Archive for September, 2016

The Sky This Week, September 27 – October 4, 2016 !

The Sky This Week, 2016 September 27 – October 4

Sights in the celestial Swan
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Messier 27, the “Dumbbell Nebula” in Vulpecula
imaged 2016 August 23 from Fishers Island, NY

The Moon returns to the evening sky by the end of the week, with New Moon falling on September 30th at 8:11 pm Eastern Daylight Time. Luna presents a slender crescent in the early morning sky before New Moon, then gradually climbs into the evening twilight after. If you’re up at 6:30 am on the morning of the 29th, look for a sliver of a lunar crescent just one degree below the glimmer of Mercury in the brightening morning twilight. You should have a much easier time spotting the waxing crescent Moon above the bright planet Venus in the evening twilight of October 3rd.

Now that the hazy skies of summer seem to be behind us we have several moonless nights to do some citizen science by counting stars for the Globe at Night program. This month’s featured constellation is Cygnus, the Swan, easily found as one of the star patterns incorporated into the Summer Triangle asterism. The Swan’s brightest star is Deneb, which is the faintest of the three bright Triangle stars. The rest of Cygnus resembles a large cross which can be easily traced out in most suburban skies. Using the finder charts on the Globe at Night website, you can estimate the brightness of the faintest stars you can see from your observing site to help map the distribution of light pollution around the world.

Once you’ve done counting stars in Cygnus, take a look at some of the more interesting features of this fine constellation. From a dark location it is embedded in some of the brightest star clouds of the Milky Way, and it is where the “Great Rift” in the Galaxy seems to begin. One of the constellation’s best treats for any sky is the star Albireo, which marks the Swan’s “head”. Viewing this star with any telescope reveals it to be a fine double star with a wonderful color contrast consisting of a bright yellow star and a fainter blue companion. I like to refer to this pair as the “Navy Double” because of this color contrast, which to me shows up best in small instruments. For dark-sky observers, there are two small constellations just southeast of Albireo which contain some interesting deep-sky objects. Both objects are visible in binoculars but are best seen in modest telescopes. You’ll find Messier 71, a compressed cluster of faint stars, in the constellation of Sagitta, the Arrow, a small line of stars about 10 degrees from Albireo. In small telescopes it is a fuzzy patch of light, but larger instruments resolve its true nature. Five degrees northeast from M71 is an “M”-shaped asterism that forms part of Vulpecula, the Fox. Just south of the center of the “M” is another fuzzy patch known as Messier 27. This object won’t resolve in any telescope since it is an expanding cloud of luminous gas surrounding a dying star. It is popularly known as the “Dumbbell Nebula” due to its resemblance to an exercise weight. There are many other interesting things to spot in this wonderful patch of the sky, so spend some time examining it.

You should now have no trouble spotting the bright planet Venus in the evening twilight sky. She pops into view shortly after sunset in the southwest and remains visible until she sets at around 8:00 pm.

Saturn continues to plod eastward above the bright stars of the constellation Scorpius. Look for him above the bright star Antares. You can still get a pretty decent view of him in the telescope during twilight and the early evening.

Mars slides eastward against the stars of Sagittarius. He begins the week above the “spout” of the “Teapot” asterism. By the end of the week he closes in on the star Kaus Borealis, which marks the teapot’s “top”.

Early risers have a chance to see Mercury in morning twilight. The fleet planet reaches his greatest elongation west of the Sun on the morning of the 28th. He will remain visible for the next week or so among the rising stars of Leo, the Lion.

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The Sky This Week, September 20 – 27, 2016 !

The Sky This Week, 2016 September 20 – 27

Things that go “Boom!” in the night.
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NGC 6979, 6992, & 6995, The “Veil Nebula” supernova remnant in Cygnus
(and lots of Milky Way background stars!)
imaged 2016 August 25 from Fishers Island, NY

The Moon wanes in the early morning sky this week, wending her way through the bright stars of the Great Winter Circle that are now prominent as morning twilight breaks. Last Quarter occurs on the 23rd at 5:56 am Eastern Daylight Time. Look for Luna high above the bright figure of Orion on the mornings of the 22nd and 23rd. The Moon ends the week as a thinning crescent near the bright star Regulus in the constellation of Leo, the Lion.

The autumnal equinox falls on the 22nd at 10:21 am EDT. This is the moment when the center of the Sun’s disc appears to cross the celestial equator as seen from a hypothetical point in the Earth’s center. At this instant the Sun will be directly over a point in the Atlantic Ocean a few hundred kilometers north of the northeaster tip of Brazil. Although the term “equinox” literally means “equal night”, the date when we actually experience 12 hours of daylight and darkness falls on the 25th here in Washington. From then until March 17th next year our nights will be longer than our days.

