January 18, 2018

AstroEvent: The Return of the SEB?

Followers of this column know that Jupiter has appeared rather odd during this years’ 2010 apparition. Specifically, the Southern Equatorial Belt, or SEB, vanished for the first time in the 21st century. This is not a unique or singular occurrence, as it happened no less than 12 times in the 20th century. It’s not completely understood why this happens, and why only the SEB is prone to this disappearing act and never its twin Northern Equatorial Belt. Now, there’s evidence that the SEB may be returning.

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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!