SUMMARY OF KEY IDEAS
Astronomers have observed disks of gas and dust orbiting young stars.
At least 1800 exoplanets have been discovered orbiting other stars.
Exoplanets ranging in mass from less than the mass of Earth to many times the mass of Jupiter have been detected.
Most of the exoplanets that have been discovered have masses roughly equal to the mass of Jupiter.
Exoplanets of sizes ranging from 0.2 to 25 Earth diameters have been observed.
Some exoplanets are observed directly, while most are detected indirectly as a result of their effects on the stars they orbit.
Exoplanets orbiting virtually all types of stars have been observed.
There are more planets than stars in our Milky Way Galaxy.
Exoplanets supporting life must be Earthlike in composition and in their stars’ habitable zones.
No life has been discovered on any exoplanet.
Some planets that are not orbiting stars have been observed.
WHAT DID YOU THINK?
Have any planets been observed orbiting other stars? Yes, at least 1800 exoplanets have been observed.
Have any Earthlike planets been discovered orbiting in the habitable zones around other stars? Yes, at least 10 Earthlike exoplanets have been observed in their stars’ habitable zones.
Have astronomers discovered evidence for life on any planets orbiting other stars? No.