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I feel those images are a little misleading. One might erroneously assume there is a dense surface akin to our star at the outer edge of these massive stars but
by jahnu 12y ago
I feel those images are a little misleading. One might erroneously assume there is a dense surface akin to our star at the outer edge of these massive stars but..
"In the outer reaches of the photosphere the density is extremely low, yet the total mass of the star is believed to be no more than 20 M☉. Consequently, the average density is less than twelve parts per billion (1.119 × 10−8) that of the Sun. Such star matter is so tenuous that Betelgeuse has often been called a "red-hot vacuum"."
https://en.wikipedia.org/wiki/Betelgeuse#Density https://en.wikipedia.org/wiki/Betelgeuse#Density
- gunn 12y agoAlso: "estimates of its mass are poorly constrained, but range from 5 to 30 times that of the Sun". Amazing for having on the order of 16 billion times its volume.
- jjoonathan 12y agoHow does that happen? Is its fuel more energetic in some sense or does the gravity-vs-pressure equilibrium simply favor lower densities for a total mass of 20M☉?
- nate_meurer 12y agoYou're right on both counts! Betelgeuse is burning helium now (post main-sequence). The higher output of helium fusion inflates the outer atmosphere like a giant floppy balloon.
- hellbanner 12y agoThose images accurately show size, correct? Stars are big.
- yourad_io 12y agoM☉ = Solar Mass[1]. Huh. > astronomers have the worst conventions in the world (for largely “historical reasons”)[2] You don't say. [1] http://en.wikipedia.org/wiki/Solar_mass http://en.wikipedia.org/wiki/Solar_mass [2] article