I can’t believe Mars is back at dawn already. It’s not easy to see just yet, but it’s in great company with Mercury and Leo’s brightest star, Regulus about an hour to 45 minutes before sunrise low in the eastern sky. All three objects, along with Venus and the dawn crescent moon, are or will soon be playing planetary musical chairs now through September 20th.
To get us started, I want to encourage you to get up about an hour before sunrise tomorrow to see a close conjunction of Mercury and the star Regulus in Leo. They’ll only be about 0.5° or one moon diameter apart. Using the map, first find Venus, then look about 12° to the lower left to see the pair. Both shine at first magnitude and will be visible to the unaided eye unless you’re dealing with haze, then just use a pair of binoculars to scan the strip of sky about one fist above the eastern horizon. Once you find this pair, see if you can track down fainter Mars (magnitude 1.8) 3° to the lower left of the pair. All three should easily fit inside the same binocular field of view.
Mercury reaches greatest elongation west — its greatest apparent distance from the sun toward the west and greatest altitude above the horizon — on the 12th. Throughout and beyond, the planet gets brighter and brighter and easier to spot. This month’s appearance is one of the better ones of the year. As Mercury loops up and then back down toward the sun, it will pass extremely close to Mars (only ¼°) on Saturday morning the 16th. When the thin moon joins the picture on the 18th, the scene should be amazing.
I’ll have a complete update on conjunctions next week, but you can get started with tomorrow’s star-planet pairing of Mercury and Regulus. If you’re wondering about aurora, all was calm last night. No second-night storm as forecast. Activity is expected to be low tonight, too.