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The Sky This Week, 2019 November 5 - 12

There's a little black spot on the Sun today...
The Moon, imaged 2019 November 4 at the U.S. Naval Observatory.
The Moon, imaged 2019 November 4 at the U.S. Naval Observatory
with the 30.5-cm (12-inch) f/15 Clark/Saegmüller refractor and a Canon EOS Rebel SL2 DSLR.

The Moon brightens the late autumn evenings this week, waxing through her gibbous phases to Full Moon, which falls on the 12th at 8:34 am Eastern Standard Time.  November’s Full Moon is popularly called the Frosty Moon or the Beaver Moon.  The latter name derives from Native American lore when indigenous people noted that beavers were particularly active as they prepared their dams and dens for the rigors of approaching winter.  Luna spends most of the week in the company of relatively dim stars, but ends the wee just west of Aldebaran, brightest star in the constellation of Taurus, the Bull.

The highlight event of the week, and perhaps the year, is the transit of Mercury across the face of the Sun on the 11th.  These events can only occur when the fleet planet passes “inferior conjunction”, where he reaches the same ecliptic longitude as the Sun.  The other ingredient necessary for a transit is that it has to occur at one of the two points in Mercury’s orbit where his orbital plane crosses the ecliptic.  These two events coincide every few years near May 8 or November 10.  Transits of Mercury occur 13 or 14 times per century and can occur at regular set intervals ranging from 3.5 to 13 years between events.  The most recent transit occurred on May 9 2016, while the next one won’t roll around until November 13 2032.  Let’s hope for good weather this time around, since the 2032 transit and that of November 7 2039 won’t be visible from the Western Hemisphere.  We’ll have to wait until May 7 2049 for the next transit that’s visible from the United States.  Here in Washington the coming transit will begin at 7:36 am EST when the tiny disc of Mercury begins to cross the Sun’s blazing disc.  It will take just under two minutes for the planet’s disc to fully ingress onto Old Sol, and Mercury will slowly move across the Sun for the next several hours.  Mid-transit will occur at 11:20 am, and egress from the solar disc will occur between 1:02 pm and 1:04 pm, when the transit ends.  Unlike a solar eclipse of the much rarer transit of Venus, this event requires a telescope to see.  Mercury’s disc is so small that your unaided eye can’t resolve it.  That said, you can project the sun’s image through binoculars or a small telescope onto a piece of white cardboard and safely watch the proceedings.  If you plan to observe the transit directly with a telescope be absolutely certain that a safe solar viewing filter is installed.  Permanent eye damage or total blindness will result if you look directly at the Sun without proper equipment.  Fortunately there will be a number of places in the Washington area where you can go to view the transit.  The public observatory at the National Air & Space Museum will be open, as will the observatories at the University of Maryland and George Mason UniversityLocal astronomy clubs will also be on hand at various locations with school science centers, planetariums, etcetera.  Stay safe and enjoy the view.  

The change back to Standard Time has given a small jolt to the setting summer constellations.  You will now find the Summer Triangle hanging in the west as evening twilight ends, and by 10:00 pm the bright stars of the Great Winter Circle are climbing into the eastern sky.  Most of the autumnal stars will be washed out by the light of the waxing Moon, but you should still be able to discern the stars of the Great Square of Pegasus, which crosses the meridian at around 8:30 pm.  Looking toward the northeast at this time you will see the bright star Capella shining with a golden yellow hue.  Capella has long been associated with late autumn and early winter, and you will find it near the meridian at midnight around the time we celebrate Thanksgiving in the U.S.  

Venus can now be spotted in deepening twilight in the southwestern sky.  The dazzling planet is drawing a bead on Jupiter, which is easy to spot higher up in the southwestern sky.  The two planets will be close to each other for several evenings around November 24th.

Saturn watches as Venus overtakes Jupiter, then awaits his turn for a visit from the swift-moving planet.  His turn will come in mid-December.  You still have a bit of time to catch a view of Saturn through the telescope, but you’ll probably want to do so before you sit down for dinner.