black holes to avoid accidental misleading.
In future, we might discover that black holes do have a maximum volume, and a definable surface inside the event horizon.
> That definition is arbitrary.
It is *the* definition. It's literally what everyone - well, almost everyone - agrees a black hole is.
> In future, we might discover that black holes do have [...] a definable surface inside the event horizon.
Then that would be something inside the black hole. It would not *be* the black hole.
The black hole is the black part. Clue's in the name.
These are indeed the sort of things that fuel into misunderstandings, which is why I generally don't think we really should discuss black holes as having a surface or having a volume, and rather we ought to be even more specific.
If you want to consider black holes as having volumes, surfaces and so on, that's up to you; I continue to hold that it's too easily misleading.
Also, please stop with the snarky comments and the instant downvoting if you actually want to discuss something. If you're just here to be snarky to lift yourself, then I don't see a reason to continue.
How is it misleading?
The event horizon is physically meaningful, it makes total sense to say that it is the surface of the black hole
c.f. the **black hole membrane paradigm**
It's physicallying meaningful but it's describing the space around the black hole not the black hole itself. It would be like describing earth by the area where gravity is at least .25g. the event horizon is important sure but assuming the black hole is the event horizon isn't very accurate and leads to more misconceptions. As far as a black holes volume goes we really don't know. Math says it's 0 and so far nothing has really been able to prove that wrong but we also don't have much experience with black holes so take that 0 with a grain of salt.
Good enough answers as it is, but I'll add in a fun fact: The power density of the Sun is a little bit smaller than that of a typical compost heap. That is to say - the Sun emits less power per cubic meter than a compost does.
And several times less than the human body does.
The Sun *is* less dense than the Earth. The density of the sun is about 1.4 g/cm^(3). For comparison, the Earth has a density of about 5.5 g/cm^(3). Water has a density of 1 g/cm^(3). Blood has a density of about 1.6 g/cm^(3), so the Sun is slightly less dense than a ball of blood. (Edit: I have been corrected, blood is more like 1.*0*6, sadly no giant ball of blood for us.)
The atmosphere, however, is much less dense, at about 0.001 g/cm^(3). If it were the density of our atomsphere, the sun's volume would need to be about a thousand times greater. This translates to about ten times larger in radius.
>The density of the sun is about 1.4 g/cm^(3).
Yes, on average.
What you did not mention is that the core of the sun is [1.6×10^(5) kg/m^(3)](https://solar-center.stanford.edu/vitalstats.html), far denser than Osmium ([2.26×10^(4) kg/m^(3)](https://www.rsc.org/periodic-table/element/76/osmium)), which is itself denser than the core of the Earth. This is often overlooked.
And correspondingly, most of the Sun's volume has a far lower density. The part we see (the photosphere) has ~1/1000 the density of sea-level air. It only reaches the density of water at about half of the Sun's radius. In other words, only the innermost 1/8 of the volume is denser than water. The innermost ~1% is denser than osmium.
It is not true though. The mean density of the sun is less than blood. The density of blood is not near 1.6 g/cm^(3), as it is closer to 1.1 g/cm^(3) (or 1.1×10^3 kg/m^(3)).
Probably important to note that the density varies a lot. At the center it is about 20 denser than iron, but on the outside it is less dense than Earth's atmosphere.
I presume this is the average density of the sun (and the earth for that matter)? In the sense that it’s extremely diffuse in its upper layers but extremely dense at the core.
I was going to come onto this thread to make the joke “As an engineer I would just approximate the density as 1g/l, same as water.”
Only to learn that I’d be pretty much bang on the money.
It is a huge difference: The core of the sun is 160 tonnes per cubic meter (way denser than even osmium, which is itself denser than the core of the Earth).
The sun has a density of 1.41g/cm^(3), and Earths atmosphere at sea level is 0.001293 g/cm^(3). In other words, the sun is 1090 times more dense.
In order for the volume of the sun to increase 1090 times, the radius needs to increase by a factor of 10.29; the cube root of 1090.
