Nov 20, 2017
Saturn is Sinking, Mercury at Maximum Visibility, and an X on the Moon!
The Moon and Planets — and a Lunar X
For an hour after sunset tonight (Sunday, November 19), look low in the western sky for the young crescent moon sitting 8.5° (somewhat less than a fist’s diameter) to the right of elusive Mercury. Both objects might be tricky to spot as they are embedded in the twilight’s glow, but binoculars should help. On Thursday, Mercury reaches the eastern limit of its orbit, placing it at its widest angle from the sun, and maximum visibility, for this latest appearance. After Thursday, it begins to swing towards the sun again.
Meanwhile, the lovely crescent moon continues to grace the western evening sky nightly, climbing east, and waxing thicker, every night — reaching its First Quarter phase around noon next Sunday. In the southwestern early evening sky on Monday, November 20, the young crescent moon will be sitting only about two finger widths (2.5 degrees) to the upper right of yellowish Saturn, making a lovely sight in binoculars.
Keep the binoculars (or telescope) handy all week, because the waxing moon is gorgeous at this time of its cycle. Peaks and craters catching the sun’s rays of light cast deep shadows along the boundary between the lit and dark sides of the moon. But wait — there’s more!
A few times a year, for a few hours around the First Quarter Moon, a feature called the Lunar X becomes visible in strong binoculars and small telescopes. When the rims of the craters Parbach, la Caille, and Blanchinus are illuminated from a particular angle of sunlight, they form a small, but very clear and bright X-shape. It’s located on the terminator about one third of the way up from the southern pole (bottom) of the Moon (at 2° East, 24° South). The prominent round crater Werner sits to the lower right.
The next Lunar X will form in late afternoon about 5 pm Eastern Time on Saturday, November 25, peak around 7:45 pm, and last until about 8:30 pm. This is a global event for observers wherever the Moon is in a dark sky during that period, adjusting for your difference from the Eastern Time zone. In North America, the Moon will be nicely positioned in the southwestern sky. Let me know if you see it!
Saturn is setting about 6:30 pm local time this week. The only planet visible with unaided eyes in the evening sky, look for it as a medium bright, yellowish object low in the southwestern sky after dusk. Before long, it will be too low to see clearly, and then altogether disappear into solar conjunction.
Blue-green Uranus, remains a good target in binoculars under a dark sky (or in small telescopes under less than ideal skies). It sits midway between the two chains of stars that form the dim constellation of Pisces (the Fishes). It’s about 3 fist diameters (or 30°) above the eastern horizon after dusk, and it remains observable for the rest of the night as it crosses the sky. To help guide you, a medium-bright star called Omicron Piscium sits about 2.5 finger widths to the lower left of Uranus and another similar star called Mu Piscium is three fingers to the planet’s lower right. (Remember that the sky rotates through the night, so the triangle of two stars and Uranus will be tilted to the west if you look later in the evening.)
Tiny blue Neptune is located in the southern evening sky about half a finger width to the lower right of the medium-bright star Hydor in Aquarius (the Water-Bearer). It is observable from full darkness until about midnight local time, but it is too faint to see without a telescope.
The eastern pre-dawn sky is where most of the showy planetary action is taking place this month! Dim, red-tinted, Mars rises first, at about 3:45 am local time. This week, it is sitting high in the pre-dawn sky, about a palm’s width above the bright star Spica in Virgo (the Maiden).
Up next (literally) is Jupiter. The very bright king of planets rises in the east about 5:30 am local time. Finally, very bright Venus, which has been descending towards the sun for weeks, rises just before dawn, about 6:20 am local time. In a couple of weeks, it will be getting too low to see clearly.
Seeing Some Deep Sky Treats
Take advantage of the dark skies again this week to look for dimmer deep sky objects, especially galaxies! Last week, I described a few and posted a sky chart here showing where they are.
Current Meteor Showers and Viewing Tips
Last week, I wrote about meteor showers, and tips for seeing them, here. The Leonid Meteor Shower or Leonids peaked overnight last Friday. But you can still keep an eye out for some stragglers over the next several days.
Astronomy Skylights for this week (from November 19th, 2017) by Chris Vaughan.
