See Mercury beneath Venus at dusk

Live in the Northern Hemisphere? If so and you’ve never seen the planet Mercury – or even if you have – take advantage of your golden opportunity to see Mercury after sunset these next few weeks. February 2020 showcases Mercury’s best appearance in the evening sky for this year for northerly latitudes. If you live in the Southern Hemisphere, you might glimpse Mercury, too, but it’ll be tougher. Your best evening view of Mercury will come in September/October 2020.

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No matter where you are on Earth, here’s how to find Mercury. Make sure you have an unobstructed horizon in the direction of sunset, and, if possible, perch yourself on top of a hill or balcony. Search first for the blazing planet Venus, the 3rd-brightest celestial body to light up the sky, after the sun and moon. People with good vision might spot Venus almost immediately after sunset, but us mere mortals may have to wait some 30 to 45 minutes after sundown to see the sky’s brightest planet. Then, as dusk deepens into darkness, look for Mercury to pop out beneath Venus and close to the sunset point on the horizon. You might see Mercury with the eye alone an hour or so after sunset. With binoculars, you can spot Mercury (and Venus) even earlier.

At mid-northern latitudes, Mercury follows the sun beneath the horizon about 1 1/3 hours after sundown. At Earth’s equator (0 degrees latitude), Mercury sets about one hour after the sun; and at temperate latitudes in the Southern Hemisphere, Mercury only stays out for about 45 minutes after sunset.

Click here for a sky almanac, giving you Mercury’s setting time in your sky.

Twilight sky with glow along dark horizon and small, dim dot above.

View at EarthSky Community Photos. | EarthSky friend Radu Anghel in Bacau, Romania, caught Mercury after sunset on February 17, 2019. He said it was about an hour after sunset. Thank you, Radu!

Mercury is often said to be elusive. Some people say they’ve never seen it. But that’s not because Mercury is faint. In fact, Mercury is super bright right now, shining some six times more brilliantly than a 1st-magnitude star.

Even so, even when it’s this bright, Mercury isn’t necessarily easy to see. That’s because Mercury only appears in the sky after sunset or before sunrise, when its luster is tarnished by the glow of twilight. Mercury, the innermost planet, orbits the sun inside Earth’s orbit and is often lost in the glare of the sun. But, at opportune times – like now, for the Northern Hemisphere – you can see Mercury fairly easily, if you go outside and look west after sunset.

At present, Mercury is nearing the outer edge of its orbit, as seen from Earth. In fact, one week from now – on February 10, 2020 – Mercury will reach its greatest elongation (maximum angular separation) of 18 degrees east of the setting sun.

Although Mercury’s greatest elongation measures the same in both the Northern and Southern Hemispheres, Mercury stays out later after dark in the Northern Hemisphere.

That’s because the ecliptic – the pathway of the sun, moon and planets in front of the constellations of the zodiac – hits the evening horizon at a steep angle in late winter, yet at a shallow angle in late summer. Therefore, this evening apparition of Mercury is particularly favorable for the Northern Hemisphere and not so favorable for the Southern Hemisphere. From the Northern Hemisphere now, Mercury should be rather easy pickings.

Mercury is bright in early February, but slowly dimming as seen from Earth, because of its waning phase. Yes, because it’s an inner planet, Mercury shows phases, like a tiny moon. You need a telescope, though, to see Mercury’s phases.

As the days pass for the next week or so, Mercury also stays out a little longer after sunset. By this month’s end, Mercury will set about 1 1/2 hours after the sun at mid-northern latitudes.

Diagram of inner solar system showing elongation and quadrature of Mercury and Venus.

An inferior planet – or a planet that orbits the sun inside of Earth’s orbit – never strays very far from the sun in Earth’s sky. An inferior planet, such as Mercury or Venus, reaches its maximum angular distance in the evening sky at its greatest eastern elongation.

Bottom line: We’re now in the midst of Mercury’s best evening showing for 2020, for the Northern Hemisphere. At northerly latitudes, watch for Mercury to show itself at dusk/nightfall – beneath Venus, and near the sunset point – for the next few weeks.

Bruce McClure