Astronomical overview
Mercury has a very thin exosphere rather than a full atmosphere, so it retains little heat.
Its heavily cratered surface is broadly similar to the Moon.
☿ · Ephemerides
Observation date
Mercury
The innermost rocky planet, known for extreme temperature swings between day and night.
- AU
- 0.441
- ECL
- 296.8°
- MAG
- 5.14
01 — Current astronomical data
Parameters and context
- Heliocentric distance
- 0.441 AU
- Ecliptic longitude
- 296.82°
- Ecliptic latitude
- -6.51°
- Apparent magnitude
- 5.14 mag
- Right ascension
- 7 h 21 min
- Declination
- 17.15°
- Altitude above horizon
- -10.2°
- Azimuth
- 43.9°
Astrological meaning
In astrology, Mercury is linked to communication, analytical thinking and how information is processed.
Mythology
The name comes from Mercury, the Roman messenger god associated with speed and movement.
02 — 05
Key facts
- 01It has no moons and no rings.
- 02Its orbit is the most eccentric among the rocky planets.
- 03Contraction scarps on the surface indicate long-term planetary cooling.
- 04Mercury is in a 3:2 spin-orbit resonance.
- 05Water-ice signatures were detected in permanently shadowed polar craters.
Parameters and context
- Sidereal day
- 58 d 15 h 30 min
- Solar day
- 176 d 0 h
- Year length
- 88 days
- Rotation speed
- 10.8 km/h • 0.26°/h
- Orbital speed
- 47.40 km/s
- Distance from Sun
- 57.90 million km
- Diameter
- 4,879 km
- Gravity
- 3.7 m/s²
- Mean temperature
- 167 °C