Venus is the brightest planet, and it’s very prominent this month in the west after sunset. Throughout May, Venus appears as a dazzling evening “star.” In May 2018, this planet is still climbing upward from the sunset point. Each evening in May, it stays out longer after the sun sets.
Look for Venus to adorn the western evening sky until October 2018.
It’ll be fun to watch Jupiter and Venus in May. Early in the month, at nightfall and early evening, look for Venus to blaze away in the west at the same time that Jupiter lights up the eastern sky. By mid-month, you should be able to see the sky’s two brightest planets – Venus in the west, and Jupiter in the east – at evening dusk.
By late May, Venus and Jupiter will be very obvious after sunset. As if they’re on two ends of a seesaw, Jupiter will be rising, while Venus is setting, after sunset.
Circle May 16-18 on your calendar. That’s when the young moon will be sweeping past Venus in the evening sky. The pairing will be especially picturesque pairing in the western twilight on May 17.
Jupiter is at its best this month for all of 2018. We go between the sun and Jupiter – bringing the planet to opposition – on the night of May 8-9, 2018. From anywhere around the globe, you’ll find Jupiter in the eastern part of the sky at nightfall – highest in the sky around midnight – and in the west around dawn. Jupiter is brighter than any star, but it’s not brighter than Venus, which is in the west after sunset, while Jupiter is in the east.
Jupiter shines in front of the constellation Libra the Scales until November 2018 (see sky chart above). Look for Libra’s brightest stars near Jupiter, Zubenelgenubi and Zubeneschamali (both star names are pronounced with the same rhythm as Obi-Wan Kenobi, of “Star Wars”).
If you aim binoculars at Zubenelgenubi, you’ll see this star as two stars. Zubeneschamali, meanwhile, is said to appear green in color, although, astronomers say, stars can’t look green.
Late in the month, let the moon guide your eye to Jupiter on the evenings of May 25, 26, 27 and 28.
Mars and Saturn rise into the southeast sky quite late at night throughout May (especially as viewed from the Northern Hemisphere). Your best view of them is in the predawn hours, when these planets appear much higher up in the sky.
You can tell Mars from Saturn because Mars has a reddish color. Saturn looks golden. Binoculars show their colors better than the eye alone.
Early in the month, on the mornings of May 4-6, the moon is sweeping past these planets, as shown on the chart below:
Mars and Saturn shine in front of the constellation Sagittarius, which marks the direction to our galaxy’s center. As the month progresses, Mars travels farther and farther east of Saturn on the sky’s dome, to move out of the constellation Sagittarius and into the constellation Capricornus by mid-May 2018. Saturn, in the meantime, stays in front of the constellation Sagittarius for a few more years.
At present, both Mars and Saturn shine as brilliantly as 1st-magnitude stars. However, Mars is brighter than Saturn. Saturn’s brilliance will increase until it peaks at its June 27 opposition, and Mars’ brilliance will also increase until it peaks at its July 27 opposition.
But Saturn’s brightness increase will be subtle, while Mars’ will be dramatic!
It’s not often that Mars outshines Jupiter, normally the fourth-brightest celestial object to light up the sky, after the sun, moon and Venus. But, for a couple of months in 2018, centered on Mars’ July 27 opposition, Mars will outshine Jupiter.
Remember Mars’ historically close opposition of August 28, 2003? That year, it was closer and brighter than it had been in some 60,000 years. This upcoming July opposition will be the best since 2003.
In early May, at mid-northern latitudes (U.S., Europe, Japan), Saturn rises about 11 p.m. local time (12 midnight local daylight saving time) and Mars follows Saturn into the sky roughly an hour later. By the month’s end, Saturn comes up just after nightfall (about when Venus sets) whereas Mars doesn’t climb above the horizon until roughly 11 p.m. local time (12 midnight local daylight saving time).
As for temperate latitudes in the Southern Hemisphere (South Africa, southern Australia, New Zealand), Saturn rises around 9 p.m. local time and Mars about an hour later, around 10 p.m. local time. By the end of the month, Saturn rises around 8 p.m (about when Venus sets) and Mars comes up about 10 p.m. local time.
Click here for recommended sky almanacs; they can give you the rising times of the planets.
Mercury, the innermost planet of the solar system, remains a fixture of the morning sky throughout May 2018, though the first half of the month offers better viewing. The present morning apparition of Mercury in April and May 2018 is the best of the year for the Southern Hemisphere, but poorest of the year for the Northern Hemisphere.
Mercury reached its greatest western elongation from the sun on April 29, 2018. At temperate latitudes in the Southern Hemisphere (South Africa, southern Australia, New Zealand), Mercury rises more than two hours before the sun during the first week of May. But at mid-northern latitudes (United States, Europe, Japan), Mercury struggles to climb over the horizon even as much as one hour before sunrise in early May.
The waning moon will sweep past Mercury just before mid-month:
What do we mean by bright planet? By bright planet, we mean any solar system planet that is easily visible without an optical aid and that has been watched by our ancestors since time immemorial. In their outward order from the sun, the five bright planets are Mercury, Venus, Mars, Jupiter and Saturn. These planets actually do appear bright in our sky. They are typically as bright as – or brighter than – the brightest stars. Plus, these relatively nearby worlds tend to shine with a steadier light than the distant, twinkling stars. You can spot them, and come to know them as faithful friends, if you try.
Bottom line: In May 2018, Venus appears in the west in evening twilight. Jupiter rises at early-to-mid evening and is low in the southwest by dawn. Mars and Saturn rise late at night but are well placed in the predawn/dawn sky. Mercury makes an appearance in the east before sunrise in the first half of April (at southerly latitudes). Click here for recommended almanacs; they can help you know when the planets rise, transit and set in your sky.
Bruce McClure has served as lead writer for EarthSky's popular Tonight pages since 2004. He's a sundial aficionado, whose love for the heavens has taken him to Lake Titicaca in Bolivia and sailing in the North Atlantic, where he earned his celestial navigation certificate through the School of Ocean Sailing and Navigation. He also writes and hosts public astronomy programs and planetarium programs in and around his home in upstate New York.