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Astronomers may have spotted the smallest possible stars

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Re: Astronomers may have spotted the smallest possible stars

#21

Post by jessriedel »

s1artibartfast wrote: post #16
munk-a wrote: post #10

Earlier quoted context omitted.

Does this also hold for rogue planets? I was under the impression that some rogue planets could form outside of any star's accretion disk.

My understanding is that smaller rouge plants do not form in isolation and are always the product of ejection. However, the categorization again is fuzzy, with definitional overlap between "planet", "sub-brown-dwarf", and "brown dwarfs" Planets cover spherical objects ranging from 0.001 Jupiter masses to stars at ~80 Jupiter masses. Brown dwarfs range from 3-80 Jupiter masses. Brown Dwarfs are planets and can form ou…

> My understanding is that smaller rouge plants do not form in isolation and are always the product of ejection.

Wikipedia says "Rogue planets may originate from planetary systems in which they are formed and later ejected, or they can also form on their own, outside a planetary system."

Re: Astronomers may have spotted the smallest possible stars

#22

Post by goodcanadian »

jessriedel wrote: post #20
goodcanadian wrote: post #7

Earlier quoted context omitted.

Is this really the standard terminology? Well, it is close enough. The definition is that a brown dwarf forms like a star through gravitational collapse within a protostellar nebula, but it just wasn't massive enough to ignite. However, a planet forms in an accretion disk around a star that is forming out of the larger cloud. Of course, nature does not always perfectly align itself within our neat categories, and it…

> The definition is that a brown dwarf forms like a star through gravitational collapse within a protostellar nebula Do you have a cite on that? (It conflicts with Wikipedia, for example.) In particular, I suspect that many people read something that describes how a certain type of star is thought to typically form and then interpret that as a definition.

Do you have a cite on that?

Off the top of my head, no, but I do have a degree in astronomy and an interest going back to childhood.

Re: Astronomers may have spotted the smallest possible stars

#23

Post by goodcanadian »

jessriedel wrote: post #21
s1artibartfast wrote: post #16

Earlier quoted context omitted.

My understanding is that smaller rouge plants do not form in isolation and are always the product of ejection. However, the categorization again is fuzzy, with definitional overlap between "planet", "sub-brown-dwarf", and "brown dwarfs" Planets cover spherical objects ranging from 0.001 Jupiter masses to stars at ~80 Jupiter masses. Brown dwarfs range from 3-80 Jupiter masses. Brown Dwarfs are planets and can form ou…

> My understanding is that smaller rouge plants do not form in isolation and are always the product of ejection. Wikipedia says "Rogue planets may originate from planetary systems in which they are formed and later ejected, or they can also form on their own, outside a planetary system."

The ones "forming on their own" would be essentially brown dwarfs. As myself and others have said, the line is fuzzy. However, to form on their own there needs to be sufficient density for them to coalesce. It is not a hard limit, but tends to mean only objects larger than about 10 Jupiter masses.

Re: Astronomers may have spotted the smallest possible stars

#24

Post by jessriedel »

goodcanadian wrote: post #22
jessriedel wrote: post #20

Earlier quoted context omitted.

> The definition is that a brown dwarf forms like a star through gravitational collapse within a protostellar nebula Do you have a cite on that? (It conflicts with Wikipedia, for example.) In particular, I suspect that many people read something that describes how a certain type of star is thought to typically form and then interpret that as a definition.

Do you have a cite on that? Off the top of my head, no, but I do have a degree in astronomy and an interest going back to childhood.

shrug I have a degree in physics and have always heard people define brown dwarfs by size (and occasionally composition) rather than formation mechanism.

Re: Astronomers may have spotted the smallest possible stars

#25

Post by jessriedel »

goodcanadian wrote: post #23
jessriedel wrote: post #21

Earlier quoted context omitted.

> My understanding is that smaller rouge plants do not form in isolation and are always the product of ejection. Wikipedia says "Rogue planets may originate from planetary systems in which they are formed and later ejected, or they can also form on their own, outside a planetary system."

The ones "forming on their own" would be essentially brown dwarfs. As myself and others have said, the line is fuzzy. However, to form on their own there needs to be sufficient density for them to coalesce. It is not a hard limit, but tends to mean only objects larger than about 10 Jupiter masses.

No. That’s not what wikipedia says, and I feel confident asserting that an Earth-mass object forming on its own would not be considered a brown dwarf by the vast majority of astronomers. (Maybe it would also not be considered a “planet”, due to some Pluto-adjacent technicalities, but then what do people call it? I’m betting they use “rogue planet” in practice.)

Re: Astronomers may have spotted the smallest possible stars

#26

Post by s1artibartfast »

jessriedel wrote: post #25
goodcanadian wrote: post #23

Earlier quoted context omitted.

The ones "forming on their own" would be essentially brown dwarfs. As myself and others have said, the line is fuzzy. However, to form on their own there needs to be sufficient density for them to coalesce. It is not a hard limit, but tends to mean only objects larger than about 10 Jupiter masses.

No. That’s not what wikipedia says, and I feel confident asserting that an Earth-mass object forming on its own would not be considered a brown dwarf by the vast majority of astronomers. (Maybe it would also not be considered a “planet”, due to some Pluto-adjacent technicalities, but then what do people call it? I’m betting they use “rogue planet” in practice.)

I think you are missing the size distinction and range for rogue planets, which I specifically highlight.

Claims about self formation pertain to rouge planets as a class, which includes brown dwarfs. That does not mean an earth mass object IS a brown dwarf.

If you want to want to focus on Wikipedia text, it also says:

>Pre-JWST observations have shown that objects below 3-5 MJ are unlikely to form on their own.[4] Observations in 2023 in the Trapezium Cluster with JWST have shown that objects as massive as 0.6 MJ might form on their own, not requiring a steep cut-off mass[1]

Those limits are ~1,000 earth masses and ~200 earth masses, respectively

https://en.wikipedia.org/wiki/Rogue_planet#Formation_like_a_...

Re: Astronomers may have spotted the smallest possible stars

#27

Post by goodcanadian »

jessriedel wrote: post #25
goodcanadian wrote: post #23

Earlier quoted context omitted.

The ones "forming on their own" would be essentially brown dwarfs. As myself and others have said, the line is fuzzy. However, to form on their own there needs to be sufficient density for them to coalesce. It is not a hard limit, but tends to mean only objects larger than about 10 Jupiter masses.

No. That’s not what wikipedia says, and I feel confident asserting that an Earth-mass object forming on its own would not be considered a brown dwarf by the vast majority of astronomers. (Maybe it would also not be considered a “planet”, due to some Pluto-adjacent technicalities, but then what do people call it? I’m betting they use “rogue planet” in practice.)

No, an Earth-mass object forming on its own would not be considered a brown dwarf, but an Earth-mass object is incredibly unlikely to form on its own. An object that small will have almost certainly been formed in an accretion disk and been ejected.
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