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The Sky This Week, 2014 June 24 - July 1

More musings on the Milky Way
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Scorpius, Sagittarius, and the galactic center, 2014 June 1
Imaged at Sky Meadows State Park, Paris, Virginia

The Moon returns to the evening sky this week following New Moon, which occurs on the 27th at 4:08 am Eastern Daylight Time.  Try to spot Luna’s slender day-old crescent six degrees to the south of bright Jupiter during evening twilight on the 28th.  On the evening of the 1st she’ll be located five degrees south of the bright star Regulus in Leo, the Lion.

The year’s latest sunset occurs on the 28th as the Sun sets at 8:38 pm EDT here in the Washington area.  Our earliest sunrise occurred back on the 14th, but Old Sol now rises about three minutes later than he did two weeks ago.  The time of sunset will gradually start to recede over the next couple of weeks, although most of us probably won’t notice the shortening days until well into the month of July. 

Despite the late sunsets, you still have most of the week to enjoy the spectacle of the summer Milky Way before the encroaching Moon begins to wash it out.  This band of amorphous light shows its most prominent sections to us during the summer months as the galaxy’s central regions wheel over the southern horizon.  The actual heart of the Milky Way is located some 30,000 light-years away in an area located just west of the tip of the “spout” of the teapot-shaped asterism formed by the brightest stars of Sagittarius.   The actual galactic center is hidden from our direct view by enormous clouds of stars and intervening dark molecular associations, but it is easy to see that the width of the ghostly band reaches its maximum in this direction.   Today, thanks to our ability to observe in multiple spectral bands, we know that the center of the Milky Way hosts a very compact but ultra-massive object: a “black hole” with a mass of several million Suns!  Fortunately for us, we’re located well away from the zone of intense X-ray and Gamma-ray radiation that this object occasionally unleashes when an unfortunate star passes too close, so we can enjoy the more benign denizens of our galactic neighborhood.  For this I suggest using binoculars on a good clear night.  If you start your viewing just to the right of the “Teapot” and work your way up the Milky Way toward the three bright stars of the Summer Triangle you’ll encounter many bright knots of star clusters and glowing clouds of diffuse gas.  All of these little gems are set against a background of a seemingly infinite number of stars.  But not quite infinite; the Milky Way is believed to contain about 200 billion stars, of which our little Sun is but one rather nondescript member.

We are now in the last couple of weeks of seeing bright Jupiter in the evening sky.  The giant planet now sets just an hour after the Sun, so your only chance to see him is in the brighter stages of evening twilight.  You’ll have one last opportunity to catch him with a thin crescent Moon on the evening of the 28th when Luna will be just to the south of the planet.  Jupiter will pass behind the Sun on July 24th, and early risers can expect to see him rising in the morning skies by early August.

Mars is now the most prominent planet in the evening sky, thanks in most part to his distinctive color.  Although he is only slightly brighter than Saturn his reddish tint makes him stand out in a field that’s otherwise sprinkled with white- or blue-tinted stars.  He continues to gain speed in his easterly trek around the sky, and this week he’ll move just over 2.5 degrees closer to the bright star Spica in Virgo.  In another two weeks he’ll pass just over a degree to the north of the star.  Through the telescope his disc has now dwindled to less than 10 arcseconds’ diameter, making it difficult for the small telescope owner to see much more than a pink gibbous dot.

Although he is still outshone by Mars, Saturn is the planet of choice for summertime observing.  Despite his southerly declination, the ringed planet is well-placed for viewing during the mid-evening hours.  Almost any form of optical aid will show the planet’s distinctive rings, and the larger the aperture you use to scrutinize him the more detail you’ll see in these mysterious appendages.  We now know that the rings are composed of billions of chunks of ice in various sizes and that their apparent structure is regulated by a swarm of small moons both inside and outside the brighter ring components.  They are also truly enormous; the distance across the visible ring system spans over 70% of the mean distance from the Earth to the Moon.  However, they are also incredibly thin, probably less than 100 meters thick!

Venus remains pretty much where she’s been for the past several weeks, wallowing in morning twilight just above the eastern horizon.  About all you can see is her slow drift toward the north as she traverses the northern reaches of the ecliptic.


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