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#11
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What dictates galaxy and planetary system sizes?
In article , jacobnavia
writes: Le 21/12/2016 =E0 13:32, Phillip Helbig (undress to reply) a =E9crit : the quantities are determined, as is everything, by the constants of nature and by initial conditions, Since most of the mass of a planetary system is in the star, the limit to its mass is the limit of the mass of a star. I'm not sure what you mean. Above a certain mass, nuclear fusion will set in, so anything more massive is a star, by definition. (There is also the Hayashi limit related to convection, so the lower limit for stable nuclear fusion might be a bit higher, around 0.08 solar masses.) The upper limit for a star is a few hundred solar masses. (Probably anything more massive can't form before what has already contracted has ignited, keeping out additional material.) I'm not an expert here, but the mass range in stars is 2--3 orders of magnitude. It is not directly (and if indirectly, very indirectly) to any size of the universe. Now, stars when they become obese, start producing antimatter that destroys the star before it is fully built, the limit on star sizes determines, as a consequence, the size of the planetary systems... Is that correct? Not sure what you mean about the antimatter. Stars have a range in mass as described above, the lower limit corresponding to the upper limit of a planet. What the lower limit of a planet is depends on the definition and, for some definitions, might depend on composition, but covers many more orders of magnitude. |
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What dictates galaxy and planetary system sizes?
Le 03/01/2017 =E0 23:55, Phillip Helbig (undress to reply) a =E9crit :
Not sure what you mean about the antimatter. For instance this: (http://astronomynow.com/news/n1001/06essence/) quote As part of the ESSENCE supernova search, astronomers have discovered a distant star that exploded when its centre became so hot that matter and anti-matter particle pairs were created. The star, known as Y-155, was once a magnificent 200 times the mass of our Sun, but around seven billion years ago it became unstable, forcing a runaway thermonuclear reaction that ended in a cataclysmic explosion visible halfway across the Universe. end quote [[Mod. note -- While some antimatter was created during the star's destruction, that does NOT say that the creation of that antimatter *caused* the destruction. In fact, it didn't -- as the passage you quoted says, a runaway thermonuclear reaction is what destroyed the star. The (small amounts of) antimatter was "just" a byproduct. -- jt]] |
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What dictates galaxy and planetary system sizes?
On 1/3/17 4:55 PM, Phillip Helbig (undress to reply) wrote:
In article , jacobnavia writes: Le 21/12/2016 =E0 13:32, Phillip Helbig (undress to reply) a =E9crit : the quantities are determined, as is everything, by the constants of nature and by initial conditions, Since most of the mass of a planetary system is in the star, the limit to its mass is the limit of the mass of a star. I'm not sure what you mean. Above a certain mass, nuclear fusion will set in, so anything more massive is a star, by definition. (There is also the Hayashi limit related to convection, so the lower limit for stable nuclear fusion might be a bit higher, around 0.08 solar masses.) The upper limit for a star is a few hundred solar masses. (Probably anything more massive can't form before what has already contracted has ignited, keeping out additional material.) I'm not an expert here, but the mass range in stars is 2--3 orders of magnitude. It is not directly (and if indirectly, very indirectly) to any size of the universe. Assuming your 2--3 orders of magnitude range galactic size (presently ~10^20 - ~10^24cm) and star planetary system size (presently ~10^13 - ~10^17 cm) contained in a Hubble radius (presently ~10^28 cm) What establishes the voids on the order of 3 orders of magnitude between and do these ratios maintain themselves with redshift and within what theoretical framework? Richard D Saam [[Mod. note -- This wording presupposes that there are "voids" and that they are "established". I know of no good reasons to reject the null hypothesis that there's no particular connection between these size scales. -- jt]] |
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What dictates galaxy and planetary system sizes?
In article , "Richard D.
