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A pair of close encounters

July 2013: Venus meets Leo's brightest star, Regulus, after sunset, and Jupiter joins Mars in morning twilight.
RELATED TOPICS: OBSERVING | VENUS | JUPITER | MARS | MERCURY
Venus and Regulus conjunction finder chart
Brilliant Venus joins 1st-magnitude Regulus as darkness falls July 21, in the first of two pretty conjunctions in one night. // Astronomy: Roen Kelly
Bright planets adorn both the early evening and predawn skies in July, while our solar system’s fainter members appear best around midnight or after. Within a span of less than 12 hours July 21 and 22, Venus meets Leo’s brightest star after sunset and Jupiter joins Mars in morning twilight. By the end of July, Mercury adds to the predawn drama.

The distant giants Uranus and Neptune display more-subtle charms as they climb high after midnight. Finally, the dwarf planet Pluto reaches opposition and peak visibility in early July. You’ll need an 8-inch telescope and excellent viewing conditions to spy it among the background stars of northern Sagittarius.

Although the Sun sets late in summer, a planetary jewel beckons observers as soon as the sky starts to darken. Venus shines brilliantly in the fading twilight all month. Unfortunately, its altitude remains low despite its increasing elongation from the Sun. Blame the shallow angle of the ecliptic — the orbital plane of the solar system’s major planets — to the western horizon after sunset at this time of year. As Venus pulls away from the Sun, it moves mostly southward along the horizon and not higher in the sky.

On July 3, Venus passes through the background stars of the Beehive Cluster (M44) in Cancer. The two lie only 25° from the Sun, however, so the star cluster will be hard to see in the twilight. From mid-northern latitudes, the pair stands just 5° high one hour after sunset. The view improves the farther south you live because the ecliptic makes a steeper angle to the horizon.

A slender crescent Moon joins Venus on July 10. The two appear 7° apart, with our satellite to the planet’s lower left. Two days later, Venus crosses into Leo. The planet then makes a beeline toward the Lion’s brightest star, 1st-magnitude Regulus. On the evening of the 21st, the two lie just 1.2° from each other.
Mars and Jupiter finder chart
Mars and Jupiter stand next to each other as twilight paints July 22's predawn sky, the coda to an eventful observing night. // Astronomy: Roen Kelly
Any telescope will reveal the change in Venus’ phase during July. On the 1st, its 90-percent-lit disk looks nearly full; by the 31st, the planet’s 83 percent illumination gives it a distinctly gibbous appearance. During the same period, Venus’ diameter grows from 11" to 13".

As twilight starts to fade, Saturn becomes prominent in the southwestern sky. The ringed planet stands some 30° high around 10 p.m. local daylight time. It shines at magnitude 0.6, far brighter than the surrounding background stars of eastern Virgo. Saturn’s retrograde (westward) motion against this starry backdrop comes to an end July 8/9, when it resumes its normal easterly motion. The planet’s glacial progress keeps it within 1° of 4th-magnitude Kappa (κ) Virginis all month.

Saturn doesn’t set until after midnight local daylight time, which provides observers with telescopes a couple of prime viewing hours each clear night. The planet’s disk measures 17" across in mid-July, when the ring system spans 39" and tips 17° to our line of sight.

Careful observers also will notice the planet’s shadow falling on the far side of the rings. The shadow appears most conspicuous when it extends farthest east of Saturn’s limb around July 28. That’s the date when the ringed world reaches quadrature, one of two points in its orbit where a line from the Sun to Earth and then to Saturn forms a right angle. Seeing the shadow on the rings gives the planet a striking 3-D appearance.

A telescope also reveals the brightest of Saturn’s 62 known moons. The most conspicuous one is 8th-magnitude Titan, which shows up through any size instrument. It appears due north of Saturn on July 1 and 17 and due south on the 9th and 25th. A 4-inch scope will reveal a trio of 10th-­magnitude satellites — Tethys, Dione, and Rhea — that lie closer to the planet. Much farther out lies two-faced Iapetus, which glows at 12th magnitude when it lies farthest east (9' away) of Saturn on July 8. It brightens to 11th magnitude by the time it passes 2' south of the planet on the 28th.
Saturns inner moons finder chart
Rhea, Dione, and Tethys point the way to Enceladus and Mimas the night of July 12/13. (Bright Titan lies 2.5 times farther west of Saturn than Rhea.) // Astronomy: Roen Kelly
A pair of inner saturnian satellites provides a stiffer challenge. You’ll need an 8-inch or larger scope and good viewing conditions to spot 12th-magnitude Enceladus and 10 inches of aperture for 13th-magnitude Mimas. Because these two orbit close to the planet, they never stray far from the glare of the rings. The best time to find them is when they appear near greatest elongation. The night of July 12/13 offers an excellent opportunity. Both moons then lie near greatest western elongation, and Dione and Rhea act as guides farther out along the same line of sight.

