Moon-Jupiter-Venus smiley face

posted: 1346 days ago, on Sunday, 2013 Oct 20 at 05:37
tags: astronomy, Moon, Venus, Jupiter.

Fun Fact or Fun Fallacy?

A burgeoning Internet meme is reporting that the crescent Moon, Jupiter, and Venus, made an amazing smiley face on 2010 May 16. The original was posted on the Tumblr site wtf-fun-facts. Is this a fun fact or a fun fallacy?

For starters, at least one reason this isn't true is that we haven't seen the one million photos of the event that Kos Coronaios would have taken.

Secondly, the appearance of Venus and Jupiter are suspiciously identical. Venus is always brighter than Jupiter, so one of the eyes should have been extra-shiny. For example, in the photo below (taken 2012 July 05 at the Waterfront, Cape Town), the brilliance of Venus gives it a "bigger" impression than fainter Jupiter.

Let's take a closer look at the wtf image and zoom in on "Jupiter" and "Venus". Within the limits of the JPG dithering, the two "eyes" are, in fact, exactly the same.

Measuring the distance between the eyes on the wtf image, and assuming the Moon is half a degree across, the separation between the eyes is about 12 arcminutes. So when were Jupiter and Venus this close in the sky? Usually for these sorts of questions, I consult the Sky Guide, the astronomical handbook for southern Africa, a very beautiful and informative work published annually by Struik/ASSA. And for about R100 a copy, you get all the information you possibly need for just 27c per day! (The Sky Guide makes an excellent gift, too. Check all the leading book shops from around mid-November for your next shopping spree.)

This time around, though, I'll use the mysteries of Celestial Mechanics to figure it out. Going to NASA's JPL Horizons, I extracted positions for the Moon, Jupiter and Venus, for the period 2007 January to 2021 December. In this interval, there are only two instances of Jupiter and Venus being 12 arcminutes apart or closer. The first will be on 2014 August 18 (12.0 arcminutes) and the second on 2016 August 27 (a mere 4.2 arcminutes apart!). So there it is - the photo is a (poor) fake.

Is it impossible for the three to make a smiley face? No, not at all. But first, a word about words. We astronomers throw around the term "appulse" for a close meeting of objects. And if they're so close that they touch (well, overlap) then it's an "occultation". Then there's also transits and eclipses, but you'll have to Wiktionary those.

Using the Horizons data, here's the low-down on appulses of Jupiter and Venus, and Jupiter and the Moon:

Jupiter and Venus (2007-2021)

2008 Jan 31 - Feb 02: Morning sky; closest is 0.589 on Feb 01
2010 Feb 16 - 17: Too near the Sun; closest is 0.535 on Feb 17
2011 May 10 - 12: Morning sky; closest is 0.569 on May 11
2013 May 28: Evening sky, 1 apart
2014 Aug 17 - 19: Morning sky; closest is 0.2 (!) on Aug 18
2015 June 29 - July 03: Evening sky; closest is 0.334 on Jul 01
2016 August 27-28: Evening sky; closest is 0.07 (!!!) on Aug 27
2017 November 12-14: Close to the morning Sun; closest is 0.263 on Nov 13
2021 Feb 10-12: closest is 0.431 on Feb 11

Jupiter and the Moon (2007-2021)

2008-Dec-29, 12h00: Moon-Jupiter = 0.658
2009-Jan-26, 06h00: Moon-Jupiter = 0.296
2012-Jul-15, 06h00: Moon-Jupiter = 0.689
2009-Feb-23, 02h00: Moon-Jupiter = 0.724
2012-Aug-11, 22h00: Moon-Jupiter = 0.275
2012-Sep-08, 14h00: Moon-Jupiter = 0.762
2012-Nov-02, 04h00: Moon-Jupiter = 0.987 [occultation]
2012-Nov-29, 02h00: Moon-Jupiter = 0.794 [occultation]
2012-Dec-26, 02h00: Moon-Jupiter = 0.431 [occultation]
2013-Jan-22, 06h00: Moon-Jupiter = 0.655
2013-Feb-18, 12h00: Moon-Jupiter = 0.905
2016-Aug-06, 06h00: Moon-Jupiter = 0.376
2016-Jul-09, 12h00: Moon-Jupiter = 0.829
2016-Sep-03, 00h00: Moon-Jupiter = 0.362
2019-Nov-28, 12h00: Moon-Jupiter = 0.892
2019-Dec-26, 10h00: Moon-Jupiter = 0.317
2020-Jan-23, 04h00: Moon-Jupiter = 0.509
2020-Feb-19, 22h00: Moon-Jupiter = 0.944

Note that none of these dates is 2010 May 16. Turns out, that on that day, Venus was in Taurus and Jupiter in Pisces, with 89 separating them. The Moon was close to Venus, so half the story is sort-of right.

But what about a possible smiley? In order to have a chance at being a smiley, all three objects must be within a reasonable angular distance of each other.

Depending on what you mean by reasonable, the table on the right gives all the instances, between 2007 and 2021, when the Moon, Jupiter and Venus lie within a circle with diameter 5. Not all will be "smiley" or "frowny" configurations, though - see for example the 2012 July 15 event.

The event on 2008 December 01 was widely observed in Southern Africa, and it was truly special. Check out the photos of this lovely "frowny" event as seen from Stellenbosch; or this view from the Philippines.

The event on 2015 July 18 will be another "frowny", beautifully visible from Southern Africa, so save the date.

Moon, Jupiter and Venus in 5 circle

2008-Dec-01
2008-Feb-04
2012-Jul-15
2015-Jul-18
2016-Sep-03
2017-Nov-17
2019-Nov-28
2021-Feb-10

nothing more to see. please move along.