Archive for May, 2014

The Sky This Week : May 27 – June 3, 2014 !

The Sky This Week, 2014 May 27 – June 3

The meteor shower was a bust, but other than that…
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Scorpius and the Great Sagittarius Star Cloud
imaged near Morattico, Virginia, 2014 May 24, ~03:15 EDT
while waiting for a few Camelopardalid meteors

The Moon returns to the evening sky this week, working her way through the last of winter’s constellations before coursing through the stars of spring.  Look for Luna to the south of bright Jupiter on the evening of the 31st.  She finishes the week by closing in on the bright star Regulus in Leo, the Lion.

The much-anticipated “Camelopardalids” meteor shower that we discussed last week turned out to be something of a bust for most skywatchers, especially those in the city.  I was able to find ideal conditions along the Northern Neck of Virginia, and over the course of about two and a half hours of observing in the wee hours counted half a dozen definite shower members, two or three probable members, and several sporadic meteors.  The half-dozen shower members were all quite bright, relatively slow, and lasted for several seconds, but they all would have probably been lost in the glow of urban street lights.  Still, this was the first time this shower has been recorded in all of history, so it was fun to be a part of the event.  Despite the shower’s poor showing, the view of the summer Milky Way was worth the loss of a few hours’ sleep. 

You can still catch a glimpse of the elusive planet Mercury in the evening sky this week, but you’ll probably need binoculars and a bit of luck with the weather to catch him.  He passed his greatest elongation east of the Sun on the 25th, but this week he begins to plunge back toward Old Sol and his brightness dims considerably.  He will linger just over 10 degrees above the west-northwest horizon about half an hour after sunset, but he’ll lose almost a full magnitude in brightness.  On the evening of the 30th the thin crescent Moon will be about 7 degrees to the south of Mercury, which will be shining at magnitude 1.2. 

The Moon wastes little time catching up to Jupiter in the evening sky.  On the evening of the 31st he’ll be about seven degrees above the lunar crescent, but unlike Mercury he will be quite easy to spot.  Old Jove is slowly drifting eastward against the background stars in a desperate but ill-fated attempt to outrun the encroaching Sun.  You can watch his progress through binoculars as he slowly adds another degree of separation from the nearby 3rd-magnitude star Wasat.  You may still be able to catch a good glimpse of his dark cloud belts and Galilean moons if you point a telescope his way during evening twilight, but he quickly settles into turbulent air as the sky darkens toward full darkness.

Ruddy Mars is also racing against the advancing Sun, and he will ultimately hold his own in the evening sky throughout the rest of the year.  However, we are rapidly losing time to spy detail on his distant face with modest telescopes as Earth pulls away from him.  He is now almost a full magnitude fainter than he was at opposition in early April, and this week his telescopic disc continues to shrink, dropping below 12 arcseconds.  Fortunately some of his most prominent albedo features will face our way for the next two weeks, so owners of modest telescopes may still be able to glimpse some of these features in moments of steady air.

Fortunately Saturn is bringing up the rear of the evening planetary parade, and he will be a welcome sight for those of you who have been squinting at Mars for an hour.  The ringed planet should be easy to spot by 10:00 pm in the southeastern sky, framed by the two second-magnitude lead stars of the constellation Libra, Zubenelgenubi and Zubeneschamali.  Careful observers may be able to note the slow retrograde motion of Saturn with respect to the former star; over the course of the week he’ll move about the apparent diameter of the Moon closer to Zubenelgenubi.  Through the telescope he will continue to do what he does best, eliciting wonder from people who see his mysterious rings.

You’ll still find Venus in the glow of morning twilight.  You’ll find her due east just before sunrise along with the rising stars of Aries, the Ram, one of the signature constellations of the autumn sky.

Mark your calendars for the evening of Friday, June 6th.  That’s the scheduled night for this year’s edition of the annual “Astronomy Festival on the National Mall”.  Astronomers from many different institutions, including yours truly, will be on hand to answer questions and show off celestial objects through telescopes.  More information will be posted next week.