Saam" writes: the quantities are determined, as is everything, by the constants of nature and by initial conditions, Since most of the mass of a planetary system is in the star, the limit to its mass is the limit of the mass of a star. I'm not sure what you mean. Above a certain mass, nuclear fusion will set in, so anything more massive is a star, by definition. (There is also the Hayashi limit related to convection, so the lower limit for stable nuclear fusion might be a bit higher, around 0.08 solar masses.) The upper limit for a star is a few hundred solar masses. (Probably anything more massive can't form before what has already contracted has ignited, keeping out additional material.) I'm not an expert here, but the mass range in stars is 2--3 orders of magnitude. It is not directly (and if indirectly, very indirectly) to any size of the universe. Assuming your 2--3 orders of magnitude range galactic size (presently ~10^20 - ~10^24cm) and star planetary system size (presently ~10^13 - ~10^17 cm) contained in a Hubble radius (presently ~10^28 cm) What establishes the voids on the order of 3 orders of magnitude between and do these ratios maintain themselves with redshift and within what theoretical framework? Richard D Saam [[Mod. note -- This wording presupposes that there are "voids" and that they are "established". I know of no good reasons to reject the null hypothesis that there's no particular connection between these size scales. -- jt]] Indeed. Note that galaxies range over more orders of magnitude in mass. Between solar-system scale and galactic scale there are things like giant molecular clouds; between galactic scale and Hubble-length scale there are groups of galaxies, clusters, superclusters. There is also the structure of dark matter, about which less is known. To a first approximation, the sizes of solar systems and galaxies don't change with the expansion of the universe. The Hubble radius changes if the Hubble constant changes. The Hubble constant has increased since the big bang, but as the universe approaches exponential expansion asymptotically, the Hubble radius will approach a constant value. [[Mod. note -- In addition to the things the poster mentioned, globular clusters and dwarf galaxies are some other important astro-things that lie between solar-system and galactic size. -- jt]] |
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What dictates galaxy and planetary system sizes?
On 1/6/17 10:03 AM, Phillip Helbig (undress to reply) wrote:
In article , "Richard D. Saam" writes: the quantities are determined, as is everything, by the constants of nature and by initial conditions, Since most of the mass of a planetary system is in the star, the limit to its mass is the limit of the mass of a star. I'm not sure what you mean. Above a certain mass, nuclear fusion will set in, so anything more massive is a star, by definition. (There is also the Hayashi limit related to convection, so the lower limit for stable nuclear fusion might be a bit higher, around 0.08 solar masses.) The upper limit for a star is a few hundred solar masses. (Probably anything more massive can't form before what has already contracted has ignited, keeping out additional material.) I'm not an expert here, but the mass range in stars is 2--3 orders of magnitude. It is not directly (and if indirectly, very indirectly) to any size of the universe. Assuming your 2--3 orders of magnitude range galactic size (presently ~10^20 - ~10^24cm) and star planetary system size (presently ~10^13 - ~10^17 cm) contained in a Hubble radius (presently ~10^28 cm) What establishes the voids on the order of 3 orders of magnitude between and do these ratios maintain themselves with redshift and within what theoretical framework? Richard D Saam [[Mod. note -- This wording presupposes that there are "voids" and that they are "established". I know of no good reasons to reject the null hypothesis that there's no particular connection between these size scales. -- jt]] It is acknowledged that the universe size (uniform?) distribution parameters are not at equilibrium. Indeed. Note that galaxies range over more orders of magnitude in mass. Size may be more important parameter. Between solar-system scale and galactic scale there are things like giant molecular clouds; between galactic scale and Hubble-length scale No, the molecular clouds are between planetary and galactic radius in a size range 15-600 light years (1.4x10^19 - 5.7x10^20 cm) The literature indicates these to be star planetary system precursors or perhaps star planetary systems that did not make it. there are groups of galaxies, clusters, superclusters. but the unit of measure is the galaxy as in clusters of and the filamentous, layered structure of these superclusters may be an indication of galaxy orthokinetic formation by shear associated with H = c/Hubble Radius. There is also the structure of dark matter, about which less is known. A very closely studied dark matter entity is the Bullet Cluster with size ~.5 Mpc (1.5x10^24 cm) falling within galaxy size. There may be more diffuse dark matter structures with a precursor star planetary characteristic analogous to molecular clouds above. To a first approximation, the sizes of solar systems and galaxies don't change with the expansion of the universe. Our solar system is the star planetary system reference with its size going out to the Kuiper Belt at 20 - 50 AU (3.0x10^14 - 7.5x10^14 cm) and out to the Oort cloud at 0.8 - 3.2 light year (7.6x10^17 - 3.0x10^18 cm) The Kepler spacecraft has found planets in other star planet systems but is not sensitive to more diffuse Kuiper and Oort like structures that probably exist. Future spacecraft may obtain information on analog Kuiper and Oort components in these star planet systems. Aren't the early galaxies (~million years after the big bang) much smaller (primitive) than present galaxies suggesting that star planetary systems had not formed at that time? The Hubble radius changes if the Hubble constant changes. The Hubble constant has increased since the big bang, but as the universe approaches exponential expansion asymptotically, the Hubble radius will approach a constant value. as perhaps galactic and star planetary system sizes approach a constant value. [[Mod. note -- In addition to the things the poster mentioned, globular clusters and dwarf galaxies are some other important astro-things that lie between solar-system and galactic size. -- jt]] In as much as a globular cluster is a spherical collection of stars that orbits a galactic core as a satellite, a globular cluster may be considered stars as part of a galaxy and within the galaxy size. Dwarf galaxies sizes fall within galaxy size range (compared to the milky way) as follows: milky way 200000 lightyear (1.9x10^23 cm) 2.5x10^11 solar mass Ursa Major II Dwarf 1800 lightyear (1.7x10^21 cm) 5.0x10^6 solar mass NGC 2419 520 lightyear (4.9x10^20 cm) 900,000 solar mass The two Dwarf galaxy masses compared to their size indicate that they are less dense than the milky way further indicating that size is a better structure comparative parameter. Richard D Saam |
#16
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What dictates galaxy and planetary system sizes?
