Sky Talk October 2011: A Meteor Shower & Two Planets

Orionids Meteor Shower

Orionids Meteor Shower Lights Up the Sky by NASA's Marshall Space Flight Center on Flickr

Skywatchers have an ideal opportunity this month to see one of the most reliable annual displays of “shooting stars” plus the rising of the two brightest planets on opposite horizons. And all this couldn’t happen at a better time, for October typically has not only some of the best skies of the year for viewing but also on average the greatest number of clear nights.

The Orionid Meteor Shower will provide another fine display of celestial fireworks as it reaches peak activity during the evening hours of the 21st into the morning of the 22nd, maximum itself coming sometime before dawn. The Moon will interfere somewhat after midnight, being just two days past Last Quarter. As many as two dozen shooting stars will be seen under good sky conditions (or about one every two minutes).
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Sky Talk September 2011: Spotting Uranus

We’ve discussed all five of the bright naked-eye planets (Mercury, Venus, Mars, Jupiter, and Saturn) in this column frequently over the years but never the outer ones due to their remoteness and dimness. However, this month we go deep into the solar system to find Uranus. Seeing it for the first time is guaranteed to excite you—and bring with it a sense of great accomplishment as an observer.

Let’s begin with a few facts about Uranus itself. It was the first planet ever discovered (the other five having been known since antiquity) by the great astronomer Sir William Herschel with his homemade 6.2-inch reflecting telescope in 1781. (It turns out that Galileo actually saw Uranus much earlier with his primitive little refractor but failed to recognize it as such.) Lying some 1.8 billion miles from the Sun (twice as remote as Saturn), its visibility at such a great distance is partly due to its size—nearly four times the diameter of our Earth.
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Sky Talk August 2011: The Great White Way

New York City’s famed “Great White Way” is not the only thoroughfare to be so named. There’s a far richer and vaster one visible from anywhere on the planet — and it’s found in the Summer sky! We’re referring to the Milky Way, the grand thoroughfare of our home Galaxy. And August is one of the best times of the year to see and experience its magnificence.

Most readers know that we’re living in a vast spiral galaxy called the Milky Way. Some 100,000 light-years across, it’s about 15,000 light-years thick at its central hub and tapers off to as little as 5,000 light-years at its very edge. We’re located about two-thirds of the way out from its center located in the direction of the constellation Sagittarius. On Summer nights we are looking into its thickest and riches regions, while in Winter we’re facing the opposite direction and seeing its thin outer portions — with the result that our Galaxy is much less obvious and striking during that season. (In Spring and Fall, the Milky Way lies along the horizon and we look out at right angles to its long dimension into intergalactic space itself.)
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Sky Talk July 2011: Saturn’s Last Harrah

July offers the final opportunity this year to view the magnificent ringed planet Saturn while still well-placed above the southwestern horizon. And thanks to a famous technique using the Big Dipper as a guide to constellation identification, it’s easier than ever to identify! Plus there’s an added bonus: while a telescope is needed to see the planet’s rings themselves, thanks to its proximity to a prominent star there’s also something here for naked-eye and binocular skywatchers as well.

Right after darkness falls on July evenings, golden Saturn graces the southwestern sky as it nears the end of this year’s apparition. The brighter planets are easy to identify not only because of their prominence in the sky but also because they don’t twinkle like stars do. (See the June 2008 installment of Sky Talk.) But right now there’s also a fascinating way to identify the ringed planet even from the heart of a light-polluted city. It uses the well-known phrase “Follow the arc to Arcturus.” This refers to following the curve of the Big Dipper’s handle downward in the sky to the radiant orange star Arcturus in the constellation Bootes. And continuing that arc also brings you to the bright bluish star Spica in Virgo.
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Sky Talk June 2011: Some Frequently-Asked Questions About the Moon

Although it’s the most readily visible (aside from the Sun itself) and nearest to us of all celestial bodies, the Moon poses puzzling questions to many people — especially those new to the hobby of skywatching. Here are some of the most often asked ones.

Q: Why is the First Quarter Moon as shown on calendars actually half full?
A: The answer here is quite simple. When the Moon appears half-illuminated or half-full, it’s one quarter of the way around its monthly orbit. Likewise, at Last Quarter it’s three quarters of the way around. Yes, simple — but still very confounding terminology indeed!

Q: Why is the Full Moon so much brighter than the First Quarter one?
A: You would expect it to be twice as bright since there’s twice the area reflecting the Sun’s light back down to us. But the Moon when full is actually 12 times brighter! The reason here is not so simple: when at its quarters phases, the Sun is shining almost horizontally at a glancing angle along the surface (especially near the terminator, or dividing line between light and dark), casting very long shadows from surface features ranging from mountains and craters to boulders and even small rocks and pebbles. All those shadowed areas reflect little or no light. But when full, the entire surface of the Moon is bathed in direct sunlight and reflected our way — there are no shadows. This explains why the best times to observe our lovely satellite with binoculars and telescopes are around the quarters when surface relief is strikingly exaggerated by shadows. The Moon when full looks flat and bland — sadly disappointing many new to observing who expect to see jagged mountain ranges and deep craters!