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The Sky This Week , May 20 – 27, 2014

The Sky This Week, 2014 May 20 – 27

Saturn in prime-time, and a possible new (and spectacular!) meteor shower.
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Saturn, 2014 May 19, 02:39 UT

The Moon wends her way through the dim autumnal constellations this week, greeting early risers as she wanes from Last Quarter to a slender crescent in the pre-dawn sky.  New Moon occurs on the 28th at 2:40 pm Eastern Daylight Time.  Luna doesn’t encounter much in the way of bright company until the 25th, when she may be found just over 2 degrees west of dazzling Venus in brightening morning twilight.

The waning crescent Moon shouldn’t be a factor for skywatchers in most of North America on the night of the 23rd and the early morning of the 24th.  With a little luck and clear skies we should have a ringside seat to see a brand-new meteor shower during this time.  We can thank a small, dim comet known as 209P/LINEAR for this potentially spectacular show which should peak somewhere between 2:00 and 4:00 am on Saturday morning here in the Washington area.  The comet was discovered in 2004 in a roughly 5 year orbit that takes it out to the vicinity of Jupiter, whose large gravity field controls the comet’s destiny.  The comet itself will pass about 5 million miles from Earth on the 29th, but on Saturday morning we should plow headlong into a stream of dust that sputtered off the comet’s nucleus at an unseen return from some 200 years ago.  Various meteor experts predict that a single observer at a dark-sky site should see anywhere from 30 to 200 meteors per hour during the peak of activity.  Unlike the more famous Perseids or Leonids, these “shooting stars” will be quite slow, actually looking like a star falling from the sky.  The shower radiant will be in the obscure northern constellation of Camelopardalis, the Giraffe, to the left of Polaris, the North Star.  The best way to enjoy the show is to set up a lawn chair with your feet pointing to the northwest horizon, bundle up against the cool night air, grab some coffee, and look up.  If the predictions hold you could be in for quite a treat.

For those of you who like to stargaze in the early evening, the elusive planet Mercury is now putting on his best evening show of the year.  You’ll find the fleet planet about 10 degrees above the west-northwest horizon at around 9:15 pm.  By this time the sky should be dark enough to see him with the naked eye, but binoculars are often a big help when trying to locate him the first time.  He reaches his greatest elongation from the Sun on the 25th.

Jupiter dominates the twilight and early evening hours in the western sky.   You’ll have no trouble spotting the giant planet as the sky darkens, and as soon as he becomes visible you should get him centered in the telescope eyepiece.  Jupiter will sink fairly quickly toward the horizon and its attendant turbulent air, but you still have a bit of time to look for his four bright Galilean moons and atmospheric cloud belts.  As the sky darkens, look above Jupiter for the twin stars of Gemini, Castor and Pollux.  Point your telescope at Castor (right-most of the two) and you’ll be rewarded with a view of what appears to be a very nice double star.  In reality, the Castor system consists of at least six stars, but we can only see two without spectroscopic equipment. 

Mars now crosses the meridian at the end of evening twilight.  His ruddy glimmer is still quite eye-catching, and this is further embellished by the view in a small telescope.  Modest-sized instruments will show a small polar ice cap along the limb of his disc, and when the air is steady you may be able to discern some of his dark surface features.  The red planet now shows a distinct gibbous phase which should be easy to see in any telescope.

Saturn is now enjoying the prime-time portion of the current apparition.  There is no mistaking this far-flung world for any other object in the sky.  His distinctive ring system may be seen in a steadily-held pair of binoculars, and every increase in the size of your optics will reveal more detail in these mysterious appendages.  A three-inch scope should reveal the dark gap in the rings known as Cassini’s Division, and in six-inch or larger instruments you should be able to see the globe of the planet peeking through the division where the rings cross the disc’s southern hemisphere.  You should also notice the subtle color changes in the rings on either side of this 5000 kilometer gap.