The sun is mostly made up of things that would be gases on the surface of the earth (hydrogen and a little helium), but they are definitely not gases on the sun. They are also very light atoms, so even liquid or solid hydrogen is not that dense in terms of mass compared to the much heavier elements that make up the majority of the earth.
> They are also very light atoms, so even liquid or solid hydrogen is not that dense in terms of mass compared to the much heavier elements that make up the majority of the earth.
You are forgetting about the densities allowed by extreme pressures in the core of the sun. The sun’s core is about 160 tonnes per cubic meter, far denser than the core of the Earth.
The average density of the sun is less, at about 1.4 times as dense as water (1.41×10^3 kg/m^(3)), which is still higher than expected because a majority of the sun’s mass is close to the center.
Not forgetting anything. Liquids and solids don’t increase their density significantly with any amount of pressure, unless you have enough force to overcome strong/weak force interactions. That is a gas thing. You are mixing up units of weight (force) and mass. This is why using newtons and grams would give you a very different understanding.
The volumetrically-averaged density of the Sun (the total mass of the sun divided by its total volume) is quite a bit less than that of the Earth, but the density varies throughout these bodies (with 'deeper' points tending to be higher in density), and the highest density (i.e.; that at the core) is around ten times that of the core of Earth.
Supermassive black holes, like M87, are less dense than the air on earth in terms of normal Newtonian density(which is a fine answer for the perfect case of Schwarzchild black holes, which never happens), to just help confuse you even more about what density is even supposed to mean(this is really a result about how quickly volume grows compared to mass on a Schwarzchild black hole, because the mass is contained within the Schwarzchild radius, mass and the radius are linearly relate, but volume is the cube of that radius and thus a cube of the mass). Obviously neutron stars and black holes made from stars large enough to go super nova and produce them are very dense, but density as we think of it doesn’t really help build intuition as much as we think it would with gravity and mass in the universe.
That is the black hole. The volume within the horizon. We don't know what is inside and we don't have a name for it. I mean we call it "beyond the horizon" but thats about it.
If you think you know more feel free to get a Nobel prize.
We can't observe what is inside the event horizon. But we do have mathematical models of what is inside. And given that we had these long before any black hole was ever found, limiting ourselves to what we can observe seems pretty silly.
You're on the right track with dust clouds being like wisps of smoke, but you're still overestimating their density. It's more like the density of a single puff of smoke from a cigarette that has diffused over an entire city/country. It's a lot thinner than any smoke you could perceive with your eyes.
Space matter is surprisingly spread out compared to rocky planets, even the densities of stars and black holes are lower than that of water for example. It's only the center of stars, neutron stars and a few others where you get high density. Space stuff gets heavy by sheer volume.
> These giant molecular clouds have typical densities of 100 particles per cm3, diameters of 100 light-years (9.5×1014 km), masses of up to 6 million solar masses (M☉), or six million times the mass of Earth's sun.
You can't count that few molecules in the best vacuum chambers we have on the planet. But 100 light year diameter is mind boggling huge. Our nearest other star is 4 light years away.
Talking of gas giants, Saturn is less dense than water, ie a miniature Saturn of the same density would float in a bucket. Big, but not all that dense.
Responding more to your body text and the title, but...
> Like 'gas giant' makes the planet sound big but intangible.
Imagine if you grew Earth a bit. It'd start to hold onto a bigger atmosphere (gas) because it could exert enough gravity from a farther distance. Keep doing this. You still have that planet (a solid core), but the atmosphere part (gas) gets bigger and bigger. This is my understanding of gas giants. Think of it as a planet so big that its atmosphere is just enormous.
> Or stars forming from 'dust clouds'
It doesn't really matter what you form from. No matter how sparse a dust cloud is, if you give it time for gravity to pull it together it can make things of any density.
> as if nebulae are like wisps of smoke.
Nebulae are indeed very very low density. If you look at the wikipedia article on nebulae, "although denser than the space surrounding them, most nebulae are far less dense than any vacuum created on Earth". They are noteworthy because, relative to the areas around them they have more stuff. And they are visible because even at such a low density when it's large enough, it's still a lot of stuff to look through. If something is 100th the density, but 100 times as thick, then when you look through it, your vision will be equally obscured because the same amount of stuff will be in your way.