Q: Is there really a dark side to the Moon?
A: Yes – and no! As the Moon orbits the Earth, its entire surface is illuminated by sunlight at one time or another, back as well as front. Known as “complimentary phases,” this means that when the Moon is full to us, its back side is totally dark. When the Moon is new and dark to us, the back is bathed in direct sunlight. In between, the back side experiences the compliment of whatever phase we are seeing. When a crescent to us, it appears gibbous there. At the quarters, both front and back are equally half illuminated.

Q: If the Moon rotates, why do we never see the back side?
A: That’s because the Moon rotates in the same period as it revolves around the Earth. To see this, stand in the middle of a room and have someone face you several feet away. Now, ask them to slowly move around you while always facing in the same direction (which means they are not rotating on their “axis” but only revolving in their “orbit” around you). As you follow their movement, you’ll first see the side of their face and then the back of their head! If the Moon didn’t rotate, we would see the back side just as in this example.

–James Mullaney
Former assistant editor at Sky & Telescope magazine and author of eight books on stargazing.

Sky Talk May 2011: Predawn Planetary Conclave

Those of you who don’t mind rising early in the morning will have a special treat this month as you look toward the eastern sky before dawn. There you’ll find a grouping of four of the major planets — and a spectacular close approach of the two brightest ones!

For a week or so around the morning of May 11th, radiant Venus and slightly fainter Jupiter will grace the eastern sky about an hour before sunrise. On that date itself the two planets will be just half a degree — or a Moon’s width — apart, creating a stunning sight even with the naked-eye. In binoculars the view both then and for several days on either side of the 11th will be truly spectacular! Watch these worlds slowly close together and then move apart over a period of days. For those fortunate enough to own a low-power, wide-field telescope like the Edmund Astroscan Plus, not only will the view be even more of a spectacle with brighter images than binoculars can deliver but at magnifications of just 20x to 30x the little disks of both planets will be visible. (Due to atmospheric turbulence this close to the horizon, don’t expect the images to be sharp. But both objects will be definitely non-stellar.)

Two additional but much less bright and obvious planets lie nearby around this time. As seen during the interval 60 minutes to 30 minutes before sunrise, elusive Mercury will appear between 1.5 and 2 degrees to the lower right of Venus and ruddy Mars will be positioned closer to the horizon some 5 degrees to the east of Jupiter. Seeing them with the unaided eye in the brightening twilight will be a challenge but both should show up well in binoculars. In wide-angle glasses having at least a 6-degree field, it will actually be possible to see all four planets in the same field of view when bunched closest together! In a telescope, Venus and Jupiter can be followed all the way up to (and beyond) sunrise itself. But extreme caution is needed here so that the scope isn’t accidentally turned onto the blazing Sun. As an aside, on the morning of May 1st, a lovely crescent Moon will grace the sky just above Jupiter. And by the 29th, one orbital revolution of the Earth later, the crescent Moon will again be near Jupiter. The sky is indeed a stage on which celestial drama continuously plays out to the delight of skywatchers!

In closing, we must not neglect to mention that magnificent golden Saturn is well placed for viewing during the evening in May. Look for it halfway up the southern sky, to the upper right of the bright bluish star Spica. Note that Saturn doesn’t twinkle — but Spica certainly does! For the reason why, see the Sky Talk column for June 2008. (All the previous installments are archived on the Edmund Scientifics web blog.)

–James Mullaney
Former assistant editor at Sky & Telescope magazine and author of eight books on stargazing.

Sky Talk April 2011: Binoculars for Stargazing

Many books and articles have been written over the years extolling the pleasures of stargazing using binoculars, all based on the premise that “two eyes are better than one.” And indeed they are! Every major class of celestial wonder from the Moon and planets to star clusters, nebulae and galaxies lie within reach of even the humblest glasses. But some are better suited than others for the purpose, and knowing something about their specifications will help in selecting a pair.

Two primary parameters of a binocular are its aperture and its magnification. Those most often used for sky viewing have objective lenses 35mm or 50mm in diameter. Ones much larger in size are difficult to hold steady and require tripod mounting, while mini-binocs really don’t pull in enough light for celestial viewing. The magnification most typically found on stargazing glasses is either 7x or 10x; thus a 7×50 binocular has objectives about 2-inches in diameter and provides 7 power. This famed “night glass” (as it’s often called) is the one typically recommended for stargazing. But while certainly very serviceable, this is not the optimum combination due to an important factor known as the exit pupil.

