Astronomers Find Tiniest Planet Ever

A new planet named Kepler-37b is just slightly bigger than Earth's moon. It's the tiniest planet yet to be found circling around a star like our sun in a newly discovered planetary system called Kepler-37, according to NASA.

The system is about 210 light-years from our planet.

Kepler-37b, about one-third the size of Earth, is one of two other planets found in a region within the planetary system where liquid water might exist. This is also known as a "habitable zone" since water is needed to support life.

Kepler-37c is three-quarters the size of Earth and Kepler-37d, the farthest planet, is twice the size of Earth.

Although the star in Kepler-37 is like our sun, "all three planets orbit the star at less than the distance Mercury is to the sun, suggesting they are very hot, inhospitable worlds," NASA wrote in a press release.

Astronomers think tiny Kepler-37b is mostly rocky and has a blistering surface temperature of around 800 degrees Fahrenheit. It also doesn't have an atmosphere, meaning it can't support life as we know it.