Counting the Night’s Lights
The waning crescent moon rises ever later in predawn skies this week. Friday it appears before 3am, and by 5am it is well placed above the southeast horizon, forming a tight triangle with golden Saturn to the right and red Antares, the heart of Scorpius, below. The ringed planet stands above the scorpion’s head, one degree of its uppermost, second-magnitude star Graffias.
By Monday the moon is a thin crescent low in the southeast at 6am. If skies are clear and you have an open view of the horizon, you might be able to catch the reappearance of Mercury. Your odds will be better with binoculars. Look to the lower left of the moon’s outside arc. The next morning, the last remnant of the waning crescent rises within an hour of the sun, and now Mercury is just a few degrees to the right of its inner curve.
Mercury never pulls far from the sun and does not climb high into the sky. Plenty of people may not even realize they have seen it when looking at an exceptionally bright “star” hugging the horizon at dawn or during evening twilight.
You shouldn’t be as hard-pressed to spot our neighbors, Venus and Mars in the west-southwest at dusk. The two are only five degrees apart at week’s end, well within the field of view of binoculars or a telescope. By Wednesday they’ve cut the distance by half on the way to a one-half-degree conjunction on the 21st. There’s no confusing the two, as Venus blazes at –3.9 magnitude, while Mars smolders at first magnitude. In the exponential calculus of stellar magnitude, that means that Mars, as bright as your average star, is 99 percent dimmer than the Evening Star.
Jupiter is a fixture of the night sky right now, rising in the east-northeast as twilight fades, almost directly overhead at midnight and clinging to the west-northwest horizon as daybreak approaches. To its right is the dim constellation of Cancer the crab, while to its left is the easy-to-identify Leo the lion.
This week marks the latest installment of the Globe at Night campaign. Its goal is for ordinary people to record and submit their star counts. The target this time around is the constellation Orion, which is high in the south by 8pm. You can download star charts and instructions at www.globeatnight.org. Your results along with thousands from around the world help astronomers measure darkness and raise awareness about the threat of light pollution.