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The Sky This Week, 2020 July 21 - 28

Comet NEOWISE begins to fade, Jupiter and Saturn are at their best.
Comet C/2020 F3 NEOWISE, imaged 2020 July 14 at the U.S. Naval Observatory.
Comet C/2020 F3 NEOWISE over National Cathedral
imaged 2020 July 14 at the U.S. Naval Observatory with a Canon EOS Rebel SL2 DSLR

The Moon waxes in the evening sky this week, providing stiff competition for Comet C/2020 F3 NEOWISE.  First Quarter occurs on the 28th at 4:16 am Eastern Daylight Time.  Look for Luna’s slender crescent just north of the bright star Regulus on the evening of the 22nd.  On the 26th you will find her northwest of the bright star Spica.

The aforementioned Comet NEOWISE has been putting on a good show for the past several weeks since it rounded the Sun on July 3rd.  It is now well-placed in the early evening sky, visible in the northwest as evening twilight fades.  This week it slides between the stars of the Big Dipper asterism and Leo, the Lion.  While it is possible to see it with binoculars from urban skies, the best views are found well way from urban light pollution.  Over the past weekend a number of people ventured west of the DC metro area to see it and were rewarded with a soft fuzzy nuclear glow and a tail reaching some 10 degrees long, visible with the unaided eye.  That said, it has begun to fade as it recedes from the inner solar system, but it is still worth looking for if you can find a good dark location.  The last easily visible comet to grace the sky for many people to enjoy was Comet Hale-Bopp in 1997.  Since then there have been a couple of other bright ones, but they were best seen in twilight and never moved into prominence in darker skies.  While NEOWISE is no Hale-Bopp, it is still worth taking the time to find.  We never know how long it will be before another one like it will swing by. 

Just in case you haven’t noticed, the days are getting shorter.  This week sunrise occurs after 6:00 am for the first time since May 10th, and Sunset occurs before 8:30 pm for the first time since June 4th.  The total length of daylight is now some 25 minutes less than it was on the solstice back on June 20th.  We are approaching the mid-point of summer in a couple of weeks, which is when I really begin to notice the shortening days and lengthening nights.  Right now I’m happier to see the later sunrise since the best time to observe Mars is still before dawn.

By 10:30 pm the summer constellations parade into view, with my favorite summer grouping, Scorpius, crossing the meridian in the south.  Scorpius is one of the few constellations that bears a strong resemblance to its namesake, and as such it is one of the most ancient constellations in our skylore traditions.  We find images of Scorpius dating back to very ancient times in pre-dynastic Egypt, where it was depicted as a symbol of power for one of the early kings on a ritual mace-head dated to around 3100 BCE.  From Egypt Scorpius would have appeared much higher in the sky than it does from our place and time, and it would have set at a time of the year near the annual Nile flood; the mace-head shows a “King Scorpion” with a hoe, ready to open an irrigation canal to direct the life-giving floodwaters to the fields.

If you have a good view to the south you can see Scorpius in all of its glory.  Its brightest star, Antares, marks the Scorpion’s heart with an appropriate ruddy tint.  To the west three stars in a vertical arc form the creature’s head, while its body curves down to the south before curling upward and ending in a close pair of stars that depict its stinger.  Northeast of the main stars of the constellation is one of the densest star fields in the summer Milky Way.  It is in this general direction, some 30,000 light-years away, is our galaxy’s center.  This is one of my favorite areas of the sky to explore with binoculars or my small rich-field telescope. 

Jupiter passed opposition last week, and you have probably noticed his bright glow in the southeastern sky at the end of evening twilight.  By 10:00 pm he should be high enough to peruse in the telescope, offering a fine view of his dark cloud belts and ever-shuffling moons.  Jupiter offers the largest apparent disc of any of the other planets, and currently he’s at his closest to Earth.

Saturn is also at opposition, some seven degrees east of Jupiter.  This is the time to look at the ringed planet in the telescope; for a few days before and after opposition the planet’s rings brighten dramatically, appearing much brighter than the disc of the planet itself.  By the end of the week, though, the rings will return to their usual brightness, matching the planet’s cloud-tops. 

Mars is high in the southeast if you get up to look for him an hour before sunrise.  He is now the brightest object in this otherwise barren part of the sky.  Modest-aperture telescope should reveal his bright south polar cap and other surface features.

Venus may be see low in the east in the hour before sunrise.  She is moving through the stars of Taurus, a reminder that the cooler nights of autumn and winter are waiting in the wings.