The exit pupil relates to that of both a binocular and the opening of the human eye. In the former case, the diameter of the bundle of light emerging from a binocular’s eyepieces is found by dividing the aperture by the magnification. Thus a 7×50 glass has exit pupils 7mm in size. In the case of the eye, the exit pupil is often given as 7mm in size if fully dark-adapted. But in reality that’s rarely the case. As people age, the pupil does not open as wide as when they were younger. And any ambient light from various sources of light-pollution (so prevalent in today’s world) around the observer also contracts the pupil. In practice, 5mm diameter exit pupils are more typically found when viewing the night sky. So some of the light of a 7×50 binocular is not able to enter the eye and wasted, while the 5mm pupils provided by a 7×35 or 10×50 glass allow full use of their objectives’ light-gathering power — making either ideal for stargazing.

In actual practice, 10×50 glasses have a decided advantage. Not only do they pick up more light and offer somewhat better resolution due to their larger objectives, but that extra 3x of power is enough to tease more detail from their images. As an example, the satellites of Jupiter (depending on where they are in their orbital dances about the planet) can be glimpsed in a 7×50 binocular but stand out much better in a 10×50.

The subject of binoculars is a vast one and space prohibits covering such matters as wide-angle and extra-wide-angle glasses, porro-prism verses roof-prism designs, and image-stabilized and zoom binoculars. But there is one other feature of binocular stargazing that simply must be mentioned. And that is using both eyes gives an amazing sense of depth perception or 3-dimentionality to what’s seen! Just look at how the Moon appears to be suspended in space — especially during a lunar eclipse, or when it glides across (or occults) a glittering star cluster like the Pleiades. While simply a physiological illusion, it’s nonetheless quite spectacular!

(See Edmund’s binocular category to browse their selection.)

–James Mullaney
Former assistant editor at Sky & Telescope magazine and author of eight books on stargazing.

Sky Talk March 2011: Mercury’s Spring Apparition

Many skywatchers have never seen the elusive innermost planet Mercury due to its rapid orbital motion and the fact that it never strays far from the Sun. (This includes lots of professional astronomers as well!) March offers a great opportunity to spot it at one of its periodic elongations. During the second half of this month, Mercury will be readily visible to the unaided eye in the darkening western sky after sunset.

As Mercury orbits the Sun every 88 days, it periodically appears briefly either east (left) of the Sun in the evening sky or west (right) of it in the morning one. These excursions are known as elongations, and when one occurs in the evening sky of spring it presents the best opportunity to see the planet due to the high inclination of its ecliptic pathway at that time of year with respect to the horizon. On the evening of March 22, Mercury will be 19 degrees east of the setting sun and stand 12 degrees above the western horizon 30 minutes after sunset.

Adding to the fun — and making it even easier than usual to locate the planet this apparition — on the evening of March 16, Mercury passes just 2 degrees north of much brighter Jupiter. A nice sight even to the unaided eye, this pairing will be spectacular as seen in binoculars and wide-field telescopes like the Edmund Astroscan Plus. Viewed in the great little Scientifics 60mm refractor with its 35x eyepiece, Jupiter will show a slightly gibbous disc while the 87x eyepiece will show Mercury like a tiny half-full Moon. While larger scopes will provide a bigger image, Mercury may well not appear as distinct due to the atmospheric turbulence typically found this close to the horizon. After the 22nd, this rapidly-moving “Winged Messenger of the Gods” quickly slides back towards the Sun and drops ever-lower into the sky until disappearing into the sunset by month’s end. Telescopically, its phase changes from half to a narrow crescent.

As a budding stargazer myself over half a century ago, I had heard how difficult Mercury was to see and so made no conscious effort to find it. Legend even had it that among others the famed astronomer Copernicus never saw Mercury! (Recent historical research now casts doubt on this.). But then once evening I saw this obvious “star” shining in the western twilight sky and checking found that it was indeed Mercury! I was quite thrilled — but also embarrassed that I had waited so long to locate it. Suffice it say that this shy and elusive planet requires careful attention to its favorable but brief apparitions to be seen. If you’re among those who have yet to spot it, I can promise you a sense of excitement and accomplishment once you do. And you’ll never have a better opportunity to look for it than this month. Don’t miss it!

–James Mullaney
Former assistant editor at Sky & Telescope magazine and author of eight books on stargazing.

Sky Talk February 2011: Why Buy a Telescope?

The best thing that we’re put here for’s to see;
The strongest thing that’s given us to see with’s
A telescope. Someone in every town
Seems to me owes it to the town to keep one.

I would expand upon these wonderful words from Robert Frost’s famous poem The Star-Splitter to say that someone in every home owes it to the home to keep one! And here’s why.

