Sky Talk March 2012: Night Sky’s Six Brightest Objects at Once!

As March opens, skywatchers will be treated to the rare opportunity of seeing Mercury, Venus, Jupiter, Sirius, the Moon and Mars all above the horizon at the same time after sunset. And while each of these objects is itself a wonderful telescopic sight, this event is best enjoyed using the unaided eye alone to sweep across this celestial panorama.

Stepping outdoors about 30 to 45 minutes after sunset the first three evenings this month, an amazing display of the sky’s six brightest objects will be found spread out from the southwestern horizon to the eastern one. Lowest in the west is the shy and elusive planet Mercury (which may require your Edmund binoculars to be well seen, depending on how bright the twilight sky is at the time you look). It’s followed higher up (and eastward) by dazzling Venus — which, as the third brightest object in the entire heavens after the Sun and Moon, can’t possibly be missed! Higher yet is Jupiter (which, as described below, will come very close to Venus at mid-month). Next is the brilliant blue-white star Sirius in the south, brightest of all the stars in the heavens. Roughly above it will be the gibbous Moon and, finally, further to its east fiery Mars. Wow — what a spectacular celestial lineup this will be!

As the month progresses, Mercury will quickly drop lower in the west and disappear into the sunset while the Moon will continue its never-ending eastward journey around the sky. Interestingly, although Mercury will have been lost to sight, Saturn rises in the east later in the evening to take its place — still leaving six of the sky’s luminaries above the horizon at the same time! But there’s more happening this month, involving the two brightest of the planets. Keeping an eye on Venus and Jupiter from night-to-night, you’ll notice the two worlds drawing closer together. On the evenings of March 12th and 13th, they will be just 3 degrees apart, both easily fitting into the field of view of any binocular. And here telescope owners will want to examine each of these objects separately, just 25x being enough magnification to show their dissimilar disks (and Jupiter’s four bright Galilean satellites).

While the two planets appear close together in the sky at this time, in reality they are quite far apart in space — Venus being about 75,000,000 miles from us and Jupiter 525,000,000. (But compared to Sirius, they are right in our backyard. Among the closest stars, it lies over 50 trillion miles from our Solar System!) These lovely worlds afterward slowly separate, ending up some 15 degrees apart by the end of March and with Venus moving higher in the sky on its way to a spectacular conjunction next month with the famed Pleiades Star Cluster (be sure to check out the April Sky Talk about this event).

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

Sky Talk February 2012: Crescent Moon Visits Venus & Jupiter

Mark the evenings of February 25th and 26th on your calendar. If clear, head out after sunset and look toward the western sky. There you will see two of the brightest objects in the night sky—the planets Venus and Jupiter—being “sideswiped” by the brightest of all nighttime objects, the Moon. The spectacle will be readily visible with the unaided eye, and a truly fascinating sight in binoculars.

Other than a meteor shower, the occasional bright comet, or an eclipse, most people think of the sky as static and unchanging. But nothing could be further from the truth—everything in the sky is constantly in motion! The most obvious example of this is the slow movement of the stars from east to west due to the daily rotation of the Earth on its axis. And the very word “planet” comes from the Greek for “wanderers,” indicating that ancient skywatchers recognized that these bodies moved in relation to the stars themselves.

Venus and Jupiter are currently slowly drawing closer together each week as they prepare to meet in a spectacular celestial embrace (or “conjunction”) in March that will be covered in the next issue of Sky Talk. Most of this movement is due to Venus rapidly gaining altitude in the sky and catching up to Jupiter. On the evening of February 25th, Venus will be joined by the beautiful crescent Moon to its upper right. The following evening, the Moon will have moved upward (actually eastward in the sky) and to the right of Jupiter. The view on either of these evenings through your Edmund binoculars will be quite a sight! And should you have a rich-field telescope with a very wide field of view such as the Scientifics’ Astroscan Plus, both Moon and planet may actually fit in the same eyepiece field for a brief time. Whether using binoculars or telescope, be sure to notice the “Earthshine” illuminating the dark portion of the Moon itself. As discussed in past Sky Talk installments, this is sunlight from the Pacific Ocean where it’s still daylight reflecting back onto our satellite. (This glow is also visible to the unaided eye.)

