Dawn Moon Sneaks Between Jupiter And Venus, And Baby It’s Cold!

This should really be a pretty lineup tomorrow morning (Jan. 31) at dawn. And hey, look who’s bringing up the rear — returning Saturn!  The ringed planet shines between 5-10° high depending on your latitude an hour-and-a-quarter before sunrise two fists to the lower left of Venus. It will get easier to spot over the next couple weeks as it climbs up from the horizon. Stellarium

Maybe you caught the moon the past few mornings still bright in the southern sky at sunrise. Maybe you even noticed it was approaching Jupiter and Venus. If you haven’t ,you’re in luck — the best is yet to come. All three objects will line up in a row 8° long tomorrow at dawn. Most striking will be the crescent and Venus, separated by just 1.5°. The further west you live the closer they’ll be. From San Francisco, only three-quarters of a degree stands between them, while from Anchorage, Alaska, the delicate crescent will hang just one full moon diameter (0.5°) below Venus.

I couldn’t resist a couple cold-weather-related photos since so much of the U.S. is experiencing bitter cold at the moment. You can almost feel the chill in this natural-color image, taken on January 27, 2019, by NASA’s Terra satellite. Cloud streets and lake-effect snow stretch across the scene, as frigid Arctic winds blew over Lake Superior (top) and Lake Michigan. Joshua Stevens / NASA

The reason the moon will be closer to Venus for western U.S. skywatchers compared to the view further east is because the Earth has to spin a couple more hours to carry the moon and planets up from below the eastern horizon. For example, when the sun is just rising in New York, it’s still dark in Denver. Two hours later, the sun rises over Colorado.

A large area of low pressure and extremely cold air usually swirls over the Arctic, but disturbances in the jet stream and the intrusion of warmer mid-latitude air masses can disturb this polar vortex and make it unstable, sending Arctic air south into middle latitudes as seen in this temperature map created by the GEOS-5 global atmospheric model. Darker blue indicates colder temperatures. NASA

During those couple hours the moon keeps moving east (to the left as seen in the northern hemisphere) along its orbit, so it steadily closes in on Venus while distancing itself from Jupiter. As a handy rule of thumb, the moon moves its own diameter in an hour.

Notice we have a third planet just now entering the morning sky — Saturn. It’s still really low, so if you want to spot it, find a location with a wide open view to the southeast and bring binoculars as backup. Mars has certainly been the evening sky’s steadfast planet, and I’m glad for it, but I really enjoy seeing the morning sky get re-populated again. Three planets and counting! All reside in constellations we normally see on summer nights. Six months from now when we’re all in shirtsleeves, Jupiter and Saturn will be beacons during the evening hours.

Make sure you dress well for tomorrow’s heavenly feast. We had 29° F below here (actual temp.) this morning at my house. I’m not sure what the wind chill was, but whew, the wind was sharp. Norman Sanker, one of our readers, points out that the close approach of the moon to Venus makes this an excellent opportunity to see the planet in the morning daytime sky. He recommends looking between 8 and 10 a.m. and standing in the shadow of a building to block the bright sun. Find the moon and then look a short distance to its upper left for Venus. Or you can use binoculars to pinpoint Venus and then use your eyes. Let us know if you succeed!

4 Responses

  1. Norman Sanker

    One more thing about this close approach of the Moon and Venus: it’s a good opportunity to spot the planet during the day. Not blazing like it was a couple months ago, the planet is still easy to see in daylight although it is fading. This Thursday is a great time to try it, especially early in the day, say between 8:00 and 10:00 AM. I’m sure you’ve done this, so you know the drill. Stand in the shade of a convenient building, scan the sky to the south or southeast to spot the Moon, squint to see Venus. Don’t give up too soon, it can take a while to “catch” it. But don’t stay out there too long if it’s prohibitively cold. Brrr.

  2. kevan hubbard

    Yes Bob the USA is very cold,grand Falls, north (or is it south?) Dakota -36c!now thatst cold and almost the same as recent figures for Yakutsk Siberia.chicago is no slouch -21c.fairbanks was only -10 c at the same time. I have just been doing some stargazing from the isle of wight off southern England at about -1c and I gave up due to the cold after an hour and -1 is nothing!mind amazing dark skies to the south no land until normandy.the following m objects naked eye;M’s 44,45,41,31,35,42 and 34. I think I got m47 too?

    1. astrobob

      Awesome work on the DSOs, Kevan! Even -1°C can feel cold under the right conditions. Speaking of naked eye deep sky, that will be my next article for Sky & Telescope next Wednesday.

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