Morning sky delights

Thanks to 2016 being a leap year, we have an extra day this month to view a gorgeous string of morning planets. Jupiter, Mars, Saturn, Venus, and Mercury spread out across more than half of the predawn sky, with the two inner planets approaching within 5° of each other for much of the month. Although February’s early evening sky offers fewer and dimmer planets, they’re worth exploring until Jupiter comes into view. Finally, observers in the western United States can watch the Moon pass in front of Aldebaran, the brightest star in Taurus.

Let’s begin our tour of the planets after sunset, knowing that the best views won’t begin for a few hours. You’ll have to work quickly to see Neptune, which lies just 5° high in the west-southwest after darkness falls February 1. Glowing at magnitude 8.0, it’s a tough target through binoculars when it hangs so low. You can find the planet in Aquarius, some 3° southwest of 4th-magnitude Lambda (λ) Aquarii. Neptune disappears in twilight after February’s first week and won’t return to view until spring.

Neptune’s neighbor proves a much easier target. Uranus stands some 40° high after darkness settles in during early February. And at magnitude 5.9, it shines brightly enough to see easily through binoculars. To find it, first locate the Great Square of Pegasus, now oriented to the western horizon like a baseball diamond.

Next, pick out Beta (β) and Gamma (γ) Pegasi, the stars at the right and left corners, respectively, of this asterism. A line from Beta to Gamma spans 20°. Extend this line 15° more and you’ll be in the part of southern Pisces where Uranus resides. The brightest star in this vicinity is magnitude 4.3 Epsilon (ε) Piscium. Center it in your binoculars and Uranus will be in the same field. The planet begins February 2° due south of the star and maintains this distance as it moves slowly northeast during the month.

Don’t confuse Uranus with a triangle of 6th-magnitude stars just to its south. Con­firm a sighting by targeting the object through a telescope. Only Uranus shows a blue-green disk, which spans 3.4".

The first hint of the looming morning extravaganza comes with the arrival of Jupiter. The giant planet rises in the east by 9 p.m. local time February 1 and about a half-hour earlier with each passing week. You won’t mistake it for any other object — at magnitude –2.4, it shines more than twice as bright as the brightest nighttime star, Sirius. The planet’s westward motion ­relative to the backdrop of southern Leo carries it within a Full Moon’s diameter of the 4th-magnitude star Sigma (σ) Leonis by month’s end.

To view Jupiter through a telescope, wait until it climbs higher in the sky in late evening. With the planet nearing its March 8 opposition, it appears near its best for the year. The gas giant’s disk grows from 42.5" to 44.3" across the equator during February, ending the month just 0.1" shy of its March peak.

Jupiter’s action-packed atmosphere offers two dark equatorial belts straddling a brighter zone coinciding with the equator. The alternating belts and zones at higher latitudes appear more subtle. Also keep an eye out for dark and bright spots, which typically show up near the turbulent edges of these belts.

A conspicuous black dot occasionally crosses Jupiter’s face. This is not an atmospheric feature but the shadow of one of the planet’s four big moons. Ganymede is the largest, and its shadow is the easiest to spot. A good time to watch is the night of February 16/17. Ganymede’s shadow starts to cross the disk shortly before 11 p.m. EST followed some two hours later by the moon itself.

Mars rises by 1 a.m. local time February 1 and climbs 30° high in the south by dawn. Unlike Jupiter, the Red Planet exhibits rapid changes during the month. It brightens by half a magnitude (from 0.8 to 0.3) and grows by 25 percent in apparent diameter (from 6.8" to 8.6"). On February’s first morning, you’ll find Mars 3° southwest of a waning crescent Moon and 1° north of Libra’s second-brightest star, magnitude 2.8 Zubenelgenubi (Alpha [α] Librae). The planet has a return engagement with the Moon February 29.

Despite Mars’ growing size, it remains a challenging object in telescopes smaller than 8 inches in aperture. The north polar cap should stand out, however, and you might glimpse a few dusky surface markings. The planet also shows a distinct gibbous phase (90 percent lit) this month.

