The Pleiades embrace Venus in an octennial “cosmic hug” this week. We’ll explore the unique circumstances and offer both observing and camera tips.

Venus meets the Pleiades eight years ago
Venus gleams within the Pleiades star cluster during its last close encounter on April 3, 2012. A repeat performance will occur exactly eight years later this coming April 3, 2020. The photo was taken with a 92-mm refractor with an exposure of 13 seconds at ISO 200 and f/4.5. A wire taped in front of the lens produced the diffraction spikes.
Alan Dyer

While so many of us shelter in place because of the coronavirus we are grateful that the planets can still wander. Whether you've been watching the game of musical chairs played by Mars, Jupiter, and Saturn at dawn or the monthly conjunctions of Venus and the crescent Moon at dusk, the celestial cycles reassure us that despite the pandemic, some things don't change.

Planetary trio at dawn
Saturn, Mars, and Jupiter (left to right) gather over Lake Superior in Duluth on March 27, 2020.
Bob King

I was reminded of this several mornings ago when I awoke to see the planets in a tight clump over Lake Superior. Waves slapped against the pebbled beach as the coming Sun reddened the eastern horizon. All at once I felt this shiver of joy at the realization that the ancient forces that shaped the world are still with us today. Wind moving the clouds, waves gnawing at rocks, and planets endlessly circling. For the rest of the day I walked on air.

The Seven Sisters
In Greek mythology the Pleiades represent the seven daughters of Atlas and Pleione. Many people know it informally as the Seven Sisters cluster.
Bob King

You can renew your own cosmic connection on Friday night, April 3rd. That's when the planet Venus will skirt the Pleiades star cluster in a spectacular dusk conjunction visible across much of the planet. Seen from North America the planet will pass only ¼° south of the cluster's brightest star Alcyone. Eastern Hemisphere skywatchers will see it creep within 11′ of 4th-magnitude Merope.

You've probably already noticed Venus nosing in the cluster's direction over the past couple weeks. It will remain within 5° of the sisters through April 9th and within 1.5° from April 1st to 5th. The planet's leisurely approach will offer nightly opportunities for observation and photography.

Venus approaches the Pleiades
Venus shines 6° southwest of the Seven Sisters on March 27th. Each night the planet inches closer to the cluster until it skirts its southeastern edge on April 3rd. Details: 35-mm lens at f/2.8, ISO 2000, and 8-second exposure.
Bob King

Connected through resonance

Conjunctions of Venus and the Pleiades happen yearly but the planet passes through the cluster only once every eight years. This happened last on April 3, 2012, and will happen again on April 3, 2028. In fact, wherever you happen to see Venus in the sky on a given night it will return to nearly the same spot eight years later.

Over time, repeated gravitational interactions between the Earth and Venus have brought the two bodies into a near resonance such that for every eight Earth years, Venus circles the Sun almost exactly 13 times. This 8:13 ratio means that the two planets return to nearly the same positions in their orbits at eight-year intervals, and Venus repeats it course across the sky. Happily, that includes a stroll across one of the most iconic open clusters!

Because both Venus and Earth orbit in ellipses rather than perfect circles, and Venus's orbit is inclined 3.4° to the plane of the ecliptic, the resonance isn't a perfect one. This is why each of Venus's passages through the Pleiades is similar yet unique. In 2028 Venus will cut a more central path across the cluster while on April 5, 2060, it will graze the western edge.

Venus in the Pleiades
Chart showing Venus's ascent to and passage through the Pleiades during the next several evenings. The time is set at 9:30 p.m. EDT.
Stellarium

Finding Venus on the special night will take little effort. Face the sunset direction during late evening twilight and look up. The planet blazes at magnitude –4.6 and through a telescope presents a fat crescent that's 45% illuminated. As the sky darkens you'll see a few stars of the Pleiades without optical aid, glittering about the planet like moths around a streetlight.

But to really appreciate the sight use a pair of 3-mm or 50-mm binoculars, or even better, a small telescope with a wide-field eyepiece. The extra light-gathering power will reveal many more cluster stars and the large field of view in both instruments will frame the duo in a beautiful way. If bad weather intervenes you can still watch the event via livestream at Gianluca Masi's Virtual Telescope site starting at 1:30 p.m. Eastern Daylight Time (17:30 UT). Masi aptly describes the infrequent pairing as a "cosmic hug" — a wonderful description.