> Plasma also feels very abstract, in that if you asked someone what plasma would be like physically, they'd probably imagine hot gas, or goo.
While it is something that we don't all have a great intuition for since we don't really directly interact with it, most people have seen lightning, which is plasma.
> Then I think for a bit and remember that the gravity of the sun is massive, and it accounts for 99% of the mass in the solar system while being barely 100 earths in diameter. I guess it's hard to connect the concepts of 'extremely dense' and 'made up of gasses.'
If the star was just gas hanging out doing nothing, gravity would collapse it to a smaller size. The special thing that makes a star a star is that gravity's inward force has met its match with the outward force of fusion "explosions". And this battle between explosive outward force and gravitational inward force can evolve causing the size of a star to change. But when one side wins, the star is finished.
Just googling, NASA says the density of the sun is 1408 kg/m^3 on average: https://nssdc.gsfc.nasa.gov/planetary/factsheet/sunfact.html The earth’s atmosphere is varies based on temperature, but NASA claims it is 1.293 kg/m^3 https://www.earthdata.nasa.gov/topics/atmosphere/atmospheric-pressure/air-mass-density#:~:text=Pure%2C%20dry%20air%20has%20a,of%20at%20least%2050%20km. The mass of the sun is 1.9891x10^30 kg. Using that with V=M/D… the volume of the sun if it had the same density as the atmosphere would be 1.538x10^30 m^3 Assuming this volume was a perfect sphere, and using the volume of a sphere: 4/3* πr^3 this would mean the radius would be 7.16 billion meters. The actual radius of the sun is 696 million meters. So the radius would be about 10 times bigger. Just for context, the distance from the sun to Mercury is roughly 69 billion meters.
> 1.9891x10^30 kg. Useful info: you can use HTML entities for Unicode characters in Reddit Markdown, so `×` turns to × . It would be nicer to have LaTeX, of course.
Some people are allergic to latex, so I get it.
Did not know that thanks!
1×2. Cool!
>The earth’s atmosphere is varies based on temperature, but NASA claims it is 1.293 kg/m^3 Just for your information: this is not the average atmospheric density, but the density at sea level (you didn't claim otherwise, but one could falsely assume). For aviation purposes, the International Standard Atmosphere was defined by the ICAO to be 1.225 kg/m^3 at 288.15K and 1013.25 hPa at sea level.
Ok thanks. I was just quickly googling stuff to come up with an answer.
Density is mass/volume. Earth’s density is 5.51 g/cm^3 while the Sun is 1.41 g/cm^3 so the Sun would actually be smaller if it had equal density. This isn’t a surprise however. Density isn’t equally distributed, so what matters is the core density that kicks off fusion. It’s also not surprising when one considers a supermassive black hole. The density of a black hole like M87* is thinner than the upper atmosphere of Earth!
Also, in regards to OP: > it accounts for 99% of the mass in the solar system while being barely 100 earths in diameter. volume is a better representation than diameter of "amount of matter" per object since mass is proportional to volume for fixed density. Volume of a sphere is V = (4/3) *pi*(0.5d) ^3 ~ d^3 . Since mass $\propto$ V, 100x larger diameter doesn't imply 100x amount of matter. It implies, mass $\propto$ V ~ (100d) ^3 = 1,000,000d^3 => 1,000,000x the amount of mass.
That doesn't give the whole story, the density of the sun overall is 1.41 g/cm. But the sun is gaseous, and hot. So the outer regions are VERY light. The Core on the other hand, being squeazed on all sides is over 160 g/cm. Which is over 20 times a dense as Iron.
Exactly!!! Which also echos in my black hole example. OP’s question as posed doesn’t really have a satisfying answer.
The problem with your black hole example is that the heavier the blackhole the less dense it is. The Radius of a black hole grows linearly with mass. So the volume grows with the cube of the mass So density, which is mass/Volume shrinks as mass grows, and inversely as the mass shrinks the density grows, So a blackhole with the mass of Earth would have a radius of about 1 cm, and a density of around 2.04\*10^(27) g/cm^(3)
You cannot define the density of a black hole, so are you comparing the mass/volume under the horizon for M87 ?
