Rocky · 1st planet from the Sun
Mercury
The smallest planet and the closest to the Sun, with the most extreme temperature swings of any planet.
See if Mercury is visible tonight from where you are
We calculate this live from your exact coordinates — nothing is stored.
Size & Distance
Diameter4,879 km
Vs. Earth's diameter0.38×
Distance from Sun0.39 AU (57.9M km)
Distance from Earth (range)91M – 208M km
Mass & Gravity
Mass vs. Earth0.055×
Surface gravity vs. Earth0.38×
Known moons0
Time
Length of day~59 Earth days
Length of year88 days
Orbit
Orbital period88 days
Planet typeRocky
Interesting facts about Mercury
- A year on Mercury (88 days) is shorter than its own day (about 176 Earth days from one sunrise to the next), because of how slowly it rotates relative to its orbit.
- Despite being closest to the Sun, Mercury isn't the hottest planet — that title goes to Venus.
- Mercury has no atmosphere to speak of, so it can't retain heat — nighttime temperatures plunge far below freezing even though daytime temperatures are scorching.
FAQ
How far is Mercury from the Sun?
An average of about 0.39 AU (57.9 million km).
How big is Mercury?
4,879 km in diameter — about 0.38× the diameter of Earth.
How much would I weigh on Mercury?
Multiply your Earth weight by 0.38 — Mercury's surface gravity is 0.38× Earth's. Try our weight calculator for an exact number.
Other planets
Cosmic Explorer Navigation Matrix
Automated internal linking across every layer of the tracker — no orphan pages.
Learn the Science: Read our complete educational breakdown on Solar Wind.Historical Archive: Track past occurrences of this cosmic phenomenon.Live Telemetry: Jump to the real-time Kp index & solar wind command matrix.
🌌 Broader Cosmic Context
🪐 Related Space Phenomena & Objects
- Space Weather Tracker — Home DashboardLive global overview
- Live Space Weather Command DashboardReal-time metrics
- Space Weather 101 — The Complete Beginner's GuideLearn the science