Northern Sky: March 3-16, 2018

Northern Sky -  March 3-16 2018

During the first half of March, the moon wanes away to the thinnest of crescents and then to a new moon on the morning of the 17th. In the process, the moon moves across the morning sky and gives us more moon-free time to enjoy the evening sky. 
 
These days we can see Venus and Mercury together above the sunset horizon. Mercury is the closest planet to the sun, and so it never appears very far from the sun, and the sun’s glare often makes it hard to catch Mercury. To see Mercury and Venus, look low in the west shortly after sunset—maybe 30 minutes after. Venus is by far the brighter planet, so it's easy to tell the two apart. Mercury climbs up and passes closest to Venus on the 3rd, when the planets will be about two moon widths apart. Mercury gets higher until the 15th, when it will be at its greatest angular distance from the sun, and then it rapidly falls into the sunset. Whenever Mercury or Venus falls into a setting sun, that's the beginning of the planet’s next trip between Earth and the sun. When it emerges from that trip it reappears in the morning sky.
 
Mercury was, of course, the messenger of the gods. And it's easy to see how it got that name. From our point of view, it's always racing back and forth between the evening and morning sky, never sticking around for very long. As for Venus, right now it’s also climbing in the evening twilight, but slowly, and it will stick around for several more months.
 
If you're out after the sky gets good and dark, enjoy the bright winter stars in the south and southwest. Next month they'll begin setting in the early evening.
 
In the morning sky, the predawn sky, we have the three outer planets that are visible to the naked eye lined up in the southeast and south. From left to right they are Saturn, Mars and Jupiter. Between Mars and Jupiter is Antares, a gigantic red star that marks the heart of Scorpius. But the real star of the show is Mars. If you can get out and watch every day, or every other day, you can see it moving eastward against the background of stars, away from Antares and Jupiter, and toward Saturn.
 
Starting on the 7th, that waning moon I mentioned comes in handy for telling all these objects apart. As it wanes, the moon sweeps from east to west across the morning sky. On the 7th, the moon is close to Jupiter. On the 8th, it appears above Antares. On the 9th, it's approaching Mars, and on the 10th, it's passed Mars and sits between Mars and Saturn. And on the 11th it has passed Saturn and appears near the bowl of the Teaspoon, which is a curved line of stars above the handle of the Teapot of Sagittarius. Over the next few mornings, the moon will be thinner and closer to the sun, and that may make it an even nicer companion to the planets and stars.
 
The Summer Triangle of bright stars is also up, high in the east, before dawn. And high in the south to southwest is Arcturus, the brightest star in Bootes, the herdsman, a lovely kite-shaped constellation.
 
With the moon mostly absent from the early evening sky, we have another chance to find the elusive zodiacal light an hour or so after sunset. It appears as a faint finger of light pointing up along the sun's path. The zodiacal light is the result of sunlight reflecting off dust in the plane of the solar system.