Venus continues to linger in the morning twilight sky, staying just ahead of the Sun as she moves northward along the ecliptic.  You’ll have a great photo opportunity before sunrise on the 25th, when the dazzling planet is close to the waning crescent Moon.

The Sky This Week : May 13 – 20, 2014 !

The Sky This Week, 2014 May 13 – 20

Planets on the move.
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Cylindrical projection map of Mars
based on observations made April – May 2014

The Moon begins the week in her Full phase, then wanes as she moves into the morning sky.  Last Quarter occurs on the 21st at 8:59 am Eastern Daylight Time.  She starts the week off near golden Saturn, then works her way along the southern reaches of the ecliptic through the heart of the southern summer constellations before venturing into the dim realm of the stars of autumn.

As Luna heads for the morning sky, we still have an opportunity to catch four of the five planets known to the ancients before a reasonable bed-time.  You can still see Venus before dawn, and get a full night’s sleep to boot.

Fleet Mercury is first in view, steadily climbing in the western sky during evening twilight.  You should start looking for him at about 9:00 pm, when he’ll be about 10 degrees above the horizon and about 10 degrees north of due west.  Each succeeding night will find him a bit higher as he climbs toward his greatest elongation on the 25th.  Binoculars are a big help when you first try looking for him, but once you’ve spotted the elusive planet you should be able to easily see him with the naked eye.  By the end of the week he passes between the stars that form the “horns” of Taurus, the Bull.  Mercury will be just three degrees south of the star on the 20th and 21st.

Jupiter will probably grab your attention long before Mercury does, since he becomes visible high in the west within a few minutes of sunset.  If you want to still get a decent look at him in the telescope, the twilight hours will be your best bet.  By 9:30 pm Old Jove is just 30 degrees above the horizon, and the combination of radiant heat from the ground and turbulence in the atmosphere will make gleaning fine details on his distant disc very difficult.  However, his Galilean moons are still easily seen in any telescope, and you can watch their comings and goings until just a few minutes before the planet sets at around midnight. 

Mars has lost a little of his ruddy luster since his opposition a month ago, but the red planet is still easy to spot in the evening sky as he moves to the meridian by 10:00 pm.  He reaches the second stationary point of the current apparition on the 21st, resuming direct eastward motion against the stars afterward.  His disc, now just a tad over 13 arcseconds across, remains a visual observer’s challenge, but a six-inch or larger telescope and moments of steady air will reveal his bright north polar ice cap and subtle dark albedo features.  One of the most prominent of these, dubbed Solis Lacus by early visual observers, will be in view by the end of the week.

I had my first good look at Saturn last week as the ringed planet finally cleared the roof of my neighbor’s house at a decent hour.  As usual, that view was still as wonderful as the first one that I can remember.  For the past several years the planet’s rings have been slowly opening toward our line of sight.  They are now generously tipped in our direction, and despite the planet’s southerly declination still show a wealth of structure in moments of steady seeing.  Saturn is probably the only sight that urban astronomers can easily see that conjures up the concept that space is a very strange place.  On a clear night there is something quite special about seeing this distant world, wrapped in its mysterious rings, surrounded by the tiny pinpoints of its many moons.

As mentioned earlier, you can pack up the telescope and be in bed by 11:00 pm with four planets under your belt.  If you’re up by 5:00 am you can add Venus to your collection.  The dazzling planet is now just about due east in the gathering morning twilight, and you should be able to keep her in view until the Sun crests the horizon.  If you happen to point a telescope her way she will resemble a small gibbous Moon as she wallows in the turbulent air.

The Sky This Week : May 6 – 13, 2014 !

