Outer space is a pretty neat and crazy place. It starts only an hour’s drive from the Earth’s surface, if our cars could drive straight up. Our solar system includes 8 planets (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune), 5 dwarf planets (Ceres, Pluto, Eris, Haumea, Makemake), and 176 moons (don’t expect me to name those) revolving around a 4.6-billion-year-old G-type main-sequence star called the Sun.
But we are not the only solar system out there. Within 50 lightyears of our planet, there are 345 stars that are known to have solar systems, 18 of which we can see without magnification. The nearest confirmed exoplanet revolves around Gliese 674, a pre-main-sequence red dwarf star about 15 light years away. Its planetary companion, simply know as “b”, is about 11 times the mass of Earth and takes only 4.7 Earth days to orbit its star.
The exoplanet closest in mass to Earth is Gliese 667-Ch, about 23 lightyears away. The smallest, Gliese 436-UCF-1.02, is only a quarter Earth’s mass and 33 lightyears away, while the largest, Upsilon Andromedae-c, is 44 lightyears away and about 4,500 times the mass of Earth. Most have really complicated science-y names like Gamma Cephei-Ab or HD 147513-b. Bonus points to anyone who can rename them something more interesting, like Elefantengerung or Jimmy.
Gliese 436-UCF-1.02 takes about 2 Earth days to complete one full orbit and is pretty similar in size to Neptune. Its surface temperature is a toasty 822ºF due to its composition of incredibly densely compressed solid water, called “hot ice” and an outer layer of hydrogen and helium. Its eccentric orbit suggests that it is being impacted by the gravitational field of another yet undiscovered star or planet.
Upsilon Andromedae-c is the second planet in its three-planet solar system. This gas giant also has an eccentric orbit, due to its proximity to Upsilon Andromedae-d and possibly a rogue planet which temporarily entered the Upsilon Andromedae system and immediately exited again. The c planet returns to a circular orbit roughly every 6,700 years.
So far exactly zero exoplanets are populated by anything other than rocks.