APOD: Explosions from White Dwarf Star RS Oph (2021 Aug 22)

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APOD: Explosions from White Dwarf Star RS Oph (2021 Aug 22)

Post by APOD Robot » Sun Aug 22, 2021 4:06 am

Image Explosions from White Dwarf Star RS Oph

Explanation: Spectacular explosions keep occurring in the binary star system named RS Ophiuchi. Every 20 years or so, the red giant star dumps enough hydrogen gas onto its companion white dwarf star to set off a brilliant thermonuclear explosion on the white dwarf's surface. At about 5,000 light years distant, the resulting nova explosions cause the RS Oph system to brighten up by a huge factor and become visible to the unaided eye. The red giant star is depicted on the right of the above drawing, while the white dwarf is at the center of the bright accretion disk on the left. As the stars orbit each other, a stream of gas moves from the giant star to the white dwarf. Astronomers speculate that at some time in the next 100,000 years, enough matter will have accumulated on the white dwarf to push it over the Chandrasekhar Limit, causing a much more powerful and final explosion known as a supernova. Starting early this month, RS Oph was again seen exploding in a bright nova.

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Re: APOD: Explosions from White Dwarf Star RS Oph (2021 Aug 22)

Post by VictorBorun » Sun Aug 22, 2021 4:28 am

A red globe with one jet spiralling down to an accretion disk? No, seriosly?

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Re: APOD: Explosions from White Dwarf Star RS Oph (2021 Aug 22)

Post 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?

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Re: APOD: Explosions from White Dwarf Star RS Oph (2021 Aug 22)

Post by De58te » Sun Aug 22, 2021 12:37 pm

Ann, cool the Sun-Earth Roche lobe system diagram is. But I have a question, where is Venus in it? Venus is practically the same mass and size as Earth. Say what would happen if Venus was at or near the L1 position? Would it double up with the Sun and increase the L1 lobe or would it add up with Earth and decrease the sun's power? Compare that if Venus was instead near L4 or L3. And would Venus have its own L1 to L5 lobes?

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Re: APOD: Explosions from White Dwarf Star RS Oph (2021 Aug 22)

Post by orin stepanek » Sun Aug 22, 2021 1:02 pm

rsoph_pparc_2953.jpg
Beautiful rendering of a nova! I didn't realize a star goes through a
series of novas!

auburn-handsome-cat-thinking-about-life-natalia-o.jpg
Kitty pondering a problem! Gonna figure it out too! :lol2:
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Re: APOD: Explosions from White Dwarf Star RS Oph (2021 Aug 22)

Post by XgeoX » Sun Aug 22, 2021 2:20 pm

Ann, thanks for the great explanation, I learn something new every day!
Orin, you’ve outdone yourself with today’s kitty picture, I’m a sucker for orange cats. They are talkers with great personalities. I believe he’s considering catastrophic explosions or how purrfect it would be if they brought back the extinct cat constellation “Felis”…
Image

Regardless it’s amazing there are these supernova machines. I read recently they think they have a white dwarf that was partially destroyed during it’s burst. I wonder what effect an irregular white dwarf (if such things exist) would have on the dynamics of the system. Could it still collect enough gas to go supernova again? What effect would an irregular dwarf have on the explosion?

Eriv

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Re: APOD: Explosions from White Dwarf Star RS Oph (2021 Aug 22)

Post by Chris Peterson » Sun Aug 22, 2021 2:29 pm

XgeoX wrote:
Sun Aug 22, 2021 2:20 pm
Regardless it’s amazing there are these supernova machines. I read recently they think they have a white dwarf that was partially destroyed during it’s burst. I wonder what effect an irregular white dwarf (if such things exist) would have on the dynamics of the system. Could it still collect enough gas to go supernova again? What effect would an irregular dwarf have on the explosion?
Nova machines. Supernovas don't repeat.
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Re: APOD: Explosions from White Dwarf Star RS Oph (2021 Aug 22)

Post by orin stepanek » Sun Aug 22, 2021 2:52 pm

XgeoX wrote:
Sun Aug 22, 2021 2:20 pm
Ann, thanks for the great explanation, I learn something new every day!
Orin, you’ve outdone yourself with today’s kitty picture, I’m a sucker for orange cats. They are talkers with great personalities. I believe he’s considering catastrophic explosions or how purrfect it would be if they brought back the extinct cat constellation “Felis”…
Image

Regardless it’s amazing there are these supernova machines. I read recently they think they have a white dwarf that was partially destroyed during it’s burst. I wonder what effect an irregular white dwarf (if such things exist) would have on the dynamics of the system. Could it still collect enough gas to go supernova again? What effect would an irregular dwarf have on the explosion?

