Universe Today
"What are those two bright stars in the morning sky?"
About once a year we can be assured that we'll start fielding inquires to this effect, as the third and fourth brightest natural objects in the sky once again meet up.
We're talking about a conjunction of the planets Jupiter and Venus. Venus has been
dominating the dawn sky for 2014
, and Jupiter is fresh off of solar conjunction on the far side of the Sun on July 24th and is currently racing up to greet it.
We just caught sight of Jupiter for the first time for this apparition yesterday from
our campsite
on F.E. Warren Air Force Base in Cheyenne, Wyoming. We'd just wrapped up an early vigil for
Perseid meteors
and scrambled to shoot a
quick sequence
of the
supermoon
setting behind a distant wind farm. Jupiter was an easy catch, first with binoculars, and then the naked eye, using brilliant Venus as a guide post.
[caption id="attachment_113821" align="alignnone" width="580"]
The view looking eastward at dawn on August 18th, including a five degree telrad (red circles) and a one degree telescopic field of view (inset). Created using Stellarium.[/caption]
And Jupiter will become more prominent as the week progresses, climaxing with a fine conjunction of the pair on Monday, August 18
th
. This will be the closest planet versus planet conjunction for
2014
. At their closest — around 4:00 Universal Time or midnight Eastern Daylight Saving Time — Venus and Jupiter will stand only 11.9' apart, less than half the diameter of a Full Moon. This will make the pair an "easy squeeze" into the same telescopic field of view at low power. Venus will shine at magnitude -3.9, while Jupiter is currently about 2 magnitudes or 6.3 times fainter at magnitude -1.8. In fact, Jupiter shines about as bright as another famous star just emerging into the dawn sky, Sirius. Such a dawn sighting is known as a
heliacal rising
, and the first recovery of Sirius in the dawn heralded the flooding of the Nile for the ancient Egyptians and the start what we now term the Dog Days of Summer.
To the naked eye, enormous Jupiter will appear to be the "moon" that Venus never had next weekend. The spurious and legendary Neith reported by astronomers of yore lives! You can imagine the view of the Earth and our large Moon as a would-be Venusian astronomer stares back at us (you'd have to get up above those sulfuric acid clouds, of course!)
Said conjunction is only a product of our Earthly vantage point. Venus currently exhibits a waxing gibbous disk 10" across — three times smaller than Jupiter — but Venus is also four times closer to Earth at 1.61 astronomical units distant. And from Jupiter's vantage point, you'd see a splendid conjunction of Venus and the Earth, albeit only three degrees from the Sun:
[caption id="attachment_113820" align="alignnone" width="580"]
Earth meets Venus, as seen from Jupiter on August 18th. Note the Moon nearby. Created using Starry Night Education Software.[/caption]
How often do the two brightest planets in the sky meet up? Well, Jupiter reaches the same solar longitude (say, returns back to opposition again) about once every 13 months. Venus, however, never strays more than
47.1 degrees elongation
from the Sun and can thus always be found in either the dawn or dusk sky. This means that Jupiter pairs up with Venus roughly about once a year:
[caption id="attachment_113819" align="alignnone" width="580"]
A list of Venus and Jupiter conjunctions, including angular separation and elongations (west=dawn, east=dusk) from now until 2020. Created by author.[/caption]
Note that next year and 2019 offer up
two
pairings of Jupiter and Venus, while 2018 lacks even one. And the conjunction on August 27
th
, 2016 is only 4' apart! And yes, Venus can indeed
occult
Jupiter, although that
hasn't happened
since 1818 and won't be seen again from Earth until – mark your calendars – November 22
nd
, 2065, though only a scant eight degrees from the Sun. Hey, maybe SOHO's solar observing successor will be on duty by then…
Venus has been the culprit in many UFO sightings, as pilots have been known to chase after it and air traffic controllers have made furtive attempts to hail it over the years. And astronomy can indeed save lives when it comes to conjunctions: in fact, last year's close pairing of Jupiter and Venus in the dusk sky nearly
sparked an international incident
, when Indian Army sentries along the Himalayan border with China mistook the pair for Chinese spy drones. Luckily, Indian astronomers identified the conjunction before shots were exchanged!
[caption id="attachment_113822" align="alignnone" width="500"]
Earth strikes back... firing a 5mw green laser at the 2013 conjunction of Jupiter and Venus. Photo by author.[/caption]
Next week's conjunction also occurs against the backdrop of Messier 44/Praesepe, also known as the "Beehive cluster". It'll be difficult to catch sight of M44, however, because the entire "tri-conjunction" sits only 18 degrees from the Sun in the dawn sky. Binocs or a low power field of view might tease out the distant cluster from behind the planetary pair.
And to top it off, the waning crescent Moon joins the group on the mornings of August 23
rd
and 24
th
, passing about five degrees distant. Photo op! Can you follow Venus up into the daytime sky, using the Moon as a guide? How about Jupiter? Be sure to block that blinding Sun behind a hill or building while making this attempt.
[caption id="attachment_113823" align="alignnone" width="580"]
The Moon photobombs the conjunction of Venus and Jupiter on the weekend of August 23rd. Credit: Stellarium.[/caption]
The addition of the Moon will provide the opportunity to catch a skewed "emoticon" conjunction. A rare smiley face ":)" conjunction occurred in 2009, and another
tight skewed tri-conjunction
is in the offering for 2056. While many national flags incorporate examples of close pairings of Venus and the crescent Moon, we feel at least one should include a "smiley face" conjunction, if for no other reason than to highlight the irony of the cosmos.
A challenge: can you catch a time exposure of the International Space Station passing Venus and Jupiter? You might at least pull off a ":/" emoticon image!
Don't miss the astronomical action unfolding in a dawn sky near you over the coming weeks. And be sure to spread the word: astronomical knowledge may just well avert a global catastrophe. The fate of the free world lies in the hands of amateur astronomers!