As Earth spins beneath the starry canopy, Saturn soon pokes above the horizon. The ringed world resides in Ophiu­chus, rising around 3:30 a.m. local time February 1 and nearly two hours earlier by month’s end. On the 3rd, the waning crescent Moon stands 4° northwest of the gas giant. The planet shines at magnitude 0.5 all month.

The view of Saturn through a telescope never fails to impress. In mid-February, the planet’s equatorial diameter measures 16" while the ring system spans 37" and tilts 26° to our line of sight. For the best views, wait until Saturn climbs higher in the sky near the beginning of twilight.

Last but not least, the two inner planets join each other in the predawn sky. On Feb­ruary 1, Venus rises nearly two hours before sunrise and Mercury follows 20 minutes later. They stand 7° apart, bracketing Sagittarius’ Tea­spoon asterism. Venus dazzles at magnitude –3.9 while Mercury manages a respectable magnitude 0.0.

A beautiful scene awaits early risers February 6 when a thin crescent Moon forms a tight triangle with the two planets. All three objects lie within a 5° circle. The Moon appears just 6 percent lit this morning. If you view the planets through a telescope, Mercury reveals a 7"-diameter disk that is 61 percent lit and Venus spans 12" with an 86-percent-lit phase. Mercury reaches greatest elongation later on the 6th when it lies 26° west of the Sun.

The gap between the two planets closes slightly during the following week. They appear closest February 12 and 13 when just 4° separate them. Still, they remain near each other as they descend toward the Sun’s glow during the latter half of the month. On February’s final day, Mercury shines at magnitude –0.3 but rises only 35 minutes before our star and will be hard to see. Meanwhile, Venus maintains its brilliance and continues to show up clearly in bright twilight.

Don’t let the chilly morning air dissuade you from viewing the spectacular lineup of bright planets. About an hour before sunrise during February’s first two weeks, five of Earth’s siblings stretch across some 120° of the predawn sky. Start with Jupiter in the western sky, then pick up Mars nearly due south, Saturn climbing in the southeast, and lastly Venus and Mercury hanging above the southeastern horizon. It’s a sight guaranteed to warm your heart, if not your body.

A final event demands the attention of those in the western United States. On the night of February 15/16, the Moon occults Aldebaran, the 1st-magnitude luminary of Taurus. Along a line that cuts across Washington, Oregon, and Idaho, the northern limb of the Moon grazes Aldebaran. Through a telescope, you can see the star disappear behind mountains and reappear in valleys several times. Luna completely hides the star from south of this line while the two just miss each other from farther north. The event occurs shortly after 1 a.m. when the pair lies low in the west.

LUNA'S VALENTINE'S DAY GIFT
Pits, bumps, and ridges litter the dark floor of Mare Sereni­tatis (the Sea of Serenity) as the waxing crescent Moon approaches First Quarter phase. On the evening of February 13, the twisting form of the Ser­pentine Ridge captures the attention of lunar observers. This feature snakes its way north to south across the eastern part of this huge impact basin, which resides slightly north of the equator.

By the following evening, the Sun has risen over the western half of Serenity’s ancient lava-filled bowl. The changing illumination brings to light some comparatively young craters. Strung out in a line running north to south are Linné G, H, F, B, and A. Despite their small sizes (F and B are the biggest at just 3 miles across), they stand out well under good seeing conditions. Surprisingly, the “main” crater itself, Linné, measures only 1.5 miles across. It doesn’t look like much at these low Sun angles, but it appears as a conspicuous white patch close to Full Moon.

The “Valentine Dome” is a gentle volcanic protrusion tucked against the western flank of Mare Serenitatis. It shows up only at the lowest of Sun angles, perfectly timed for viewing on the evening of Valentine’s Day (February 14). The dome’s somewhat heart-shaped swelling crests less than 400 feet above the mare floor. You won’t be able to miss the handful of older peaks that poke above the dome. One Earth night later, the shading of the dome’s gentle slopes has disappeared under the higher Sun angle, leaving but a trace of the tiny peaks.

