A Sky-full of Halloween Treats
As the sun sets Friday, see if you can spot Mercury dangling low against the southwest horizon before it too sets within a half-hour. While fleeting, this is Mercury’s best evening apparition. At this point, Mercury is at its greatest eastern elongation, meaning that, as seen from Earth, the innermost planet is its farthest to the east of the sun, in this case 24 degrees. Even at its best, Mercury is a tough target, often easier to spot scanning the horizon with binoculars.
Don’t confuse much brighter Mercury, at magnitude –0.2, for the red-hued pair of Mars and Antares 20 degrees higher to the east. Both shine around first magnitude and are at their closest this week, less than five degrees apart. An easy way to gauge distance in the night sky is that your fist at arm’s length covers roughly 10 degrees of space.
By 8pm, Mars and Antares are dipping beneath the west-southwest horizon, just as Jupiter rises in the northeast. Aldebaran, the red eye of Taurus the bull, is 10 degrees higher, while golden Capella trails old Jove by some 20 degrees.
In the hour before dawn, Jupiter shines above the west horizon, while Venus rises in the east, by far the brightest star-like object.
Friday is the full Hunter’s Moon. All full moons rise as the sun sets and set as the sun rises. But each year in September and October, the moon shines from dusk to dawn for a couple days to either side of full, a result of the moon’s eccentric orbit around the earth. Most of the year, the moon sets 50 to 60 minutes later each night. These moons rise only a half-hour later.
That near-full moon will light the way for trick-or-treaters Wednesday night, as they unknowingly commemorate the ancient Celtic holy day of Samhain, itself a commemoration to the earth’s celestial midpoint between the autumnal equinox and the coming winter solstice.