Archive for August, 2014

The Sky This Week, August 26 – September 2, 2014 !

The Sky This Week, 2014 August 26 – September 2

Fine sights for summer’s last nights.
M4_140705_01small.jpg
Globular Cluster Messier 4 in Scorpius, with the bright star Antares
and the smaller globular cluster NGC 6144

Imaged from Morattico, Virginia, USA
with an 80mm (3.1-inch) f/6 Antares Sentinel refractor and Canon EOS Rebel T2i DSLR

The Moon waxes in the evening sky this week, scudding along the southern reaches of the ecliptic and into the bright starfields of the summer Milky Way.  First Quarter occurs on September 2nd at 7:11 am Eastern daylight Time.  Look for Luna some two degrees east of the bright star Spica low in the southwest about an hour after sunset on the 29th.  Two nights later she forms an attractive grouping with the planets Mars and Saturn.  On the evening of the 1st you’ll find her just over a degree north of the star Graffias, the northernmost of the three stars that form the “head” of Scorpius.

For the first few evenings of the week you’ll have another great opportunity to get to know our home galaxy, the Milky Way.  All week long Luna sets before midnight, and at that time the gauzy glow of our fellow galactic stars will bisect the sky for viewers in dark locations.  Take advantage of the last long weekend of the summer to view this wonderful sight with whatever you have at hand, be it a telescope, binoculars, or your unaided eye.  The naked-eye view inspired much lore among ancient people.  To the ancient Greeks it represented milk spilled from the breasts of the goddess Hera while nursing the infant Heracles.  The Inuit see it as “The Pebbly River”, with the stars of the constellation of Cygnus representing a man in a kayak paddling between the bright “stones”.  Binoculars begin to reveal its true nature as an unbounded sea of stars, especially through the vast star clouds found off the western tip of the “teapot” asterism in the constellation of Sagittarius.  You’ll also see clumps of brightness interspersed among the countless stars; examination of these with small to modest telescopes will show them to be clusters of stars and bright clouds of glowing hydrogen gas fluorescing from the radiation of hot newborn stars in their hearts.  Take note as well of the many dark rifts and patches interspersed among the star clouds.  These are especially prominent from southern hemisphere locales, where they were seen as “anti-constellations” by the ancient Inca people.

Early in the evening spend some time looking at the waxing Moon, especially on the evening of the 31st.  You won’t have to move the telescope very far to enjoy Luna along with Mars and Saturn, which will form a nice grouping in the southwest as evening twilight falls.  Take a moment to examine each object in turn and compare their apparent sizes.  The Moon will show exquisite detail on her battered face, while Mars will be little more than a tiny pink dot, scarcely bigger than the smallest visible lunar craters.  Mars is about twice the size of the Moon, but he’s some 500 times farther away.  Saturn will show a more generous disc, but his special feature is his magnificent system of rings, which should be easily visible in any telescope.  Saturn is over 7.5 times farther away from us than Mars, and the distance across his rings is over 70 percent of the distance from the Earth to the Moon!  They form the flattest and thinnest structure in the solar system with a thickness of one or two hundred meters.

As the Sun steadily rises later each morning you don’t have to get up at “oh-dark-thirty” to admire the bright planets of the morning sky, Venus and Jupiter.  If you’re up by 6:00 am you should be able to spot them in the eastern sky despite the glow of twilight.  If you don’t mind rising a bit earlier, you’ll also see the rising stars of the Great Winter Circle make their entrance to the sky.  It won’t be very long before the glow of the summer Milky Way will be replaced by the fixed glimmers of these bright stars.

Advertisements

The Sky This Week, August 19 – 26, 2014 !

The Sky This Week, 2014 August 19 – 26

Planets in the morning, planets in the evening…
M22_140705_01small.jpg
Globular star cluster Messier 22 in Sagittarius
Imaged with an 80mm (3.1-inch) f/6 Antares Sentinel refractor
and a Canon EOS Rebel T2i DSLR
from near Morattico, Virginia USA

The Moon wanes in the early morning sky this week, wending her way through the rising stars of winter as she heads toward New Moon, which will occur on the 25th at 10:13 am Eastern Daylight Time.  Luna passes above the bright stars of Orion as the week opens, then drifts through southern Gemini before drawing a bead on Venus and Jupiter in the gathering morning twilight by the week’s end.  You’ll have a nice photo opportunity to catch the Moon with Venus and Jupiter half an hour before sunrise on the 23rd.

The bright Moon did a pretty effective job of limiting my observations of the peak of the Perseid meteor shower last week, but the shower is still producing a handful of bright, swift meteors for those of you who might be out and about under dark skies in the wee hours.  There is also an uptick in background “sporadic” meteor rates as well as several minor meteor showers that come and go in late August and September, so you chances of spotting a few are better than average.  In addition, the absence of the Moon means that the summer Milky Way is visible from dark-sky locations, cutting a ghostly luminous swath that bisects the sky by around 11:00 pm.  I had a very enjoyable night in late July picking out star clusters and nebulae with my telescope from dark New England skies before the Moon became my nemesis.

