Astro Bob: Crescent moon jams with Jupiter, veers near Venus
A wiry moon lights up the western sky with visits to Venus and Jupiter. It's also space station time!
A fingernail-clipping moon always bring extra joy to evening skywatching especially when bright planets are visible at the same time. Because the moon closely follows the same path the planets take around the sky, it routinely passes near them in events called conjunctions. One is in store for Wednesday, March 22.
If you're reading this from Reykjavik, Iceland, you're in luck! Icelanders will see the moon and Jupiter just 1° at the exact time of conjunction. By the time it gets dark over the Americas, the moon will have moved a couple degrees to the left (east) in its orbit, increasing the gap between them to just under 2°. Although we won't see the actual conjunction, they'll still be eye-catchingly close.
To see this pretty sight find a place with an unobstructed view to the west and watch from 30 minutes to an hour after sunset. You'll find your local sunset time at timeanddate.com/sun . Binoculars will enhance the moon's appearance and reveal the rough, almost serrated appearance of the crescent's inner edge. Low-angled light from the rising sun skims along this edge — called the terminator — and creates deep shadows that strongly contrast with the bright, sunlit rims of the lunar craters.
If clouds ruin the view, the moon will climb up the western sky in the coming nights and shine near Venus, too. Those won't be conjunctions, at least not from North America, but the pairings will undoubtedly get your attention.
The upcoming Jupiter-moon pairing will be the last time we'll have an easy way to spot the giant planet. It's fast sinking into the solar glare and will be in conjunction with the sun April 11. On that date it will sit less than a degree south of the sun and accompany it across the sky in daylight. Don't even try to see it!
Like the moon, the sun will also pass Jupiter and leave it behind. When it does, the planet will reappear low in the dawn sky to begin its next period of visibility called an apparition. Jupiter's next apparition begins at the end of April.
Have you been watching Mars these past few weeks? It's really moving! On March 21, the Red Planet stands about two fists directly above Orion the Hunter in the constellation Taurus the Bull. Traveling at the rate of about 1/2° (one full-moon diameter) to the east or left each night, it enters Gemini on March 26. Mars is the easiest planet to watch shift against the starry background because it's one of the closest. Can you spot its movement after just one night?
Get your binoculars ready because from March 29 through the 31st, Mars will pass about 1° north of the bright star cluster M35 in Gemini. While the first quarter moon will brighten the sky at the time, I think you'll still see the cluster as fuzzy pile of faint stars to the lower left of the planet. It's worth a try, anyway. Just point the binoculars at Mars, and the two will share the same field of view. I recommend 7x35, 8x42, 7x50 and 10x50 models.
While you're planet-gazing, you can also watch the International Space Station pass by. It will sail the dusky skies through early April for locations in the northern hemisphere. Watch for it to rise in the western sky and travel east, taking about five to six minutes to complete a pass. If you see it suddenly fade and disappear, have no fear. It's just entering Earth's shadow. Without sunlight to render it visible the station goes dark.
To find out when and where to see it, go to Heavens Above and select your city by clicking on the blue "Change your observing location and other settings" link. Then return to the home page and click on the blue ISS link to see a 10-day table of passes that includes time, direction, brightness and altitude. Ten degrees (10°) of altitude is equal to one fist held at arm's length against the sky.
The higher the negative number in the brightness column, the brighter the pass. Click on any pass time and a map will appear showing the station's path across the sky. All times shown are local times on the 24-hour clock for your location, so 18:30 = 6:30 p.m. local time and 2:15 = 2:15 a.m.
You can also get a list of customized passes and alerts by downloading the free ISS Spotter app for iPhone and ISS Detector for Android devices. Or you can sign up for alerts at NASA's Spotthestation site.
I'm looking forward to warmer nights ahead now that spring has arrived. Clear skies!