April 5, 2020

AstroEvent: Mercury puts on its Evening Best for 2012.

Path of Mercury through Mid-March.

(Created by the Author in Starry Night).

Enjoying the “Planetary Bonanza” that is Spring of 2012? While you’re watching bright Jupiter and Venus head towards a spectacular close conjunction next week and Mars rising in the east, don’t forget to hunt for the tiny inner-most world of Mercury low in the dusk. The fleeting world puts on its best evening showing of six apparitions this year (three in the morning west of the Sun and three in the evening east of it) this week, with greatest eastern elongation occurring on Monday, March 5th at 09:00UT/04:00EST. Start scanning low to the west with binocs about 10 minutes after local sunset; bright Jupiter and Venus make a good rough “guide post” to draw the imaginary line of the ecliptic down to the horizon near were Mercury lies. For those equipped with a telescope, you might just be able to pick out faint 6th magnitude Uranus 3.1° degrees south of -0.9 magnitude Mercury on the evening of March 6th. Tiny Mercury will start the month with a gibbous phase 6.4” arc seconds across, while distant ice giant Uranus has a visible disk of 3.3”. Can you nab it one final time this season before it is lost in the glare of the Sun? Mercury will begin to show a tiny crescent phase 25% illuminated as it slips below 10 degrees elevation for early evening viewing starting on March 10th.

This particular elongation is only 18.2° degrees east of the Sun, nearly the smallest it can be at about 17.9°. This is because Mercury has the most eccentric orbit of the planets in our solar system (20% to be precise) and it just passed perihelion on March 2nd. So, what makes this apparition so “great?” Well, the angle of the evening ecliptic is nearly perpendicular this time of year for observers in mid-northern latitudes; that means we get almost all of that 18.2° degrees above the horizon. This also sets us up for a fine morning elongation of 27.5° degrees west on the morning of April 18th, and perhaps some opportunities for daytime Mercury spotting!

And speaking of mornings, don’t forget to check out 7th magnitude C/2009 P1 Comet Garradd, currently in the constellation Ursa Minor. Comet Garradd makes its closest approach to Earth on March 5th at 1.27 A.U.s distant, and is already circumpolar for viewers above latitude 30° degrees north. In fact, comet Garradd will be only 19° degrees away from the north celestial pole next week on March 11th before beginning the plunge south. I showed off Garradd last fall at a star party to great effect and have easily tracked its fuzz ball/globular-like appearance with binocs on the rare clear February morning. Garradd has thus far been the best cometary performer for the northern hemisphere in 2012.

…And mornings are crucial to tracking down faint fuzzies this week, as the Full Worm Moon occurs on March 8th at 9:41UT/4:41EST. This month’s Full Moon occurs in Leo about 9° degrees away from a brilliant Mars that just passed opposition last week. Other springtime related names for the March moon are the Full Sap, Crow, Crust, Sugar or the Lenten Moon.

…And in the bizarre astronomy department: March 7th marks the anniversary of the 1970 total eclipse of the Sun that passed over the Canadian Maritimes. Over the years, this has been suspected to have been one of two eclipses referred to in Carly Simon’s “You’re So Vain,” the other being an eclipse that occurred on July 10th, 1972. Just who flew their “Learjet up to Nova Scotia to see a total eclipse of the Sun,” and when did they do it? Hints have been dropped over the years, but Carly isn’t talking…

So that’s our tiny corner of the universe this week; and don’t forget to Spring forward 1 hour Sunday March 11th if you live in a region that still participates in this anachronism… or you could just say “Down with DST!”

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