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The Sky This Week, 2020 May 26 - June 2

Make time for the Moon and some nice double stars.
Crescent Moon, Venus, and Mercury, imaged 2020 May 23 from Mollusk, Virginia.
ICYMI: Crescent Moon, Venus, and Mercury, imaged 2020 May 23 from Mollusk, Virginia
with a Canon EOS Rebel SL2 DSLR and 55-250mm EFS lens @ 116mm, f/6.3, ISO 800. HDR composite of 3 images.
The star near the top is El Nath (Beta Tauri).

The Moon waxes in the evening sky this week, passing through the signature constellations of spring.  First Quarter occurs on the 29th at 11:30 pm Eastern Daylight Time.  Luna starts the week next to the Twin Stars of Gemini, Castor and Pollux, then wends her way eastward past the bright star Regulus on the 28th and 29th.  She will be about seven degrees north of the bright star Spica on June 1st.

This is another good week to observe and get to know our nearest neighbor in space, the Moon.  As her waxing phase brightens more of the overnight hours she beckons from her lofty perch for your attention, and deservedly so.  A small telescope is all that is needed to see a stunning variety of lunar landforms that range from the relatively flat “seas” to towering mountain ranges and uncountable numbers of craters.  Some of my most enjoyable views of the Moon have been through my 4-inch refractor telescope.  While more detail can be gleaned through larger instruments, the small-aperture telescope is less affected by turbulence in our atmosphere.  Nonetheless, it is possible in moments of steady air to see craterlets as small as a couple of kilometers across.  With that concept in mind it may perhaps be a bit easier to put the size of the easily visible craters in context.  Most of these more prominent formations are up to well over 100 kilometers across and the impacts that created them must have been truly enormous events.  As the phase increases night to night and more of the Moon’s surface becomes visible, the sheer number of craters bears testimony to the violence of the early times of the solar system’s evolution.  Fortunately for us, the last of the prominent craters formed well over 100 million years ago, and no objects large enough to cause such an impact scar are currently known to enter our part of the solar system.

There are other treats for the small telescope as the Moon consumes more of the darkness.  Some of my favorites are double stars, and the springtime sky offers a wide variety for your examination.  The first such star that I ever observed was Mizar, the star that forms the bend in the “handle” of the Big Dipper, now high overheat at around 10:00 pm.  Keen-sighted people can spot fourth-magnitude Alcor next to Mizar with the unaided eye, but any king of telescope will quickly split Mizar itself into two components.  I discovered this for myself with my first telescope, a very modest affair with an aperture of 60 millimeters (2.4 inches).  Somewhat more challenging is the star Algieba, which lies just under 10 degrees north of Regulus in Leo.  Here you will find a close pair of golden yellow stars that show very nicely in my 4-inch scope.  Another interesting duo may be found just southeast of the Moon on the evening of the 31st.  Second-magnitude Porrima is a tight pair of blue-white stars with an orbital period of 169 years.  This makes it one of the few double stars whose separation and position angle change appreciably from year to year.  Back in 2006 I had to use the venerable 12-inch telescope at the Observatory to split the pair, but last week I was able to easily resolve them in my 4-inch instrument.

If you want to catch a last glimpse of Venus before she vanishes from the evening sky, find a location with a flat western horizon and look that way right after sunset.  The dazzling planet is now racing between Earth and Sun as she passes us on her inner, faster orbit.  The end of May brings her too close to the Sun to safely observe, and she slips into the morning sky after solar conjunction on June 3rd.  

The fleet planet Mercury is still quite visible in the west after sunset, but he is beginning to fade in brightness.  You can find him about 10 degrees high in the west half an hour after sunset.  Early in the week he will be about halfway between the second-magnitude stars El Nath in Taurus and Alhena in Gemini.

Jupiter and Saturn greet early morning skywatchers, rising between 11:30 pm and midnight.  They are very easy to spot just east of the “teapot” asterism of Sagittarius, and they will remain close together in the sky for the remainder of the summer and fall. 

Ruddy Mars continues to plod eastward through the faint stars of Aquarius, and should be easy to spot if you’re up well before dawn.  He is gradually brightening as Earth catches up to him, and there is nothing even remotely as bright or red-tinted in this part of the sky.  He will continue to brighten until opposition in early October, when he will outshine mighty Jupiter!

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