Take a picture

While you can carefully hold up a cellphone to photograph Venus and the brighter Pleiads at dusk, the image scale will be small. Unfortunately, zooming in rarely helps because the resulting images are often grainy and of poor quality. Instead, mount a pair of binoculars on a tripod and hold the cellphone camera against the rubber eyecup of one of the eyepieces. Keep it absolutely still and press away.

Exposure times will vary depending on when you take the picture — shorter exposures in early twilight and longer ones when the sky darkens. For starters, set the ISO to 800 and expose between 2 to 6 seconds. Check the screen and adjust the exposure as needed for the best image.

Photographing Venus in the Pleiades
Focus is crucial when using a digital camera. With the lens set to manual press the live view button for a preview of the scene on the back screen. Point the camera at either the Moon or Venus, press the magnify button to 5× or 10× and then manually focus the image.
Bob King

DLSR owners have more flexibility and offer much higher resolution than most cellphones. You can compose a scene with a medium-wide lens like a 35-mm or go in tight with a telephoto. To avoid star trails use a high ISO and short exposure. I abide by the 400 Rule, a more stringent interpretation of the 500 Rule. Divide 400 by the focal length of the lens to determine the longest exposure in seconds you can make before stars start to trail. For example: 35 mm = 11 seconds; 200 mm = 2 seconds. Wide-angle lenses allow for lower ISOs (less grain and noise); long lenses will require high ISOs to capture an image in a brief amount of time.

Attach the camera to a tripod. Set the shutter speed to "M" (manual), click the switch on the side of the lens barrel to "M" and open the lens to its widest setting — usually f/2.8 or f/4. Next, press the live view button (found on the back of the camera) and carefully focus on Venus. You will only need to focus once per lens for the entire session. I recommend a 35-mm lens to include a scene, an ISO of 800 or 1600, and an exposure between 5 and 10 seconds in mid- to late twilight.

Whether you watch alone or with family I hope this cosmic hug will buoy your spirits during a time of crisis.

Comments


Image of Anthony Barreiro

Anthony Barreiro

March 31, 2020 at 6:11 pm

Thanks Bob. You're lucky you can get to the lakeshore. The picture of Jupiter, Mars, and Saturn, with Jupiter's light glistening on the water, is beautiful.

I've been enjoying watching Venus' waning phase through my little refractor, and watching her close in on the Pleiades through image-stabilized binoculars. I've encouraged neighbors, friends, and family to watch the show -- anybody can find Venus, and most people have at least heard of the Pleiades. Fingers crossed for clear skies in the early evening Friday.

It just dawned on me -- as seen from Venus, Earth would come to opposition against the same background stars every 13 years.

You must be logged in to post a comment.

Image of Bob King

Bob King

April 1, 2020 at 11:02 am

Thanks, Anthony. I'm glad you're encouraging others to watch, too. Great insight on Earth's cycle as seen from Venus. Too bad you'd have a to wait a few million years for a clear night!

You must be logged in to post a comment.

Image of Anthony Barreiro

Anthony Barreiro

April 1, 2020 at 3:38 pm

I guess the weather on Venus would be even worse than San Francisco.

You must be logged in to post a comment.

Image of fred_76

fred_76

April 6, 2020 at 3:08 am

Nice article. Note that in the 400 rule you divide 400 by the focal length, not 350. And for pinpoint stars, you would better use the NPF rule, more precise.

I made a photography of Venus in the 7 sisters cluster and succeeded in catching the nebulosities. This is not a fake (as we can see some everywhere) : https://telescopius.com/pictures/view/56749/deep_sky/pleiades/by-fred_76

Clear sky to all !

Fred

You must be logged in to post a comment.

Image of Bob King

Bob King

April 6, 2020 at 8:27 pm

Thanks, Fred for pointing that out! The "350 rule" is even more stringent ... and I almost went there — the reason I accidentally left that number in place.

You must be logged in to post a comment.

Image of Jakob

Jakob

April 1, 2020 at 1:53 pm

Bob! I was out yesterday morning and the air was cold and the sky was very transparent! The trio of planets made their best to warm me, and they did. Just Love the sky action (-: Jakob

You must be logged in to post a comment.

Image of Rod

Rod

April 2, 2020 at 11:02 pm

FYI, I was out tonight from 1930 until 2100 EDT viewing Venus et al. Earlier I created star charts using Starry Night and Stellarium 0.20.0 for my views. Here is a note from my log.

