Wandering Neptune?

I was perusing headlines the other day when I noticed one about Neptune. Normally, a headline about one of our planets grabs my attention and I read the article, but I was pressed for time that day, and decided to skip the article. Now I wish I'd read it.

The headline stated that all it would take to unravel our solar system was a star passing by and perturbing the orbit of Neptune. I have so-o-o many questions now about this possibly impending doom.

How big a star would it need to be? How big is the average rogue star? How close would the star have to get? How would that star appear to us here on Earth? Would we be able to feel any gravity or heat or radiation from that star? How much would it need to disrupt Neptune's orbit? What exactly would happen to the rest of the planets, once Neptune started to wander? How long would Earth have before it ultimately became uninhabitable?

So many questions, and no answers, because I didn't read the article. So I just now looked the article up, and read it.

Apparently, all it would take would be for the average distance between Neptune and the sun to be altered by 0.1%. Such a tiny change would increase the chance of the solar system descending into chaos 10 times higher. This 0.1% perturbation would be about 4.5 million kilometers (2.8 million miles). It would result in subtle changes to the orbits of the inner planets, reaching the Earth and Mars in about 20 million years. (Whew! I was afraid I might need to worry about it happening within my lifetime, or what's left of it.)

The team conducting the study ran 2,880 simulations with varying amounts of perturbations. 960 simulations had perturbations too small to be measured. In 4 of those, the resulting perturbation to Mercury's orbit resulted in it hitting Venus. In the remaining models, there were 26 that end in chaos; collisions between Mercury and Venus, Earth and Mars colliding, and some where Uranus, Neptune or Mercury were thrown out of the system.

They also estimated the chance of a star getting close enough to cause any of that, and concluded there were only about 20 chances over the next 100 billion years. So it doesn't seem very likely, given that our sun is only expected to last another 5 billion years.

 

https://www.iflscience.com/small-changes-to-neptunes-orbit-by-a-passing-star-could-wreck-the-entire-solar-system-64354

Death Throes

We've all heard that you can't take it with you. Well, scientists have discovered a dying star that is trying very hard to take its entire planetary system with it.

G238-44, a white dwarf located some 86 light-years away, seems determined it is not going alone. It's already made one attempt to end its system. You see, a white dwarf is what results when a star that is up to 8 times the mass of our sun reaches the end of its life. Once that star runs out of material to fuse, it puffs up to red giant size before ejecting its outer material. Then the core collapses to form a dense object that shines bright with the light of residual heat.

This process can put the inner planets right in the middle of that red giant until the outer shell is ejected and the core collapses. Scientists have discovered some planets that appear to have survived being gobbled up by a red giant phase, but not many, and they certainly don't appear to have any atmosphere or water left on them. When our sun hits that stage in a few billion years, the red giant produced could reach as far as Mars.

But we were talking about G238-44, which has reached the white dwarf stage, so it is currently much more dense than it used to be. Scientists studying it have been examining G238-44's atmosphere, and have found a plethora of 'heavy' elements, such as carbon, nitrogen, oxygen, magnesium, aluminum, silicon, phosphorus, sulfur, calcium, and iron. Most of these would have come from rocky worlds and inner system asteroids that probably 'survived' the red giant phase. The denser star is pulling them in and eating them.

But the nitrogen—and there seemed to be a lot of it—probably came from frozen worlds and asteroids such as exist in our Kuiper Belt. Apparently, the shift in gravity has perturbed their orbits, and the star is pulling them in and eating them also.

I wonder what the system will look like when all the planets and asteroids have been eaten, and the star cools into a massive hunk of... what? A huge rocky planet? A frozen gas giant with a big rocky core? What do you think it will be?

 

https://www.msn.com/en-us/news/technology/a-dead-star-has-been-caught-ripping-apart-its-planetary-system/ar-AAYGGzI?ocid=mailsignout&li=BBnb7Kz