Astronomy/planetary nebulas


Why do 5 solar mass stars form planetary nebulas, (thus shedding their mass and allowing them to turn into white dwarfs) but 10 solar mass stars do not?

The gas in the solar corona has a temperature of millions of degrees, yet it would not burn your bare hands.  How is this so?


The issue of solar mass thresholds for stars - i.e. whether they become neutron stars or black holes - still isn't settled, but I'd warrant even a 5 solar mass star certainly will not end up as a white dwarf.

The white dwarf - planetary nebulua phenomenon is typically reserved for stars with the mass of the Sun or maybe slightly more. Thus, the Sun will expand to the Red Giant stage after its hydrogen has mostly been consumed, and ultimately its outer layers will be hurled off (under extreme temperatures of 100 million K or more) and become a planetary nebula with the Sun now reduced to a white dwarf.

In larger mass stars, i.e. in the 5-10 solar mass range, this doesn't happen as the star's fate ends with a supernova on account of the much heavier elements (Cobalt, Nickel, Iron) built up in its core. These stars - after hurling off their outer layers in the supernova event - then become black holes. As we know, black holes  (such as Cygnus X-1)exhibit astounding gravitational force so that for any ejected matter no 'rings' (such as one detects in planetary nebula-white dwarf systems)  will be observed.

Re: the solar corona, because it is essentially a vacuum and has very few particles (low
thermal capacity) there is not the mass present to burn hands or burn anything. Burning requires sufficient mass density of particles which the corona lacks.

However, while low in density, those corona particles have very high velocities, so
possess extremely high 'kinetic temperatures' which is what accounts for the '2 million Kelvin' degree temperature often estimated.


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Philip Stahl


I have more than forty years of experience in Astronomy, specifically solar and space physics. My specialties include the physics of solar flares, sunspots, including their effects on Earth and statistics pertaining to sunspot morphology and flare geo-effectiveness.


Astronomy: Worked at university observatory in college, doing astrographic measurements. Developed first ever astronomy curriculum for secondary schools in Caribbean. Gave workshops in astrophysics and astronomical measurements at Harry Bayley Observatory, Barbados. M.Phil. degree in Physics/Solar Physics and more than twenty years as researcher with discovery of SID flares. Developed of first ever consistent magnetic arcade model for solar flares incorporating energy dissipation and accumulation. Develop first ever loop solar flare model using double layers and incorporating cavity resonators.

American Astronomical Society (Solar Physics and Dynamical Astronomy divisions), American Mathematical Society, American Geophysical Union.

Solar Physics (journal), The Journal of the Royal Astronomical Society of Canada, The Proceedings of the Meudon Solar Flare Workshop (1986), The Proceedings of the Caribbean Physics Conference (1985). Books: 'Selected Analyses in Solar Flare Plasma Dynamics', 'Physics Notes for Advanced Level'. 'Astronomy and Astrophysics: Notes, Problems and Solutions'.

B.A. Astronomy, M. Phil. Physics

Awards and Honors
American Astronomical Society Studentship Award (1984), Barbados Government Award for Solar Research (1980), Barbados Astronomical Society Award for Service as Journal Editor (1977-91)

Past/Present Clients
Caribbean Examinations Council, Barbados Astronomical Society, Trinidad & Tobago Astronomical Society.

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