"No game has made it possible to fly down to a planet, and for it to be planet-sized, and feature life, ecology, lakes, caves, waterfalls, and canyons, then seamlessly fly up through the stratosphere and take to space again".
The Sun and Moon used to be planets.
But many objects agreed to be planets have not completely cleared their orbits.
Too small to be planets, too big to be ignored, they can reveal a great deal about our primordial history.
At that time astronomers confirmed that other stars have objects that appear to be planets in orbit around them.
"False positives" — objects that appear to be planets but are not — have bedeviled astronomers since they started tracking the known number of planets in the universe.
They found 474 incidents of microlensing, just 10 of which were brief enough to be planets of around Jupiter's size.
The table below lists Solar System bodies once considered to be planets.
A few astronomers, such as Alan Stern, consider dwarf planets and some moons to be planets based on a geophysical definition of a planet.
Starting in 1801, astronomers discovered Ceres and other bodies between Mars and Jupiter which were for some decades considered to be planets.
