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The Sky This Week, 2020 August 11 - 18

Meteors, planets, and a celestial swan.
Jupiter & Saturn, imaged from the U.S. Naval Observatory, Washington, DC, 2020 August 11.
Jupiter & Saturn, imaged from the U.S. Naval Observatory, Washington, DC, 2020 August 11
with the 30.5-cm (12-inch) f/15 Clark/Saegmüller refractor.

The Moon wanes in the pre-dawn sky this week, making her way through the rising winter constellations as the first light of dawn begins to brighten the eastern horizon.  New Moon occurs on the 18th at 10:42 pm Eastern Daylight Time.  You will find Luna just north of the bright star Aldebaran in Taurus, the Bull, on the morning of the 13th.  Luna will be close to dazzling Venus before dawn on the 15th.

As we mentioned last week, the annual Perseids meteor shower peaks on the nights of the 11th-12th and 12th-13th.  However, these aren’t the only nights to see members of this famous shower.  Activity from the Perseids will continue through the end of the month, and the shower will maintain about a quarter of its peak strength until late in the week.  Moonlight becomes less of a factor as the week passes, so if conditions aren’t great for viewing on the peak nights you can still see a decent show for a while longer.

The absence of the Moon means that it is time for the August campaign for the Globe at Night citizen-science program.  So far this year the program has recorded over 20 thousand observations from all around the world to help scientists understand the impacts of light pollution on a global scale.  The program started as a project initiated during the International Year of Astronomy in 2009 and has been going strong ever since.  This month the featured constellation is Cygnus, the Swan, whose brightest star, Deneb, is one of the apexes in the Summer Triangle asterism.  Deneb is the faintest and most northerly of the Triangle’s stars, but it can be easily seen even from the most urban locations.  The rest of Cygnus extends toward the middle of the Summer Triangle, with the Swan’s head, Albireo, nearly at its center.  This star is one of my favorite targets for small telescopes; it is an easily split double star with blue and gold components which I like to call the “Navy star”.  Between Albireo and Deneb lie the other stars in the constellation.  Suburban skywatchers should be able to see a cross-shaped grouping of stars that, with a little imagination, can be seen as a swan in flight.  Pick a clear night to find Cygnus, then go to the Globe at Night Web App to record your observation.

From a dark location you should be able to see Cygnus in all its splendor.  The swan seems to be “flying” along the path of the Milky Way, which seems to cleave into two parts along its path.  This feature continues down to the horizon and is known as the Great Rift.  While it has the appearance of being somewhat devoid of stars, it is actually an enormous cloud of cold, non-luminous gas and dust blocking the light from even more distant star clouds in our galaxy’s spiral arms.  These dark clouds are a feature of the summer Milky Way, and they continue along the parts of the galaxy that can only be seen from more southerly climes.  Indeed, the ancient Inca people and their relatives created much of their sky lore from the shapes of these dark features in the soft glow of the southern Milky Way.  We northerners only get to see a small part of them.

I finally had my first really good evening for observing Jupiter.  Due to its extreme southern declination it is very hard to see from my house during the brief time that he passes between my neighbor’s chimney and a large tree.  Almost invariably the time when Old Jove is in the right place a cloud scurries in front of him.  Such is the lot of the suburban astronomer.  However, I was able to have a nice session with Jupiter using the Observatory’s 125-year-old 12-inch refractor, whose old glass still provides great views.  The famous Great Red Spot was prominently featured, and the moon Europa was leading its shadow across the disc.  You don’t need a big telescope to enjoy these features, though; a good four-inch scope should show these features quite nicely.

Saturn was next on my agenda after Jupiter.  I can honestly say that even after decades of looking at the ringed planet through dozens of different telescopes there is still a certain sense of awe whenever I train the 12-inch on it.  Yes, occasionally I will lapse into a state of disbelief that such an amazing sight appears in Nature.

I’m looking forward to the views of Mars that I’ll get this fall, but even now the red planet beckons.  Mars now rises just before 11:00 pm, and you will have no trouble picking him out of the sparse stars of Autumn during the late night and early morning hours.  Modest telescopes will show many of his enigmatic surface features and dazzling polar ice cap.  Other than the Moon and Mercury, Mars is the only pother place in the solar system where you are looking at a solid surface.

Venus gets a pre-dawn visit from the Moon on the morning of the 15th.  She is now moving through the heart of the rising Great Winter Circle, drifting among the stars of Gemini.