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Betelgeuse is closer and smaller than previously thought

Betelgeuse's fading
Images taken by Europe’s
Very Large Telescope in Chile

The uncertainty of science: A new analysis by scientists of Betelgeuse, triggered by its dip in brightness in 2020, has concluded that the red giant star is both closer and smaller than previously estimated.

Their analysis reported a present-day mass of 16.5 to 19 solar mass—which is slightly lower than the most recent estimates. The study also revealed how big Betelgeuse is, as well as its distance from Earth. The star’s actual size has been a bit of a mystery: earlier studies, for instance, suggested it could be bigger than the orbit of Jupiter. However, the team’s results showed Betelgeuse only extends out to two-thirds of that, with a radius 750 times the radius of the sun. Once the physical size of the star is known, it will be possible to determine its distance from Earth. Thus far, the team’s results show it is a mere 530 light years from us, or 25 percent closer than previously thought.

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.

As for the dimming, the scientists concluded (as other have) that the dimming in ’20 was due to the passage of a dust cloud in front of the star.

Genesis cover

On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.

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  • 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.

  • LocalFluff

    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.

  • wayne

    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… “

  • wayne

    “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

  • LocalFluff

    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.

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