Comments on: Betelgeuse is closer and smaller than previously thought

By: LocalFluff

LocalFluff — Sun, 07 Feb 2021 07:25:54 +0000

@wayne
It takes on average 10,000 years for a photon generated in the fusing core of the Sun to reach the surface and beam out through space. There’s so much compact stuff in the way of its 400,000 miles random walk. In your example, virtually no light from the post Helium fusion would become visible until it goes supernova.

By: wayne

wayne — Sun, 07 Feb 2021 01:09:20 +0000

“Stages in the Life of a 25 Solar Mass Star”
-hydrogen burning – 7 million years
helium – 700K years
cabon – 600 years
neon – 1 year
oxygen – 6 months
silicon – 1 day

http://hosting.astro.cornell.edu/academics/courses/astro201/highmass.htm

By: wayne

wayne — Sun, 07 Feb 2021 00:55:49 +0000

Blair–
can’t find the chart I want, but when a star starts ratchetting up the periodic table toward iron, the end is ‘relatively near.’

…” it takes 100,000 years for the carbon to burn into oxygen, 10,000 years for the oxygen to burn into silicon, and one day for the silicon to burn into iron… “

By: LocalFluff

LocalFluff — Sat, 06 Feb 2021 09:49:00 +0000

Betelgeuse is too bright for the Gaia space telescope. So I don’t think it is known how it moves, whether it will be closer or further away from the Sun in 100,000 years. Its variability (huge sunspots and flares) also makes it tricky to pinpoint its distance and radial movement. Only 10 or so years ago, tables had it at only 470 light years distance, then they almost doubled the estimation, and now 530 ly.

@Blair K Ivey
Betelgeuse is only 8 million years old. More massive stars have higher pressure from gravity and burn their fuel much faster, a larger core is fusing. Betelgeuse is only about 18 times as massive as the Sun, there are stars 100+ the mass of the Sun that exist for less than a million years. That’s why more massive stars are much less frequent, they don’t necessarily form more rarely, they just live 1/1000th or so as long as stars less massive than the Sun. Still, the spirals in galaxies are visible because of the small share of massive stars that dominate the brightness of 100s-1000s of times more common red dwarfs and Sun-like stars. Galactic gas is compressed in a standing spiral wave so that stars form much more easily there. And the massive stars don’t live long enough to leave the spiral where they formed.

By: Blair K Ivey

Blair K Ivey — Sat, 06 Feb 2021 06:25:26 +0000

Robert related: “The research also suggested that the star is in the initial stages of burning helium rather than hydrogen, and so it likely more than 100,000 years from going supernova.”

That seems like an incredibly short time for things that hang around for billions of years. While I am aware of the main sequence fuel cycle, I had no idea it happened on that sort of timescale. I am sure there are many on the forum who can shed some light.