The Sky This Week, 2014 May 6 – 13
Five planets in one night.
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The Moon and Mercury, 2014 February 1
Imaged from Alexandria, Virginia

The Moon brightens the evening sky this week, waxing from First Quarter to Full as she passes through the constellations of spring. Full Moon occurs on the 14th at 3:16 pm Eastern Daylight Time. May’s Full Moon is variously known as the Grass Moon, Milk Moon, Flower Moon, or Corn Planting Moon. Luna passes six degrees south of the bright star Regulus in Leo, the Lion on the evening of the 7th. On the 10th and the 11th you’ll find her in the company of ruddy Mars; on the latter night she is located a few degrees west of the bright star Spica as well. By the week’s end she is closing in on yellow-hued Saturn low in the southeastern sky as twilight ends. If you look at her with binoculars on that night you’ll find her less than half a degree north of the second-magnitude star Zubenelgenubi, the brightest star in the constellation of Libra, the scales.

This is one of those rare weeks when you have an opportunity to see all of the planets known to the ancients during the course of the night. Four of them are well-placed for viewing before midnight, while the fifth can be seen just before sunrise. The evening show begins with the appearance of Mercury, which owns the dubious distinction of being the most difficult of these worlds to observe. Fortunately for us the fleet planet is beginning his best evening apparition of the year, and he should be fairly easy to spot from about May 10th until early June. Mercury seems to leap up from the horizon this week as evening twilight deepens. If you have a flat western horizon start looking for him on the 10th at around 9:00 pm. He’ll be about five degrees above the horizon that evening, glowing at a respectable -1 magnitude. He gains about a degree per day in altitude with each successive evening, becoming more prominent above the horizon haze. He’ll continue to climb until he reaches elongation on the 25th, so you should have plenty of time to get him in your sights. Binoculars will often help to locate him in brighter twilight, but once you’ve found him he should be an easy naked-eye target.

The next planet you’ll encounter is giant Jupiter, who pops out of evening twilight in the western sky shortly after sunset. Old Jove remains the brightest planet in the evening sky so you should have no trouble identifying him. A quick view with binoculars should reveal various combinations of his four bright Galilean moons. Jupiter has been providing us with some great telescopic views since the beginning of the year, but he’s now beginning to sink into the turbulence of the atmosphere above the horizon. His apparent disc is now about three-quarters the size that it was at opposition in January, so it’s becoming increasingly difficult to spot fine structure in his atmospheric cloud belts.

As Jupiter heels over toward the west, Mars makes his move toward the meridian. This planet is also pretty hard to miss thanks to his distinct rosy hue. By 10:30 he’s nearing his highest altitude of the evening, beckoning modest telescope owners for a look. While his apparent disc is less than half the size of Jupiter’s, he has one distinction that sets him apart from all of the other easily observable planets. When you eke out details in moments of good seeing, you’re looking at a solid surface rather than the tops of dense atmospheres. This has tantalized observers since the invention of the telescope and is still a source of fascination today. You should be able to see the small white north polar ice cap in moments of steady air, and whitish patches near the center of the disc are water-ice clouds forming around a large volcano in a region called Elysium.

Saturn reaches opposition on May 10th, rising at sunset and remaining in the sky until dawn. Saturn can be a welcome respite for those who’ve spent long hours trying to view small details on Mars. Yes, the details on Saturn’s globe are quite subtle, but the overall appearance of the planet is anything but. This planet is probably the most unusual sight a novice can see through a telescope, and the first view that someone has of Saturn spinning inside its rings invariably brings reactions of incredulity. We now know that the rings are composed of countless icy bodies ranging in size from dust grains to hundreds of meters across, each in an independent orbit around the planet itself. Saturn will be spending the rest of the spring and early summer with us, so you’ll have plenty of chances to get a good view.

Our last planet has also been with us in the morning sky since the beginning of the year. Bright Venus is usually very well-placed in our skies, but this year she’s being shy for northern hemisphere observers. You’ll find her in the gathering morning twilight just above the eastern horizon.

The Sky This Week : April 29 – May 6, 2014 !

The Sky This Week, 2014 April 29 – May 6
Don’t overlook the Moon!
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The Moon Before First Quarter

The Moon returns to the evening sky this week, quickly passing through the setting stars of the Great Winter Circle before moving into springtime’s constellations. First Quarter occurs on May 6th at 11:15 pm Eastern Daylight Time. She shares the evening spotlight with Jupiter on the evenings of the 3rd and 4th.

