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Venus joins the Moon

February 2012: Although distant Neptune hides in the Sun's glare throughout February, the solar system's six other planets brighten the nighttime stage.
Moon-and-Venus finder chart
The Moon and Venus form a stunning pair after sunset February 25. At closest approach, only 3° separate the two. Astronomy: Roen Kelly
Although distant Neptune hides in the Sun’s glare throughout February, the solar system’s six other planets brighten the nighttime stage. Early evening is the time for breathtaking views of the two brightest planets, Venus and Jupiter. Mercury and Uranus also share the western sky, although you’ll have to look more carefully to spy them. Ruddy Mars nears the peak of its biennial apparition as midnight approaches. And glorious Saturn puts on a wonderful show during the early morning hours.

As darkness starts to fall, Venus blazes through the deepening twilight. On February 1, it shines at magnitude –4.1 and stands 25° above the horizon an hour after sunset. The brightest planet doesn’t dip below the horizon until around 8:30 p.m. local time. But it gets even better. Venus sets approximately 2 minutes later each day, so by month’s end, it appears higher in a darker sky and remains visible until 9:30 p.m. local time. It also shines brighter, gleaming at magnitude –4.3 on February’s final evening.

Venus’ dramatic appearance arises from a combination of two factors. First, its elongation from the Sun steadily increases. And second, the ecliptic — the apparent path of the Sun across the sky that the planets also follow closely — makes its ­steepest angle to the western horizon during the Northern Hemisphere’s late winter and early spring.

Be sure to catch the crescent Moon and Venus after sunset February 25. The two pass within 3° of each other and will make a lovely pair both in twilight and after darkness fully sets in.

The best time to observe Venus through a telescope is during twilight. The planet’s higher altitude then delivers sharper views and the added sky brightness cuts the glare. Venus exhibits phases much like the Moon. During February, the planet’s phase wanes from 74 percent to 64 percent lit while its apparent diameter grows from 15" to 18".
Uranus-and-Venus finder chart
Find Uranus 0.3° south of Venus the evening of February 9. Look for the outer planet's blue-green color through a telescope. Astronomy: Roen Kelly
Venus also serves as a guide for locating Uranus. Between February 3 and 15, the two planets lie in the same field of view through 7x50 binoculars. If you swing your binoculars to Venus before February 9, Uranus lies above and slightly to its left. After the 9th, the distant world lies below and slightly to the right of Venus. A few nearby stars shine almost as bright as ­Uranus, so use a star chart to check their identities. The “star” that doesn’t appear on the chart will be the planet. Mount the binoculars on a tripod to make your observing easier.

The two planets appear just 0.3° from each other the evening of February 9. A ­telescope at low power will show both at once. Notice the brightness difference — Venus shines precisely 10,000 times brighter than the magnitude 5.9 Uranus. You’ll need to crank up the magnification to see Uranus’ 3.4"-diameter disk. If you wait until the background sky darkens ­completely, you also should detect the dimmer planet’s blue-green hue.

During the month’s final 10 days, Mercury joins the twilight scene. The innermost planet passes on the opposite side of the Sun from Earth February 7, but it emerges into the early evening sky soon after. (It benefits from the ecliptic’s steep angle to the horizon like Venus does.) A good night to look for Mercury is February 22 when a waxing crescent Moon lies 5° to its right. The planet then shines at magnitude –1.2 and shows up easily in the twilight a half-hour after sunset.

During the next week, Mercury climbs higher but dims slightly. On the 29th, it shines at magnitude –1.0 and appears 10° high 30 minutes after the Sun sets. (The planet sets an hour after that.) When viewed through a telescope, Mercury appears 6" across and about two-thirds lit. It will reach the peak of this ­evening apparition in the first week of March.
Mercury finder chart
A thin crescent Moon points the way to innermost Mercury after sunset February 22. The pair sets about an hour after the Sun. Astronomy: Roen Kelly
Higher in the southwestern sky after sunset is mighty Jupiter. The giant planet lies among the background stars of southern Aries, but you won’t need any help spotting it. The second-brightest point of light in the sky shines at magnitude –2.3 and stands out on any clear evening.

Jupiter doesn’t set until midnight approaches, leaving plenty of time to observe it through a telescope. And even the smallest instruments deliver stunning views. The planet’s disk spans a majestic (as far as the planets go) 39" as February opens, and it shrinks by only 3" during the month as the world recedes from Earth.

