Mercury at Greatest Western Elongation 2021
Planetary Event
On this day, Mercury reaches its greatest western elongation of 27.3 degrees from the Sun. This is the best time to see the planet in the early morning sky, when it is at its highest point above the eastern horizon. Get up early and look to the east just before sunrise and you may spot a small bright dot – that is Mercury.
Mercury is the closest planet to the Sun, so it is very hard to observe. However, at special times of the year when it reaches greatest elongation, the planet can stand out if you know the right time and direction to look.
The planet orbits inside Earth’s orbit, which means it always appears close to the Sun, usually just before sunrise or just after sunset.
Elongation is the angle between the Sun and a planet as seen from Earth. For planets orbiting inside Earth’s orbit, such as Venus and Mercury, western elongation occurs when the planet is west of the Sun on the celestial sphere, which means it appears in the eastern sky before dawn.
If you love astronomy, don’t miss this special occasion to enjoy the beauty of the sky!