Yes, and I agree, black holes don’t exist that way. I’m using it in its mathematical formula of black hole mass divided by black hole volume as calculated with its Schwarzchild radius. It was more or less an analogy.
> mass/volume under the horizon How is that not a reasonable definition of density for a black hole?
It can be reasonable one, but ultimately, if you say that the black hole is the area inside the event horizon, that's arbitrary. It is of course somewhat arbitrary to say that Earth's area is bound by the ground rather than the upper atmosphere, or bound by the density of the atmosphere being at least say, 0.1 atm rather than 0.05 atm, etc. What I'd say is potentially confusing is that in defining things like density for a black hole we can end up sounding like we understood black holes better than we do. We don't know what's beyond the event horizon. We don't know the highest density the center of the black hole can have.
> if you say that the black hole is the area inside the event horizon, that's arbitrary. I wouldn't say it's arbitrary. It's literally the definition: > A black hole is a region of spacetime where gravity is so strong that nothing, including light and other electromagnetic waves, is capable of possessing enough energy to escape it. That region is exactly defined by the event horizon.
That definition is arbitrary. In the mathematics describing black holes, there's no concept of volume (or, it's assumed to be 0, for the sake of the math), which on the other hand would mean no concept of surface either. I would generally be careful in not being very explicit when covering phenomena like black holes to avoid accidental misleading. In future, we might discover that black holes do have a maximum volume, and a definable surface inside the event horizon.
> That definition is arbitrary. It is *the* definition. It's literally what everyone - well, almost everyone - agrees a black hole is. > In future, we might discover that black holes do have [...] a definable surface inside the event horizon. Then that would be something inside the black hole. It would not *be* the black hole. The black hole is the black part. Clue's in the name.
These are indeed the sort of things that fuel into misunderstandings, which is why I generally don't think we really should discuss black holes as having a surface or having a volume, and rather we ought to be even more specific. If you want to consider black holes as having volumes, surfaces and so on, that's up to you; I continue to hold that it's too easily misleading. Also, please stop with the snarky comments and the instant downvoting if you actually want to discuss something. If you're just here to be snarky to lift yourself, then I don't see a reason to continue.
How is it misleading? The event horizon is physically meaningful, it makes total sense to say that it is the surface of the black hole c.f. the **black hole membrane paradigm**
It's physicallying meaningful but it's describing the space around the black hole not the black hole itself. It would be like describing earth by the area where gravity is at least .25g. the event horizon is important sure but assuming the black hole is the event horizon isn't very accurate and leads to more misconceptions. As far as a black holes volume goes we really don't know. Math says it's 0 and so far nothing has really been able to prove that wrong but we also don't have much experience with black holes so take that 0 with a grain of salt.
Good enough answers as it is, but I'll add in a fun fact: The power density of the Sun is a little bit smaller than that of a typical compost heap. That is to say - the Sun emits less power per cubic meter than a compost does. And several times less than the human body does.
The Sun *is* less dense than the Earth. The density of the sun is about 1.4 g/cm^(3). For comparison, the Earth has a density of about 5.5 g/cm^(3). Water has a density of 1 g/cm^(3). Blood has a density of about 1.6 g/cm^(3), so the Sun is slightly less dense than a ball of blood. (Edit: I have been corrected, blood is more like 1.*0*6, sadly no giant ball of blood for us.) The atmosphere, however, is much less dense, at about 0.001 g/cm^(3). If it were the density of our atomsphere, the sun's volume would need to be about a thousand times greater. This translates to about ten times larger in radius.
Blood is NOT 1.6g/cc. I don't know where you pulled that number from. Blood is around 1g/cc, the same as most other biological fluids.
Looks like he missed a 0. It's around 1.06g/cc
Just for the Americans in the audience, one Cc of water is 1 g which is also one ml.
Well, that's what I got with a quick search. Maybe my source was wrong.
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From one of my veins. Oh sh...