If you are new to astronomy, you may wonder why everyone refers to Jupiter as a giant when a first peek through a telescope shows a huge field of view with a tiny disk at its center. When you reflect on the fact that Mars gets only about half this big even at its best and the other outer planets are smaller than that, you can begin to appreciate what Jupiter offers.
Europa's shadow stands out on Jupiter's clouds February 22. This shadow transit happens just after Europa crosses the jovian disk. Astronomy: Roen Kelly
The treasures of this gas-giant world show up best once you’ve trained your eye to see tiny details. And this takes more than a quick look through the eyepiece. On
a night that delivers steady images, an eye that studies Jupiter for many minutes will see half a dozen belts and zones, tiny dark spots, and the soft pink color of the Great Red Spot.

When you view Jupiter, also look for its four bright moons: Io, Europa, Ganymede, and Callisto. If you see fewer than four, it means at least one is either hiding behind the great planet or passing directly in front of it.

From an observational standpoint, the latter occasions are more appealing because two separate events occur. First, the moon itself passes in front of Jupiter in what astronomers call a transit. Then, the moon’s shadow crosses the planet’s disk. A shadow stands out particularly well because it appears inky black and creates a strong contrast with the ­planet’s bright cloud tops.

Perhaps the best tandem transit takes place February 22. Europa is already transiting Jupiter as night falls in the eastern half of North America. As the moon gets ready to leave Jupiter’s western limb (or edge), its shadow appears on the eastern limb. The shadow makes its first mark at 7:40 p.m. EST, 5 minutes before the moon’s disk clears the planet’s limb. The shadow takes more than 2 hours to cross Jupiter’s face, lifting back into space at 10:02 p.m. EST.
Comet C/2009 P1 (Garradd) heads north during February and has a pretty encounter with the bright globular cluster M92. Astronomy: Roen Kelly
Mars rises shortly before 9 p.m. local time February 1 and just a few minutes after the Sun sets at month’s end. The Red Planet reaches ­opposition and peak visibility during March’s first week, and the views this month are nearly as good.

As February opens, Mars lies among the background stars of western Virgo. It heads westward relative to this backdrop, however, crossing into Leo on February 3. The planet’s steady motion carries it to a point about 5° south of 3rd-magnitude Theta (θ) Leonis by month’s end. Mars nearly doubles in brightness during February, leaping from magnitude –0.5 to –1.2. It’s the brightest object in Leo all month except when the nearly Full Moon passes by between February 7 and 9.

If you haven’t observed Mars through a telescope yet this year, don’t wait any longer. Subtle details show up to those who spend more time looking. The planet’s apparent size grows from 11.8" to 13.8", just shy of its early March peak. You should have little trouble seeing the white north polar cap because the planet’s north pole now tips in Earth’s direction. It’s currently late spring in Mars’ northern hemisphere. See if you can spy changes in the cap this month as solar heat continues to warm the ices and turn them directly to gas.

Some 3 hours after Mars rises, Saturn pokes above the eastern horizon. It’s visible by midnight local time in early February and 2 hours earlier by month’s close. You can find it among the stars of Virgo, 7° east-northeast of Spica. The planet shines at magnitude 0.5 in mid-February, slightly but noticeably brighter than the star.

Unlike with Jupiter and Mars, it doesn’t take practice to enjoy the view of Saturn through a telescope. Every observer marvels at its beauty whenever they observe it. The best views this month occur shortly before dawn when the planet lies highest in the south. The spectacular ring system spans 41" and tilts 15° to our line of sight in mid-February. The rings’ full breadth more than doubles the 18"-diameter of Saturn’s disk.

Any telescope will show 8th-magnitude Titan, Saturn’s biggest moon and the solar system’s second largest after Jupiter’s Ganymede. During each earthly month, Titan orbits Saturn roughly twice. You’ll find the moon north of the planet February 7 and 23 and south of the planet February 15. Iapetus, Saturn’s outermost major moon, reaches greatest western ­elongation February 8. The satellite then glows at 10th magnitude, nearly 2 magnitudes brighter than when it lies far east of the planet. You’ll find Iapetus nearly 9' west of Saturn, equivalent to about 13 ring diameters.
Sporadics on the prowl
February and March are the quietest months of the year for meteor observers, particularly those in the Northern Hemisphere. No major showers occur, and the only minor ones pepper far southern skies with just a few streaks.

The Alpha Centaurid shower produces about six meteors per hour under optimal conditions at its February 8 peak. Unfortunately, this year the peak coincides with the bright light of a Full Moon, which will wash many out.

That leaves the background rate of sporadic meteors. A typical observer will see about six of these per hour on a moonless night. Occasionally, a brilliant sporadic will flash across the sky. The best time to see one is in the hour or two before dawn. Just be sure you’re wrapped up against the cold. The Moon is out of the morning sky during February’s last week, making that your best bet.
The Moon's north pole boasts three large craters — Byrd, Peary, and Nansen — named after famed polar explorers. NASA/JPL/USGS
Mount an expedition to the lunar pole
The intrepid explorers who ventured deep into Earth’s polar regions left their marks in our history books. But they also made an impression on the lunar cartographers who named the craters near our ­satellite’s north pole. That’s where you’ll find the likes of Byrd, Peary, and Nansen commemorated.

