Archive for August, 2016

The Sky This Week, August 30 – September 6, 2016 !

The Sky This Week, 2016 August 30 – September 6

Take a holiday among the stars.
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Venus & Jupiter in close conjunction (with interloper)
imaged 2016 August 27 from Alexandria, Virginia

The Moon returns to the evening sky this week, gracing the twilight hours with a gradually growing crescent. New Moon occurs on September 1st at 5:03 am Eastern Daylight Time. If you have a flat western horizon and a good clear sky try to sight the very slender crescent Moon just half a degree from Jupiter. You’ll probably need binoculars to make this sighting as the duo will only be five degrees above the horizon about 20 minutes after sunset. On the following night you should be able to find the Moon about six degrees to the east of Venus and see both objects with the unaided eye. By the evening of the 6th Luna will be about four degrees above the star Zubenelgenubi in the constellation of Libra, the Scales.

The upcoming holiday weekend offers vacationing skywatchers a fine way to say farewell to summer. Whether you’re in the mountains or at the shore the opportunity to be away from city lights offers splendid views of the season’s signature constellations and the most luminous parts of the Milky Way that we can see from the Northern Hemisphere. By 10:00 pm the summer Milky Way glimmers high in the sky, bisecting the celestial sphere from the southwest to the northeast. The Galaxy’s densest star clouds may be seen to the south, just off the “spout” of the “Teapot” asterism formed by the brighter stars of the constellation Sagittarius. If you have binoculars handy, use them to gradually sweep the Milky Way from the horizon to the zenith. You’ll be surprised at the number of luminous knots strewn about the clouds of innumerable stars that the binoculars will reveal. Also notice the seeming “voids” among these star clouds. Hundreds of these were discovered and catalogued by the great American astronomer Edward Emerson Barnard in the early 1900s. They are not real voids, but rather obscuring clouds of cold, dark gas and dust that may someday form new stars and planetary systems. So too is the “Great Rift” that bisects the Milky Way as it passes through the bright stars of the Summer Triangle, which lies directly overhead in the late evening. If you have a telescope, re-trace your binocular steps to view star clusters, glowing gaseous nebulae, and millions of faint background stars. You don’t need a large telescope for this; a small-aperture low-power instrument is ideal for this kind of exploration.

The evening twilight hour finds the bright glimmer of Venus low on the western horizon. Fresh from her close encounter with Jupiter on the 27th, she rapidly outpaces the giant planet, gradually climbing a bit higher each night. You’ll find her sharing the limelight with the slender crescent Moon on the evening of the 3rd.

If you’ve been following ruddy Mars over the past few weeks you will have watched him pass by the star Dschubba, then between the planet Saturn and the star Antares. He is now crossing the Milky Way’s densest star field and should offer a wonderful sight in the low-power telescope as his bright ruddy hue contrasts with the blue-white background stars.

Saturn has now been passed by ruddy Mars and is slowly creeping eastward above the star Antares. You can get a decent view of him in the telescope as soon as he pops out of evening twilight, and he should remain high enough to show his distinctive rings for a couple of hours before he sinks toward the southwest horizon.

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The Sky This Week, August 9 – 30, 2016 !

The Sky This Week, 2016 August 9 – 30

The summer vacation edition.
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Waiting for darkness, Stellafane Observatory
imaged 2016 August 5 from Breezy Hill, Springfield, Vermont

We’ll be taking our annual summer vacation over the next couple of weeks, hopefully encountering clear dark skies for some pleasant nights of stargazing.

The Moon waxes in the evening sky this week, brightens the overnight hours during the week of the 16th, then wanes in the morning sky thereafter. Full Moon occurs on the 18th at 5:27 am Eastern Daylight Time, with Last Quarter falling on the 24th at 11:41 pm EDT. August’s Full Moon is popularly known as the Corn Moon, Grain Moon, or Sturgeon Moon, indicating the time of year when crops mature for the harvest and fish return to their spawning grounds. Luna forms a very attractive grouping with Mars, Saturn, and the bright star Antares on the evening of the 11th. Over the course of the next few evenings the Moon will pass through the stars of Sagittarius before transiting the star-poor autumnal constellations. She won’t encounter any bright objects until the 25th and 26th, when she drifts past the bright star Aldebaran in the pre-dawn hours.

The highlight of the August sky is the annual Perseid Meteor Shower, which typically peaks in the wee hours on the morning of the 12th. This year you’ll need to stay up well past 1:00 am that morning to see the shower after the Moon has set. Several astronomers who study these phenomena predict that we may be in for an unusually rich display this year since a dense stream material from the parent comet may have been perturbed by Jupiter to pass a little closer to the Earth. This comet, known as 109P/Swift-Tuttle, was co-discovered by astronomers Lewis M. Swift and Horace P. Tuttle in 1862 and orbits the Sun once every 134 years. Each year at this time in August we cross paths with debris shed by the comet as it passes through the inner solar system, and it produces the most consistent of the year’s annual meteor displays. Horace Tuttle went on to have a career at the U.S. Naval Observatory in the latter part of the 19th Century. In addition to the interfering Moon, you should also try to find a viewing location away from city lights. Perseids are noted for their fast speed across the sky and their brightness. About 5 to 10 percent of Perseids produce bright fireballs that leave persistent glowing trains in their wake that can last for several seconds. From a good dark-sky site a single observer may see as many as 100 or more meteors per hour! City dwellers will see much less, but a bright one may be visible from urban yards every few minutes. Observing them is simple; find a place out of the direct glare of street lights, lie down, and look up.