"Sunset near 1931 EDT tonight or 7:31 PM. Clear skies, temperature near 10C, NW winds. The waxing gibbous Moon in Cancer was bright. I viewed Venus and the Pleiades using 10x50 binoculars and telescope at 40x. Venus nearly half-moon shape with some 20 or more stars of M45 visible in the eyepiece, especially after 2000 EDT or 8:00 PM. This would have made a great astrophoto. Tomorrow night, Venus is in M45 open star cluster near 2030 EDT. Using the binoculars, I could just see M44, the Beehive cluster in Cancer near the bright Moon. M42 in Orion, I could see four of the six stars in the Trapezium and some nebulosity at 40x with the telescope. The southern region of the Moon full of craters near Longomontanus crater region along the terminator line. Nothing like being under COVID-19 house arrest under the sky that is there tonight ---Rod

You must be logged in to post a comment.

Image of screedy

screedy

April 4, 2020 at 4:29 am

How do I upload my DSLR picture of the Venus conjunction with the Pleades?

You must be logged in to post a comment.

Image of Bob King

Bob King

April 4, 2020 at 10:16 am

Hi Screedy,
Go here: https://skyandtelescope.org/communities/online-gallery/ and click "Share Your Photos".

You must be logged in to post a comment.

Image of Antonnyi

Antonnyi

April 5, 2020 at 8:40 pm

Hi Bob, I clambered up onto my rooftop in suburban Sydney (Australia) to catch the view on Saturday evening. As the sky turned a gorgeous peachy-mauve, each of the Pleiades came into view with a brilliant Venus sitting just to the south of Atlas (equidistant to Pleione) as the cluster plunged toward the north-western horizon. Unfortunately I had no camera gear with me, just my binoculars to catch the wonderful sight as a 747 roared into the frame from Sydney airport and briefly hung there next to and at the same size as the cluster as it head off to some unknown destination. But I do have a sketch in my observing diary to remember the occasion.

You must be logged in to post a comment.

Image of Joe P.

Joe P.

April 6, 2020 at 8:08 pm

Venus' octennial cycle is the subject of the oldest astronomical text (a tablet from Nineveh).  

In eight years, it makes a sequence of five harmonious loops around Earth.  These are described and shown in "Venus, the Rose, and the Heart" by Nick Kollerstrom: www.skyscript.co.uk/venusrose.html . 

Though such geocentric patterns are usually ignored, they are among the most beautiful and elegant movements in astronomy.  I first became aware off them in a wonderful book, Joachim Schultz, "Movements and Rhythms of the Stars" ( http://www.florisbooks.co.uk/book/Joachim-Schultz/Movement+and+Rhythms+of+the+Stars/9780863156694 .)  

Although Kollerstrom wrote that the mandala-form of this dance was unrecognised until the 1980s, here's a diagram showing it, along with Saturn's, from the first edition of the Encyclopedia Brittanica, 1771 (based on earlier drawings by Giovanni Cassini, 1625-1712): https://commons.m.wikimedia.org/wiki/File:Cassini_apparent.jpg?fbclid=IwAR2j5vTmvsYoQgsxmmfK2J_5KbZ3QzPiudPHCod8jnngR8O3gQU1puIqtn8 

Kepler famously computed Mars' (from his "New Astronomy," 1609): https://en.wikipedia.org/wiki/History_of_Mars_observation?fbclid=IwAR2L4oX9kvdr1wJBvMeE3kqk_yxmvPBqgw87SLX43SkDlvUBSyaRzlsNHdM#/media/File:Kepler_Mars_retrograde.jpg 

Here are computer-generated versions of these and others:  www.keplerstern.com/assets/download/New%20View%20Autumn%202011%20Hartmut%20Warm.pdf (more here: http://www.keplerstern.com ); http://astrosoftware.com/PlanetMandalasAndNewScience.htm . 

I'd be grateful for any other references, especially historical ones.  

You must be logged in to post a comment.

Image of Joe P.

Joe P.

April 15, 2020 at 8:22 pm

Here are animations of the Earth-Venus relation showing the same pattern from geo-, hello-, and Veno - centric perspectives:  www.gci.org.uk/Tango.html 

You must be logged in to post a comment.

Image of Bob King

Bob King

April 17, 2020 at 3:27 pm

Very nice, Joe. Thank you!

You must be logged in to post a comment.

You must be logged in to post a comment.