Distant Pluto reaches opposition July 1. The dwarf planet then lies opposite the Sun in our sky and glows brightest, though, at magnitude 14.0, “bright” is not a very descriptive term. An 8-inch scope gathers enough light to reveal Pluto under great conditions, but a bigger instrument makes the task easier.

The dim world appears against the Milky Way backdrop of northern Sagittarius, approximately 2.7° east of open star cluster M25 and 4.3° north-northeast of globular cluster M22. This region lies highest in the south around 1 a.m. local daylight time in early July. For a detailed finder chart and further tips on observing, see “How to hunt down Pluto” (p. 60).

After you locate Pluto, finding Neptune should be a breeze. The distant ice giant glows at magnitude 7.8 and shows up nicely through binoculars or a telescope. You can find it in central Aquarius, a constellation that rises in mid-evening and appears highest in the south as morning twilight begins.

The sparsely populated background makes it easier to identify the planet. First locate Sigma (σ) Aquarii, a magnitude 4.8 star located near the center of the Water-Bearer. Neptune resides 0.7° northwest of Sigma on July 1 and 1.1° west of the star on the 31st, well within the same low-power field of view. Use a medium-power eyepiece to reveal the planet’s 2.3"-­diameter blue-gray disk.
Mercury, Mars, Jupiter, and Moon finder chart
The winter stars return to the morning sky in late July. This year, Mercury, Mars, Jupiter, and the Moon enhance the scene. // Astronomy: Roen Kelly
Uranus rises around midnight local daylight time in mid-July and shows up best once it climbs high in the southeast before dawn. The planet glows at magnitude 5.8 against the backdrop of Pisces the Fish. You won’t find many bright stars in this region — the most conspicuous one is magnitude 4.4 Delta (δ) Piscium 3.5° north of the planet. You can spot both with naked eyes under a dark sky or through binoculars from the suburbs. A telescope reveals Uranus’ blue-green disk, which spans 3.6".

Morning twilight starts to break before any other planet appears. Mars rises first, at least during July’s first three weeks. It shines at magnitude 1.6 and will be a challenge to follow as the eastern sky brightens. Binoculars should reveal the planet July 6, when it lies 4° to the upper left of a waning crescent Moon. Mars crosses from Taurus into Gemini around mid-July and passes just south of open star cluster M35 on the 16th and 17th. The objects’ low altitude and the advancing twilight make this a tough conjunction to see.

Giant Jupiter rises earlier each day and will pass within 1° of Mars on July 22, coincidentally the morning following the previous evening’s conjunction between Venus and Regulus. The duo will be visible together through a telescope at low power, which will accentuate their great contrast. Jupiter’s yellowish disk spans 33" while ruddy Mars appears just 4" across. And the giant planet has four bright moons that show up clearly. North American viewers also should look for Europa’s black shadow crossing Jupiter’s face.

Mercury joins the cavalcade of morning planets during July’s final week. On the 25th, the innermost planet lies 7.5° below Mars and just 5° above the horizon 45 minutes before sunrise. You’ll likely need binoculars to see its magnitude 1.0 glow. But ­Mercury brightens quickly, reaching magnitude 0.0 and rising a few degrees higher in the east-northeast before sunrise by the 31st.

The three morning planets all reside in Gemini the Twins, to the right of Castor and Pollux and to the left of the rising stars of Orion the Hunter. Higher up you’ll find Auriga and Taurus, with a waning crescent Moon just a few degrees to the right of the latter constellation’s Pleiades star cluster (M45). The gathering of planets, stars, and our Moon delivers a stunning sight to early risers.
Furnerius and Mare Australe finder chart
A pair of features near the Moon's southeastern limb reveals our changing viewpoint during July. // Consolidated Lunar Atlas/UA/LPL
VIEW THIS LUNAR DANCE WITH PERSPECTIVE
Although the Moon seems to keep the same face pointed toward Earth at all times, that’s not precisely true. Every month, our satellite performs a subtle dance with Earth for all to see; you just have to know what to look for. This month, we’ll concentrate on one aspect of this movement — the dip and rise.

Turn to the “Path of the Planets” on p. 40 and 41 and locate Saturn among the stars of Virgo. To its left, you’ll see the blue path of the Moon arcing below the orange-brown path of the Sun and then rising above it. This down and up motion results from the tilt of the Moon’s orbit relative to Earth’s.

As the two objects twirl across the solar system’s dance floor, the Moon’s face rises and drops. As a waxing crescent the evening of July 13, it’s somewhat below us, and the bright dimple of the crater Furnerius tucks against the lower right of the face. With each passing day, as Luna rises up, the dimple climbs away from the limb and we see more “under the chin.”