Eriv
I love domestic animals and respect wild life! I had an orange cat when I was a boy! He was a free spirit! I had a dogs since I was married. they are good babysitters and friends!
I didn't know stars would repeat novas until I read about it today! If ever it goes over the Chandrasekhar Limit, we may get to see a nice glow as it goes super! :shock:
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Re: APOD: Explosions from White Dwarf Star RS Oph (2021 Aug 22)

Post by Chris Peterson » Sun Aug 22, 2021 3:12 pm

orin stepanek wrote:
Sun Aug 22, 2021 2:52 pm
I didn't know stars would repeat novas until I read about it today!
Probably all systems that experience novas are recurrent, it's just that only a relatively small percentage have a recurrence interval short enough for us to have seen more than one event. We know of around ten systems in the Milky Way like RS Oph where the novas recur over just a few decades, instead of the centuries or millennia that likely define other novas.
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Re: APOD: Explosions from White Dwarf Star RS Oph (2021 Aug 22)

Post by Ann » Sun Aug 22, 2021 4:35 pm

De58te wrote:
Sun Aug 22, 2021 12:37 pm
Ann, cool the Sun-Earth Roche lobe system diagram is. But I have a question, where is Venus in it? Venus is practically the same mass and size as Earth. Say what would happen if Venus was at or near the L1 position? Would it double up with the Sun and increase the L1 lobe or would it add up with Earth and decrease the sun's power? Compare that if Venus was instead near L4 or L3. And would Venus have its own L1 to L5 lobes?
There is undoubtedly a Sun-Venus Roche lobe system, and I'm sure Venus has its Lagrangian points, too.

The Earth doesn't come into play when we talk about the Sun-Venus system, because the Earth and Venus are sufficiently lightweight and sufficiently far from one another that they don't affect each other very much. I very seriously doubt that there is an Earth-Venus Lagrangian point!

Actually, there can't be one. The Earth and Venus don't orbit one another, which in all probability rules out any shared Lagrangian points in any case.

So what about a Sun-Venus-Earth Lagrangian point? Possibly, but such a Lagrangian point couldn't be stable, since the Earth and Venus are not locked to one another in their orbits around the Sun.

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Re: APOD: Explosions from White Dwarf Star RS Oph (2021 Aug 22)

Post by neufer » Sun Aug 22, 2021 7:37 pm

Ann wrote:
Sun Aug 22, 2021 4:35 pm
De58te wrote:
Sun Aug 22, 2021 12:37 pm

Venus is practically the same mass and size as Earth. Say what would happen if Venus was at or near the L1 position? Would it double up with the Sun and increase the L1 lobe or would it add up with Earth and decrease the sun's power? Compare that if Venus was instead near L4 or L3. And would Venus have its own L1 to L5 lobes?
  • The L1 & L2 lobes of Earth & Venus are unstable :!:

    If Venus & Earth are placed in their opposite's L1 & L2 lobes they would quickly
    • 1) migrate into nearby Horseshoe trajectories encompassing the L4, L3 & L5 lobes and
      2) then to co-orbit the Sun in the same manner that Epimetheus & Janus co-orbit the Saturn:
https://en.wikipedia.org/wiki/Janus_(moon)#Orbit wrote: Epimetheus (lower left) and Janus (right) seen on 20 March 2006, two months after swapping orbits. The two moons appear close only because of foreshortening; in reality, Janus is about 40,000 km farther from Cassini than Epimetheus.

Janus's orbit is co-orbital with that of Epimetheus. Janus's mean orbital radius from Saturn was, as of 2006, only 50 km less than that of Epimetheus, a distance smaller than either moon's mean radius. In accordance with Kepler's laws of planetary motion, the closer orbit is completed more quickly. Because of the small difference it is completed in only about 30 seconds less. Each day, the inner moon is an additional 0.25° farther around Saturn than the outer moon. As the inner moon catches up to the outer moon, their mutual gravitational attraction increases the inner moon's momentum and decreases that of the outer moon. This added momentum means that the inner moon's distance from Saturn and orbital period are increased, and the outer moon's are decreased. The timing and magnitude of the momentum exchange is such that the moons effectively swap orbits, never approaching closer than about 10,000 km. At each encounter Janus's orbital radius changes by ~20 km and Epimetheus's by ~80 km: Janus's orbit is less affected because it is four times as massive as Epimetheus. The exchange takes place close to every four years; the last close approaches occurred in January 2006, 2010, 2014, and 2018, and the next in 2022. This is the only such orbital configuration known in the Solar System.

The orbital relationship between Janus and Epimetheus can be understood in terms of the circular restricted three-body problem, as a case in which the two moons (the third body being Saturn) are similar in size to each other.>>
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