Mercury, the solar system’s innermost planet, orbits the sun inside of Earth’s orbit. Therefore, Mercury always stays close to the sun in Earth’s sky and is often lost in the sun’s glare. But Mercury reaches its greatest elongation – greatest angular distance – east of the sun on May 25, so this world can now be spotted low in the west-northeast as dusk ebbs into darkness. As always, binoculars help out with any Mercury quest.
The planet Jupiter is the first “star” to pop out after sunset. If you’re familiar with the star Regulus, you can draw an imaginary line from Regulus and past Jupiter to locate Mercury near the sunset point on the horizon. (See sky chart below.) Given a clear sky and unobstructed horizon, Mercury could be visible to the unaided eye about 60 to 90 minutes after sunset. If not, try binoculars.

Although Mercury shines more brightly than Regulus does, you might see Regulus first because it’s not as obscured by the glow of evening twilight. What is the ecliptic?

…and don’t forget the morning sky, which features the dazzling planet Venus and a thin waning crescent moon on Monday, May 26.

Setting times of the sun and Mercury in your sky

At an elongation of 23^o Mercury lies far enough east of setting sun to stay out until the end of astronomical twilight (at mid-northern latitudes). By definition, astronomical twilight ends in the evening sky when the sun is 18^o below the horizon. For reference, the sun’s diameter equals one-half degree, and your fist at an arm length approximates 10^o.

Because Mercury is setting a maximum amount of time after sunset right now, this is your chance to catch Mercury low in the west at late dusk or nightfall. But don’t tarry when seeking this elusive yet surprisingly bright world, for Mercury – even now – follows the sun beneath the horizon around nightfall. At mid-northern latitudes, astronomical twilight ends nearly two hours after sunset, at about the same time that Mercury sets beneath the horizon.

End of nautical twilight and Mercury’s setting time in your sky

We should mention that the Northern Hemisphere enjoys the better view of this particular evening apparition of Mercury. That’s because the ecliptic – the pathway of the planets – hits the horizon at a steeper angle as the sun sets in the Northern Hemisphere sky.

What is the ecliptic?

Mercury stands higher over the horizon at sunset in Northern Hemisphere than at comparable latitudes in the Southern Hemisphere. For instance, at 40^o north latitude – the latitude of Philadelphia, Pennsylvania – Mercury’s altitude at sunset is about 19^o. In contrast, at 40^o south latitude – the latitude of Wanganui, New Zealand – Mercury’s altitude is less than 11^o at sunset.

No wonder Mercury sets more than 100 minutes after sunset at mid-northern latitudes but less than 80 minutes after sunset at mid-southern latitudes. The farther north you live, the later that Mercury sets after sunset; and the farther south you live, the sooner.

Although this evening apparition of Mercury favors the Northern Hemisphere, everyone worldwide has a reasonably good chance of catching Mercury after sunset right now. Look for Mercury above the sunset point on the horizon some 60 to 75 minutes after sunset.

Mercury might be visible to the unaided eye for another week or so, but binoculars always help out with your search for Mercury, the solar system’s innermost planet.

Bruce McClure  EarthSky News

May 2014 is Saturn’s month. We pass between Saturn and the sun on May 10, bringing the planet closest for this year. May is great for other planets, too! Charts, pics, info here.

Jupiter and Mars both pop into view as soon as darkness falls on these May 2014 evenings. Both are very, very bright. It’s not likely that you’ll mistake one planet for the other. They are in different parts of the sky, and exhibit different colors. Jupiter appears cream-colored and Mars reddish. At early evening, golden Saturn rises over southeast horizon, and though not as bright as Jupiter or Mars, its brilliance is on par with the sky’s brightest stars. And, by rights, this is Saturn’s month. The ringed planet is closest to us in May 2014 for this year.

Saturn is the planet to watch in May 2014. As seen from the whole Earth, Saturn sits low in southeast at nightfall and early evening. Earth in its smaller, faster orbit passes between the sun and Saturn on May 10, bringing the planet opposite the sun in our sky (opposition). In 2014, Saturn shines in front of the constellation Libra, making a triangle with the constellation’s two brightest stars, Zubenelgenubi and Zubeneschamali. Look for the almost full moon to couple up with Saturn on the night of May 13!

Mercury will present its best evening apparition of the year for the Northern Hemisphere in May 2014. This month, you almost certainly need to be in the Northern Hemisphere or southern tropics for any chance of seeing Mercury, which is the innermost planet of the solar system and which, therefore, stays near the sun in our sky. Northerly latitudes will see Mercury starting the second week of May. Mercury will reach its greatest eastern elongation – greatest angular distance from the setting sun on our sky’s dome – on May 25. Look for the slender lunar crescent near Mercury after sunset on May 30.

Venus, the sky’s brightest planet is still prominent in the eastern predawn/dawn sky throughout May. In fact, dazzling Venus will remain the most brilliant star like object in the morning sky until late October 2014, at which time it will shift over into the evening sky. The lovely waning crescent moon swings close to Venus on May 25.