February 25, 2018

Astro Event: A Very Close Dawn Conjunction.

Tomorrow morning has something worth getting up for; one of the closest planetary conjunctions of the year. Specifically, the planets Jupiter and Uranus sit about 26’ arc minutes apart, as seen through binoculars. Both will also fit nicely in a low power telescopic field for the next week or so. Jupiter has been very much in the news as of late, as it first became suddenly “one striped” a few weeks ago and was recently smacked again by an impactor. When we first caught wind of this, our first instinct was hoax, such as the “Mars is the closest this August in 50,000 years!” email that circulates every summer. But it does indeed appear that another impactor has struck the giant world, on the same calendar date and discovered by the same observer! We’ve definitely received a lesson in Jupiters’ role as a cosmic vacuum cleaner as of late, although no true impact scar has yet to reveal itself. It’s also worth noting that the impact longitude will be on the planet’s central meridian at 4:21 EDT tomorrow the 8th as well, another reason to check out Jupiter. The impact video that circulated revealed the hit to be right at the longitude of the missing Southern Equatorial Belt. Uranus will be slightly fainter than a typical Galilean moon and display a grayish green disk. The pair rises around 3AM local and a waning crescent Moon will be nearby. Fun fact: did you know that Galileo missed the opportunity to discover another outer world, Neptune, during a close conjunction? He even drew its position change next to Jupiter in his notebook! Probably the reason that he didn’t make the intuitive leap was because no one at the time supposed that there should be any undiscovered planets!

The Astro-Word for this week is Appulse. This is another term that points back to astronomy’s hoary roots with astrology. We say an object (usually two planets or a planet and the Moon) are at appulse on their closest apparent approach. Of course, this is only line of sight from our vantage point; in reality, objects such as Jupiter and Uranus are millions of miles apart. The term appulse has sort of fallen to the wayside in favor of its synonym, conjunction, but it certainly doesn’t raise the eyebrows like another related mystical sounding term, occultation. I’m just glad that professional astronomers no longer have to subsidize their income by casting horoscopes for kings, as they did in times of yore!


  1. Here near Jacksonville Oregon (lat 42 N) we’re seeing Jupiter and Uranus as a single very bright object in the NW sky at say 10pm. That is with the naked eye. It is so bright we had to figure out what it was. But none of the astronomy sites mention this fact, that the two are visible to the naked eye in this way—the sort of sighting that would have had the royal astronomers in a kerfuffle hundreds of years ago, and the peasants worrying.

  2. David Dickinson says:

    You’re seeing Venus low in the evening skies at dusk. Jupiter and Uranus are visible in the early AM. From that high a latitude, its common to see Venus almost until midnight!


  1. [...] This post was mentioned on Twitter by David Dickinson and Rebecca Setzer, Todd Barrow. Todd Barrow said: RT @Astroguyz: http://bit.ly/9MgtXY Astro-Event of the Week: A Very Close Dawn Conjunction. Get the binocs out; Jupiter&Uranus are in ap … [...]

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