The Sky this Week: June 19–28, 2015

Your daily digest of celestial events coming soon to a sky near you.

Friday, June 19
A waxing crescent Moon hangs low in the west after sunset this evening. It appears some 7° below Venus, while Jupiter stands the same distance to Venus’ upper left. Naked eyes will show you our satellite’s 13-percent-lit disk; you’ll need a telescope to spy Venus’ fatter crescent, which is 42 percent illuminated. Although Jupiter is only the third-brightest member of this trio, no other object elsewhere in the night sky rivals it.

Saturday, June 20

The waxing crescent Moon perches some 5° to Jupiter’s lower left this evening. The two objects join with Venus to dominate the evening sky from a half-hour after sunset until they dip below the horizon after 11 p.m. local daylight time. Only 6° separate Venus and Jupiter tonight; the gap between the two will continue to narrow over the next 10 days as the pair heads toward a spectacular conjunction in late June and early July.

Sunday, June 21

Earth’s June solstice occurs at 12:38 p.m. EDT, when the Sun reaches its farthest point north in the sky. This marks the official beginning of summer in the Northern Hemisphere, and the day of the solstice has more hours of sunlight than any other. For astronomy buffs, however, long days translate into short nights and extended twilight, which limit our time under the stars.

Monday, June 22

With the Moon now having pulled away from the evening planets, it’s a good time to target magnitude –1.8 Jupiter through a telescope. The giant planet appears best about an hour after sunset, when it still lies relatively high in the west and its light passes through less of Earth’s image-distorting atmosphere. A telescope reveals Jupiter’s 33"-diameter disk, which should show lots of cloud-top detail, and its four bright moons

Tuesday, June 23

The Moon reaches apogee, the farthest point in its orbit around Earth, at 1:00 p.m. EDT. It then lies 251,116 miles (404,132 kilometers) from Earth’s center.

Wednesday, June 24

The First Quarter Moon lies high above the southwestern horizon as darkness falls. Our satellite officially reaches First Quarter phase at 7:03 a.m. EDT, so it appears a little more than half-lit in this evening’s sky. You can find it among the background stars of Virgo the Maiden.

Mercury reaches greatest elongation today, when it lies 22° west of the Sun and stands 7° high in the east-northeast a half-hour before sunrise. The innermost planet shines at magnitude 0.4 and shows up easily through binoculars if you have an unobstructed horizon. Don’t confuse it with Aldebaran, the ruddy 1st-magnitude star in Taurus, which lies 2° south (lower right) of the planet. When viewed through a telescope, Mercury appears 8" across and about one-third lit.

Mercury hangs low on mornings around June 24, when it lies 22° west of the Sun at its summertime peak for Northern Hemisphere observers.

Thursday, June 25

Venus crosses the border from Cancer the Crab into Leo the Lion this evening as the gap between it and Jupiter closes to 3°. (The separation between the two brightest planets will continue to shrink over the next five nights, reaching a minimum of 20' on the 30th.) While Jupiter’s telescopic appearance remains the same this week — its diameter stays stuck at 33" — Venus’ changes noticeably. On June 19, its disk spans 28" and appears 42 percent lit; by the 28th, its apparent diameter swells to 31" and the Sun illuminates 35 percent of its disk.

Friday, June 26

Asteroid 2 Pallas appeared opposite the Sun in our sky barely two weeks ago (on the 11th), and it lingers in the sky all night. The 9th-magnitude object — the second-largest body located between the orbits of Mars and Jupiter — lies among the background stars of Hercules. This region stands more than halfway to the zenith as darkness falls and climbs nearly overhead by midnight local daylight time. Using binoculars or a telescope, target the area 1° east of magnitude 3.1 Delta (δ) Herculis. If you are unsure which point of light is the asteroid, sketch the field and return to it a night or two later. The object that moved is Pallas.

Saturday, June 27

For people who live near 40° north latitude, today marks the latest sunset of the year. Although Earth’s summer solstice and the Northern Hemisphere’s longest day occurred nearly a week ago (on the 21st), latest sunset happens several days after and earliest sunrise several days before. The specific dates depend on your latitude, however — latest sunset at 30° north takes place July 1. In general, latest sunset occurs closer to the solstice the farther north you live.

The typically minor June Boötid meteor shower occasionally reminds us of its presence. After decades of inactivity, the shower produced up to 100 meteors per hour in 1998. It then returned with about half that number in 2004. Although astronomers aren’t predicting an outburst this year, veteran observers know that the only way to be sure is to actually watch the sky. The shower peaks before dawn today, and conditions should be excellent after the waxing gibbous Moon sets around 2 a.m. local daylight time. The meteors appear to radiate from a point, called the “radiant,” located in the northern part of the constellation Boötes the Herdsman.

Sunday, June 28

Beautiful Saturn reached opposition and peak visibility in late May, and it remains a spectacular sight from nightfall until after 3 a.m. local daylight time. It currently lies among the background stars of eastern Libra and climbs highest in the south around 10 p.m. local daylight time. This evening, the waxing gibbous Moon helps point the way as it passes 2° north of the planet. Saturn shines at magnitude 0.2 and is the brightest object in the Moon’s vicinity. When viewed through a telescope, the planet’s dramatic ring system spans 41" and tilts 24° to our line of sight.source

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