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Venus meets Jupiter at dusk

Although Venus reaches its peak in the evening sky in early June, the highlight of the planet’s month comes when it slides 0.3° from Jupiter on June 30.
Brilliant Venus passed a few degrees to Jupiter's upper right in evening twilight March 14, 2012.
Brilliant Venus passed a few degrees to Jupiter’s upper right in evening twilight March 14, 2012. The two worlds will appear even closer during a return engagement in late June.
Jamie Cooper
Although June nights are the shortest of the year in the Northern Hemisphere, in 2015 they pack a powerful punch. Venus and Jupiter will top most observers’ lists by dominating the evening sky all month. Keep a watch on the two brightest planets as the weeks pass, and you’ll notice them pulling closer. The drama builds to a stunning climax when they pass within 0.3° of each other as the calendar turns from June to July.

But the thrills don’t stop there. June also features Saturn just a few weeks past its peak, Uranus and Neptune coming into sharper focus after midnight, and Mercury making a brief appearance before dawn.

June’s first evening reveals two brilliant planets lighting up the western sky. Venus and Jupiter stand 20° apart that night. Although Venus appears lower, it shines 10 times brighter than its companion (magnitude –4.4 compared with magnitude –1.9). You’ll spot Venus easily within 30 minutes of sunset, when it appears 30° above the horizon. A half-hour later, the planet is a stunning jewel set against the darkening sky.

Venus lies among the background stars of eastern Gemini on the 1st, forming a straight line with the Twin’s brightest stars, Castor and Pollux. The inner world crosses into Cancer the Crab on June 3. It reaches greatest elongation three days later, when it lies 45° east of the Sun and sets after 11:30 p.m. local daylight time. Venus slides less than 1° north of the Beehive star cluster (M44) June 12 and 13, making a splendid sight through binoculars. The best views will come about an hour after sunset, before the planet dips too low.

As Venus pulls within 7° of Jupiter on June 19, a crescent Moon joins the scene some 7° below Venus. Compare our satellite’s 13-percent-lit disk to a telescopic view of Venus’ fatter crescent, which is 42 ­percent lit. The next evening, the waxing Moon lies 5° to Jupiter’s lower left.
The stars of the Beehive Cluster (M44) made a stunning backdrop for Venus on July 3, 2013.
The stars of the Beehive Cluster (M44) made a stunning backdrop for Venus on July 3, 2013. The planet revisits the cluster June 12 and 13.
Luis Argerich
Venus crosses into Leo the Lion on June 25. The separation between it and Jupiter has now shrunk to 3°, and the brilliant planets look like a pair of cat’s eyes catching a car’s headlights in the dark. The gap keeps closing over the next five nights, reaching a minimum of just 20' (two-thirds of the Full Moon’s diameter) on the 30th. Both planets will appear in a single field of view through a telescope at low power.

Although conjunctions between Venus and Jupiter typically occur every year or two, this event is the first and closest in a rare triple conjunction. The second occurs July 31 in the evening sky and the third October 26 before dawn. An even closer conjunction (4' separation) comes August 27, 2016, but the pair then will be in bright twilight.

If you want to view Venus through a telescope, do so before darkness fully settles in. Twilight reduces the stark contrast between the planet and sky and makes detail stand out. On June 1, Venus appears 22" across and just over half-lit. It reaches 50 percent illumination at greatest elongation on the 6th, when it resembles a miniature First Quarter Moon. By month’s end, the planet’s disk spans 32" and is about one-third lit.

As with Venus, Jupiter benefits from early evening observing. The giant planet then lies higher in the sky, so its light passes through less of Earth’s image-distorting atmosphere. For the same reason, early June offers superior views because Jupiter lies more than a third of the way to the zenith an hour after sunset.

Once you’ve sampled the delicate details in Jupiter’s cloud tops — the alternating series of bright zones and darker belts, turbulent eddies, and giant storms — turn your attention to the planet’s four bright moons. These so-called Galilean satellites orbit Jupiter with periods ranging from 1.8 to 16.7 days. Because both Earth and the Sun now lie in the plane of the orbits, one moon may cross in front of another (an occultation) or pass through another’s shadow (an eclipse). Unfor­tunately, the current series of mutual events is winding down, and with Jupiter visible for only a few hours each night, North American observers can see only a half dozen or so during June.
All of Saturn's bright moons appear near the planet the evening of June 8, including distant Iapetus, which then lies due north of the gas giant.
All of Saturn’s bright moons appear near the planet the evening of June 8, including distant Iapetus, which then lies due north of the gas giant.
A nice event visible from the continent’s eastern half occurs as darkness falls June 3. Ganymede eclipses Io for 28 minutes starting at 9:43 p.m. EDT. Io shines only three-quarters of its normal brightness at mideclipse. Ganymede — the solar system’s largest moon — adds extra spice by appearing in transit across the planet’s disk during the event. Io begins to transit Jupiter at 10:47 p.m. EDT followed by its shadow at 11:56 p.m. Just one minute after that, Ganymede clears the gas giant’s disk. The big moon’s shadow, which got this whole affair started, touches the jovian cloud tops beginning at 12:58 a.m. EDT, after Jupiter has set for East Coast observers.

