April 2, 2020

AstroEvent: 2xBright Planets in the Dawn Sky.

Jupiter, Venus, & Mercury+a 1 degree FOV on the morning of May 11th.

(Created by the author in Starry Night).

The planetary conjunctions reach a climax this week, with a close apparent pass of the two brightest worlds in our solar system, Jupiter and Venus in the dawn sky.  These worlds seem to meet on the morning of May 11th, with Jupiter shinning at magnitude -1.9 about 0.5 degrees from -3.8 magnitude Venus. This will place both within the same field of view using a low power eyepiece, and may illicit queries of “what are those two stars low in the sky?” from fellow co-workers. And don’t forget that both Mercury just past greatest morning elongation on May 7th and Mars are also close by, to the right and left of the grouping respectively.

May 10th also presents us with a good time to hunt for our friends, the Werner X and a feature known as the Lunar Straight Wall, as the Moon reaches 1st Quarter at 4:33 PM EDT. Another interesting event transpires earlier the same day for North American observers around 6 AM EDT as the asteroid 349 Dembowska occults a +10 magnitude star for up to 7.6 seconds from a path spanning Central Florida across the Gulf of Mexico into New Mexico and Arizona. This even passes over Astroguyz HQ!

Finally, last week’s topic of discussion, asteroid 10 Hygiea, reaches opposition and magnitude +9.1 May 13th in the constellation Libra. Never seen it? Now’s your chance to cross the fourth largest known asteroid off of your life list… c’mon, birders do it, why can’t we?

The astronomy word for this week is: Heiligenschein. This is a backscattering effect caused by a concentration of light being reflected back to the observer, usually apparent around a shadow cast from the Sun. This is similar in nature to the Seeliger or Opposition effect. This word literally means “Holy shine” in German and is apparent on aircraft if the sun angle is right; looking out the window, you may see a glow around the aircraft shadow being reflected off of the moisture present in the cloud tops below. I mention this because I frequently see this effect on the springtime dew around my own shadow in the mornings…

…and did you know, this effect can be seen around the shadows cast by the helmeted heads of astrononauts on the Moon? How can this be, you might ask, as there is no dew or air present? Well, lunar Heiligenschein is caused by the focusing and backscatter of light by crystals embedded in the lunar regolith! A good FYI, next time a would-be Moon landing conspiracy theorist tries to trump you with that old saw. The more you know…

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