Moonlight wipes out the views of the Milky Way until later in the month, but those views are some of the summer’s best nighttime treats. During the month the sun sets a bit earlier each evening, so by the time the end of the month rolls around the Milky Way should be seen in all its glory by 9:30 pm.

It’s a busy month for the visible planets. During the first week you can still see all five of the naked-eye planets in the evening sky, but by month’s end only three are easily seen.

Venus and Mercury still skulk around the western horizon during early evening twilight. They are spaced by a bit over five degrees for most of the month, with brighter Venus trailing the fading glow of Mercury just a few degrees above the horizon. Binoculars will be a big help in locating them.

Jupiter continues his headlong plunge toward the sunset horizon and can only be seen now in evening twilight. By the end of the month he briefly entertains Venus and undergoes an exceptionally close conjunction with the dazzling planet on the evening of the 27th. This will also occur just a few degrees above the horizon, so binoculars will be helpful to watch the event.

Mars begins the month just south of the second-magnitude star Dschubba, middle star in the “head” of Scorpius, and over the course of the next few weeks overtakes and passes Saturn in his eastward trek along the ecliptic. On the evenings of the 23rd and 24th he passes just under two degrees north of the ruddy star Antares, whose name means “Rival of Mars”. These are good nights to compare the colors of the two objects.

Saturn reaches the second stationary point in the current apparition on the 13th, slowly resuming eastward motion along the ecliptic thereafter. He is now the only planet that is easily recognized in the telescope thanks to his distinctive ring system, but by the later evening hours he too is swinging toward the southwestern horizon and the denser layers of air will distort the view.

The Sky This Week, August 2 – 9, 2016 !

The Sky This Week, 2016 August 2 – 9

More Milky Way Meanderings
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The Summer Triangle Milky Way and the “Great Rift”
imaged 2013 August 12 from Fishers Island, NY

The Moon returns to the evening sky this week, waxing through her crescent phases as she moves along the ecliptic’s southern reaches. Try to locate her shortly after sunset on the evening of the 4th; the fleet planet Mercury will be within a degree to her west, and the brighter glow of Venus will be about 10 degrees farther west, just above the horizon at 9:00 pm Eastern Daylight Time. On the evening of the 5th Luna will be just over a degree from Jupiter in the gathering evening twilight. First Quarter occurs on the 10th at 2:21 pm EDT.

During the early part of the week you can still get a nice view of the summer Milky Way once evening twilight ends. We discussed the galactic center last week, so this time let’s look a bit farther north at the bright band that pierces the Summer Triangle marked by the stars Vega, Deneb, and Altair. By 10:30 pm the sky should be fully dark, and the Triangle will be nice and high in the east. From a dark location this is one of the most spectacular parts of the Milky Way as it is here that the luminous band appears to be split by a dark rift that continues down toward the southern horizon. If you look at this rift with binoculars or a telescope you’ll soon discover that there are many fewer stars in the rift. This is due to vast clouds of opaque gas and dust that define the plane of the Galaxy. Long-exposure images will show many discrete dark clouds. Fromm extremely dark locations many of these can just be glimpsed with the naked eye. In fact, many ancient Mesoamerican cultures identified these dark patches as their version of “constellations”. Unfortunately there aren’t that many locations left in the U.S. where we can enjoy such pristine skies, but the bright parts of the Milky Way are still a wonderful hunting ground for other sights such as star clusters and bright nebulae. The constellation of Cygnus, the Swan, dominates the visible stars within the Summer Triangle. The bright star Deneb marks the Swan’s tail, and the third-magnitude star Albireo, located almost squarely in the Triangle’s center, marks its head. It doesn’t take too much imagination to draw out a stick-figure swan flying toward the south along the Milky Way. One of my favorite depictions of this constellation comes from Inuit skylore; they see a man paddling a kayak along the “Pebbly River”. For a nice easy telescopic treat, look at the star Albireo. It resolves in almost any telescope into a beautiful double star with blue and gold colors.

You can still see all five of the naked-eye planets this week. The best time to do so would be the evening of the 4th. As mentioned earlier the Moon is quite close to Mercury then, and since the fleet planet is probably the most difficult to spot this will be your best chance to see him.

You should start looking for Venus just after sunset in the western sky. Use binoculars to find her bright glow about six degrees above the horizon 15 minutes after sunset.

Jupiter gets a visit from a slender crescent Moon on the evening of the 5th. He is now only visible during the waning evening twilight, losing a little more ground to the advancing Sun each evening. He’ll be gone from the sky in another few weeks.

Mars continues to move eastward through the stars that for the “head” of Scorpius. Watch him close in on the star Dschubba, the middle star of the three that form the head. By the week’s end the red planet will pass just under a degree south of the star and set his sights on Saturn.

Saturn crosses the meridian just before 9:00 pm, so you have plenty of time to enjoy viewing him above the stars of Scorpius. He stands about six degrees north of the Scorpion’s brightest star Antares and forms an ever-changing triangle with the star and Mars during the course of the week. This triangle will continue to flatten over the next several weeks. This will turn into a line around August 23rd.