Through a telescope at a magnification of about 30x, Venus will appear just over half-full (or slightly gibbous) during February. The best time to observe it is during twilight when the bright sky background cuts down on the glare from this radiant orb, which overpowers the planet in a dark sky. At the same magnification, Jupiter’s four bright Galilean satellites will be visible in constantly changing positions as they orbit the giant planet. And after it passes Venus and Jupiter, the Moon moves out of the scene in its never-ending eastward journey, clipping along at an orbital velocity of over 2,200 miles per hour. Truly, the heavenly canopy above us is not static but rather an ever-changing (and absolutely free) skyshow!

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

Sky Talk January 2012: The Astronomy of 2012: Fact vs. Fiction

With so much hype and misinformation concerning the year 2012 currently in books, on television, in movies, and the subject of various conferences, this month’s column is designed to hopefully bring some science and common sense to this sensational topic as we begin the much-heralded year marking the end of the fabled Mayan calendar.

Let’s begin by asking just what’s so special about the “Galactic Alignment” we’re hearing so much about? Nothing! Every year on or about December 21st the Sun “aligns” with the center of our Milky Way Galaxy at the Winter Solstice. Supposedly it’s going to be more closely lined up than in recorded history. Yet, as is well-known to astronomers, it was actually closer to the center in 1998! (This stems from the subtleties of the galactic and ecliptic coordinate systems, which space prohibits covering here.) But in any case, the Sun will still be several degrees from being exactly over the galactic center in 2012. Even more significant is the fact that the alignment is only an apparent one—the actual center of our Galaxy is 26,000 light-years away (that’s 26,000 x 6,000,000,000,000 miles!). There can be no sudden drastic influx of radiation precisely at midnight on the 21st from the nucleus’ black hole devastating the Earth’s population, as is being claimed by some—nor will we be sucked in as others fear!

There’s also the “Great Dark Rift” that’s being talked a lot about as a kind of “roadway” into the center of the Galaxy. What’s being referred to is one of the many areas of dark obscuring clouds of gas and dust that line the spiral arms of the Galaxy. And there are at least six of these arms, with our Solar System here in the galactic boondocks being imbedded in an outer one. The dark rift seen in the summer and fall Milky Way in our local arm does not lead to the center of the Galaxy!

The thing that really puzzles me the most about the 2012 fiasco, as an astronomer, concerns the planet Venus. As the third brightest object in the sky after the Sun and Moon, this radiant orb held great importance to the Maya. And yet a very rare and spectacular event involving Venus that will occur during 2012 has been largely ignored by 2012 writers and speakers. On the late afternoon of June 5th, Venus will transit the face of Sun—an event that can be seen even with the unaided eye! (The transit will be featured in the June installment of Sky Talk along with tips on safely viewing it.) This happens in pairs separated by 8 years—the last having occurred in 2004—and then not again for more than a century (2117 being the next one)! Surely the Maya attached great significance to this spectacle. Should we not also?

I would like to conclude on a positive note about 2012. Raising public consciousness of the universe and our place in it as citizens of our home Galaxy is definitely happening because of all the attention being focused on 2012. This in turn leads to that “cosmic perspective” that my late friend and mentor Carl Sagan always talked about and felt was crucial to our survival as a species. In that sense, this year of 2012 is indeed significant.

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

Sky Talk November 2011: Jupiter (and Its Belt) Returns!

Brilliant Jupiter is now well-placed in the eastern evening sky and once again has a surprise in store for telescope users. As reported here last year, the giant planet lost one of its two main equatorial belts (while its famed Great Red Spot increased in prominence after being nearly invisible for some time). But the belt is back! And adding to the show are Jupiter’s four bright moons waltzing around the planet from night-to-night. All you need to see the action for yourself is a clear sky and a good telescope.
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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.