A Hot Planet And An Old Moon Chase The Horizon At Dawn

Mercury will be bright but very low tomorrow morning (Sept. 6). Look three fists below and left of the crescent moon. Regulus is right next store and should be visible in binoculars. You’ll need a spot with a wide open horizon to the east as the planet will only be about 6° high at the time. Stellarium

Mercury pops in and out view for only a few weeks at a time before disappearing in the solar glare. Its appearances are brief compared to the other planets because it orbits close to the sun. From mid-northern latitudes the fleet planet is always caught up in the glow of dusk or dawn and never visible in a dark sky.

Mercury’s been out at dawn the past couple weeks and remains visible very low in the eastern sky about 40 minutes before sunrise. Because it’s looping back toward the sun’s direction in a hurry, we only have a couple mornings left to see it. Mercury always grows brighter in the dawn sky the lower it sinks in the east because it’s waxing to full phase. Through a telescope it looks like a very tiny full moon. Tomorrow, it shines at magnitude –1.1 or just a little bit fainter than the brightest star, Sirius, which also happens to be visible at dawn.

Joining them both will be a thin crescent moon about 3 days before new. It floats three fists above and to the right of the planet. That’s not all. Through binoculars you might just be able to spy Regulus, Leo’s brightest star, in conjunction with the planet and located just 1° to its right (south).

See the moon before it flips over to the evening sky. “Old” refers to the moon’s age. When first visible in the evening sky, it’s a “young” crescent. It then ages to half and full before until it’s oldest at dawn before cycling back into the evening sky. Stellarium

Our next opportunity to see Mercury  — a challenging one — doesn’t happen until late October when it pairs up with Jupiter very low in the southwestern sky at dusk. But there’s another exciting visual challenge happening Saturday morning (Sept. 8), again about 40 minutes before sunrise. That’s when an extremely thin crescent moon sits just 1.5° above Regulus. You may need binoculars for Regulus, but the moon should be an arresting sight. Aw heck, bring out the binos anyway to better appreciate the lunar delicacy before you!

4 Responses

  1. Edward Boll

    Did anyone report a bright fireball last night. I was driving at about 9 PM, and this bright meteor? appeared about 50 degrees high in the north at about magnitude minus 7 or minus 8. It traveled slowly for about 3 seconds till it was about 20 degrees above the horizon and then it vanished from view.

  2. Edward Boll

    I was a mile and a half west of the Minnesota South Dakota border. And I was about 10 miles south of US Highway 14. It is hard to pinpoint an exact location. I was 3-4 miles south west of Ward, SD. I doubt that Ward has 50 people in the town.

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