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The Sky This Week, 2019 July 30 - August 6

Wading in the Milky Way's Lagoon.
Messier 8, the Lagoon Nebula, imaged 2014 July 5 from Morratico, Virginia.
Messier 8, the Lagoon Nebula, imaged 2014 July 5
with an 80 mm (3-inch) f/6 Antares Sentinel refractor and a Canon EOS Rebel T2i DSLR
from Morattico, Virginia.

The Moon returns to the evening sky this week, with her waxing crescent moving through the departing constellations of the late springtime.  First Quarter occurs on August 7th at 1:31 pm Eastern daylight Time.  Look for the Moon a few degrees north of the bright star Spica on the evening of the 5th. 

As August opens we enter a period of enhanced meteor activity.  Currently there are a couple of minor showers, the Southern Delta Aquariids and the Alpha Capricornids that are reaching their peak activity.  Neither one is a “show-stopper”, but observers at dark locations may see up to 20 meteors per hour from radiants in the southeast in the hours before sunrise.  Also active is the annual Perseid shower, which is gradually building towards its peak on the night of August 12-13.  The radiant for the Perseids rises in the northeast at around 11:00 pm, but the best activity once again occurs in the early morning hours.  The Perseids can be very productive at their peak, producing up to 100 meteors per hour at their peak.  Unfortunately this year the 94% illuminated Moon will wash out much of the activity on the peak night, but for the upcoming week they should produce decent numbers after midnight.

August is one of my favorite months for stargazing.  The nights are gradually growing longer, so we don’t have to wait as long to start enjoying the splendors of the summer sky.  At the end of evening twilight one of the season’s signature constellations may be seen in all its glory as it crosses the meridian in the southern sky.  Scorpius is one of the most distinctive stellar groups in the sky, rivalling its winter counterpart of Orion.  Both constellations share similar elements, with most of their stars formed in physical associations.  Each constellation also has a “red supergiant” star as their most prominent luminaries.  Antares in Scorpius and Betelgeuse in Orion are highly evolved stars that are near the end of their evolutionary tracks.  These stars have distinctive reddish tints, indicating a relatively cool surface, but both stars are gargantuan in size.  If they were placed in the Sun’s position in our solar system Betelgeuse would engulf the orbit of the Earth, while Antares would swallow up Mars!  In mythology Orion and Scorpius are mortal enemies, so they are on opposite sides of the sky.  Thanks to this arrangement you will never see Antares and Betelgeuse in the sky at the same time.  Scorpius is one of the few constellations that looks like its namesake, and for Northern Hemisphere observers this is the best time of year to see it.  My favorite feature of Scorpius is the “fish hook” asterism formed by its southernmost stars that ends in a close pair of blue-hued stars that mark the Scorpion’s stinger.  Known as Shaula and Lesath, this naked-eye pair was called the “Swimming Ducks” by the Skidi Pawnee of the American Midwest.

Rising upward from Scorpius are the rich star clouds of the summer Milky Way.  By 11:00 pm the luminous band of our home Galaxy arcs high over the eastern horizon.  One of the most striking features of the Milky Way are the seeming “voids” that bisect it from the stars of the Summer Triangle down to the southern horizon.  Far from being empty space, these dark regions are teeming with cold dust and gas that obscures the light of more distant stars.  The stuff that makes up these dark clouds is the very stuff that stars and planets are formed by.  Dotted here and there along the Milky Way you’ll find glowing patches of light against the dark clouds.  These are areas where stars are forming.  One of the easiest to find is Messier 8, also known as the Lagoon Nebula.  You can find it as a misty patch of softly glowing light in a pair of binoculars about halfway between Jupiter and Saturn.  Sweep northeastward along the Milky Way and you will encounter several more of these glowing knots, proof that our galaxy is still very busy making stars.

Jupiter crosses the meridian at the end of evening twilight, offering you the best view of the giant planet as darkness falls.  Try to get him in the telescope at this time; as the night progresses he will start losing altitude as he moves into the southwestern sky.  On the evening of August 2nd you should have a great view of the planet flanked by his four Galilean moons.  They will be far enough from the planet to be visible in binoculars.

Saturn crosses the meridian at around 11:30 pm, so once you’ve finished looking at Jupiter you’ll have plenty of time to view the ringed planet.  Saturn is one of the most spectacular objects that you can view in the sky.  When people see it for the first time they usually don’t believe their eyes.  Often I’ll hear comments from people at star parties expressing disbelief, eliciting a variety of interesting comments.  My favorite is “Wow, it looks just like the pictures!”  The “live” view is way better than any image, though.  When you see its distinctive outline suspended in the eyepiece, it is currently some 1.36 billion kilometers (845 million) miles away and you are seeing it as it was 75 minutes ago!

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