HUNTING A DIFFERENT KIND OF METEOR
Although February is normally a quiet month for meteor viewers, unexpected meteors can enliven any observing session. Most arrive from random directions and truly can be called sporadics. Others come from the “antihelion” (opposite the Sun) direction, which lies 12° east of the opposition point. This radiant is not a point but rather a broad region of sky along the ecliptic that spans roughly 30° by 15°. At this time of year, it resides in southern Leo the Lion.

Astronomers think the antihelion source is the remnant of many ancient meteor showers that have dwindled to a light sprinkle of a couple of meteors per hour. The low numbers prevent researchers from identifying any specific shower. The lack of major meteor showers in February and March make the Moon-free periods during these months excellent ones to search for such meteors.

COMET CATALINA VISITS KEMBLE'S CASCADE
Comet Catalina (C/2013 US10) passes near the North Celestial Pole in early February, which keeps it on view throughout the night for Northern Hemi­sphere observers. Even better, this first-time visitor from the distant Oort Cloud should shine around 6th magnitude — bright enough to see through binoculars under a dark sky and a telescope from the suburbs.

The comet begins February just a few degrees from Polaris, then drifts slowly southward (upward) through sprawling Camelo­pardalis the Giraffe toward the winter Milky Way. We’re lucky that binoculars can reveal Catalina’s fuzzy glow because there are no bright stars in this nearly unrecognizable constellation.

You can expect to see a fair bit of detail in a comet this bright. To tease out the most, view it at different magnifications. The coma typically stands out best. This roughly spherical glow surrounds the comet’s nucleus — the source of the gas and dust that creates the entire display. Crank up the power to look for the so-called false nucleus, the dense cocoon of dust that shrouds the true surface from view.

The solar wind drives the gas away to form an ion tail while the Sun’s radiation pressure gently pushes tiny particles away to produce a dust tail. Use averted vision — a technique for seeing faint detail by not looking directly at your subject — to trace out the last tendrils of these tails. You also should notice that the dust tail appears curved and more diffuse compared with the straight ion tail.

Imagers should be on alert for a nice wide-angle photo opportunity in mid-February when Catalina passes 3° from the large but faint face-on spiral galaxy IC 342. Your best views will come in late evening or the wee hours after the Moon sets. On the 24th, before the waning gibbous Moon rises, the comet sits 0.5° from planetary nebula NGC 1501, which lies next to the picturesque string of stars known as Kemble’s Cascade.

AN ICE GIANT MEETS A GIANT BOULDER
The Moon usually acts as a nemesis when it comes to finding many of the solar system’s fainter objects. But on the evening of February 12, our satellite points the way to both asteroid 4 Vesta and the ice giant planet Uranus. During the rest of the month, the easiest way to Vesta’s home is to draw a line diagonally across the Great Square of Pegasus, from magnitude 2.5 Beta (β) to magnitude 2.8 Gamma (γ) Pegasi, and then continue that line for an equal distance.

Although more than four months past its peak magnitude of 6.2, Vesta remains the brightest of the minor planets at 8th magnitude. A 3- or 4-inch telescope will reveal it from the city, while binoculars will be enough under a darker sky. Use the chart below to navigate from the brighter background stars of Pisces to the wanderers. Vesta will appear as a point of light, but a telescope at moderate magnification should show you Uranus’ 3.4"-wide disk and blue-green color.

You can see the asteroid move from one night to the next whenever one or more of Pisces’ background stars lies nearby. Occasionally, you can see significant motion in an hour or two. Great opportunities arrive both February 8 and 14, when Vesta splits two closely spaced stars.

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Martin Ratcliffe provides planetarium development for Sky-Skan, Inc. from his home in Wichita, Kansas. Meteorologist Alister Ling works for Environment Canada in Edmonton, Alberta.