White dwarf chewing a planet to bits.

[PB666]

http://www.nasa.gov/ames/kepler/nasa-k2-finds-dead-star-vaporizing-mini-planet

There is something a miss here in the logic.

1. Step 1, Star

2. Step 2, Red giant, has expanded to consume all short period planets

3. Step 3. Contraction

4. Step 4. White dwarf

OK, so how is it that a planet can exist in the short period planets zone if the previous state of the star already consumed the planets in that Zone.

[Shpaget]

It was "aerobraking" during the red giant phase?

[J.Random]

I thought that expansion and contraction goes on at the same time. Outer layer expands as hot gas (red giant) while at the same time innards condense into a white dwarf. Then gas cloud cools down and what remains is a dwarf.

[Hannu]

When a sun like main sequence star becomes a red giant volume of outer layers increases with huge factor. However, its mass is constant and most of it stays in relatively small core. Outer parts of red giant have very low density. Rocky planets can survive long time in such atmosphere. They lose orbital energy (drag) and mass (thermal evaporation) but it takes very long time before planet is completely destroyed. Sometimes planet (or part of the planet) can survive.

[Technical Ben]

Yep. If a comet can survive a close call (look up the videos ) a planet can too.

[PB666]

Yep. If a comet can survive a close call (look up the videos ) a planet can too.

Yes, but the popular dogma is that stars drag and chew up the planet.

Planet earth inside a red giant.

1. Atmosphere is lost

2. Suns molecules are bombarding the earths surface at 40,000 miles per hour. Imagine the earth in perpetual reentry, except a magnitude more intense per unit surface area. The entire surface of the earth would be

like in the hottest blast furnace that humans could possibly make. It would be like bombarding the entire surface with a rubidium laser.

I'm pretty sure but not absolutely certain that being bombarded at 40000 miles per hour would cause the heaviest metals to start vaporizing and be dragged off into the star.

3. As the surface heats up even more from the collisions the surface begins to boil molten metals and degassing metal itself. The cessation of cooling at the surface and the ongoing uranium radiativity of the core would cause the entire upper layers to boil with huge eruptions that cough large amounts of surface into space.

4. The moons orbit is destabilized and after forming a highly eliptical orbit collides with earth.

5. planet would have to survive this for 5 billion years. Each orbit spiraling closer to the star.

[magnemoe]

Yes, but the popular dogma is that stars drag and chew up the planet.

Planet earth inside a red giant.

1. Atmosphere is lost

2. Suns molecules are bombarding the earths surface at 40,000 miles per hour. Imagine the earth in perpetual reentry, except a magnitude more intense per unit surface area. The entire surface of the earth would be

like in the hottest blast furnace that humans could possibly make. It would be like bombarding the entire surface with a rubidium laser.

I'm pretty sure but not absolutely certain that being bombarded at 40000 miles per hour would cause the heaviest metals to start vaporizing and be dragged off into the star.

3. As the surface heats up even more from the collisions the surface begins to boil molten metals and degassing metal itself. The cessation of cooling at the surface and the ongoing uranium radiativity of the core would cause the entire upper layers to boil with huge eruptions that cough large amounts of surface into space.

4. The moons orbit is destabilized and after forming a highly eliptical orbit collides with earth.

5. planet would have to survive this for 5 billion years. Each orbit spiraling closer to the star.

Correct except 5 the red giant phase don't last 5 billion years, it last some millions.

You would get aerobraking inside the star atmosphere who would lower the orbit.

However the force has to be just right too low and it would disapear into the star, too high and it would not be close enough to the white dwarf for it to do anything with it.

Now tidal forces try to circulate an orbit and its lots of forces here as tides is ripping the planet up. It might be orbital changes in the aftermath of the red giant phase who lower Pe for an planet enough to pull it into an low orbit.

[cryogen]

Here's the paper (33 pp),

http://arxiv.org/abs/1510.06387

[Hannu]

Yes, but the popular dogma is that stars drag and chew up the planet.

Of course planet takes heavy damage inside or near red giant. But astronomers think that there are conditions in which the core of the planet can survive, if orbit is not too low and red giant phase is not too long. Conditions are harsh but not as harsh as "inside a star" sounds and planets are relatively massive and tight bounded objects. Giant phase lasts only tens or hundreds of millions of years, depending on mass of the star (more massive are quicker)).

Density is as important factor as a temperature. There are regions in Jupiter's magnetosphere where the temperature of "gas" is hundreds of millions of kelvin. However, space probes have no problems to go through (thermal problems, radiation is another story). There are small amount of particles with very high kinetic energy but an atom here and an ion there does not heat the probe significantly.

[PB666]

Of course planet takes heavy damage inside or near red giant. But astronomers think that there are conditions in which the core of the planet can survive, if orbit is not too low and red giant phase is not too long. Conditions are harsh but not as harsh as "inside a star" sounds and planets are relatively massive and tight bounded objects. Giant phase lasts only tens or hundreds of millions of years, depending on mass of the star (more massive are quicker)).

Density is as important factor as a temperature. There are regions in Jupiter's magnetosphere where the temperature of "gas" is hundreds of millions of kelvin. However, space probes have no problems to go through (thermal problems, radiation is another story). There are small amount of particles with very high kinetic energy but an atom here and an ion there does not heat the probe significantly.

Yes but inside the light emmitting crown of a star, even one that produces in the low energy part of the visible spectrum is density suitable to create drag when the satellite is orbiting around the star what are we

150,000,000,000 * 2 * 3.14. / 365.25*86400 (31557600) = 29865 m/s. KE generated = 455,000,000 joules per kg of stellar gas. so 4180 joules to boil 1 liter if water so 1 kilo of stellar gas can basically burn of 100,000 liters of ocean. Consider that the earth is traveling at 29865 m/s and its radius is 6371000, making its crossectional area along the path of travel 1.275 e 14 meters squared or an area of space captured of 3.8 e 18 cubic meters covered per second.

The suns current mass is 2e30, at a radius double earths orbit it would have a gas density of 0.0001 kg per cubic meter 3.8 e 14 kg per second. This times. 455,000,000 joules per kg gas = 1.79e23 joules per second. Energy flow at the boundary of forward motion (6371000 x 2 x pi) = 4.3e15 joules per meter per second. This of course is going to be a combination of heated gas, hv, vaporized metals, particularly along the boundary, a simply the flow of molten earth along its surface, where the local gas flow is highest chunks of molten metal will simply lift off and be carried into space wher its orbit would decay into the sun.

Edited October 22, 2015 by PB666

[andrewas]

380TW is 1/458 of the solar energy currently received by Earth's surface. We can probably forget about that compared to the energy that will be radiated from the hot gas that surrounds Earth.

Also, whether or not Earth would survive if enveloped in Sol's red giant phase it doesn't say much about another planet. It could have been bigger to start with, or been right on the edge of the star after expansion. Or perhaps it was in an eccentric orbit, and spent only a brief period within the star until its orbit was circularized by drag and it started to spiral in.

[problemecium]

Indeed. There's been all this buzz about "super-Earths" lately, so perhaps such a planet got dragged down into a red giant, but some of it was still left after the star's outer layers dispersed.