This is another great week to get to know our nearest celestial neighbor. She is very well-placed for telescopic examination of her crescent phases, and you can watch the line between her daylight and night hemispheres, the terminator, slowly advance across her battered landscape. During the first few days of each lunation her visage is dominated by a number of the vast lava plains first identified by early observers as “seas”. These great expanses of relatively smooth terrain are pock-marked with many small to medium-sized craters from impacting meteoroids. Although they look small in the telescope, typical bowl-shaped craters in these plains are tens of miles across, dwarfing the famous Meteor Crater that’s not far from our Flagstaff, Arizona observing station. When the sun angle is low you can also see the meandering, frozen ridges of solidified lava known as “wrinkle ridges”, which look like static waves in some frozen arctic ocean. By the time the First Quarter phase rolls around, the terminator reveals the much older and battered terrain of the lunar highlands. Here the craters are generally much larger and more densely packed together, mute testimony to the ferocious assault of infalling planetessimals that formed the proto-planets some four billion years ago. Almost all of these features have names, and if you spend a few nights at the eyepiece with a good lunar atlas you will get to know them as landmarks for subsequent telescopic tours. Even though the same features are revealed month after month as Luna goes through her phases, observing these familiar places is always a bit different from night to night as subtle changes in the lighting highlights hidden detail that you may not have seen before. It is often said that the Moon is “looked over, then overlooked” by new telescope owners, but she is still the only other world in our solar system that we can see in great detail. She always gets a number of looks from my telescope each passing month.

Looking at the Moon may set you up for some disappointment when you turn your attention to the bright planets that inhabit the evening sky. Jupiter is the next logical target since you’ll want to catch him before he gets too low for detailed viewing. Jupiter’s apparent disc is about the size of an average lunar crater, but if you spend a few minutes and wait for moments of steady air you can begin to detect some features on his cream-colored face. Almost any telescope will show his light brown equatorial cloud belts, and if you have a scope that’s four inches or more in aperture you should be able to spot some structure in these bands. Any telescope will show the planet’s four bright Galilean moons, and a good six-inch scope will resolve their tiny discs. For a sense of scale, the two innermost of these worlds, Io and Europa, are comparable to our fair Luna in size.

You’ll now find Mars in the southeastern sky as evening twilight fades. The red planet is quite conspicuous due to his brightness and distinctive tint, which contrasts nicely with the bright star Spica some 10 degrees away. Mars’ apparent disc is less than half the size of Jupiter’s, but a steady four-inch telescope should reveal some details on that disc. Early this week the planet’s most prominent albedo feature, the Syrtis Major, is well placed for viewing between 9:00 pm and midnight. This feature looks a bit like the Indian subcontinent against the pink backdrop of martian dessert. You will also probably see a large whitish area bordering the Syrtis that looks like a polar cap. In reality this is a huge impact basin called Hellas, and the white stuff is formed by clouds trapped within the basin’s walls. The actual polar cap is on the limb opposite the “pointy” end of Syrtis Major and marks the planet’s north pole.

Saturn becomes visible in the southeast by the end of evening twilight. This far-flung world is located in the obscure constellation of Libra, the scales and outshines all of that constellation’s bright stars. Saturn will reach opposition on May 10th, so we’re now right in the middle of its prime observing season. If you get eyestrain trying to eke out detail on Mars, swing the scope over to Saturn before retiring. You’ll be treated to one of the most exotic sights in all of Nature, the gaseous orb of the planet spinning inside its icy rings.

Early risers can take in the view of Venus in the southeastern sky as morning twilight brightens the horizon. The planet is steadily marching through the rising constellations of autumn, which are quickly overwhelmed by the first faint rays of dawn. Venus, however, will blaze away until the Sun comes up, and if you know just where to look you can follow her in broad daylight for a time.

Next week the planet Mercury becomes visible in the evening sky, so we’ll have a chance to glimpse all of the planets known to the ancients.