Pretty Sky Alert

February 27, 2009 Dr. Tony Phillips
Pretty Sky Alert
A Moon-Venus conjunction in Dec. 2008 photographed by Tamas Ladanyi of Mönichkirchen, Austria. This month's conjunction will be even tighter and brighter.

Be careful, this sort of thing can cause an accident. On Friday evening, Feb. 27th, the 10% crescent Moon will glide by Venus, forming a gorgeous and mesmerizing pair of lights in the sunset sky.

Moon-Venus conjunctions are not unusual, but this conjunction has some special qualities:

(1) Venus is at maximum brightness: magnitude -4.6. The planet is twenty times brighter than Sirius, the brightest star in the sky. It is so luminous that it can actually shine through thin clouds and cast subtle shadows on the ground.

(2) As seen from North America, the Moon-Venus separation is only a little more than 1o. Stick up your thumb and hold it out at arm's length. Venus and the Moon will fit comfortably behind the thumb-tip. Tight conjunctions like this are the most beautiful of all.

(3) Not only is the Moon a crescent, but so is Venus. A small telescope pointed at the glittering planet will reveal a slender 20%-illuminated disk.

Add it all together and you've got a major distraction. Evening drivers should pull to the verge. Staring at Venus and the Moon could be riskier than texting!

Venus is a crescent because, like the Moon, it has phases. The planet can be be full, gibbous, new, or anything in between. The illuminated fraction we see on any given date depends on how much of Venus' nightside is turned toward Earth.

It might seem odd that Venus is brightest now when it is a crescent. That reverses our commonsense experience with the Moon, which is brightest when it is full. A 6-month animation of Venus created by Hong Kong astrophotographer "Wah!" solves the mystery at a glance:

(click for animated version)

The crescent phase of Venus occurs when Venus is close to Earth, very big and bright. The full phase of Venus, on the other hand, occurs when Venus is on the opposite side of the Sun, far away and relatively dim.

Crescent Venus is so bright, you can see it in broad daylight. During the day on Friday, scan the sky for the crescent Moon. Hint: Stand in the shadow of a tall building to block the glare of the Sun. At noon, the Moon will be due east of the Sun's position. Got it? Look a few thumb-widths around the Moon and—voilà!—Venus pops out of the blue. The planet is surprisingly easy to see when you know where to look.

Once daytime Venus has been located, you might feel tempted to examine the planet with binoculars or a telescope. Don't. The nearby Sun can damage your eyes if you accidentally point your optics in that direction.

Wait until the Sun sets and behold the pair framed by deepening twilight blue, first with your unaided eyes, then with a small telescope. On the Moon, you will see mountains, craters, and a vast expanse of nighttime lunar terrain gently illuminated by Earthshine. On Venus, you will see a delicate little crescent of impenetrable clouds.

It's a nice way to end the day.

Source: by Dr. Tony Phillips, Science@NASA

Explore further: Venus rules the dusk skies at greatest elongation

Related Stories

Venus rules the dusk skies at greatest elongation

January 12, 2017

"What's that bright light in the sky?" The planet Venus never fails to impress, and indeed makes even seasoned observers look twice at its unexpected brilliance. The third brightest natural object in the sky, Venus now rules ...

A challenging daytime occultation of venus for Europe

March 30, 2016

Sometimes, the universe seems bent on hiding the most glorious of events right in plain sight. Just a such an event occurs next week, when the slender waning crescent moon occults the planet Venus for observers across Europe, ...

Would Earth look like a habitable planet from afar?

June 30, 2014

Even when a distant world has the trademarks of habitability—it's Earth-sized, it's in the zone around its star where liquid water is possible—finding signs of life is tricky. The telescope technology of today falls short ...

Dramatic pairing of crescent moon and venus on September 8th

September 3, 2013

Soon after the Sun dips below the western horizon on Sunday, September 8th, anyone looking in that direction will see a dramatic sight: a pretty crescent Moon paired closely with the dazzling planet Venus, the "Evening Star."

The moon occults Jupiter this weekend

July 7, 2016

So are you catching sight of the waxing crescent moon returning this week to the early PM sky? The start of lunation 1157 gives folks observing Ramadan here in Morocco a reason to celebrate, as it marks the end of dawn-to-dusk ...

Recommended for you

Video: A colorful 'landing' on Pluto

January 20, 2017

What would it be like to actually land on Pluto? This movie was made from more than 100 images taken by NASA's New Horizons spacecraft over six weeks of approach and close flyby in the summer of 2015. The video offers a trip ...

Freeze-dried food and 1 bathroom: 6 simulate Mars in dome

January 20, 2017

Crammed into a dome with one bathroom, six scientists will spend eight months munching on mostly freeze-dried foods—with a rare treat of Spam—and have only their small sleeping quarters to retreat to for solace.

The evolution of massive galaxy clusters

January 20, 2017

Galaxy clusters have long been recognized as important laboratories for the study of galaxy formation and evolution. The advent of the new generation of millimeter and submillimeter wave survey telescopes, like the South ...

Image: Wavemaker moon Daphnis

January 20, 2017

The wavemaker moon, Daphnis, is featured in this view, taken as NASA's Cassini spacecraft made one of its ring-grazing passes over the outer edges of Saturn's rings on Jan. 16, 2017. This is the closest view of the small ...

Astronomers search for signs of life on Wolf 1061 exoplanet

January 19, 2017

Is there anybody out there? The question of whether Earthlings are alone in the universe has puzzled everyone from biologists and physicists to philosophers and filmmakers. It's also the driving force behind San Francisco ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

rubberman
1 / 5 (1) Mar 01, 2009
IT was pretty cool.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.