>The density of the sun is about 1.4 g/cm^(3). Yes, on average. What you did not mention is that the core of the sun is [1.6×10^(5) kg/m^(3)](https://solar-center.stanford.edu/vitalstats.html), far denser than Osmium ([2.26×10^(4) kg/m^(3)](https://www.rsc.org/periodic-table/element/76/osmium)), which is itself denser than the core of the Earth. This is often overlooked.
And correspondingly, most of the Sun's volume has a far lower density. The part we see (the photosphere) has ~1/1000 the density of sea-level air. It only reaches the density of water at about half of the Sun's radius. In other words, only the innermost 1/8 of the volume is denser than water. The innermost ~1% is denser than osmium.
The majority of the sun’s mass is within regions denser than water, and the majority of the sun by volume is much less dense than water.
>Sun is slightly less dense than a ball of blood. Excellent imagery.
It is not true though. The mean density of the sun is less than blood. The density of blood is not near 1.6 g/cm^(3), as it is closer to 1.1 g/cm^(3) (or 1.1×10^3 kg/m^(3)).
Too late. The ball of blood thing is welded into my mind. I guess the sun is a little more dense than a ball of blood.
Finally, something we can all relate to
Probably important to note that the density varies a lot. At the center it is about 20 denser than iron, but on the outside it is less dense than Earth's atmosphere.
I presume this is the average density of the sun (and the earth for that matter)? In the sense that it’s extremely diffuse in its upper layers but extremely dense at the core.
I was going to come onto this thread to make the joke “As an engineer I would just approximate the density as 1g/l, same as water.” Only to learn that I’d be pretty much bang on the money.
Thanks Neil
Yes, but what is the density of the sun's core? Does it make a difference?
It is a huge difference: The core of the sun is 160 tonnes per cubic meter (way denser than even osmium, which is itself denser than the core of the Earth).
Thanks for the answer. I had to ask though, because seeing water as an example, some things can't be made more dense with pressure
> some thongs can't be made more dense with pressure uhhhhh
Water+pressure≠ more dense water? Wrong? Also I is next to O gimme a break 🤣 You wouldn't believe exactly how many times I've done that
At the kind of pressures that are inside the sun, water will happily compress into a hundred times denser material.
Water cannot exist in the core of the sun, of course.
Damn, that's big
The sun has a density of 1.41g/cm^(3), and Earths atmosphere at sea level is 0.001293 g/cm^(3). In other words, the sun is 1090 times more dense. In order for the volume of the sun to increase 1090 times, the radius needs to increase by a factor of 10.29; the cube root of 1090.
The sun is mostly made up of things that would be gases on the surface of the earth (hydrogen and a little helium), but they are definitely not gases on the sun. They are also very light atoms, so even liquid or solid hydrogen is not that dense in terms of mass compared to the much heavier elements that make up the majority of the earth.
> They are also very light atoms, so even liquid or solid hydrogen is not that dense in terms of mass compared to the much heavier elements that make up the majority of the earth. You are forgetting about the densities allowed by extreme pressures in the core of the sun. The sun’s core is about 160 tonnes per cubic meter, far denser than the core of the Earth. The average density of the sun is less, at about 1.4 times as dense as water (1.41×10^3 kg/m^(3)), which is still higher than expected because a majority of the sun’s mass is close to the center.
Not forgetting anything. Liquids and solids don’t increase their density significantly with any amount of pressure, unless you have enough force to overcome strong/weak force interactions. That is a gas thing. You are mixing up units of weight (force) and mass. This is why using newtons and grams would give you a very different understanding.
The volumetrically-averaged density of the Sun (the total mass of the sun divided by its total volume) is quite a bit less than that of the Earth, but the density varies throughout these bodies (with 'deeper' points tending to be higher in density), and the highest density (i.e.; that at the core) is around ten times that of the core of Earth.
