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The Sky This Week, 2015 June 2 - 9

Markarian's Chain, the heart of the Coma-Virgo Galaxy Cluster
Messier 86 and 84 are the two prominent galaxies at center-right
Imaged from Morattico, Virginia on 2013 April 14.

The Moon wanes from the full phase this week, skirting the southern horizon as she moves into the barren star-scapes of the autumnal sky. Last Quarter occurs on the 9th at 3:42 pm Eastern Daylight Time. Luna stands squarely over the top of the “Teapot” asterism of Sagittarius in the early morning hours of the 4th. After that she finds few bright companions to meet for the rest of the week.

As the Moon slips into the morning sky we begin to get a few precious hours of dark-sky time, but we have to wait up awhile to enjoy them. June is the moth of the solstice, and full astronomical darkness now doesn’t occur until around 10:30 pm! At this hour the bright rose-tinted star Arcturus may be found near the meridian high in the sky. About halfway between Arcturus and the southern horizon is another bright star, Spica, brightest star in the constellation Virgo. Just to the west of these stars is the region known to thousands of amateur astronomers as the “Realm of the Nebulae”, the heart of the Virgo Galaxy Cluster. From a good dark sky location you can spot several of the cluster’s brightest galaxies as small fuzzy blobs of light in a steadily-held pair of binoculars. A three-inch aperture telescope will reveal a few dozen of these distant star systems, while a six-inch can show hundreds more. One of the most amazing sights I’ve seen in the sky is the view of the central part of the cluster through my 14.5-inch reflecting telescope, with the ghostly glow of a dozen galaxies gently wafting through the field of a wide-angle eyepiece. Each of these galaxies is shining with the light of a hundred billion suns whose light has taken over 50 million years to traverse the gulf of space to arrive at my eye. Stepping back from the eyepiece and gazing eastward we now see the rising star-clouds of the summertime Milky Way, which is itself a far-flung outlier of those distant wisps of light that I’ve just been looking at. Yes, the universe is a very big place!

One of those stars in the Milky Way galaxy is our Sun, and whirling around it are a number of objects that attract our attention in the night sky. Two of the brightest of these are now best seen in the fading twilight of the mid-evening, dominating the western sky. The brightest of these is Venus, often referred to as Earth’s “sister planet”. Physically Venus is just a bit smaller than our fair world, but her surface is perpetually hidden under a global deck of bright clouds that cause her to shine with dazzling brilliance. Under those clouds lies a surface that is truly hellish to imagine, with a global surface temperature hot enough to melt lead and a crushing atmosphere which belies her pleasing appearance in our skies. Venus is now appearing to close in on the planet Jupiter, and by the end of the month she will be quite close to the giant planet in the sky. This closeness is really an optical illusion; Jupiter never gets closer than a few hundred million miles to the dazzling planet!

Jupiter is now best placed for viewing shortly after sunset and remains high enough in the sky for telescopic viewing as evening twilight fades. Despite a brighter sky background, the planet still offers a wonderful sight in the telescope. His four large Moons offer constantly shifting configurations from night to night, and the alternating dark belts and bright zones are a testament to the violent forces at work in the planet’s huge atmosphere. If you observe him at around 9:00 pm on the 6th you’ll see the famous Great Red Spot crossing the center of the planet’s disc as well as a nice view of all four of the planet’s moons.

Saturn is easily seen in the southeastern sky by the end of evening twilight. His yellow glow contrasts nicely with the surrounding blue-tinted stars in the head of Scorpius. Viewing Saturn in a telescope invariably elicits surprise from those who’ve never seen it before, and even seasoned observers take a few moments to ponder the planet’s rings. Saturn will be with us in the evening sky for most of the summer, so you’ll have plenty of chances to get a nice view.

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