How can we know what exoplanets are made of if we can't visit them?
When planets transit their stars, starlight filters through their atmospheres. Different molecules absorb specific wavelengths, creating chemical fingerprints in the light spectrum. By analyzing these absorption features, astronomers identify gases like water vapor, methane, and carbon dioxide. Density (from mass and radius measurements) reveals whether planets are rocky, gaseous, or water-rich.
Could we ever travel to an exoplanet?
With current technology, no. Even our nearest exoplanet, Proxima Centauri b, lies 4.2 light-years away. Our fastest spacecraft would take over 70,000 years to reach it. However, proposed technologies like light sails pushed by powerful lasers could potentially achieve 15-20% light speed, reaching Proxima in 20-30 years. Generation ships or suspended animation remain science fiction for now.
Why do so many exoplanets orbit so close to their stars?
This is partly selection bias – close-in planets are easier to detect because they transit more frequently and cause larger stellar wobbles. However, planetary migration is real. Planets can form farther out where there's more material, then migrate inward through gravitational interactions with the disk or other planets. Our solar system's stable architecture might be relatively unusual.
Have we found any moons around exoplanets?
Not definitively yet, though candidates exist. Exomoons are extremely difficult to detect – if finding exoplanets is like finding a needle in a haystack, finding exomoons is like finding a specific atom on that needle. However, large exomoons could be common and potentially habitable. Future telescopes might detect them through their transit timing effects or direct imaging.
Do all stars have planets?
Statistical analysis of Kepler data suggests most stars host at least one planet. Multi-planet systems appear common. Even binary stars can host planets, either orbiting one star or both. The old view of planets as rare cosmic accidents has completely reversed – planets appear to be natural, almost inevitable outcomes of star formation.