As we head toward late summer our selection of planets is limited to early evening and early morning hours.  Shortly after sunset you can catch the glimmers of ruddy Mars and yellowish Saturn in the southwestern sky.  Over the past few weeks the red planet has covered quite a bit of celestial real estate to home in on Saturn, and this week he’ll pass the ringed planet on his eastward trek around the ecliptic.  If you have a good dark site or access to binoculars you can watch mars from night to night as he first passes just over a degree south of the star Zubenelgenubi on the evenings of the 20th through the 22nd.  After that he’ll scoot just over three degrees south of Saturn.  Binoculars should show an interesting color contrast between the white glow of the star and the warmer tints of the two planets.  Binoculars will also show that Zubenelgenubi is a wide double star.  Small telescopes will further enhance the differences between the two planets: Mars is a small rocky world that will show a tiny pink-hued disc, while Saturn’s orb will be twice as big and surrounded by the planet’s distinctive rings.  While they appear close together in the sky, keep in mind that Saturn is over 800 million miles (1.31 billion kilometers) farther away from us than is Mars!

In addition to the rising constellations of winter, early risers can catch the other two bright planets in gathering morning twilight.  Venus and Jupiter have just had a very close conjunction over the past few mornings (unfortunately obscured by clouds for me), and even though Venus is drawing away from Old Jove the pair will still be prominent above the eastern horizon for the rest of the week.  Jupiter is gradually rising a little earlier each day while Venus rises a tad later, but they form an attractive pair that will be further enhanced by the slender crescent Moon on the morning of the 23rd.  Venus has been with us in the morning sky since the beginning of the year, but she is now beginning her final plunge to conjunction with the Sun in mid-October.  By that time Jupiter will be rising at around midnight, ready to start dazzling us in the evening sky with the start of the new year.

The Sky This Week, July 23 – August 19, 2014 !

The Sky This Week, 2014 July 23 – August 19

M8_140705_04small.jpg
Messier 8, the “Lagoon Nebula” in Sagittarius
Imaged from near Morattico, Virginia, 2014 July 5
with an 80mm (3.1-inch) f/6 Antares Sentinel refractor and a Canon EOS Rebel T2i DSLR

“The Sky This Week” will be taking a few weeks’ vacation away from the hustle and bustle of Washington, DC.  Here are a few things to note during our absence.

The Moon will be new on July 26th at 6:42 pm Eastern Daylight Time.  First Quarter falls on August 6th at 8:50 pm.  The Full Sturgeon Moon occurs on the 10th at 2:09 pm EDT, within hours of the closest lunar perigee for the year.  Yes, at this time Luna will be about 12% bigger and 30% brighter than it was in January, when Full Moon occurred near lunar apogee, but you’d be hard-pressed to notice much of a difference between now and then.  This is being touted as yet another “Super-Moon” by popular and social media for reasons that I still can’t fathom, but for the most part it is a “non-event” that is almost purely hype.  Last Quarter will occur on the 17th at 8:26 am EDT.  Look for nice groupings of the Moon, Mars, and Saturn on the evenings of August 2nd, 3rd, and 4th.

The usual highlight of August is the annual Perseids Meteor shower, which are active throughout the month but peak on the night of August 12/13.  This is one of the year’s most reliable displays, with hourly rates of from 50 – 75 per hour for a single observer at a dark site.  Unfortunately this year’s shower coincides with a nearly-full Moon which will wipe out all but the brightest shower members.  Fortunately the Perseids are known for having numerous bright “fireballs”, so you may still be able to catch a few in the hours after midnight.  Look toward the northeastern sky for your best chance at spotting one.

In the early evening sky ruddy Mars moves over 15 degrees during the time we’re away.  By August 19th he’s cozying up to Saturn and the third-magnitude star Zubenelgenubi.  In the meantime Saturn plods just half a degree eastward as he resumes direct motion against the stars.

For me the summer highlight is the magnificent summertime Milky Way, which is now ideally placed for late-night enjoyment.  I’ll have a few good nights to view it from a dark-sky site before the waxing Moon washes out its delicate structure, and I’ll have a few days with a waning Moon to view it before I return home.  On those nights when I can enjoy it I hope to spend many quiet hours exploring its many interesting features, and hopefully many of you will be able to do the same.  Despite its subtle, gauzy glow it is one of the most amazing sights for exploration with a small telescope.

Early risers can watch the rising of the bright winter constellations in the gathering morning twilight over the course of the next several weeks.  If you have a good ocean horizon that faces to the east you can repeat an observation that was one of the first absolute time markers for the ancients, the “heliacal rising” of the star Sirius.  This phenomenon, which now occurs for our latitude during the second week of August, occurs when the brightest star in the night sky can be seen cresting the horizon just before sunrise.  To the ancient Egyptians this event marked the beginning of their secular year and was the harbinger of the annual flooding of the Nile.  Due to the precession of the Earth’s rotational axis this event occurred for them about a month earlier than it does today.  The Romans adopted this yearly marker when they conquered Egypt.  Since Sirius was the brightest star in the constellation of Canis Major, the Large Dog, they called the days subsequent to the heliacal rising the “Dies Canicularum” or “Dog Days”, a tradition that seems especially true in Washington at this time of the year!

We hope that your next few weeks are peaceful and enjoyable and that you have ample chances to go out and enjoy the splendors of the nighttime sky.  We’ll be back in a few weeks, but if we see something interesting while we’re away we’ll share it on the USNO’s Facebook page.