As the Moon moves deeper into the morning sky we once again have the opportunity to see the best of the late summer sky during the evening hours. From dark locations the brightest star clouds of the Milky Way bisect the sky from northeast to southwest at 9:00 pm. The summer constellations Scorpius and Sagittarius are still visible in the southwest along with the Milky Way’s densest star clouds, which lie along our line of sight toward the galactic center. The sheer scale of our home galaxy is something that’s very hard to fathom. Even measuring the distances in terms of light-years begins to boggle the mind when we look at just the bright stars in the Summer Triangle. Altair, the southernmost, is just under 17 light-years distant. Vega, the brightest, is another 10 light-years more distant. Deneb, the northernmost, is well over 100 times farther away than Altair, making it one of the most luminous stars known in the heavens. The thousands of stars that are revealed when you sweep the Milky Way in the area of the Summer Triangle are even more distant. Deneb marks the “tail” of Cygnus, the Swan. Not far from Deneb, at the tip of the Swan’s southeastern wing, is a “deep-sky” target that may be a preview of what Deneb will look like in the distant future. Since it is so luminous and massive, Deneb will go out with a bang as a supernova, spewing energy and pieces of itself far and wide. Between 5000 to 10,000 years ago a similar star exploded where we now see an object known as the Veil Nebula. Today the remnant is an expanding circle of wispy gas tendrils that covers about three degrees of the sky. My favorite views of it are with my small 80mm low-power refractor equipped with a filter to block natural sky glow. Larger telescopes will show details in the faint tendrils, but the wide view gives mute testament to the power of the force that created it.

The dazzling planet Venus is gradually making progress into the evening sky. You can see her low in the west in deepening evening twilight. Her gradual pace will increase over the next few weeks, and in another month she will seem to vault into the darker evening sky.

Saturn is slowly progressing eastward above the stars of Scorpius. You can mark his slow progress relative to the bright star Antares, about six degrees to the ringed planet’s south.

Mars spends the week traversing one of the Milky Way’s biggest star clouds, passing very close to the direction of the galactic center. By the end of the week you’ll find him placed over the “spout” of the “Teapot” asterism in Sagittarius.

The Sky This Week, September 13 – 20, 2016 !

The Sky This Week, 2016 September 13 – 20

The “Coathanger” in the cosmic closet.
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Collinder 399, “The Coathanger” in Vulpecula
imaged 2016 August 25 from Fishers Island, NY

The Moon brightens the overnight hours this week, with Full Moon occurring on the 16th at 3:05 pm Eastern Daylight Time. Since this is the Full Moon that occurs closest to the autumnal equinox it is widely recognized in the Northern Hemisphere as the “Harvest Moon”. Most of our monthly Full Moon names have origins in Native American skylore, but the Harvest Moon is named for an actual phenomenon peculiar to this time of the year. At north temperate latitudes the angle that the Moon’s orbital plane makes with the horizon is very shallow at the point where the Moon rises. This results in the Moon appearing to rise at nearly the same time on successive nights around the time of Full Moon. Here in Washington that interval is about 30 minutes, but as you travel farther north the interval decreases. It’s 20 minutes in northern Scotland and just two minutes in Tromsø, Norway. Venture to Svalbard and you’ll find that the Moon actually rises a few minutes earlier on successive nights! All of this means that back before the use of artificial lighting the rising Moon added a little extra light at the end of the day that farmers could use to bring in a bit more of their crops. A similar phenomenon occurs in the Southern Hemisphere, but it happens in March, when we experience the vernal equinox.

The days continue to shorten as we approach the equinox. With the earlier times of sunset and twilight we can enjoy the pleasures of the sky at increasingly reasonable hours. This week we lose nearly 20 minutes of total daylight, and by this time next week we’ll see longer nights that will last for six months.

The Moon moves through the dim constellations of the autumn sky, thoroughly washing out the faint star patterns of the season, but we still have summer’s bright stars to enjoy. Last week we highlighted a pair of double stars that are easy to locate in small telescopes; this week we’ll help you find a very distinctive asterism that is popularly known as “The Coathanger”. This group of 10 stars lies in the very obscure constellation Vulpecula, The Fox, a grouping invented by the Polish astronomer Johannes Hevelius in the 17th Century. While the constellation is almost impossible for even experienced amateur astronomers to trace out, The Coathanger is quite distinctive and comparatively easy to find in binoculars. It was first described by the Persian astronomer Al Sufi in the year 964 CE and was cataloged as a widely scattered galactic star cluster by the Swedish astronomer Per Collinder in 1931. We now know that it is a chance alignment of stars that form its distinctive shape. You can find it about one-third of the way along a line from the star Altair to the star Vega along the western side of the Summer Triangle. It is easy to find even from urban skies in binoculars, and on moonless nights from dark sky sites you might be able to spot it with the unaided eye.

