Mercury is the smallest planet in our solar system. Explore its size, extreme temperatures, core structure, and comparison with Pluto.

The 1.5-day-old moon will be in close conjunction with Mercury on Feb. 18. You may be able to spot Venus in binoculars about ...

Mercury stands stationary at 3 A.M. EDT amid the stars of Cancer. The solar system’s smallest planet will now start sliding westward, or retrograde, appearing to “fall” back toward the Sun as it moves ...

Late last July, a University astrophysicist helped discover the smallest planet ever detected outside the solar system — without even seeing it. Using a planet-finding technique called "gravitational ...