Comet NEOWISE Departs The Dawn, The Old Moon Turns New And Mercury’s Up Before The Sun

A hole in the clouds at dawn this morning (July 19) offers a brief peek of Comet NEOWISE Bob King

If you live in the northern U.S., Canada or northern Europe you can eke out 2-3 more dawns with Comet NEOWISE, but the good viewing has shifted over to the evening sky. I made my final pre-sunrise foray today. When I arrived at the site the entire sky was clear save for a low brow of cloud in the north that temporarily blocked the comet from view. Stargazing teaches both hope and patience, and with a little of each, I succeeded in catching sight of NEOWISE before the sky grew too pale.

The “old moon” rises in the northeastern sky in mid-twilight this morning, July 19 just 32 hours before new moon. You can make out the entire outline due to earthshine — sunlight reflected from the Earth to the moon and back. Bob King

I plan to look again tonight, and I won’t miss a single night if I can help it because I’ve waited years for a comet like this. Like that perfect ear of corn on the cob I’m going to relish every kernel. The comet wasn’t the only sight worth seeing at dawn. A very old crescent moon climbed into view at 4:20 a.m. looking like a shaved rose petal. I say “old” because the thin morning crescent traditionally marks the end of a lunar cycle that began 29 days earlier at new moon. New, half, gibbous, full, waning gibbous, last half, waning crescent. Say it out loud a few times and the rhythm of the words echoes the ancient rhythm of the lunar cycle which begins afresh on July 20 with the next new moon.

Mercury joined the moon this morning. The planet was relatively faint at magnitude 0.6 and low in the sky, but it will brighten in the next 2 weeks and become easier to see at dawn. Bob King

My moon was only 32 hours from new, hardly a record, but it looked like it might crumble if you poked it too hard. Just 5° to the right of the moon I could make out the planet Mercury in binoculars. The moon disappears from view tomorrow morning and then moves into the evening sky as a crescent in reverse starting July 21. Mercury on the other hand will stick around and grow brighter, putting it a nice appearance by next weekend. I’ll have more about how to find it then.

The Big Dipper and stars of Ursa Major the great bear will help you keep track of Comet NEOWISE in the evening sky. This map depicts the sky looking northwest about an hour and half after sunset local time with positions marked every 3 nights. Stellarium with additions by the author

Enjoy the dark evening sky and Comet NEOWISE while you can. It’s fading now — currently around magnitude 3 — and the moon will be around to flood the night before you know it. Southern hemisphere skywatchers will finally see the comet again starting about July 27. I’ll post fresh maps for both hemispheres next weekend.

The narrow, blue gas tail (left) extends nearly straight up from the head of Comet NEOWISE Sunday night, July 19. The dust tail is curved. Our eyes see the bright plume, but the camera reveals a vast sheet of dust fanning to the right of the plume. Details: 70mm focal length at f/2.8, ISO 800 and 89-second exposure on a tracking mount. Bob King

While the comet is fading it remains in fine form. On a clear, dark night most observers can see its foggy, dust tail extend some 10° up and to the right of the bright, little head. In 10×50 binoculars it reaches even further, about 15°. The narrow gas tail is fainter and requires binoculars. On Sunday night, July 19, I followed it all the way up to the Pointer Stars in the Dipper’s Bowl, a distance of about 19°.

I’ve labeled the parts of the comet. A long time exposure reveals that the dust tail is much broader compared to what the unaided eye can see. Details: July 19, 35mm lens, f/2.8, ISO 800, 72-second exposure. Bob King

1 Response

  1. Edward M Boll

    In the Spring of 2002 we had a comet return that had been seen before in 1661, but in 2002 it only got about as bright as Neowise is now and was more poorly placed than Neowise is

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