You should now be able to spot dazzling Venus in deepening evening twilight. As the third-brightest object in the sky she should become visible at or just before sunset in the west. As the sky darkens on the evening of the 18th look at Venus with binoculars as she passes two degrees above the bright star Spica.

Saturn may be found in the southwestern sky as twilight fades. The ringed planet is about six degrees north of the bright star Antares in the constellation Scorpius. You can still get a very nice view of the planet and its enigmatic rings during the early evening hours. As the hazes of summer give way to the clearer skies of autumn you can follow Saturn a bit longer as he settles toward the horizon.

Mars continues to race eastward through the signature constellations of summer. This week he closes in on the “teapot” asterism in Sagittarius. He forms an elongated triangle with Saturn and Antares, and you can watch that triangle become a bit flatter on each successive night.

The Sky This Week, September 6 – 13, 2016 !

The Sky This Week, 2016 September 6 – 13

Sights to see on Moonlit nights.
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Epsilon Lyrae, the “Double-double” star in Lyra
imaged 2015 November 16 from Alexandria, Virginia with a 23.5-cm (9.25-inch) telescope

The Moon waxes in the evening sky this week, skirting the southern horizon as she passes through the dense star clouds of the Milky Way. First Quarter occurs on the 9th at 7:49 am Eastern Daylight Time. Luna forms a line with the planet Saturn and the bright star Antares on the evening of the 8th, presenting a very nice photo opportunity. On the following evening you’ll see her just under 10 degrees northeast of ruddy Mars. After passing above the “Teapot” asterism of Sagittarius the Moon begins the long traverse through the sparse starfields of the rising autumnal constellations.

This is the time of the year when we notice the most rapid change in the length of the day. While a similar situation occurs in the spring, I find it more noticeable now since the days are rapidly getting shorter rather than longer. Length of day decreases by about 2.5 minutes per day from now through the end of October, and I have particularly noticed this at sunset. From my point of view this is a good thing since I can set up my telescope and begin enjoying the night sky at a decent hour!

The waxing Moon washes out the fainter objects of the sky including the star clouds of the summer Milky Way, but there are still a number of treats to entertain the telescope owner. High overhead as twilight ends are the three bright stars that form the asterism known as the Summer Triangle. While the star clusters and nebulae fall victim to the scattered light of the Moon, you can find plenty of interesting stars to look at including some of the best of the sky’s double stars. The prime example for this time of year is the star Albireo, which can be seen from suburban skies almost in the center of the Summer Triangle. Your eyes will see this star as a single object, but virtually any telescope with a magnification of 25X or more will reveal two stars with a wonderful color contrast. I like to call Albireo the “Navy Double” due to the contrasting blue and gold colors. This double is ideally suited for small telescopes as larger apertures tend to wash out the apparent colors. For a more challenging target, center the brightest star in the Summer Triangle, Vega, in your finder scope. Two degrees east of Vega you’ll see a pair of stars that form a very wide double that’s easy to see in binoculars. However, if you point a good 3-inch or larger telescope at this wide pair you’ll see that each component is itself a very close double star, thus making the whole system a quadruple group!

The early evening finds bright Venus gradually climbing higher above the western horizon. You may still be able to catch a fleeting glimpse of Jupiter before 8:00 pm, but you’ll need an exceptionally clear night and a flat open horizon. Venus, however, should be quite easy to find as evening twilight deepens.

The Moon pays a visit to Saturn on the evening of the 8th, when she passes just three degrees above the ringed planet. Saturn is also lined up with the bright star Antares in the constellation Scorpius. If you train your telescope on Saturn as soon as you see him in twilight you can enjoy about an hour’s view before he begins to sink toward the horizon haze.

Mars is moving briskly eastward against the background stars, passing between the brighter stars of Scorpius and the “Teapot” asterism of Sagittarius. He has lost much of his luster from opposition in late May, but his distinctive ruddy tint contrasts nicely with most of the stars in the area. You might still try to catch a glimpse of features on his surface, but his disc is now just 10 arcseconds across so you’ll need a good-sized telescope and very steady air.