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The Sky This Week, 2020 October 6 - 13

'Tis the time for Mars Mania.
Mars, imaged 2020 OCT 6 from Alexandria, Virginia.
Mars, imaged 2020 OCT 6, 04:35 UT from Alexandria, Virginia
with a Celestron 23.5-cm (9.25-inch) f/10 Schmidt-Cassegrain telescope,
Orion 2X 3-element "Shorty" Barlow lens, and a ZWO ASI224MC color imager.

The Moon wanes in the morning sky this week, climbing through the dim stars of the autumnal constellations as she works her way toward winter’s rising luminaries.  Last Quarter occurs on the 9th at 8:40 pm Eastern Daylight Time.  Luna begins the week among the stars of Taurus, the Bull, before arcing high over Orion and through the heart of Gemini over the next few nights.  Early risers can see her just south of Gemini’s twin stars Castor and Pollux before dawn on the 10th.  She closes out the week chasing down the bright glow of Venus.

By now I’m sure that most of you have noticed the bright reddish “star” that dominates the eastern sky before midnight.  Far from being a star, it is actually the second-smallest planet in the solar system after Mercury, the object that the ancients called Mars.  Of all the objects in the sky, Mars probably carries the most distinctive color, and it’s not much of a stretch to see how earlier cultures associated it with their various gods of war.  Mars is at his peak brilliance this week, outshining all of the nighttime objects in the sky except for the Moon and Venus.  His prominence and brilliance are due to a rare combination of events: the planet’s perihelion and position along the ecliptic.  The red planet takes red planet completes one orbit of the Sun in 687 days, and it is best placed in our sky about every 780 days.  This means that each opposition of the planet occurs just over 2 years apart and two Zodiacal constellations to the east along the ecliptic.  However, Mars has a fairly eccentric orbit, so oppositions that occur when it is near its perihelion only take place every 15 to 17 years.  This is one of those oppositions.  While the opposition of 2018 brought the planet a bit closer than the current one, Mars was poorly placed along the southernmost reaches of the ecliptic for Northern Hemisphere observers to get a good look at him through the telescope.  This year he’s much higher in the northern sky and passed perihelion only 2 months ago.  Mars is closest to the Earth on the 6th, a mere 62,066,500 kilometers (38,566,350 million miles) distant.  This sounds like a huge distance (and it is!) but under ideal circumstances he can’t approach any closer than 55,790,00 kilometers (34,847,000 miles).  He reaches opposition on the 13th, when he’s visible from sunset to sunrise.  We won’t have as favorable an opposition of the red planet until September 15, 2035, so take advantage of this relatively rare opportunity.

So why all the fuss about Mars?  Since antiquity his color and motion through the stars has fascinated humanity.  Soon after the first telescopes were pointed at his face it became apparent that the faint, dusky markings that observers saw were permanent features, indicating that Mars was a world with a solid surface.  Only the Moon and Mercury present tis kind of view; on all of the other planets you’re looking at the tops of clouds.  In the 19th Century better telescopes and diligent observers charted the Martian surface, and in 1877 the Italian astronomer Giovanni Schiaparelli announced the detection of what he termed “canali”, Italian for “channels”.  These were subtle linear features that appeared and disappeared in moments of good “seeing” in Earth’s atmosphere.  Percival Lowell, a wealthy American amateur astronomer, took the “canali” one step further at the close opposition of 1894, sketching out a vast network of features that he called “canals” and hypothesizing that they were true watercourses.  Lowell speculated that these features were the work of an advanced civilization on the red planet and went to his grave in 1916 firmly in that belief.

Sadly, the Canals of Mars do not exist, but we now know more about this smallish world than we do about any other place in the solar system.  And you can see some of these tantalizing features on the surface of a distant world from the comfort of your back yard.

Jupiter and Saturn share the limelight with Mars, but even Jupiter can’t outshine the red planet for the next couple of weeks.  These two “gas giant” planets are currently plodding eastward along the southern reaches of the ecliptic, making them less-than-ideal targets for northern observers.  Still, both planets deserve a look, especially on nights when the air is still.  Jupiter offers an apparent disc almost twice the size of Mars, and his ever-changing cloud belts and bright moons offer much to look at.  On the evening of the 8th Old Jove’s innermost Moon, Io, will start to drag its shadow across the planet’s cloud tops at around 9:00 pm EDT.

Saturn offers his spectacular rings, which have no rival in the solar system.  Composed of billions of chunks of ice, they appear as solid planes surrounding the planet.  On nights of steady air look for a dark gap toward the rings’ outer edge.  Known as Cassini’s Division, the gap is an area where the gravity of Saturn’s innermost moons keeps ring particles from congregating.

Dazzling Venus beams down from the stars of Leo, the Lion before sunrise.  I’ve gotten to know her well from early morning dog walks.  Look for the waning crescent Moon next to Venus before dawn on the 14th.