The A Capella Science YouTube channel offers a remarkably good adaptation of the song “A Whole New World” from Disney’s Aladdin. In this version, it’s about the hunt for exoplanets orbiting other stars, concluding with a brief reference to the possibility of reaching them. Seriously, it’s way better than you might expect.
(My thanks to Derek Roff for pointing this out. The words to the song can be found at the link above. Someone really needs to annotate them, ideally with links to relevant web pages.)
The song makes reference to naïve past opposition in Congress to providing the modest funding needed and the early failures. Since exoplanets started being discovered Congress shifted to supporting the project, which still costs only a microscopic fraction of the budget.
There are two main methods used to detect planets. The more general is to look for Doppler shift in starlight showing a planet’s gravity pulling on the star and causing it to shift slightly toward and away from us. The other method works only for those very rare planets whose orbits are aligned so as to cross between the star and us, letting us detect a slight brief drop in the brightness. We can get far more information from these transits, and though they are rare, there are so many stars out there that we’ve found well over 3000 planets this way, with thousands more possible discoveries awaiting verification.
Some exoplanets have been directly imaged, though few have been found that way. Most notably, however, some likely “rogue planets” — planets ejected from solar systems to wander through interstellar space or else formed on their own, away from a star — have been observed by infrared telescopes. Such free-agent planets are very, very hard to find, but there’s a good chance there are lots and lots of them, perhaps even more than those that orbits stars.
Could we ever send spacecraft to any planets outside our solar system? A surprisingly popular misconception is that the vast distances involved make interstellar probes infeasible, but that’s demonstrably false. Humans, specifically Americans, have been launching interstellar spacecraft since the 1960s None of them will reach any other star systems for thousands of years, long after they have ceased to function. But they will eventually reach them. Moreover, there are credible proposals to send tiny probes using sails that capture light from powerful lasers in the solar system. Even then it will take decades for them to reach another solar system, but there’s a good chance they’ll still be able send back data.
Astronauts are another matter. Interstellar missions will take at least a large fraction of a human lifespan, maybe several lifespans, but there are at least conceivable ways to deal with that, such as multi-generation spaceships. The Earth itself travels through space carrying many generations of humans, so we have at least one prototype. Or we might be able to put people into suspended animation during the journey, so astronauts may indeed reach and even colonize other worlds. I’m not suggesting it’s certainty, only that it’s not an impossibility.
Even more realistically we might find some rogue planets at distances that make a round-trip visit feasible. Most likely they’d be cold and lifeless, but not necessarily. Some of may be pretty hot internally, as the Earth is. Their surfaces might be frigid, but underneath they might have bodies of liquid water and even life.