NIGHT SKY HAPPENINGS

The Sky for June 2017
By Faylene Roth

The Summer Triangle—formed by Lyra (Vega), Deneb (Cygnus), and Altair (Aquila)—in the evening sky foretells the warm summer nights ahead. 0-magnitude Vega and 1st magnitude Deneb appear (about 20° apart) in the northeastern sky. 0-magnitude Altair (about 40° south of Deneb) rises due east as astronomical twilight overtakes the night sky. Take advantage of the moonless evenings June 17-27 to follow the Milky Way across the sky from Cassiopeia in the north through Cepheus, Cygnus, and Aquila. The Milky Way swings westward as the earth rotates towards a morning sky, sweeping Sagittarius and Scorpius into view in the southern sky. The center of our galaxy lies in the eastern region of Sagittarius.

Twilight extends the period of daylight in three stages at each end of the day. Morning twilight begins with astronomical twilight—about 1-1/2 hours (nearly 2 during summer months) before sunrise—as the eastern horizon brightens. Nautical twilight continues—as the overhead sky turns blue and color returns to the surrounding landscape—for another 30-40 minutes. The final stage—civil twilight—provides adequate light for most outdoor activities for the half hour before the sun crests the horizon. The opposite progression occurs after sunset.

VISIBLE PLANETS
Evening (Before Midnight)
Jupiter –At sunset a brilliant Jupiter shines directly overhead. Look for it as twilight darkens the sky in the western half of Virgo—about 15° to the right of Virgo’s bright blue star Spica. Jupiter sets a few hours after midnight. (Magnitude -2.0)
Saturn – The yellow disk of Saturn rises in the southeastern sky as the sun sets in the northwest. Look for it directly overhead—in Ophiucus (above the head of Scorpius) soon after midnight. Saturn presents its full face to Earth on June 15 when it reaches opposition (opposite side of Earth from the sun). (Magnitude +1.1 in)

Morning (At Twilight)
Saturn – Saturn sets about the same time the sun is rising in the northeast. Look for it during early morning twilight as it descends towards the southwestern horizon. (Magnitude +0.9)
Venus – The brilliance of Venus rising in the northeast several hours before sunrise will be much easier to spot than the fading yellow disk of Saturn setting in the southwest. Venus passes through Pisces, Cetus, Aries, and Taurus this month. It reaches aphelion with the sun on June 12 which puts it at its farthest distance from the sun, but it is not directly opposite the Earth as with Saturn’s opposition. Venus’s orb is currently about 55% illuminated, about what we see after a quarter moon. (Magnitude -4.3)

MOON HAPPENINGS
June 1 – Waxing first quarter moon lights the evening sky then sets soon after midnight.
June 9 – Full moon (7:10am) rises at 8:49pm.
June 17 – Dark evening skies return with the waning last quarter moon rising after midnight.
June 23 – New moon (8:31pm) yields dark skies for several nights.

(The moon rises later each day—as little as 30 minutes to as much as one hour. Time of moonrise and moonset may also be delayed in mountainous terrain.)

Twilight is often the best time to look for Venus and Mercury because they frequently rise or set within one-half to one hour of sunrise or sunset. Twilight transitions between night and day in three stages at each end of the day. Morning twilight begins with astronomical twilight as the eastern horizon brightens —about 1-1/2 hours (nearly 2 during summer months) before sunrise when the sun is 18 ̊ below the horizon. Nautical twilight takes over for another 30-40 minutes—as the sun passes 12 ̊ below the horizon and the overhead sky turns blue and color returns to the surrounding landscape. The final stage—civil twilight—begins when the sun ascends to 6 ̊ below the horizon and provides adequate light for most outdoor activities for the half hour before the sun crests the horizon. The opposite progression occurs after sunset. Civil twilight covers the period after sunset during which daytime light quality persists for about one-half hour. Color then fades from the landscape during the 30-40 minute period of nautical twilight during which the overhead sky darkens while the western sky retains color. Astronomical twilight then transitions to night skies that are now darkened along the horizon.

NO MAJOR METEOR EVENTS IN JUNE

Primary Sources: USGS; U.S. Naval Observatory; Your Sky at http://www.fourmilab.ch/yoursky/
To find out when the space shuttle and International Space Station are visible from your location, go to: http://spaceflight.nasa.gov/realdata/sightings/index.html and click on Sighting Opportunities.

The star chart approximates the sky from astronomical twilight to midnight. As the night and month progresses, the constellations shift toward the northwest. The celestial equator is measured in hours (h). The ecliptic is measured in degrees

Note: Hold your hand at arm’s length to measure apparent distances in the sky. The width of the little finger approximates 1.5̊. Middle, ring, and little finger touching represent about 5̊. The width of a fist is about 10̊. The fist with the thumb extended at a right angle equals 15̊. The hand stretched from thumb to little finger approximates 20̊-25̊. The diameter of both the full moon and the sun spans only 0.5̊. Adjust for the size of your hand.