Skychart by A. Fazekas, SkySafari
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In this simulated view, the Earth and Saturn shine brightly to the upper left of Mercury, our solar system’s innermost planet.

Skychart by A. Fazekas, SkySafari

This Week's Night Sky: Mercury Hits Prime Time

Venus guides the way to a pretty star cluster, and remnants from Halley’s comet streak by in the night.


Saturn, the lord of the rings, and Mercury, the closest planet to the sun, offer amazing views worldwide this week.

Lord of the rings. Stay up late on Monday, May 4, and gaze toward the southeast sky for a view of the nearly full moon and its close companion Saturn. The cosmic duo will be separated by only 6 degrees, which is slightly more than the width of your three middle fingers held at arm’s length.

The planet is easy to see with unaided eyes even from brightly lit city suburbs. Viewing its beautiful system of rings, however, will require a small backyard telescope.

By Tuesday, the moon will have sunk closer to the horizon and jumped to the other side of the ringed world.

Aquarids peak. Late Tuesday night, May 5, and through the rest of the week, look for a flurry of shooting stars from the peak of the annual Eta Aquarid meteor shower.

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Look for the nearly full moon perched to the upper right of yellow-tinged Saturn on Monday, late in the evening.

The Eta Aquarids appear to come from the Aquarius constellation—hence the shower’s name. The nearly full moon will unfortunately wash out most of the fainter meteors, but astronomers still expect a dozen to 30 meteors per hour streaking through northeast skies, starting at 10 p.m. and continuing into the early hours of the following morning.

The Eta Aquarids’ claim to fame is not how many meteors fall, but where they come from. Every shooting star you see that night was left behind by the famous comet Halley. Halley’s comet last visited our corner of the solar system in 1986, and won't be back until 2062. But every year we can see sand-grain-sized particles shed by this icy visitor burn up high above our heads.

Prime time for Mercury. Set your sights on the low western horizon about 30 minutes after sunset on Thursday, May 7, when the planet Mercury puts on its best evening performance of 2015.

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This week at dusk, Mercury will be at its farthest point from the sun as seen from Earthly skies, allowing sky-watchers to easily hunt it down.

At dusk, Mercury reaches greatest elongation, meaning it reaches its largest angle away from the sun, about 21 degrees. For sky-watchers, this means the faint, elusive planet closest planet to the sun will be visible to the naked eye as the “evening star” for up to two hours before it sets. Remember to first use binoculars to spot Mercury in the twilight.

If you get clouded out on Thursday evening, Mercury will continue to be a great sight for up to a week later. Don’t wait much longer, though. The planet will quickly drop back towards the horizon and get lost in the glare of sunset.

Venus visits cluster. After nightfall on Sunday, May 10, the planet Venus shines bright above the western horizon. If you train binoculars just underneath it, you'll find a pretty open star cluster named Messier 35. Look for this cluster about 2 degrees (equal to about four full moons) below Venus.

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This skychart show the brilliant planet Venus pairing up with an the star cluster Messier 35. This deep-sky treasure shows off its true beauty through binoculars and small telescopes.

Messier 35 consists of several hundred stars and measures about 24 light-years across. In our Earthly skies, it takes up about the same chunk of sky as the full moon does. The 2,800 light-year-distant cluster is visible to the naked eye from a dark sky, but a pair of binoculars will reveal its details, even from a light-polluted suburban backyard.

Check out the color of the stars and you will notice they are blue and white, which indicates to astronomers that these stars are fairly young, about 150 million years old. That may sound ancient, but these are just spring chickens compared to our middle-aged sun, which is estimated to be about 5 billion years old.

Happy hunting!

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