What would happen if a star or large planet entered our solar system?
813735
the nearest star passing the solar system is barnard's star passing the solar system in a distance larger than 3 lightyears no earlier than 10.000 years in the future .. soo  no star in sight...\n\na dark object the size of jupiter ..hmm... \nthe direct gravitational influence of ALL yet known planets within the solar system can't match up with the suns gravitational force.\nThe whole system must have been stable since more than a billion years now (4 billion ?). A few years ago all planets where in a row and some people claimed we are about to have severe floodings cause of that.  nothing happens. \n\nif such a planet would appear it has loooooots of space to run through the system without hitting anything and it must come with the correct speed and the correct vector to get caught in an orbit. the chances are very very small that this is the case.\n\nif such a planet would cross near the earth i bet it would cross so fast that you are not even able to take out your camera to make a photo of it. And depending on simple newtonian mechanics the earth mass is high enough to have such a momentum that no major trajectory change should occur.\n\nwhat possibly happens is, that a jupiter sized mass running through the system would change trajectories of a few asteroids which may cross the planets path.\nthose asteroids may cause a concern, but as already mentioned above SPACE is huuughe the solar system has alot of it and the chances that such an asteroid hits our tiny blue pearl are really really small. \nIf you take a look at Nasa's NEO website you may freak out for having so many asteroids nearby but from statistics .. we get hit approx. every 300.000 years  soo .. <shrug>...  space is called space cause its basically empty space\n\nand if that is not enough\nthe oldest objects in space are 'globular clusters' like M13 for example. Those clusters are made of up to more than 100.000 stars which orbit each other in a relative small section of space without colliding since billions of years. If these objects exists since such a long time without destroying themselves in collisions, why then should a small body like jupiter should mess up our solar system which appears to be stable since at least 1 or 2 billion years ?\n\nchances are better to win the lottery, don't you think ?  ;-)
1152640
While I agree with other people here that we should take better care of our planet, eventually the Earth will be destroyed.  Even if all comets and planet-killing asteroids miss us, the sun will eventually expand into a red giant and engulf the Earth.   Though that isn't likely to happen for possibly another billion years, it will eventually happen.\n\nThat being said, the more planets that we as a species inhabit, the greater our chance of survival.  Especially when we consider the possibility of colonizing other worlds in distant solar systems.  The endeavor will not be an easy one, and is indeed not possible at our current level of technology.  However technology may eventually advance that allows us to traverse great distances of space in but a few moments, perhaps through the creation of artificial wormholes.  Maybe we'll be lucky enough to see it in our lifetime.
802495
Interactions with massive giant molecular clouds and other stars are what can swipe angular momentum of objects in Oort clouds sending them falling straight down into the inner parts of the Solar System (in this context 'inner' means inside of Neptune's orbit). These are the same mechanisms that fluffed out the Oort cloud in the first place.  (This is why the Oort cloud has a diameter roughly the scale of the distances between stars in the outer solar system.)\n\nIf you think about it, Jupiter could only eject early solar system comets or throw them into highly elliptical but still Jupiter crossing orbits, so it is these same interactions that build up the Oort cloud in the first place (otherwise, eventually Jupiter ejects everything)
970270
it won't be for a long time from now, like 1000s of years, but it will happen.  Planets are basically stars and stars burn out sooner or later.  If it isn't earth that ends first, it'll be the sun that burns out and we can't survive without the sun.
454185
The sun is not massive enough to supernova.  The Sun will however eventually swell into a giant that will consume all the inner planets (when the hydrogen fuel is depleted 5 billion years or so from now) and then shrink into a white dwarf star.
1171177
We have already found planets orbiting other stars in our solar system. They detect them by the "wobble" of the star. The wobble tells them something is orbiting the star. Knowing the stars aproximate mass, they can tell roughly how big the planet is. We have found almost one hundred planets outside of our solar system.
304584
Yes, new stars and new planets can form from the remnants of dead stars.  We can see this process happening, although it is extremely slow, a process that take millions of years.\n\nEven our sun is thought to be a 3rd generation star.  When our sun dies, it will expand to become a Red Giant star, eventually cooling/contracting into a white dwarf, as this happens, a lot of stellar meterial will be released and will float off into space to make new stars in the future.
386163
we'd all DIE!!!\ni dont know!\nyou should go ask an astronomer
961908
Chance.\n\nMany stars in the galaxy are part of binary systems.  As the gaseous nebula that forms a solar system collapses, the mass can distribute in many ways.  The Sun got the majority of the mass, and Jupiter carries much of the residual mass of the solar system (2.5x the mass of the other planets).  If more mass had gone to Jupiter, we might be in a binary solar system.  If the majority of the mass went to Jupiter, it would be the Sun, and vice versa.
285416
We really only know our solar system planets, and we know from probes that have been sent, from the effects on their moons and other bodies coming close or even hitting into them. We can observe how the spectrum of the atmosphere changes when the planet goes behind or for Mercury and Venus, in fron of, the sun's halo. Or when the planet "occults" another star whose spectrum is known.
632221
They burn. Every star burns and die. But the lifetime of a star can reach up to 8-10 billions years. So, the constellations will change eventually, but nobody will even remember they're names probably. And the constellations as we know them, have the arrangement of the component stars the same only in the vicinity of our solar system. If the human kind will spread in the universe, then the constellations will be lost in oblivion. But others will appear, with every planet we will colonize and every dreaming human mind to contemplate the local night sky.
1097113
The sun will die because the hydrogen inside it will eventually be used up. This will create enormous pressure and make the sun increase in size, in fact so large that it will engulf the earth. This enlargement is called a red giant. Then it will blow up and all that will remain is the core or a red dwarf that may collapse in on its self creating a black hole. And all this will happen in about 7 billion years, so no need to worry!
390316
The sun is a star. When it becomes a red giant the earth will be vaporized. thats a few billion years off but it will happen. So yes it does.
472607
planets orbit stars, satellites orbit planets
477262
No one knows, at it's current rate of energy useage, a few million years. Which planet would I choose? Can't, you & I are already dead, besides all planets in our solar system would be lifeless (no sun).
1173785
Stars don't move our sun is a big star it is our planet that orbits our star so that is why it seems like the stars move my lov.
759134
I'm afraid its "Goodnight Vienna" for us. As this is unlikely to happen for another 5 billion years or so though, there is a fair chance that we will have blown ourselves up or evolved into something a little more intelligent and cleared off elsewhere by the time it happens.\n\nAlthough the Sun uses up around 5 million tons of hydrogen every second, it still has enough left in its core to last for another 5 billion years or so. When it finally does run out of fuel, though, it will swell up to many times its present size and become what is known as a red giant. \n \nThe outer layers of the Sun will grow to swallow up the planets Mercury and Venus and they may even reach out as far as Earth. Way before the Earth is swallowed the surface of our planet will be scorched, its oceans boiled dry and most of the atmosphere will be stripped away.\n\nAs a red giant, the Sun might be able to exist for a few more million years. During this time it will shed matter quite quickly. The solar wind will strengthen to a solar gale. Finally, the Sun may cast off most of its outer layers as a bright shell of gas called a planetary nebula.\n\nAll that will be left behind is a very hot, dense core. The Sun, in fact, will have become a white dwarf - a star no bigger than the Earth. Gradually, over many millions of years, even this small star will cool. The Sun will end its days quietly as a dimming ember in space.\n\nThe attached link shows a photo of a star similar to the Sun in its death throes.