To date it has been a superb winter for viewing the queen of the planets, Venus.
February marks the pinnacle of the evening visibility of Venus as it stands like a sequined showgirl nearly halfway up in the western sky at sunset. Currently shining at its greatest brilliance for this current apparition, this dazzling evening “star” currently appears as a distinct crescent shape in small telescopes, which is growing progressively larger in size as it approaches our Earth. On Valentine’s Day (Feb. 14), its cloudy disk will be 27% illuminated and shrinking nightly but its diminishing phase exactly offsets the gain in brightness from its growing apparent size. It is what astronomers call the “greatest illuminated extent” of this planet’s disk.
And be sure to get outside after sunset tonight (Feb. 1). For that evening a lovely crescent moon will appear to snuggle up close to Venus, particularly for skywatchers across the Western Hemisphere. It will make for an eye-catching scene as the two brightest sky objects of the night dominate the early evening scene for about three hours after sundown; even those who do not normally look up will likely have their attention drawn to this “dynamic duo.” What will make this array especially attractive is the fact that it will look almost three-dimensional; the moon will look almost like an eerily illuminated blue and yellow ball hovering next to the brilliant-white diamond that is Venus.
Dating back to last August, there have been a total of four well-placed Venus-moon pairings.
Sadly, this will be the last in the current series of close evening get-togethers between the two, for on March 1 they will appear three times farther apart compared to Saturday. Also, during March Venus will slide rapidly down into the sunset glow and by later that month will disappear from our evening sky until the spring of 2026.
Here then, is some background information to help you better understand (and enjoy) what you’ll be seeing in the sky on Saturday evening.
If you’re looking for binoculars or a telescope to observe Venus, the moon or anything else in the night sky, check out our guides for the best binoculars and the best telescopes to find options that work for you.
Be sure to also check out our guides for tips on how to photograph the moon and how to photograph the planets.
Ghostly Earthshine
So why is it that when the moon is a crescent phase, we can also see its darkened portion faintly glowing?
As seen from the moon, Earth would loom in the sky nearly 3.7 times larger than the moon does for us. In addition, the land masses, the oceans and clouds make Earth a much better reflector of sunlight as compared to the moon.
In fact, Earth’s reflectivity varies as the clouds, which appear far more brilliant than the land and seas, cover greater or lesser parts of Earth’s visible hemisphere. The result is that our Earth shines between 45 and 100 times more brightly than the moon.
And as viewed from the moon, Earth also goes through phases, just as the moon does for us, although they are opposite from what we see from Earth. The term for this is called “complementary phases.”
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On Wednesday, Jan. 29, for example, there was a new moon for us, but as seen from that part of the moon that faces our planet on that day, there would appear in the lunar sky a brilliant full Earth. Later on in the week, the first appearance of a hairline sliver of a crescent moon appearing low in our western twilight sky is a sky signal by which the ancients set their calendars.
With each passing night as, the crescent slowly widens and it begins to appear against a progressively darker background, its entire globe can be glimpsed; the waxing crescent moon appearing as a thin arc of yellowish-white light enclosing a ghostly bluish-gray ball.
Sunlight is responsible for the crescent, yet the remainder of the moon appears to shine with a dim blush-gray tone. This vision is known as Earthshine, sometimes called “the old moon in the young moon’s arms.” Leonardo da Vinci (1452-1519) was the first to recognize it as earthshine.
In da Vinci’s Codex Leicester, circa 1510, there is a page entitled “Of the Moon: No Solid Body is Lighter than Air.” He stated a belief that the moon — like our Earth — possessed its own atmosphere and oceans. The moon was an excellent reflector of light, da Vinci believed, because it was covered with so much water. As for the “ghostly glow,” he explained, that was due to sunlight bouncing off Earth’s oceans and, in turn, hitting the moon.
We know today of course, that the moon has no oceans or seas, and so far as the ghostly glow was concerned, as was noted above, the effect is due chiefly to sunlight reflected off clouds as opposed to being reflected off the oceans.
Nonetheless, da Vinci had the right idea; that faint bluish-gray glow is light from the Earth reflected back to the moon. The Earth’s light of course is reflected sunlight, so Earthshine is really sunlight which has been bounced through space no fewer than three times: reflected first off of Earth, then out to the moon … and then in turn reflected back to Earth.
Feb. 1: Snuggle time!
Tonight is the night when the Americas will be greeted with a gorgeous Venus-crescent moon conjunction. The pairing will persist from before sunset on into the depths of darkness. The time when the moon and planet will appear closest will be around 7:25 p.m. Eastern time, which corresponds to 6:25 p.m. in the Central time zone; 5:25 p.m. for Mountain Time and 4:35 p.m. for Pacific Time.
Venus will appear to hover approximately 2.5-degrees to the upper right of the 15-percent illuminated moon (the moon itself appears one-half degree in diameter). For cities situated in the Central time zone, the time of closest approach will come during evening twilight, while for those in the Mountain time zone it takes place around, or just after sunset.
Daytime sighting?
For those in the Pacific time zone, the closest approach will come about an hour before sunset, but here is an opportunity for you to try and spot Venus during the daytime. At that hour of the day, face southwest and look about half-way up in the sky for the waxing crescent moon. Now look just off to the right of the lunar crescent and see if you can see Venus. It should appear as a tiny white speck against the blue background sky. If you don’t see it with your unaided eye, use binoculars. Venus will pop readily into view. Then, look again with just your eyes and now, knowing precisely where to look relative to the moon you should have no problem in seeing Venus.
From other places around the world, the pairing will appear a bit different primarily because the moon appears to move much more rapidly against the background stars than Venus, and also because of the effect of parallax: different viewing angles from different points on our planet.
From Europe, for instance, Venus will appear to hover majestically about 4.5-degrees directly above the moon at sunset. South Americans will see the moon with Venus sitting almost directly below it; the pair low in the west-northwest at dusk. From Australia, the moon will be positioned well to the lower left of Venus on the evening of Feb. 1 and a somewhat similar distance to its upper right the following evening.
Which is brighter?
Finally, if you’re watching with some friends, here’s a trivia question you might want to pose to them: Of the two, which do they believe is the brighter: Venus now close to its peak brilliance or the 3.5-day-old crescent moon? The almanacs say that the moon is 11 times (2.6 magnitudes) brighter, but because its light is not concentrated into a point like Venus, they may have a difficult time believing this!
Editor’s Note: If you snap a good photo of the planet parade this month, and would like to share it with Space.com’s readers, send your photo(s), comments, and your name and location to spacephotos@space.com.
Joe Rao serves as an instructor and guest lecturer at New York’s Hayden Planetarium. He writes about astronomy for Natural History magazine, the Farmers’ Almanac and other publications.
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