SKY HAPPENINGS

The Sky for June 2013
By Faylene Roth

DAYLENGTH
Long days and short nights dominate the month of June. The length of the period of daylight varies by only eleven minutes this month peaking at 14 hours 52 minutes for a period of six days, centered on the solstice, and then slowly shortens by a minute every few days over the next several weeks. Due to variations in Earth’s velocity and position in its orbit, the earliest sunrise of the year occurs about one week before the solstice and latest sunset of the year occurs about one week after the solstice.

Summer twilight in June creates the dimly-lit, long, dusky evenings that linger until nearly 11:00pm before the sky reaches true darkness. Civil twilight spans the 30-minute period after sunset when adequate light still fills the sky. During June, the next two periods of fading twilight—nautical twilight and astronomical twilight—are longer than usual since the sun’s rays strike so far north of the equator. (The reverse progression occurs at dawn.) These lingering dimly-lit evenings continue through most of July.

SOLSTICE
The northern hemisphere swings its full tilt to the sun—here in Moab—just before midnight on June 20. At 11:04pm MDT the sun reaches its northernmost position in the sky. In some cultures the June solstice marks the first day of summer in the northern hemisphere. In others it marks the mid-point of summer. Meteorologists count the seasons in full months with summer beginning on June 1.

MOON HAPPENINGS
June 8 – New Moon occurs at 9:56am.
June 16 – First Quarter Moon sets several hours after midnight.
June 23 – Full Moon occurs 5:32am and rises at 9:03pm. June 30 – Last Quarter Moon rises soon after midnight.
(The time of moonrise and moonset assumes a flat horizon. Actual time may vary.)

SUPERMOON
The June full moon occurs just 23 minutes after it passes its closest point to Earth this year—making it appear larger and brighter than the average full moon. Since the full moon occurs in the early morning hours of June 23, it presents two opportunities for watching it rise. A 99% full moon rises on the southeastern horizon on two evenings: Saturday, June 22, at 8:05pm and again Sunday, June 23, at 9:03pm. Adjust rising time for the elevation of surrounding landscape features.

METEOR EVENTS
Minor meteor activity occurs throughout the month with radiants from many different directions. The first half of June offers the best viewing opportunities providing least interference from the moon.

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

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.

VISIBLE PLANETS

Jupiter – The second brightest planet may be visible for the first few June evenings a few degrees below Venus on the western horizon. It then begins its pass around the back side of the sun from our point of view. It reaches superior conjunction (opposite the earth on the far side of the sun) on June 19 and reappears in mid-July in the morning sky. (Magnitude -1.6)

Mercury – Our most elusive planet swings out to its greatest elongation (furthest distance from the sun and highest position in the sky) on June 12. Best viewing time is 45 to 60 minutes after sunset. Mercury appears above Venus until June 18-20 when Venus closes in to about two degrees of Mercury. Venus then claims the upper position. Mercury remains in Gemini throughout the month, and both disappear into the glare of the setting sun by month’s end. (Magnitude -0.3 dimming to +1.3)

Saturn – Arcturus (Boötes), Vega (Lyra), and Saturn are the first three objects visible in the overhead evening sky. Saturn’s steady golden light differentiates it from the strong white light of Vega and the red-orange hue of Arcturus. Look for Saturn between Virgo’s bright star Spica (to the west) and the four stars that form Libra (to the east). On the night of June 19, Saturn appears above the waxing gibbous moon. (Magnitude (+0.9)

Venus – Its brightness and location low on the western horizon after sunset makes Venus easy to identify. View from a high vantage point with a clear view of the western horizon. On June 10 a thin waxing crescent moon appears south of Venus with Mercury between them—about four degrees from Venus. Castor and Pollux (Gemini) may be visible on the horizon. Venus moves higher above the western horizon each evening. By month’s end it appears in Cancer. (Magnitude -3.7)


Note: Apparent magnitude values range from -4 to +6 for most planets and visible stars. The lower the value the brighter the object. A decrease of 1.0 magnitude is 2.5 times brighter.

Bright stars Vega (Lyra), Deneb (Cygnus), and Altair (Aquila) form the Summer Triangle—an asterism, which is a recognizable shape that is not designated a constellation. The Big Dipper (aka Plough or Wagon) forms an asterism within Ursa Major. Look for the Summer Triangle in the early evening eastern sky. The Milky Way runs through it from north to south. Follow its path southward to Sagittarius, and you will be looking into the center of the galaxy.

Hold the star chart high above your head and match the compass directions to the direction you are facing. Adjust the star chart by orienting Ursa Major (Big Dipper) to match its position in the sky.

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.