Perhaps the best event for those living in western North America occurs the evening of June 10. Ganymede occults Io from 9:55 to 10:18 p.m. PDT while both moons are transiting Jupiter.

As Jupiter descends in the western sky, Saturn climbs in the east. Although it reached opposition and peak visibility in late May, the ringed planet’s appearance hardly suffers in June. It dims almost imperceptibly this month, from magnitude 0.1 to 0.2, and its size when viewed through a telescope shrinks only 2 percent. Saturn’s higher altitude and better visibility during the evening hours easily make up for these minor losses.

The solar system’s second-largest planet is set against the faint backdrop of eastern Libra, though it’s not far from the riches of Scorpius. It lies a bit more than 10° northwest of 1st-magnitude Antares, the Scorpion’s brightest star. The Moon appears Full when it passes near Saturn the evening of June 1 and shows a bright gibbous phase when it returns on the 28th.

A telescope turns Saturn from a steadily shining point of light into a wondrous ringed world. In mid-June, the planet’s globe measures 18" across its equator while the rings span 42" and tilt 24° to our line of sight. The best views come within an hour or so of when Saturn climbs highest in the south, at roughly midnight local daylight time June 1 and two hours earlier by the 30th.

After savoring the photons reflecting off Saturn and its rings, turn your attention to the planet’s array of bright moons. Giant Titan glows at 8th magnitude and shows up through any telescope. It’s the brightest point of light in Saturn’s vicinity except on June 23 and 24, when the planet and its attendants slide within 2' of a 7th-magnitude background star.
Mercury hangs low on mornings around June 24, when it lies 22° west of the Sun at its summertime peak for Northern Hemisphere observers.
Mercury hangs low on mornings around June 24, when it lies 22° west of the Sun at its summertime peak for Northern Hemisphere observers.
Titan revolves around Saturn once every 16 days. Three 10th-magnitude moons — Tethys, Dione, and Rhea — circle the planet inside of Titan’s orbit. They appear clearly through 4-inch and larger scopes. An 8-inch instrument will bring in 12th-magnitude Enceladus when this inner moon lies farthest from Saturn.

Outer Iapetus is the Dr. Jekyll and Mr. Hyde of solar system objects. One of its hemispheres reflects light like newly fallen snow, while the opposite side more closely resembles coal. The moon’s brightness varies from 10th magnitude when it lies farthest west of Saturn and its reflective side faces us to 12th magnitude when it stands farthest east. The easiest times to spot it this month come on the evenings of June 7–9 when it passes north of Saturn and glows at 11th magnitude. Iapetus fades thereafter as it heads toward greatest eastern elongation June 28.

Neptune is a binocular object before dawn, when it lies in the southeastern sky among the background stars of Aquarius. It remains 2° southwest of 4th-magnitude Lambda (λ) Aquarii all month. The planet glows at magnitude 7.9, so it is a dim object in 7x50 binoculars, and the handful of similarly bright stars in its neighborhood makes identification difficult. To confirm a sighting, point your telescope at the suspected planet. Only Neptune will show a blue-gray disk measuring 2.3" across.

Like its outer neighbor, Uranus shows up best shortly before dawn starts to paint the sky. The magnitude 5.9 planet lies against the faint stellar backdrop of Pisces. Use magnitude 5.2 Zeta (ζ) Piscium as a guide. Uranus lies within 1° of this star all month and passes 0.5° due south of it June 18. A telescope reveals Uranus’ 3.5"-diameter disk and blue-green color.

Our final solar system target appears low in the east-northeast before dawn in late June. Mercury reaches greatest elongation on the 24th, when it lies 22° west of the Sun and stands 7° high a half-hour before sunrise. Shining at magnitude 0.4, it shows up easily through binoculars if you have an unobstructed horizon. Don’t confuse it with ruddy Aldebaran, the 1st-magnitude luminary of Taurus, which lies 2° south (lower right) of the planet that morning. A telescope will show Mercury’s disk, which appears 8" across and about one-third lit.

Only Mars remains invisible this month. It passes behind the Sun from our viewpoint June 14.
Catch lunar history on display when the Sun illuminates 132-mile-wide Schickard Crater in the days around Full Moon.
Catch lunar history on display when the Sun illuminates 132-mile-wide Schickard Crater in the days around Full Moon.
Consolidated Lunar Atlas/UA/LPL

One lunar feature nicely encapsulates much of the Moon’s history. The crater Schickard stands out near the southwestern limb in the days around Full Moon (June 2 this month). Your eyes will thank you if you reduce the lunar disk’s excessive glare. Using a smaller telescope than usual, pumping up the magni­fication, or screwing in a dark filter will help.

