by Ann » Sun Aug 22, 2021 5:15 am
Click to play embedded YouTube video.
The red star of the RS Ophiuchi system is filling its Roche lobe, and because it is an irregularly pulsating giant star of class M, it occasionally overflows its Roche lobe and spills mass onto its companion.
Note that although the illustration at right says that the red star at left is a main sequence star, I think it is extremely unusual that a red main sequence star, which is very small and compact, would overflow its Roche lobe. Almost all stars that fill their Roche lobes are evolved giant puffed-up stars that don't hold on to their outer layers very well.
The Youtube video at left shows an animation of the binary Beta Lyra system, where at least one of the stars is filling its Roche lobe. Beta Lyra is a system of two evolved, giant stars which orbit so close to one another that one has built up a thick accretion disk around itself (not visible in the video) and the other is distorted into a teardrop shape as it orbits its companion.
Linda Hall Library wrote:
The Roche limit is applicable to any two mutually orbiting bodies, such as the Earth and the Moon. The Roche limit is the minimum distance that the Moon (or any satellite held together only by gravity) can be from the Earth (or any large body) without breaking up. If the Moon comes any closer than the Roche limit, it will break apart because of tidal forces. Thus no planet can have a moon that lies within the Roche limit – it can have only rings.
...
The Roche lobe comes into play when the two orbiting bodies are gaseous, as with a binary star. If the stars are close enough, gas will be pulled from each star toward the other, and the tear-shaped envelope of gas is the Roche lobe
Can't keep this illustration of the Sun-Earth Roche lobe system and its Lagrangian points from you. Cool, eh?
Ann
[float=left][youtube]https://www.youtube.com/watch?v=ASDwtaEE4G4[/youtube][/float][float=right][img3="Diagram of a binary star system, showing the Roche lobes of a red giant star (left) and a white dwarf (slideplayer.com)/Linda Hall Library."]https://www.lindahall.org/wp-content/uploads/sites/5/2019/10/roche5.jpg[/img3][/float]
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The red star of the RS Ophiuchi system is filling its Roche lobe, and because it is an irregularly pulsating giant star of class M, it occasionally overflows its Roche lobe and spills mass onto its companion.
Note that although the illustration at right says that the red star at left is a main sequence star, I think it is extremely unusual that a red main sequence star, which is very small and compact, would overflow its Roche lobe. Almost all stars that fill their Roche lobes are evolved giant puffed-up stars that don't hold on to their outer layers very well.
The Youtube video at left shows an animation of the binary Beta Lyra system, where at least one of the stars is filling its Roche lobe. Beta Lyra is a system of two evolved, giant stars which orbit so close to one another that one has built up a thick accretion disk around itself (not visible in the video) and the other is distorted into a teardrop shape as it orbits its companion.
[quote][url=https://www.lindahall.org/edouard-roche/]Linda Hall Library[/url] wrote:
The Roche limit is applicable to any two mutually orbiting bodies, such as the Earth and the Moon. The Roche limit is the minimum distance that the Moon (or any satellite held together only by gravity) can be from the Earth (or any large body) without breaking up. If the Moon comes any closer than the Roche limit, it will break apart because of tidal forces. Thus no planet can have a moon that lies within the Roche limit – it can have only rings.
...
The Roche lobe comes into play when the two orbiting bodies are gaseous, as with a binary star. If the stars are close enough, gas will be pulled from each star toward the other, and the tear-shaped envelope of gas is the Roche lobe [/quote]
[float=left][img3="The Roche spheres of the Sun (yellow) and the Earth. L1 – L5 are the Lagrange points where the gravitational forces of the two bodies are neutralized. (Wikimedia commons)"]https://www.lindahall.org/wp-content/uploads/sites/5/2019/10/roche4.jpg[/img3][/float]
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Can't keep this illustration of the Sun-Earth Roche lobe system and its Lagrangian points from you. Cool, eh?
Ann