In article , "Richard D.
Saam" writes: [[Mod. note -- This wording presupposes that there are "voids" and tha= t they are "established". I know of no good reasons to reject the null hypothesis that there's no particular connection between these size scales. -- jt]] It is acknowledged that the universe size (uniform?) distribution parameters are not at equilibrium. If you mean that the sizes of SOME things change with time, then yes. Indeed. Note that galaxies range over more orders of magnitude in mass= .. Size may be more important parameter. Why? Between solar-system scale and galactic scale there are things like giant molecular clouds; between galactic scale and Hubble-length scale No, the molecular clouds are between planetary and galactic radius in a size range 15-600 light years (1.4x10^19 - 5.7x10^20 cm) This is also between solar-system scale and galactic scale. (It is also between atomic scale and galactic scale.) Normally one uses the next lower and next higher scales to denote a range. but the unit of measure is the galaxy as in clusters of This is somewhat arbitrary, based on objects visible to and recognized by us. and the filamentous, layered structure of these superclusters may be an indication of galaxy orthokinetic formation by shear associated with H =3D c/Hubble Radius. Why? There is also the structure of dark matter, about which less is known. A very closely studied dark matter entity is the Bullet Cluster with size ~.5 Mpc (1.5x10^24 cm) falling within galaxy size. There may be more diffuse dark matter structures with a precursor star planetary characteristic analogous to molecular clouds above. Clusters are rare objects. Most galaxies are not in clusters. Most dark matter is probably not in clusters. The Bullet Cluster is not representative of the universe. To a first approximation, the sizes of solar systems and galaxies don't change with the expansion of the universe. Our solar system is the star planetary system reference with its size going out to the Kuiper Belt at 20 - 50 AU (3.0x10^14 - 7.5x10^14 cm) and out to the Oort cloud at 0.8 - 3.2 light year (7.6x10^17 - 3.0x10^18 cm) The Kepler spacecraft has found planets in other star planet systems but is not sensitive to more diffuse Kuiper and Oort like structures that probably exist. Future spacecraft may obtain information on analog Kuiper and Oort components in these star planet systems. Right. Aren't the early galaxies (~million years after the big bang) much smaller (primitive) than present galaxies Yes; galaxies grow with time. suggesting that star planetary systems had not formed at that time? Planetary systems probably formed along with the corresponding stars, but this is unrelated to the size of the galaxy. The Hubble radius changes if the Hubble constant changes. The Hubble constant has increased since the big bang, but as the universe approaches exponential expansion asymptotically, the Hubble radius will approach a constant value. as perhaps galactic and star planetary system sizes approach a constant value. Why? The scales of galaxies and planetary systems are not influenced by the size of the universe. [[Mod. note -- In addition to the things the poster mentioned, globular clusters and dwarf galaxies are some other important astro-things that lie between solar-system and galactic size. -- jt]] In as much as a globular cluster is a spherical collection of stars that orbits a galactic core as a satellite, a globular cluster may be considered stars as part of a galaxy and within the galaxy size. It seems like you are defining things to meet your expectations. |
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