The solar system’s remaining planets lie in morning twilight. Try to glimpse
Venus in early December before it succumbs to the Sun’s brilliance. On the 1st, it appears just 2° high in the east-southeast 30 minutes before sunrise. Because Venus shines so brightly, at magnitude –3.9, you should be able to spot it if you have a clear sky and an unobstructed horizon. The planet will pass on the far side of the Sun in early January and will return to view after sunset in late February.
Mercury reappears before dawn in late December. On the 21st, you can find the innermost planet 6° above the southeastern horizon 45 minutes before sunrise. It shines dimly, at magnitude 0.6, so you’ll likely need binoculars to pick it out of the twilight glow. A telescope reveals the planet’s 8.7"-diameter disk, which appears one-quarter lit.
Mercury becomes much easier to see during the month’s final 10 days as it climbs higher and glows brighter. On the 31st, it appears 9° above the horizon 45 minutes before sunup. Even better, it shines at magnitude –0.3 and should stand out under good viewing conditions. If you use binoculars, look for 1st-magnitude Antares, the brightest star in Scorpius the Scorpion, 10° to Mercury’s right. When viewed through a telescope that morning, the inner world’s disk spans 6.9" and the Sun illuminates 59 percent of it.
The Full Moon that occurs December 3 likely will garner a lot of attention. That’s because it occurs just 17 hours before our satellite makes its closest approach to Earth during its monthly orbit. The coincidence between the two events means this is the largest Full Moon of 2017, and you can expect to hear the phrase “Super Moon” frequently in the days before.
Just how special is this Super Moon? Luna’s disk spans 33.4' at its Full phase, which works out to 7 percent more than average. That’s too small a difference for most people to notice, but you can bet a lot of them will go out the evening of the 3rd, see the bright Moon hanging low above the horizon, and be astonished at its size. But it’s really an illusion — viewing the Moon near familiar foreground objects tricks the mind into thinking it looks bigger.
The Moon also takes center stage the afternoon and evening of December 30. Observers across most of the United States and Canada can watch as our satellite occults (passes in front of) the bright star Aldebaran in Taurus. The dark limb of the waxing gibbous Moon covers the star sometime between 6 and 7 p.m. EST — the exact time depends on your location. Observers in the eastern half of the continent can see the disappearance after sunset; the event occurs during daylight farther west. Aldebaran returns to view from behind the Moon’s bright limb roughly an hour later. Check out
www.lunar-occultations.com/iota/bstar/bstar for precise times for your viewing site.