You may be wondering if you should buy a telescope for yourself and/or your family. Begin by considering that a good telescope is not just another gadget or technical possession but rather a marvelous, magical gift from the Universe to all of us. It’s a “window on creation,” a “time machine,” and a “spaceship of the mind” all rolled into one! And it’s also a superb investment, for a properly-cared-for quality telescope will last a lifetime (and in most cases well beyond) while providing countless memorable hours of enjoyment.

A telescope lets you view nature at its grandest — from the relatively nearby Moon and planets to remote galaxies at the edge of creation. In between these extremes, are comets, and asteroids, and moons of planets, colorful double and multiple stars, pulsating supergiant suns, glorious glittering star clusters, and eerie glowing nebulae where stars are both being born and dying. Looking through the eyepiece of a telescope is very much like peering through the “porthole” of a spaceship at the universe. As one stargazer expressed it, “It’s the next best thing to actually being out there!” So look upon your new telescope as your very own personal “spaceship”!

Another exciting thing about a telescope is that the further out into space you look the further back into the past you’re seeing, since it takes time for light from celestial objects to reach us. That’s why skywatchers are often called “time travelers.” (See the March Sky Talk.) The light you see from the Moon left there less than two seconds ago, and that of the planets anywhere from minutes to hours to reach your eye. But when it comes to the stars and other objects beyond the Solar System you’re looking back into time anywhere from a few years, to millions of years in the case of remote galaxies. As you view objects through your magic glass, it’s fun to reflect upon what was happening in your life or on our planet when their light left out there.

Perhaps the greatest value of a telescope is its most subtle — the cosmic perspective it gives you and others with whom you share the celestial wonders it reveals. Everyone needs a look through a telescope to get their priorities straight, especially in today’s troubled world. We end as we began, with a quote. This one comes from the dedication of the famed 200-inch reflecting telescope on Palomar Mountain: “Adrift in cosmos whose shores he can’t even imagine, man spends his energies fighting with his fellow man over issues which a single look through this telescope would show to be utterly inconsequential.”

–James Mullaney
Former assistant editor at Sky & Telescope magazine and author of eight books on stargazing.

Additional Resources:

  • All About Telescopes – a 200 pg classic book, referred to as “the amateur astronomer’s bible”
  • How to Use Your Telescope – a 36 pg book that includes tips on selecting a telescope, understanding telescope terminology and finding sky objects.

Sky Talk January 2011: Winter’s “Other” Meteor Shower

December’s Geminid meteor shower was overshadowed (or you could say “eclipsed!”) as discussed in last month’s installment by a spectacular total eclipse of the Moon. Also, the light of a first-quarter Moon compromised evening viewing on the night of its peak activity until it set around midnight. But there’s another great annual display of shooting stars to be seen and enjoyed at this time of the year — the Quadrantids. And the Moon will not be in the picture at all!

Among the annual meteor showers that appear in our skies each year, the Quadrantids is right up there with the best of them, including the famed Perseids in August and last month’s Geminids. The shower’s radiant — that point on the sky from which the meteors appear to emanate — lies in the obsolete constellation Quadrans Muralis (thus its unusual name), which is part of Bootes today. For this reason, some observers prefer to call this display the “Bootids” rather than the Quadrantids.

This year’s event occurs on the evening of January 3rd into the morning of the 4th, with peak activity expected sometime between 2:00 a.m. EST and dawn. The Moon itself will be New on the 4th and so dark skies will prevail. If clear, observers can expect to see upwards of 100 or more shooting stars during this time. And although Bootes itself doesn’t fully rise until well after midnight in January, meteors can still be seen shooting from over the northeastern horizon after darkness falls on the 3rd with meteoric activity increasing throughout the night as the constellation climbs higher in the sky. But there’s an additional factor involved here impacting the number of Quadrantids actually seen. During the evening hours we’re on the side of the Earth “facing away” from the direction we’re moving and the meteors are coming, so they have to “catch up” to us. But after midnight our Spaceship Earth is turned into the direction of the radiant, its 66,000 miles-per-hour orbital motion resulting in them slamming into the atmosphere at much higher speeds than during evening hours. This causes not only many more being seen, but those that are to typically appear brighter and more spectacular. So staying up late for a meteor watch (no matter which shower it happens to be) is well worth losing some sleep!

Since meteor observing sessions usually run many hours, reclining on a lawnchair is normally recommended. But on a frigid January night, you may prefere instead to remain standing and keep moving to stay warm! And while this is basically a naked-eye activity in order to canvass as large an area of the sky as possible, using your Edmund binoculars is also encouraged for following the fascinating drifting “smoke” trails or trains left behind by many of the really bright meteors. And for an added thrill, point your glasses at the radiant itself. If you’re patient (and very lucky!), you may suddenly see a point of light growing rapidly in brightness and then going out in a spectacular burst or flash. This is a Quadrantid meteor heading right at you — one meant just for you!

–James Mullaney
Former assistant editor at Sky & Telescope magazine and author of eight books on stargazing.