It’s much easier to trek across the lunar highlands and north polar region with your eye than to embark on a journey to our planet’s pole. The trick to exploring these craters through your telescope is to choose the right time.

You’ll want to target this region around a Full Moon when the lunar north pole tilts toward us. Wait until our satellite lies below the ecliptic plane in Leo or Virgo. (Use the “Path of the planets” map at the center of this magazine to see when this happens.) When the Moon’s there, we peer “over the top” of our sister world.

On the evening of February 5, our view will be similar to the color-enhanced image at right taken by the Galileo spacecraft almost 20 years ago. Use the landmark craters Plato, Anaxagoras, and Goldschmidt to guide you first to Byrd, then to Peary and Nansen. The back walls of these last two should appear brighter than in the photo.

Return the next five evenings to watch the shadows on the crater rims rotate from one side of the southern flank to the other. Finally, look closely for a thin black line on Peary’s back wall. This is Peary’s shadow being cast onto the rim of farside crater Rozhdestvenskiy.
When to view the planets
Mercury (west) Mars (southeast) Mars (west)
Venus (west) Saturn (southeast) Saturn (southwest)
Jupiter (southwest)

Uranus (west)

2006 T1 finder chart
Comet P/2006 T1 (Levy) treks through Lepus and Canis Major, where the winter Milky Way makes a splendid backdrop. Astronomy: Roen Kelly
Cosmic snowballs head on diverging paths
Comet viewers have a pair of worthy targets to keep them busy nearly all night long. For those who prefer observing shortly after darkness falls, Comet P/2006 T1 (Levy) fills the bill. Nicely placed in the southern sky, this periodic visitor scoots under the feet of Lepus the Hare and Canis Major the Big Dog. Astronomers predict the comet will fade from 8th to 9th magnitude during February. For the best views, find a dark-sky site and observe around midmonth when the Moon’s additional light pollution doesn’t interfere.

The splendid stardust of the winter Milky Way provides a beautiful backdrop to Comet Levy. Enjoy some wide-field views before boosting the power and taking closer looks.

Well-known author and Astronomy columnist David H. Levy discovered this comet in 2006. It is a small ball of ice and dirt that loops from Jupiter to Earth and back every 5.24 years. Because its orbital period is 3 months longer than an integral number of Earth orbits, it won’t have another favorable encounter for four more orbits (until 2033).

Your reward for observing past midnight local time is a brighter and more detailed comet. C/2009 P1 (Garradd) should glow around 7th magnitude in February. Be sure to look for it on the 2nd and 3rd when it cruises less than 1° from the bright globular star cluster M92 in Hercules. (See the finder chart above.)

A highlight could come the night of February 14/15 when the comet’s fan-shaped glow orients edge-on to us and produces two tails. The so-called anti-tail that points toward the Sun is a trick of perspective, but it can be a sight you’ll treasure nonetheless. Will this tail be noticeable a night before or after? We don’t know, so have a look.

Comet Garradd treks steadily northward across Draco’s tail and edges into Ursa Minor at February’s close. This track favors observers at more northerly latitudes.
The asteroid Astraea glows at 9th magnitude in late February when it passes just south of 4th-magnitude Nu (ν) Virginis. Astronomy: Roen Kelly
Astraea — planet killer extraordinaire
Trailing several degrees behind Mars in the eastern sky, the modest main-belt asteroid 5 Astraea shows up best during late evening after it has climbed well above the horizon. This 75-mile-wide space rock travels slowly through Virgo this month. That’s a nice coincidence because Greek mythology recounts that Astraea, a daughter of Zeus, left Earth to shine in the heavens as the constellation Virgo.

Astraea isn’t particularly bright, although it does improve from magnitude 10.0 to 9.3 during February. Plenty of background stars make the task of finding it a bit challenging. Consider quickly sketching the field one night and returning a night or two later to see which object moved. German amateur astronomer Karl Hencke used this technique to discover the asteroid in 1845. It marked the beginning of the end for the planetary status of the first four asteroids — Ceres, Pallas, Juno, and Vesta — which had stood alone for 38 years.

In contrast to the distant Astraea, which never ventures closer to the Sun than Mars’ orbit, asteroid 433 Eros can approach Earth. It makes its best appearance in 37 years in this winter’s sky. See the story on page 48 for details.

Martin Ratcliffe provides professional planetarium development for Sky-Skan, Inc. Alister Ling is a meterologist for Environment Canada.


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