The planet Mercury is shrinking. It’s contracted by several miles since its birth. And it’s continuing to get smaller even now.

Mercury is the closest planet to the Sun. It’s also the smallest major planet in the solar system – a little more than 3,000 miles in diameter – about the width of the 48 states. It has a core of iron and nickel, surrounded by dense layers of rock. And it’s topped by a thin crust.

The surface of the planet is marked by lots of impressive cliffs. The biggest is more than 600 miles long and about two miles high. They formed as Mercury lost heat from its interior. As the planet cooled, it shrank.

Estimates of how much it’s contracted have ranged from about a mile to about nine miles.

A recent study narrowed the range a little bit. It measured the most dramatic features, then scaled that to the surface of the entire planet. The result suggests that Mercury has shrunk by about three to five miles as a result of its cooling. And when you add in some other causes, the total contraction is about four to seven miles. And Mercury is still getting smaller today.

This incredible shrinking planet is quite low in the southeast in the dawn twilight for the next few days. It looks like a bright star, but you need a clear horizon to spot it. And because of the viewing angle, it’s easier to spot from more southern latitudes. Tomorrow, the Moon stands to its right or upper right.

Script by Damond Benningfield