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The Sky This Week, 2020 June 2 - 9

Where the scorpion lurks...
Antares and Messier 4, imaged 2014 July 5 from Morattico, Virginia.
Antares and globular cluster Messier 4, imaged 2014 July 5 from Morattico, Virginia
with a Canon EOS Rebel T2i DSLR and 80mm (3-inch) f/6 Antares Sentinel refractor.
Note the more distant globular cluster Messier 80 and the large reflection nebula around Antares.

The Moon visits the southern reaches of the ecliptic this week, casting her pale glow across the greening landscapes of late spring.  Full Moon falls on the 5th at 3:12 pm Eastern Daylight Time.  June’s Full Moon is variously known as the Mead Moon, Rose Moon, Strawberry Moon, and Honey Moon, each name hinting at the slightly amber color that Luna can take on when she is scudding above the southern horizon.  Look for Luna among the stars that form the “head” of Scorpius, the Scorpion on the evening of the 4th.  Early risers on the 8th and 9th can see the waning gibbous Moon in the company of Jupiter and Saturn.

As the Moon rises on the evening of the 4th, look a few degrees below and to the left for the rising star Antares, the red-tinted heart of Scorpius.  After Betelgeuse in Orion, Antares is probably the best-known red supergiant star in the sky.  These stars are highly evolved massive stars that have reached the last phase of their life cycles.  Unlike our Sun, these stars are massive enough to sustain fusion of elements heavier than hydrogen and helium.  Their core temperatures allow fusion of elements up to iron, the 26th element in the periodic table.  A consequence of this is that their outer levels swell to enormous sizes.  If Antares occupied the Sun’s position in our solar system all of the inner planets out to Mars would lie within it, and long-period pulsations might increase its girth to the orbit of Jupiter!  Like Betelgeuse, it can vary in its brightness over time with a period of around four to five years.  Located some 550 light-years from us, it shines with the equivalent luminosity of around 75,000 Suns!

Betelgeuse and Antares are related in other ways as well.  In our Greco-Roman skylore tradition Orion and the Scorpion were mortal enemies.  In one of many versions of the tale, Orion’s boast that he could kill any animal on Earth angered Gaia, goddess of the Earth and sister of Artemis, the goddess of the hunt.  To punish Orion for his boast Gaia sent a lowly scorpion to kill the hunter, which the creature successfully did by stinging Orion on his heel.  Artemis, who was secretly in love with Orion, appealed to Zeus, who raised Orion’s body to the sky.  The scorpion didn’t come away unscathed, however, and was crushed by Orion’s enormous weight when the hunter fell mortally wounded on it.  Zeus also put the scorpion in the sky, but in such a position that the two would never encounter each other again.  This is why, for mid-northern latitudes, you will never see Betelgeuse and Antares in the sky at the same time.  

Orion as a constellation is probably better known to most people since he dominates the long nights of winter from a high perch in the sky.  Scorpius, on the other hand, barely glides over the southern horizon from our vantage point.  That said, Scorpius is a wonderful sight to behold from more southerly locations.  Seeing the constellation in its full context, with its “tail” dipping downward and then upward, leaves little doubt as to how it got its name.  Both constellations have very distinct outlines made up of bright blue supergiant stars that are moving through space in association with each other.  Inn early June Scorpius crosses the meridian at around 1:00 am local time.

After many months gracing the early evening skies dazzling Venus is now passing between the Earth and the Sun.  By the end of the month she will join Mars in the early morning sky.

You may still be able to catch a glimpse of Mercury during early evening twilight.  The fleet planet may be found moving through the lower portions of Gemini, about halfway between the Twin Stars Castor and Pollux and the horizon at around 9:00 pm.  Binoculars should help you find him as he fades during the course of the week.

Jupiter and Saturn now both rise before midnight, and they cross the meridian at around 4:00 am.  Early risers still get the best view, but the duo are making inroads to the evening sky and will be up all night long by mid-July. 

Mars plods eastward against the faint stars of Aquarius, but his bright ruddy glow should make him stand out in an otherwise bland patch of the sky.  By the end of the week the red planet will reach zero magnitude and be second only to Jupiter among the planets in the morning sky.

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