I'm Wondering About Dead Planets

Jerry Gerber:
Let's say there's a solar system somewhere in a galaxy and the star of that system reaches the end of its life-cycle.   The star may collapse into a black hole, or it may explode into a supernova, but what happens to the planets?  Do they get vaporized or sucked into the black hole?  Or is it possible there are billions of dead planets in the universe, planets that didn't get destroyed by their sun's demise, but instead just became lonely wanderers outside the gravitational grasp of any particular sun?

We're only about 31 years or so into finding the first exoplanets, and we're beginning to find earth-sized planets orbiting other stars.  It seems that it will be a long time before we might discover a planet that has been "orphaned" by its once powerful sun and is aimlessly wandering the galaxy that once contained its solar system.

Just wondering...

Gabriel Perano:
I'm no astronomer either so don't take every word I say to be 100% correct/accurate

Just to clarify, supernovas are the result of a star dying which forms either a black hole or a neutron star. In this process of the high mass star dying, the star will start to collapse under its own weight. The star collapses with such great force, it causes the core to shrink in size & thus become more dense. Depending on the force of the collapsing star (the higher the mass of the star is the greater the force will be), will determine if the pressurized core will become a black hole or neutron star. The vast majority of high mass stars won't to be able to produce the needed conditions for the black hole to form due to the shear force needed, & instead the majority will result in a neutron star. However a small percentage will become low mass black holes. The collapsing outer sections of the star will cause the core of the star to condense (creating either a black hole or neutron star) will then be reflected off the core & pushed back out, creating a supernova. This event is so incredibly bright it can be observed from atleast millions of light years away, & quite easily in some circumstances, showing the shear amount of energy produced.  

Now to your question, the vast majority of planets in the given star system you could imagine would be destroyed due to there close proximity to there host star. It's maybe possible some of the outer planets with a fair distance from there star might survive & just lose there orbit, creating what is known as a rogue planet which is what you implied above. However the vast majority of planets would be destroyed in a instant.

Not exactly a rogue planet, but there are planets known to have survived supernova & still orbit there host star of which is now a Neutron star, an example being funny enough the first ever exo planet to be discovered (PSR B1257+12 B) of which actually was orbiting around a neutron star (a pulsar to be specific). Proving that planets can certainly survive supernovas, its just likely to be very rare & require very specific conditions. Because of this, I see no reason why a planet further out could survive but in this process lose their orbit due to the supernovas forces. 

Its also possible that rogue planets could form through other means too! For example its possible in the early formations of star systems, planets gravitationally interacting which each other might manage to sling shot each other out of the local star system, creating again a rogue planet. 

I hope this helps you out! 

Clear skies, 

Gabriel

Arun H:
Here is a nice article from Astronomy magazine on what the night sky might look like (and its consequences for astronomy conducted by some imagined civilization on an imagined exoplanet) inside a globular cluster. A quote from the article:

At the center, our planet would be surrounded by a few hundred stars per cubic light-year (several thousand stars per cubic pc), which is thousands of times the stellar density of the Sun’s neighborhood in the Milky Way’s suburbs. The typical distance from our hypothetical planet to the closest star, however, still would be substantial — about 0.05 light-year (0.015 pc). In our solar system, this would place it beyond the inner edge of the Oort Cloud of comets. Unless the closest stars happen to be red giants, none of them would have angular diameters large enough to resolve with the human eye, so all the stars still would appear as points of light. Across the entire sky, inhabitants of our hypothetical world would see 10,000 stars brighter than 1st magnitude — compared with just 29 in Earth’s sky — and more than a thousand brighter than Earth’s most brilliant nighttime star, Sirius. The brightest suns would blaze at apparent magnitudes brighter than –9, or 100 times more luminous than Venus appears from Earth. More than 130,000 stars would shine brighter than 6th magnitude, the naked-eye limit, compared with 6,000 from Earth

Life inside a globular cluster.pdf