To get the full effect of viewing Schickard, start observing a couple of evenings early. On May 30, the first rays of sunlight strike the flooded crater at a glancing angle, highlighting ­differences in the heights of smaller features. You’ll quickly discern that this is an old crater because its rim appears battered; in contrast, the smaller craters pocking the smooth floor display the classic sharp edges of relative youth. Schickard’s western wall, which would have been steep at the moment of formation, abruptly slumped down into terraces that remain visible today. The higher Sun on the following two evenings seemingly erases these features.

Schickard transforms into a two-faced depression on the following nights, with an unusual stripe of lighter gray material painted across the middle of the floor. A large impact carved out this 132-mile-wide crater some 4 billion years ago. Lava soon welled up and covered its central peaks. Then the giant Mare Orientale impact to the west sprayed the whole region with lighter-colored material. A final surge of lava covered the northern and southern portions of the bowl but did not rise high enough to erase the lighter stripe.

When the Sun returns to the crater June 28, it displays dramatic shadows that camouflage the different shades. Within a couple of days, however, the stripe returns to prominence.
Observers should be on the lookout for the slow-moving meteors of the June Bootid shower, which peaks June 27.
Observers should be on the lookout for the slow-moving meteors of the June Boötid shower, which peaks June 27.
All illustrations: Astronomy: Roen Kelly
Northern Hemisphere meteor observers face two obstacles during June. First, the month delivers the shortest nights of the year, with areas north of 50° north latitude never achieving complete darkness. Second, June offers no major meteor showers.

This month’s best minor shower is the June Boötids, which peaks June 27. Astronomers don’t expect much activity this year, but you won’t know if you don’t look. The waxing gibbous Moon sets around 2 a.m. local daylight time on the 27th, leaving an hour or two of darkness for those at mid-northern latitudes. June Boötid meteors hit Earth at “only” 11 miles per second, the slowest of any shower.
Evening Sky
Midnight Morning Sky
Venus (west)
Saturn (south)
Mercury (northeast)
Jupiter (west)

Uranus (east)
Saturn (southeast)

Neptune (southeast)

Comet Catalina should glow at 8th or 9th magnitude in June as it chisels its way south through Sculptor.
A possible naked-eye object late this year, Comet Catalina should glow at 8th or 9th magnitude in June as it chisels its way south through Sculptor.
Will the comet gods deliver on their next promise? Astrono­mers predict that Comet Cata­lina (C/2013 US10) will be visible to the naked eye late this year. Observers have a chance to catch a preliminary view of this visitor from the Oort Cloud ­during June as it dives south through Sculptor.

This constellation hangs low in the southeastern sky shortly before morning twilight begins. (Observers in the Southern Hemisphere can find Sculptor just below 1st-magnitude Fomalhaut as it climbs in the eastern sky after midnight.) Comet experts expect Catalina to be glowing around 8th or 9th magnitude in June. The comet should look nearly round at this stage, though its northeastern flank will look slightly more defined where solar radiation pushes against the comet’s dusty envelope.

Northern Hemisphere viewers will have to wait for Catalina to make a long sojourn through the southern sky before it returns to view in late November. By then, the comet could be glowing at 4th or 5th magnitude as it shares the morning sky with Venus. It then will cruise past magnitude 0.0 Arcturus as the calendar ticks over to 2016. Astronomers with the U.S.-based Catalina Sky Survey discovered the comet October 31, 2013. The designation “US” in its official name comes from the chronological order of its discovery, however, and not the country of those who found it.
Pallas reaches its peak at opposition June 11, though the 9th-magnitude asteroid will be easy to spot all month among the stars of Hercules.
Pallas reaches its peak at opposition June 11, though the 9th-magnitude asteroid will be easy to spot all month among the stars of Hercules.
Asteroid 2 Pallas stands out from the family of asteroids like a black sheep. Unlike most main-belt objects, Pallas’ orbit inclines steeply to the plane of the solar system. (Of the first 1,000 asteroids discovered, Pallas’ 35° inclination is the highest.) A big impact likely kicked it into this odd orbit.

Pallas reaches opposition and peak visibility June 11, though it’s easy to find through binoculars or a telescope all month. It glows at 9th magnitude among the background stars of Hercules, a region already halfway to the zenith in the eastern sky as night settles in. Use the StarDome map at the center of the magazine to zero in on magnitude 3.1 Delta (δ) Herculis, your jumping-off point for finding Pallas.

You can hop quickly to Pallas June 12–14 when it passes 33' (just over one Full Moon diameter) south of magnitude 4.4 Lambda (λ) Her. The asteroid will be even easier to find June 30 when it pulls within 26' of Delta Her. You can detect Pallas’ motion in a four-hour observing session June 3, 5, 7, and 11 when background stars provide a convenient framework.

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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