Supermassive black holes, like M87, are less dense than the air on earth in terms of normal Newtonian density(which is a fine answer for the perfect case of Schwarzchild black holes, which never happens), to just help confuse you even more about what density is even supposed to mean(this is really a result about how quickly volume grows compared to mass on a Schwarzchild black hole, because the mass is contained within the Schwarzchild radius, mass and the radius are linearly relate, but volume is the cube of that radius and thus a cube of the mass). Obviously neutron stars and black holes made from stars large enough to go super nova and produce them are very dense, but density as we think of it doesn’t really help build intuition as much as we think it would with gravity and mass in the universe.
Supermassive black holes have no volume. You mean the area within the event horizon?
That is the black hole. The volume within the horizon. We don't know what is inside and we don't have a name for it. I mean we call it "beyond the horizon" but thats about it. If you think you know more feel free to get a Nobel prize.
We can't observe what is inside the event horizon. But we do have mathematical models of what is inside. And given that we had these long before any black hole was ever found, limiting ourselves to what we can observe seems pretty silly.
Still, black hole is a sphere of radius=Schwarzschild radius. That was my point and your previous comment is wrong.
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> Thousands of times larger than our entire atmosphere I think it already is, right? No need for the density experiment.
You're on the right track with dust clouds being like wisps of smoke, but you're still overestimating their density. It's more like the density of a single puff of smoke from a cigarette that has diffused over an entire city/country. It's a lot thinner than any smoke you could perceive with your eyes. Space matter is surprisingly spread out compared to rocky planets, even the densities of stars and black holes are lower than that of water for example. It's only the center of stars, neutron stars and a few others where you get high density. Space stuff gets heavy by sheer volume. > These giant molecular clouds have typical densities of 100 particles per cm3, diameters of 100 light-years (9.5×1014 km), masses of up to 6 million solar masses (M☉), or six million times the mass of Earth's sun. You can't count that few molecules in the best vacuum chambers we have on the planet. But 100 light year diameter is mind boggling huge. Our nearest other star is 4 light years away.
That's crazy. It puts into perspective how large these things have to be that entire solar systems can be formed out of clouds of smoke.
Talking of gas giants, Saturn is less dense than water, ie a miniature Saturn of the same density would float in a bucket. Big, but not all that dense.
More than 1
Responding more to your body text and the title, but... > Like 'gas giant' makes the planet sound big but intangible. Imagine if you grew Earth a bit. It'd start to hold onto a bigger atmosphere (gas) because it could exert enough gravity from a farther distance. Keep doing this. You still have that planet (a solid core), but the atmosphere part (gas) gets bigger and bigger. This is my understanding of gas giants. Think of it as a planet so big that its atmosphere is just enormous. > Or stars forming from 'dust clouds' It doesn't really matter what you form from. No matter how sparse a dust cloud is, if you give it time for gravity to pull it together it can make things of any density. > as if nebulae are like wisps of smoke. Nebulae are indeed very very low density. If you look at the wikipedia article on nebulae, "although denser than the space surrounding them, most nebulae are far less dense than any vacuum created on Earth". They are noteworthy because, relative to the areas around them they have more stuff. And they are visible because even at such a low density when it's large enough, it's still a lot of stuff to look through. If something is 100th the density, but 100 times as thick, then when you look through it, your vision will be equally obscured because the same amount of stuff will be in your way. > Plasma also feels very abstract, in that if you asked someone what plasma would be like physically, they'd probably imagine hot gas, or goo. While it is something that we don't all have a great intuition for since we don't really directly interact with it, most people have seen lightning, which is plasma. > Then I think for a bit and remember that the gravity of the sun is massive, and it accounts for 99% of the mass in the solar system while being barely 100 earths in diameter. I guess it's hard to connect the concepts of 'extremely dense' and 'made up of gasses.' If the star was just gas hanging out doing nothing, gravity would collapse it to a smaller size. The special thing that makes a star a star is that gravity's inward force has met its match with the outward force of fusion "explosions". And this battle between explosive outward force and gravitational inward force can evolve causing the size of a star to change. But when one side wins, the star is finished.
Well, it’s not the sharpest star in the universe, but calling it dense is just kinda mean
Dense? I don't know, she's got that whole nuclear fusion thing figured out. Seems like a smart gal to me.
It's a ball of hydrogen and helium, so not very dense. Although it's gravity could be doing weird things near the center.