Mercury tonight

Tonight in London

How to find it

Mercury never gets more than 28° from the Sun, so it only shows low on the horizon: in the evening shortly after sunset or in the morning before sunrise, a few weeks at a time. From northern latitudes the best chances are spring evenings and autumn mornings, when the ecliptic rises steeply and the planet climbs higher. Look for a yellowish point where the Sun has just set or will soon rise; if Venus is up, Mercury is often not far from it.

The nearest bright signpost now is Venus: Mercury is 5° from that planet, in the same binocular field. Light takes 9 minutes to reach the Earth from the planet now.

When it shows over the next 12 months

Mercury is in the evening sky 2 Feb – 6 Feb, 17 May – 29 May, and in the morning sky 14 Nov – 26 Nov. Brightest on 2 Feb (−0.7), closest to the Earth on 21 Jun, 83 million km.

Month by month

On the 15th of each month: when the planet rises and sets, its brightness, constellation and distance from the Earth.

Key dates

The inner planets show best when farthest from the Sun (greatest elongation) and not at all around conjunction with the Sun.

Phase and size over the coming months

Every two weeks, Mercury as a telescope shows it, at one scale: as it nears the Earth the planet grows but turns into an ever thinner crescent.

The Moon next to the planet

Every month the Moon passes Mercury, the easiest way to find the planet. The next close passes:

Where the planet is in the Solar System

The view from above: the Sun in the centre, orbits scaled down. Today Mercury is 166 million km from the Earth; over the year the distance ranges from 83 million km to 216 million km.

What kind of planet

Mercury is the smallest planet in the Solar System, only a little larger than the Moon. It orbits the Sun in 88 days but turns so slowly that one solar day there lasts 176 Earth days. With almost no atmosphere, the surface heats to 430 °C by day and cools to −180 °C at night. Its cratered surface looks like the Moon's, and its huge iron core fills about 85% of the planet's radius, more than in any other planet.

In binoculars

Binoculars help a lot in finding Mercury in a bright twilight: it is often easier to catch with binoculars first and only then with the naked eye. You will see a point, no detail. The key rule: never sweep binoculars towards the Sun while it is above the horizon; even a moment with the Sun in the field can permanently damage your eyes.

In a telescope

From about 75–100× a telescope shows Mercury's phase: like Venus it appears as a crescent, a half or a nearly full disc. The disc is tiny (5–12″), and surface detail is all but impossible for amateurs. Experienced observers follow Mercury in daylight, high in the sky, pointing by coordinates, but that is only safe if you know how to keep the Sun out of the instrument.

Exploration

The first spacecraft at Mercury was Mariner 10, which flew past three times in 1974–1975 and photographed about half the surface. NASA's MESSENGER orbited from 2011 to 2015, mapped the whole planet and found water ice in permanently shadowed polar craters. The European–Japanese BepiColombo mission, launched in 2018, is to enter orbit after a series of flybys and study Mercury with two spacecraft.

Name and history

The planet is named after Mercury, the Roman messenger god (the Greek Hermes), because it moves fastest across the sky. The ancient Greeks at first thought the morning and evening Mercury were two different objects. Now and then Mercury crosses the face of the Sun, a transit that happens about 13 times a century; the next is on 13 November 2032 (to be watched only through a proper solar filter).

Facts

Other planets