By the 18th, the first hint of the delicate tattoo of Mare Australe (Southern Sea) comes into view. This patchwork of darker markings reveals more of itself, peaking at Full Moon on July 22. This sea is the edge of a large farside basin partially filled
with frozen lava. The Moon has reached the peak of its motion and slowly drops back down, but the change in the southeastern quadrant now takes place in darkness and out of our sight.
Southern Delta Aquarid meteor shower finder chart
Viewers could see up to 10 meteors per hour coming from Aquarius on July 30, when a crescent Moon slightly hinders the view. // Astronomy: Roen Kelly
DUST PARTICLES FLARE WHILE PLANETS GATHER
As you prepare to view the morning planets July 30, enjoy the peak of the Southern Delta Aquarid meteors. This minor shower has many faint meteors, created when dust specks burn up in Earth’s atmosphere, but occasional bright streaks from bigger particles will punctuate the night sky. The Moon, one day past Last Quarter, rises around midnight and will drown out some “shooting stars.”

You also might see an early Perseid meteor from the major shower that starts in mid-July and peaks next month. Delta Aquarid meteors appear to radiate from the constellation Aquarius, while Perseids emanate from Perseus.
WHEN TO VIEW THE PLANETS
Evening Sky
Midnight Morning Sky
Venus (west)
Saturn (southwest)
Mercury (northeast)
Saturn (southwest)
Uranus (east)
Mars (northeast)

Neptune (southeast)
Jupiter (northeast)


Uranus (southeast)


Neptune (south)
Comet PANSTARRS (C211 L4) finder chart
As spring's best comet heads back to the outer solar system, it passes nearly in front of the distant spiral galaxy NGC 5678. // Astronomy: Roen Kelly
A FINAL LOOK AT SPRING'S BRIGHT VISITOR
Comet observers may be suffering a case of the doldrums due to the brief lull between the lovely spring show put on by C/2011 L4 (PANSTARRS) and the highly anticipated spectacle of C/2012 S1 (ISON) in a few months. But this is a perfect opportunity to sharpen your abilities to see subtle, low-­contrast details in a comet. And you have all night thanks to PANSTARRS’ position not far from the North Celestial Pole.

You’ll want to be away from city lights and use an 8-inch or larger telescope to catch this faint fuzzy. It’s also best to avoid the Moon’s bright light near its July 22 Full phase. The comet tracks not far from Thuban (Alpha [α] Draconis), which was the pole star back when the Egyptians built the Great Pyramid. It’s the lone bright star located about halfway between the Little Dipper’s bowl and the kink in the Big Dipper’s handle.

Whether you star-hop to the comet’s position or use a go-to scope, you may not see the 10th-magnitude pale-gray puffball immediately at low power. Confirm the pattern of stars, and then scan around the field, using your light-sensitive averted vision to pick up the faint glow.

If you still don’t see it, swap in a higher-power eyepiece to darken the background sky and make the comet larger, then try scanning again. Take time to gain experience using various magnifications, looking for differences between the comet’s sharper sunward edge and the more diffuse opposite flank. This training will help you detect structure and possible tail disconnections in brighter comets.

On the night of July 17, PANSTARRS shares the same field with the 11th-magnitude spiral galaxy NGC 5678. Push the magnification past 100x
to better compare their shapes and structures. That power will provide a dark background and good contrast, especially if you put a dark cloth over your head and eyepiece. Now scoot over to the Pinwheel Galaxy (M101) in Ursa Major, and use these same skills to check out its satellite galaxies, which should look a ­little bit like the fading comet.
Path of Hebe finder chart
Tenth-magnitude Hebe arcs in front of the Serpent during July, ending the month 1° west of 4th-magnitude Mu (μ) Serpentis. // Astronomy: Roen Kelly
A MINOR PLANET AVOIDS THE SERPENT’S GRASP
This is a great time of year to relax during an evening stargazing session and enjoy the celestial clockwork. As Earth rotates from east to west, Saturn and Arcturus appear to sink in the western sky. Almost due south and halfway up the sky when dusk ends lies a zigzag of stars that forms the head of the constellation Serpens the Serpent. Magnitude 3.5 Mu (μ) ­Serpentis lies at the base of the Serpent’s head.

A 4-inch scope under a dark sky provides plenty of aperture to track the main belt asteroid 6 Hebe. With a bit more patience and care, you can ferret it out through the suburban sky glow. Start at Mu with a low-power eyepiece, and then slide about 2° north-northwest to the 5th-magnitude star 25 Ser, which lies near the center of the chart below. From there, it is a relatively straightforward hop to the 120-mile-wide asteroid.

When Hebe lies in a sparsely populated area, it will be obvious, but in richer regions the starry background can prove confusing. If so, make a quick sketch of the star pattern and return to the field a night or two later. The dot that has shifted position is Hebe.

The asteroid, named after the Greek goddess of youth, appears to be diving south because it is on the downward slope of its fairly inclined orbit. Hebe’s path around the Sun tilts 15° to Earth’s orbit. Remarkably, astronomers estimate that some 40 percent of all meteorites found on Earth were once part of Hebe.

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.
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